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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260217T110000
DTEND;TZID=Asia/Kolkata:20260217T130000
DTSTAMP:20260415T080237
CREATED:20260213T055505Z
LAST-MODIFIED:20260213T055505Z
UID:10000115-1771326000-1771333200@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) :Experimental Investigation of Autoignition Pathways and Shock-Train Dynamics During Mode Transition in a Dual-Mode Supersonic Cavity Combustor
DESCRIPTION:Hypersonic propulsion systems capable of sustained atmospheric flight are critical enablers for future reusable launch vehicles\, long-range high-speed transport\, and responsive global strike platforms. Among the various air-breathing concepts\, scramjet engines offer unmatched efficiency at hypersonic speeds by utilizing atmospheric oxygen and avoiding the mass penalties associated with onboard oxidizers. However\, the practical realization of scramjet propulsion is fundamentally constrained by two interrelated challenges: reliable ignition and flame stabilization under extremely short residence times\, and robust operation across a wide flight envelope that necessitates smooth transition between supersonic (scramjet) and subsonic (ramjet) combustion modes. Dual-mode scramjets (DMSJ) are designed to address this requirement\, but their operability is limited by complex\, strongly coupled interactions between shock structures\, boundary-layer separation\, fuel-air mixing\, chemical kinetics\, and unsteady pressure fields during mode transition. A central difficulty in hypersonic combustors is that global flow conditions typically yield Damköhler numbers well below unity\, rendering conventional flame-holding ineffective. Localized enhancement of thermochemical coupling through elevated temperature\, pressure\, and residence time is therefore essential to initiate and sustain combustion. Cavity-based flameholders have emerged as a promising solution due to their passive\, low-drag configuration and ability to generate recirculation zones that promote autoignition and flame anchoring. Nevertheless\, cavity-stabilized combustors introduce additional challenges: strong sensitivity to geometry\, concentration of thermal loads\, susceptibility to unsteady shear-layer oscillations\, and complex coupling with shock-train dynamics during scram-to-ram transition. Despite extensive cold-flow investigations of isolator shock trains\, their behaviour under reacting\, high-enthalpy conditions where heat release actively modifies the flow remains insufficiently characterized. This doctoral research discusses a systematic experimental investigation of autoignition pathways\, flame stabilization mechanisms\, and shock-train dynamics in a cavity-stabilized dual-mode supersonic combustor. Experiments are conducted in a direct-connect high-enthalpy facility at the Advanced Propulsion Research Laboratory (APRL)\, Indian Institute of Science. The combustor operates at flight relevant conditions of total temperature of 1500 ± 30 K and static pressure of 43 kPa\, which corresponds to Mach 5.5 flight conditions at 28 km altitude. The experimental test article features an optically accessible supersonic combustor with a single/twin cavity configuration and is designed for an inlet Mach 2.5. Time-resolved Schlieren imaging\, CH* and C2* chemiluminescence\, and high-frequency wall-pressure measurements are employed to resolve unsteady flow-flame interactions governing ignition and mode transition. Two cavity geometries with identical depth but different length-to-height ratios (L/H = 5 and 8.5) were examined to quantify the influence of geometry on ignition robustness and shock–flame coupling. For the L/H = 5 configuration\, ethylene ignition occurred downstream in the diverging duct at a global equivalence ratio of ϕg ≈ 0.3\, followed by upstream flame propagation and eventual stabilization along the shear layer. In contrast\, the L/H = 8.5 cavity enabled earlier and more robust ignition upstream\, triggered by shock-assisted autoignition behind an X-type shock formed through interaction between the cavity reattachment shock and a top-wall separation bubble. The larger cavity generated stronger pressure deficits\, deeper shear-layer penetration\, and self-sustained oscillations at approximately 527 Hz\, highlighting the critical role of cavity geometry in enhancing local Damköhler numbers. Optical diagnostics technique of two-wavelength chemiluminescence (CH* and C2*) revealed ignition kernels forming preferentially in high-temperature lean regions before stabilizing near stoichiometric zones. Shock-induced compression was shown to significantly reduce ignition delay\, enabling autoignition even for fuels with substantially longer chemical timescales. Fuel-blending experiments established a limiting ignition-delay threshold\, providing quantitative guidance for fuel selection in practical hypersonic combustors. The scram-to-ram mode transition occurred at ϕg ≈ 0.58 for both geometries and was marked by the formation of a pre-combustion shock train\, initiated due to combustion induced boundary layer separation. The L/H = 8.5 cavity sustained stable ram-mode operation\, whereas the L/H = 5 configuration frequently reverted to early scram-mode behavior\, indicating weaker shock-flame coupling and reduced buffering capacity against back-pressure fluctuations. Scaling analysis of shock-train dynamics yielded Strouhal numbers (St) an order of magnitude lower than the reported values in the literature based on isothermal shock-train oscillation studies. This demonstrated the dominant influence of heat release and shock-train coupling. Proper orthogonal decomposition (POD) analysis further revealed tight coupling between shock-train motion and upstream flame propagation\, identifying critical regions in the combustor with substantial heat release fluctuations. Finally\, symmetric dual-cavity configurations were explored to assess coupled shear-layer dynamics. While dual cavities enhance residence time\, their interaction introduces additional unsteady modes\, underscoring the need for geom etry-aware stabilization strategies. Overall\, this work directly addresses critical propulsion challenges for hypersonic vehicles by elucidating the mechanisms governing ignition reliability\, shock-assisted autoignition\, and mode-transition stability in cavity-based dual-mode scramjets. The findings provide mechanistic understanding and scalable design guidelines essential for the development of robust\, operable hypersonic air-breathing propulsion systems. \n  \nSpeaker :  Sumit Lonkar \nResearch Supervisor: Pratikash Prakash Panda
URL:https://aero.iisc.ac.in/event/ph-d-engg-experimental-investigation-of-autoignition-pathways-and-shock-train-dynamics-during-mode-transition-in-a-dual-mode-supersonic-cavity-combustor/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/02/SUMIT.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260211T150000
DTEND;TZID=Asia/Kolkata:20260211T170000
DTSTAMP:20260415T080237
CREATED:20260203T104201Z
LAST-MODIFIED:20260203T104201Z
UID:10000114-1770822000-1770829200@aero.iisc.ac.in
SUMMARY:AE Seminar-Dr Maanasa Bhat: Low-cost and Low-emissions Strategies for Resolving Challenges in the Hydrogen Supply Chain
DESCRIPTION:Abstract: \nThe Net Zero Emissions 2050 (NZE 2050) initiative sets an ambitious target to eliminate net CO2 within the next two decades. Achieving this goal demands widespread decarbonization across energy\, transportation\, residential\, and industrial sectors. Carbon-free and carbon-neutral fuels are central to this effort. Hydrogen\, an abundant\, high-energy-density\, carbon-free fuel is expected to play a critical role in this transition. While hydrogen is already used in sectors such as chemical production and refining\, expanding its role into transportation and electricity generation requires significant infrastructure development. Key challenges include improving production technologies\, enhancing storage safety\, enabling long-distance transport\, and ensuring economic viability. \nThe current talk discusses low-cost and low-emissions strategies to tackle challenges across three stages of the hydrogen supply chain: production\, storage\, and transportation. Both experimental methodology and big-picture techno-economic and life cycle analysis approaches are utilized as needed. For the production stage\, a low-cost spray synthesis method is investigated for manufacturing mixed metal oxides for potential catalyst use. For hydrogen storage\, improvement of operational safety is discussed by studying the development of highly sensitive hydrogen leak detection sensors working on the chemiresistive principle. For transportation\, a techno-economic and life cycle assessment of intercontinental hydrogen delivery from Australia to Japan is conducted to evaluate the feasibility of using hydrogen carriers such as methanol\, e-LNG and ammonia. Together\, these contributions present economically and environmentally viable strategies to support hydrogen infrastructure development by improving production efficiency\, ensuring safe storage\, and enabling long-distance transportation\, thereby accelerating progress toward NZE 2050 goals. \nAbout the Speaker: \nDr. Maanasa Bhat is a recent PhD graduate from the Department of Mechanical Engineering at Massachusetts Institute of Technology (MIT)\, Cambridge MA\, USA. She conducted her PhD research at the Deng Energy and Nanotechnology Group (PI: Prof. Sili Deng) and the MIT Energy Initiative (PI: Dr. Guiyan Zang). Her research focus is on the development of materials and processes for applications in energy storage and conversion. She is particularly interested in clean energy applications\, focusing on carbon-free fuels and Li-ion batteries. Her approach utilizes both experimental methodologies to tackle fundamental questions and techno-economic and life cycle analysis for problem-solving on a larger scale. She graduated with a Master of Technology (By Research) in 2019 from the Department of Aerospace Engineering at Indian Institute of Science (IISc)\, Bengaluru. She was a recipient of the NASAS medal for best academic performance. She has a Bachelor of Engineering in Mechanical Engineering from R.V College of Engineering\, Bengaluru. In addition to research\, she has a keen interest in community engagement and has served in leadership roles as the President of the Indian Students Association at MIT and Chairman of IISc Kannada Sangha Nityotsava.
URL:https://aero.iisc.ac.in/event/ae-seminar-dr-maanasa-bhat-low-cost-and-low-emissions-strategies-for-resolving-challenges-in-the-hydrogen-supply-chain/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/02/DR-MANASA-STC.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260209T111500
DTEND;TZID=Asia/Kolkata:20260209T130000
DTSTAMP:20260415T080237
CREATED:20260202T091939Z
LAST-MODIFIED:20260204T061202Z
UID:10000113-1770635700-1770642000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Multi-Agent Coordination using Convex Formations and Binary Tree Structures
DESCRIPTION:Multi-agent systems are increasingly deployed in missions involving large-scale tasks with complex objectives that are beyond the capability of a single agent. Such missions demand computationally efficient coordination strategies that ensure safety\, reliable operation\, and ease of implementation\, particularly in dynamic and uncertain environments. This thesis investigates coordination strategies in multi-agent systems\, specifically addressing the problems of distribution of agents on an enclosing boundary\, cooperative target capture and containment\, and traversal through constrained spaces.\n\nThe first part of the thesis presents a convex layer-based strategy that assigns collision-free paths to a swarm of point-sized agents to reach an enclosing circular boundary. Leveraging the construction of convex layers from the initial positions of agents\, a novel search space for an agent on a convex layer is defined as an angular region enclosed between the lines passing through the agent’s position and normal to its supporting edges. A goal assignment policy is proposed\, which designates a unique goal position on the boundary within the search space of an agent. Subsequently\, the proposed framework is extended to polygonal boundaries\, considering disc-shaped agents. Therein\, the proposed policy assigns a goal position to each agent in order of decreasing overlap between their search spaces and the polygonal boundary\, while excluding angular regions corresponding to already assigned goal positions. Further\, a layer-wise speed assignment rule is proposed\, which ensures collision-free trajectories for the agents. Simulation studies assess the proposed method under various real-world considerations\, including the finite size of the agents\, a six-degree-of-freedom quadrotor model\, uncertainties in initial position information\, and communication delays.\n\nIn the second part\, the problem of multiple pursuers engaging a single evader is considered in two complementary scenarios. Firstly\, the problem of capturing the evader in an unbounded region is addressed. As the key construct\, the evader’s proximity region is characterized by the region generated by the Voronoi diagram constructed using the positions of the pursuers and the evader. Pursuers’ velocity inputs are deduced as a function of the position and velocity of the vertices of the evader’s proximity region and the evader. A motion policy is proposed that directs the vertices of the evader’s proximity region toward its centroid\, under which the region is analytically shown to shrink exponentially over time\, irrespective of the evader’s motion policy. In addition\, using the Chebyshev radius of the proximity region\, an upper bound on the time of evader capture is derived. Simulation studies demonstrate the effectiveness of the proposed method under various evader maneuvers and in scenarios where evader position information is noisy. In a scenario complementary to evader capture\, a containment problem is considered\, wherein multiple pursuers are desired to encapsulate a moving evader. Considering the engagement between the evader and the centroid of the convex hull of pursuers\, a variable deviated pursuit guidance law is proposed\, which achieves a tail-chase rendezvous between the evader and the centroid. Subsequently\, a cooperative control strategy is presented\, which drives the convex hull of pursuers to confine the evader through a prescribed edge while preserving the formation rigidity. Simulation results demonstrate the efficacy of the proposed method under various evader maneuvers.\n\nThe final part of the thesis addresses the problem of sequential traversal of multiple UAVs through a narrow gap. A hierarchical binary tree is constructed with its nodes defined by the UAVs’ initial positions and the gap entry point\, presenting a routing framework that provides an ordered sequence of waypoints to each UAV. A cost function is formulated that accounts for the UAV path lengths and the angles between branches at the tree nodes\, and a binary tree is constructed by minimizing that cost using a genetic algorithm coupled with a greedy strategy. In conjunction\, a decentralized scheduling policy is proposed\, in which each UAV is assigned conflict-free time slots at nodes that are identified with potential collisions. Simulation scenarios illustrate the effectiveness of the proposed method\, and Monte Carlo studies assess its scalability.\n\nOverall\, the thesis presents deterministic and computationally efficient multi-agent coordination strategies by leveraging ideas from convex geometry and binary trees. Experimental flight trials on a nano-quadrotor platform are also conducted\, further demonstrating the practicality of the proposed coordination methods.\n\nSpeaker : Gautam Kumar \n\nResearch Supervisor : Ashwini Ratnoo
URL:https://aero.iisc.ac.in/event/ph-d-engg-multi-agent-coordination-using-convex-formations-and-binary-tree-structures/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/02/Gautam.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260119T150000
DTEND;TZID=Asia/Kolkata:20260119T170000
DTSTAMP:20260415T080237
CREATED:20260116T043058Z
LAST-MODIFIED:20260119T103611Z
UID:10000112-1768834800-1768842000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) :  Turbulence Energy Cascade in Physical  Space in a Turbulent Channel Flow
DESCRIPTION:A comprehensive investigation of the energy and enstrophy cascade in physical space in a turbulent channel flow is presented for four Reynolds numbers. Bandpass filtering techniques are employed to isolate scales and quantify inter-scale interactions through kinetic energy flux\, enstrophy generation\, and enstrophy flux. Two bandpass filter formulations used in the literature are quantitatively assessed by comparing the output.\nThe mean energy and enstrophy cascades are shown to be predominantly local for all the Reynolds numbers. Away from the wall\, the degree of locality decreases while a broader range of scales participate in the cascade. Interestingly the distance at which the inter-scale flux peaks shows a distance-from-wall scaling\, implying relevance of the attached-eddy formalism to energy cascade in scale space (in addition to its relation ​ to momentum transport in physical space). Vorticity stretching as the underlying mechanism of cascade is studied through vorticity alignment statistics. The vortices show preferential alignment with intermediate eigenvector for smaller scale ratios and closer to the wall\, while alignment with the most extensional eigenvector is observed at larger scale ratios and away from the wall. The preferential alignment shows a complex dependence on the wall-normal distance\, suggesting that the wall has important influence on both energy transfer rates and the geometry of structures. Notwithstanding this\, the contribution from most extensional eigenvector dominates enstrophy generation for all conditions. The scaling of energy flux with scale size\, scale ratio\, wall-normal distance\, and Reynolds number is obtained using dimensional arguments and is validated against numerical results.  As the cascade progresses\, the energy at small scales gets concentrated in a small region of space\, reflected as intermittency in enstrophy and energy fluxes. The skewness and kurtosis increase at smaller length scales but they show weak increase with the Reynolds number. The morphology of energy flux and enstrophy iso-surfaces are characterized through Minkowski functionals. Enstrophy structures at small scales are like flattened long tubes\, while large-scale structures are blob-like or short-tube-like. The large-scale structures generally exhibit lower values of filamentarity. Energy flux structures show a similar behaviour\, with near-wall structures being more flattened compared to those farther from the wall. These findings remain unaffected by an increase in threshold for getting the iso-surfaces.\nOverall\, the present study provides new insights into the locality\, scaling\, and morphology of the energy and enstrophy cascade in the channel flow\, offering a unified framework for interpreting multi-scale turbulence dynamics in wall-bounded flows.\n\nSpeaker :  Aditya Anand\n\nResearch Supervisor :  Sourabh Suhas Diwan
URL:https://aero.iisc.ac.in/event/ph-d-engg-turbulence-energy-cascade-in-physical-space-in-a-turbulent-channel-flow/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/01/Aditya123.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260112T160000
DTEND;TZID=Asia/Kolkata:20260112T170000
DTSTAMP:20260415T080237
CREATED:20260109T053022Z
LAST-MODIFIED:20260112T112429Z
UID:10000110-1768233600-1768237200@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Compression & LVI of closed-cell metallic foam
DESCRIPTION:Innovative high-performance structural designs play a critical role in mitigating insecure events such as low-velocity and ballistic impacts. These events involve significant kinetic energies\, requiring structures that are lightweight\, safe\, and capable of absorbing energy effectively. Closed cell metallic foams have been widely adopted in aerospace\, marine\, civil\, mechanical\, and automotive industries due to their superior resistance to such impacts. Despite extensive research over the years\, further advancements are still required in the design of lightweight protective structures. In impact applications\, the impactor need not always strike perpendicular to the structure. Characterization of dissipation energies \, impact load histories\, and load–displacement curves under varying impact angles revealed\, Contact force intensity and penetration time decrease as the impact angle increases. Energy absorption increases while penetration time decreases with increasing impact angle. Contact force decreases and contact time increases as the angle decreases. Displacement under oblique impact increases with increasing angle. The study was extended to finite element simulations of low-velocity impact behaviour in silicon–aluminium composite foams using ABAQUS/Explicit®. Numerical estimations of both full and partial damage were carried out for different impactor shapes and velocities. Key parameters such as dissipation energies\, impact load histories\, and load–displacement behaviour under penetration were systematically reported. The numerical scheme was validated against available experimental results\, confirming the accuracy and reliability of the model. The following observations were made: Impact velocity effects: Contact force intensity and penetration time decrease with increasing impact velocity. Energy absorption increases while penetration time reduces as velocity increases. Impactor nose radius effects: Contact force reduces with smaller nose radii. Contact time is enhanced as the nose radius decreases. Impactor shape effects: The computed energy absorption effectiveness factor revealed that performance depends not only on material properties but is also strongly influenced by the geometry of the impactor. The study was further extended to numerical simulations of aluminium foam subjected to low velocity impacts. Both full and partial damage estimations were performed on foam samples across varying impact energies and thicknesses. Dissipated energy\, impact load histories\, and load–displacement responses were systematically reported under different penetration conditions. Foam samples with a thickness of 10 mm exhibited bending and global failure\, characteristic of thin plate behaviour. In contrast\, samples thicker than 10 mm underwent local failure\, displaying behaviour typical of thick plates. For partial penetration cases\, contact force\, dissipated energy\, deformation\, and penetration time all increased with rising impact energy. For fully penetrated samples\, contact force\, dissipated energy\, and deformation increased monotonically with impact energy\, while penetration time decreased significantly. Across all aluminium foam samples\, greater thickness led to monotonic increases in contact force\, dissipated energy\, deformation\, and contact time. These findings underscore the critical influence of plate thickness in governing the impact resistance of aluminium foam structures. Furthermore\, closed cell foam was modelled at the mesoscale to replicate the intrinsic geometry of real foam structures. LVT based 3-D models were employed to generate complex morphologies\, including irregular pore sizes\, uneven cell wall thicknesses & geometric variability. Morphological parameters such as equivalent diameter & sphericity factor were used to quantify pore size & irregularities. The influence of pore number & porosity on cell wall thickness was examined & the quasi-static compressive behaviour was assessed through load-displacement & stress-strain responses\, alongside energy absorption & plastic dissipated energies. Results revealed that plateau strength exhibited only a marginal increase with pore number\, while energy absorption showed a slight counterintuitive decline. Plastic dissipation energy increased monotonically with increasing pore number. Conversely\, increasing porosity led to a monotonic decrease in yield point\, energy absorption capacity & plastic dissipation energy. The study underscores that energy absorption capacity is strongly governed by porosity\, cell wall thickness & pore size. These parameters must be incorporated into the design of closed-cell foams to ensure safe & reliable performance in protective structural applications. \n  \nSpeaker: THIMMESH T \nResearch Supervisor: Dineshkumar Harursampath
URL:https://aero.iisc.ac.in/event/ph-d-engg-compression-lvi-of-closed-cell-metallic-foam/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/01/Thim.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260105T110000
DTEND;TZID=Asia/Kolkata:20260105T130000
DTSTAMP:20260415T080237
CREATED:20260102T043026Z
LAST-MODIFIED:20260105T113025Z
UID:10000108-1767610800-1767618000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) :Studies on the Mixing Layer Between Supersonic Supersonic Co-flows
DESCRIPTION:Two supersonic streams merging together in a co-flow configuration are encountered in several engineering systems\, such as high-speed propulsion devices and supersonic ejectors. The thin mixing layer that develops between the two streams is dominated by compressibility effects and is prone to shock interactions in shock-dominated flows. The convective Mach number is defined relative to dominant large-scale structures in the mixing layer and is typically used to characterise the mixing layer. A key observation from previous studies on canonical supersonic-supersonic mixing layers having zero streamwise pressure gradient (ZPG-ML)\, which has a significant bearing on system design\, is that the growth of the mixing layer is significantly reduced as the convective Mach number increases. In applications\, however\, streamwise pressure gradients can exist due to the flow topology\, but there are very few studies on the effects of the streamwise pressure gradient on the growth of mixing layers (SPG-ML)\, especially in shock-dominated flows\, which motivates this study. Further\, there is a need to enhance mixing rates for compact design\, which can be carried out using passive geometric modifications\, and the effects of techniques such as discrete injection through holes and vortex generators like lobes on SPG-ML are not well studied. We study the mixing layer between supersonic-supersonic coflows in a specially designed supersonic mixing layer experimental facility\, and using high-fidelity Large Eddy Simulations carried out using the OpenFOAM framework. The Mach number combinations of the two streams (2.0\, 3.0) and (2.5\, 3.0)\, with a typical convective Mach number of 0.23\, are investigated. The flow is experimentally examined using high-speed schlieren and wall static pressure measurements. First\, the LES framework is validated on existing experimental/DNS computations on ZPG-ML\, and the computations are found to simulate the mixing layer characteristics well. The flow topology of the SPG-ML involves the generation of an oblique shock and an expansion fan at the point of confluence\, as well as the development of the mixing layer downstream in the presence of a streamwise pressure gradient. The shock further reflects from the wall and impinges on the mixing layer. The wall static pressure profiles obtained from the LES simulations agree well with the experimental wall static pressure measurements. The mixing layer growth rate of the SPG-ML before shock interaction is 15% higher than ZPG-ML. Shock interaction significantly increases the three-dimensionality of the turbulent structures in the mixing layer\, particularly in the p resence of high baroclinic torques\, and enhances the growth rate. In the current study\, the mixing layer is found to curve after the shock interaction\, thereby sustaining an increase in the mixing layer growth rate compared to previous studies. Two different techniques of introducing streamwise vortices into the mixing layer are investigated\, the first where discrete holes connect the high-pressure side to the low-pressure side\, leading to a jet into the supersonic stream\, generating counter-rotating vortices. In the second technique\, elliptic lobes generate large streamwise vortices. Both techniques are found to increase the mixing layer growth rate before the interaction. Shock interaction is found to break up vortices and promote three-dimensionality in the milder case of the jet through the holes. In the case of lobes\, the streamwise vortices are strong enough to retain their connectedness despite getting significantly modified by the shock interaction. These observations have implications for the application of such techniques to enhance mixing in shock-dominated flows. Detailed comparative investigations of different supersonic-supersonic mixing layer configurations are examined using experiments and LES data \n  \nSpeaker:  PANCHABUDHE LAKHAN MADANJI  \nResearch Supervisor: Srisha Rao M V
URL:https://aero.iisc.ac.in/event/ph-d-engg-studies-on-the-mixing-layer-between-supersonic-supersonic-co-flows/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/01/PANCHABUDHE-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251230T103000
DTEND;TZID=Asia/Kolkata:20251230T130000
DTSTAMP:20260415T080237
CREATED:20251229T130027Z
LAST-MODIFIED:20251231T083130Z
UID:10000107-1767090600-1767099600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Enhancing Precise Label Prediction and Imbalance Robustness in Multi-Label Learning
DESCRIPTION:Multi-label learning (MLL) addresses learning problems in which a single data instance may simultaneously belong to multiple semantic categories. This formulation arises naturally in many real-world applications\, including image and video understanding\, medical diagnosis\, text categorization\, and bioinformatics. In many of these settings\, it is not sufficient to merely rank relevant labels higher than irrelevant ones; instead\, models must accurately identify the exact set of labels associated with each instance. Such exact label prediction is critical when each label carries direct semantic or operational meaning\, for example when detecting disease conditions in medical data or identifying pedestrians and traffic signs in autonomous driving scenes. In addition\, real-world deployments frequently expose multi-label models to out-of-distribution (OOD) inputs caused by domain shifts\, novel concepts\, or evolving environments\, making reliable OOD detection an important requirement. Many practical applications are also sequential in nature\, where data and label spaces evolve over time\, leading to the continual multi-label learning (CMLL) problem in which models must acquire new knowledge while mitigating catastrophic forgetting. Together\, these considerations motivate the need to study multi-label learning with emphasis on exact label prediction\, robustness to data imbalance\, improved OOD detection\, and learning under continual data arrival. \nThe first contribution of this thesis introduces Bipolar Networks\, a novel architectural formulation for multi-label classification designed to improve exact label prediction. Unlike conventional single-output architectures that produce continuous confidence scores per label\, Bipolar Networks represent each label using two complementary outputs that encode positive and negative evidence. The final label decision is derived from the relative difference between these outputs\, enabling exact label predictions. To support effective training of this architecture\, the thesis develops a family of bipolar loss functions by reformulating standard objectives such as Binary Cross-Entropy and Focal Loss\, along with margin-based variants. Extensive experiments on benchmark datasets demonstrate that Bipolar Networks consistently improve F1 scores while maintaining competitive mean average precisions. \nBuilding on the improved discriminative behaviour of Bipolar Networks\, the second contribution addresses out-of-distribution detection in multi-label learning. While most existing OOD detection methods are designed for single-label classification or rely on computationally intensive mechanisms\, this thesis proposes a bipolar joint energy score tailored to the bipolar architecture. By leveraging the improved exact label prediction capability of Bipolar Networks\, the proposed scoring function enables more effective separation between in-distribution and out-of-distribution samples in multi-label settings\, demonstrating that stronger multi-label classification performance on in-distribution data can naturally translate into improved OOD detection. \nThe third contribution presents Learn What Matters\, a generalizable training framework that enhances exact label prediction without modifying model architectures or loss formulations. Learn What Matters operates at the optimization level by selectively masking parameter updates based on the ratio of gradient to parameter magnitudes\, suppressing low-information updates while rescaling the remaining gradients to preserve learning dynamics. This approach acts as a form of dropout during backpropagation and directs learning toward informative regions of the parameter space. Applied to standard single-output multi-label networks trained with ranking-based losses\, Learn What Matters yields substantial improvements in F1 score with only marginal impact on mAP scores\, providing a model-agnostic alternative to architectural modifications. \nThe fourth contribution explores biologically inspired learning approaches for multi-label classification. Drawing inspiration from neural computation in the human brain\, the thesis develops several bio-inspired models\, including Bipolar Spiking Neural Networks\, Adaptive Margin Spiking Neural Networks\, and NIMBLE\, a neuro-inspired multi-label learning framework. These methods leverage spike-based computation\, selective update mechanisms\, and adaptive stability–plasticity behavior to naturally support exact label prediction and efficient learning. Experimental results demonstrate that these biologically motivated designs improve exact label prediction and imbalance robustness in multi-label settings. \nFinally\, the thesis extends the proposed architectures and learning algorithms to the continual multi-label learning setting\, where data arrives sequentially without access to past samples or task identities. The resulting methods are task-agnostic and memory-free\, and empirical evaluations across multiple benchmarks show consistent improvements in exact label prediction and reduced catastrophic forgetting. Overall\, this thesis presents a unified framework spanning architectural design\, optimization strategies\, and biologically inspired learning for advancing exact label prediction\, OOD detection\, and continual learning in multi-label learning models. \n  \nSpeaker :  Sourav Mishra \n  \nResearch Supervisor: Prof. Suresh Sundaram
URL:https://aero.iisc.ac.in/event/ph-d-engg-enhancing-precise-label-prediction-and-imbalance-robustness-in-multi-label-learning/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/12/Sourav.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251222T150000
DTEND;TZID=Asia/Kolkata:20251222T170000
DTSTAMP:20260415T080237
CREATED:20251218T100932Z
LAST-MODIFIED:20251218T100932Z
UID:10000104-1766415600-1766422800@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Characterization of time-frequency behavior of flow intermittency in transitional boundary layers
DESCRIPTION:The importance of transitional flow studies can be realized from the fact that it acts as a bridge between the laminar and turbulent flows. The present work deals with the investigation of time-frequency characteristics of transitional flows and their modelling\, which is presented in three parts.\nFirst\, we propose a wavelet-transform based smooth detector function which is used to detect the presence of turbulent spots in a signal. We also propose a novel wavelet transform based algorithm to calculate the intermittency for various transitional and turbulent boundary layers with the primary objective to remove the subjectivity of current methods. The method is also used to calculate the intermittencies for temporal and spatial distributions of velocities of a computational dataset. The algorithm involves calculation of a sensitive detector and then obtaining an indicator based on Monte-Carlo like iterations. A cut-off on the number of iterations ​is obtained based on RMS of the laminar part of the signal. The method is also able detect the turbulent/non-turbulent interface in wall-normal and wall-parallel planes. This wide spectrum of results prove the generality of the scheme\, which to our knowledge has been demonstrated for the first time.\nSecondly\, the substructures of stream-wise velocity fluctuations within a turbulent spot are investigated using time-spectral and probability density function(PDF) based analyses. The pre-multiplied Fourier spectrum shows that the turbulent spots appear rather  “suddenly” at the onset of transition. The high frequency structures inside a near-wall turbulent spot at the onset of transition are found to be highly time localized. The presence of large amplitude events near the onset location hints towards a near “singular” structure within a nascent spot that has high frequencies\, amplitudes and time localization. It is also seen that the transition process only modifies the structures at higher frequencies and the lower frequencies remain almost unchanged. For lower frequencies\, the structure throughout the transition zone\, for all the transition as well as the turbulent boundary layer cases show a universal nature.\nIn the third part\, Cellular Automaton (CA) is used to model the growth\, propagation and merging of turbulent spots. CA simulations are shown to handle a variety of different practical/theoretical spot generation scenarios. These simulations are computationally inexpensive and easily parallelizable. They represent a promising avenue for modelling the kinematics of turbulent spots.\n\nSpeaker : Satyajit De\n\nResearch Supervisor : Sourabh S. Diwan
URL:https://aero.iisc.ac.in/event/ph-d-engg-characterization-of-time-frequency-behavior-of-flow-intermittency-in-transitional-boundary-layers/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/12/Satyajit.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251219T110000
DTEND;TZID=Asia/Kolkata:20251219T130000
DTSTAMP:20260415T080237
CREATED:20251212T053059Z
LAST-MODIFIED:20251218T103035Z
UID:10000101-1766142000-1766149200@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Investigations on Elastic Deformation of Ferromagnetic Rods and Ribbons
DESCRIPTION:Bulk ferromagnetic materials exhibit Joule magnetostriction with characteristic strain magnitudes on the order of (10^{-6}) to (10^{-4})\, which is often insufficient for the displacement requirements of modern soft robotic and adaptive structural systems. Ferromagnetic elastic slender structures provide a promising alternative\, offering the potential for large actuation displacements under small external magnetic fields. This enhanced response results from a rich coupling between magnetic and elastic phenomena in slender structures\, where external magnetic fields can induce significant displacements with relatively small field strengths. This thesis develops a novel unified theoretical framework to describe the coupled magnetoelastic behavior of ferromagnetic elastic rods and ribbons. The framework formulates the total energy functional\, incorporating elastic and magnetic energy components for both soft and hard ferromagnetic materials. The elastic energy is derived from Kirchhoff and Wunderlich models for rods and ribbons. The magnetic energy is formulated using the micromagnetic energy functional composed of exchange\, anisotropy\, magnetostriction\, demagnetization\, and Zeeman energies. Central to the framework is the interplay between elastic energy and the competing magnetic effects: demagnetization energy in soft ferromagnets and Zeeman energy in hard ferromagnets. \nIn the first part of this thesis\, we construct the total energy formulation for ferromagnetic rods undergoing planar deformation and utilize Kirchhoff kinetic analogy for our investigation. A detailed bifurcation analysis distinguishes the Hamiltonian phase portraits of elastic rods and soft ferromagnetic rods in longitudinal and transverse magnetic fields\, revealing distinct subcritical and supercritical pitchfork bifurcations. The extension of Kirchhoff’s kinetic analogy to ferromagnetic rods enables the prediction of equilibrium shapes under various boundary conditions and applied fields. However\, the kinetic analogy framework does not directly address the stability of these equilibrium states. \n\n                                                                                                                                            Motivated by this limitation\, the second part presents a comprehensive one-dimensional model for ferromagnetic elastic rods/ribbons systematically incorporating micromagnetic energy for curved geometries. The resulting equilibrium equations are derived for both soft and hard magnetic cases\, which are then solved numerically to trace load–deflection responses. Stability analysis via a Sturm–Liouville eigenvalue approach reveals tensile critical buckling loads for soft ribbons and uncovers novel stable post-buckling configurations\, especially for fixed-fixed boundary conditions under transverse magnetic fields. For hard ferromagnetic ribbons\, the buckling loads are shifted\, but the corresponding equilibrium shapes approach those of purely elastic ribbons. The restriction to planar deformations\, however\, leaves open the question of whether these configurations remain stable with respect to fully three-dimensional perturbations.\nTo address this issue\, the third part extends the study to spatially deforming ferromagnetic elastic rods subjected to combined magnetic and terminal mechanical loading. The Hamiltonian derived from the total energy is analyzed\, revealing a significant difference: the purely elastic and hard ferromagnetic rods exhibit subcritical pitchfork bifurcations\, whereas the soft ferromagnetic rod shows no bifurcation under similar conditions. Furthermore\, localized buckling deformation of soft ferromagnetic rod shows non-collinear straight segments.\nThis work is\, to the best of our knowledge\, the first to demonstrate the role of demagnetization energy in the large deformation of ferromagnetic slender structures. As one of the dominant contributions to the micromagnetic energy functional\, the demagnetization energy is inherently geometry dependent and therefore crucial to structural deformation. As the slender structure deforms and its geometry changes and the demagnetization energy is correspondingly modified. Our results provide an understanding of the interplay of magnetic and elastic forces\, paving the way for the design of advanced smart materials and potential applications in magnetically-actuated soft robots\, adaptive medical devices\, and remote actuation.\n\nSpeaker:  Mr. G R Krishna Chand Avatar\n\nResearch Supervisor : Dr. Vivekanand Dabade
URL:https://aero.iisc.ac.in/event/ph-d-engg-investigations-on-elastic-deformation-of-ferromagnetic-rods-and-ribbons/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/12/Krishna.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251215T110000
DTEND;TZID=Asia/Kolkata:20251215T120000
DTSTAMP:20260415T080237
CREATED:20251210T103048Z
LAST-MODIFIED:20251213T093321Z
UID:10000100-1765796400-1765800000@aero.iisc.ac.in
SUMMARY:Flow-Aware Simulation Technique (FAST) for AI-Enabled\, Physics-Integrated Turbulence Computations
DESCRIPTION:Data-driven approaches have generated tremendous excitement in turbulence modeling\, but enthusiasm has often outpaced scientific rigor. Many current AI/ML turbulence models lack physical interpretability\, exhibit limited generalizability across flow regimes\, and do not reflect the true dynamical nature of turbulence. A new strategy is needed—one that leverages AI while remaining fully compliant with the physics of flow evolution. This talk proposes a flow-aware AI paradigm that integrates data-driven learning with physical constraints and local flow-regime awareness. Recognizing that turbulence spans a wide spectrum of coherent and stochastic behaviors\, we propose an adaptive framework that allows AI to dynamically select modeling pathways—switching between physics-based closures and selective scale resolution as conditions demand. This approach improves robustness in complex flow regimes\, enabling AI to enhance rather than replace traditional models. The presentation will clarify the limitations of current ML methods and illustrate how physics-aware hybridization can accelerate accurate and efficient turbulence simulations. The goal is not to abandon classical turbulence modeling\, but to augment it with AI-enabled predictive insight\, producing simulations that are consistently reliable\, interpretable\, and deployment-ready in unseen flows.  \nSpeaker : Prof. Sharath Girimaji \nBiography: \nDr. Sharath S. Girimaji is a Professor of Aerospace Engineering and Department Head of Ocean Engineering at Texas A&M University\, where he holds the Wofford Cain Chair position. His research expertise spans turbulence modeling\, computational fluid dynamics\, compressible and high-speed flows\, and complex fluid dynamics. Dr. Girimaji received his B.Tech from Indian Institute of Technology Madras (1983) and his M.S. and Ph.D. from Cornell University (1990). Before joining academia\, he spent nine years as a research scientist at NASA Langley Research Center. He has graduated 25 PhD students to date. He is a Fellow of the American Physical Society (APS) and an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA).
URL:https://aero.iisc.ac.in/event/flow-aware-simulation-technique-fast-for-ai-enabled-physics-integrated-turbulence-computations/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/12/Sharath.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251201T110000
DTEND;TZID=Asia/Kolkata:20251201T130000
DTSTAMP:20260415T080237
CREATED:20251201T040004Z
LAST-MODIFIED:20251201T040004Z
UID:10000097-1764586800-1764594000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Autorotation of Single-Winged Spinning Samaras
DESCRIPTION:Nature has consistently served as a powerful source of innovation\, offering elegant and sustainable solutions to complex engineering problems. Among these\, the spinning samara seed stands out as a biologically efficient system for passive aerial transport. Samaras\, such as those from mahogany and Buddha coconut trees\, exhibit stable autorotative descent\, making them strong candidates for biomimicry in aerial delivery systems. Understanding and replicating the flight mechanics of samaras requires accurate analytical modelling. The dynamics of a single-winged spinning samara can be described using Newton’s laws and Euler’s rigid‐body equations\, while the aerodynamic forces acting on the wing can be derived from the Navier–Stokes equations or using Blade Element Momentum Theory (BEMT). Together\, these frameworks provide a foundation for predicting its motion\, thrust generation\, and stability in samara-inspired designs. Building on this theoretical basis\, the present thesis delivers a comprehensive experimental study on the bioinspired engineering of single-winged spinning samaras\, focusing on their aerodynamic behavior\, kinematic characteristics\, structural morphology\, and wake dynamics. To investigate the kinematics\, a custom-designed drop rig was developed to capture high-resolution visual data of the steady-state descent. Parameters such as descent velocity\, coning angle\, wingtip trajectory\, and precession were extracted and analyzed. The results revealed a complex motion involving coupled coning and precession\, challenging simplified theoretical models that typically assume a steady\, non-precessing descent. Parallel morphological studies using high-resolution 3D scanning of natural samaras highlighted spanwise variations in chord length\, camber\, and sweep\, which contribute significantly to aerodynamic performance. Five 3D printed models incorporating geometric variations were fabricated to evaluate their aerodynamic efficiency. Experimental observations showed that models featuring variable chord\, sweep\, and anhedral/dihedral configurations achieved the lowest descent velocities\, underscoring the importance of structural morphology in enhancing autorotative performance. To examine local flow physics in detail\, a custom low-Reynolds-number vertical wind tunnel was developed and characterized. Flat-plate airfoils were studied using Particle Image Velocimetry (PIV) across a wide range of angles of attack and Reynolds numbers\, revealing flow regimes ranging from steady attached flow to unsteady vortex shedding. Wake flow physics of samaras were further captured within a transparent glass chamber using seeded PIV\, revealing stable wingtip vortices extending several diameters downstream and confirming the presence of a windmill-brake state analogous to helicopter autorotation. Induced velocities computed using Momentum Theory showed close agreement with theoretical predictions. To evaluate practical feasibility\, a bioinspired delivery system was designed and tested through drone-based release experiments. Six models (FR01 to FR06) were fabricated and deployed under varying payloads and wind conditions. All models demonstrated successful autorotation and stable descent\, confirming the viability of samara-inspired mechanisms for passive aerial delivery. This research advances the understanding of samara aerodynamics and opens pathways for bioinspired applications in unmanned aerial systems. Future work should explore 3D motion capture\, high-fidelity simulations\, and optimization of geometries and materials. The insights from this thesis provide a strong foundation for future innovations in samara-inspired flight technologies. \nSpeaker :  G.YOGESHWARAN \n  \nResearch Supervisor: Gopalan Jagadeesh \nCo-Research Supervisor: Srisha Rao M V
URL:https://aero.iisc.ac.in/event/ph-d-engg-autorotation-of-single-winged-spinning-samaras/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/12/YOGESHWARAN.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251027T110000
DTEND;TZID=Asia/Kolkata:20251027T130000
DTSTAMP:20260415T080237
CREATED:20251015T064811Z
LAST-MODIFIED:20251015T064811Z
UID:10000088-1761562800-1761570000@aero.iisc.ac.in
SUMMARY:Taming Waves through Non-Hermiticity: From Invisible Tunneling to Unidirectional Nonlinear Pulses
DESCRIPTION:Non-Hermitian wave dynamics challenge our conventional understanding of wave propagation\, revealing transport behaviors inaccessible in Hermitian systems. In this seminar\, I will present a few intriguing phenomena arising from these dynamics. In the first part\, I will show a counterintuitive tunneling effect at the interface of a non-Hermitian system sandwiched between two Hermitian ones. Here\, the non-Hermitian skin effect creates barriers at the boundaries\, yet under the right conditions\, a wave can tunnel through as if the interface were invisible. This phenomenon is explored in both quantum and classical regimes\, with experimental demonstrations using an active electric circuit platform. In the second part\, I turn focus to nonlinear systems\, addressing generation of unidirectional\, narrow pulses (solitons) that propagate without distortion in active mechanical setups. I present a theoretical model for generating stable unidirectional solitons by carefully balancing nonlinearity and nonreciprocity\, and show how these pulses are realized experimentally\, supported by analytical results and numerical simulations. \nReferences: \nInvisible tunneling through non-Hermitian barriers in nonreciprocal lattices. Sayan Jana\, Lea Sirota\, Physical Review B (Letter) 111 (10)\, L100301\, (2025).\nHarnessing Nonlinearity to Tame Wave Dynamics in Nonreciprocal Active Systems\, Sayan Jana et al.\, arXiv:2502.16216 (2025). \n  \nSpeaker :  Dr. Sayan Jana \nBiography:  \nDr. Sayan Jana is a Postdoctoral Researcher at the Department of Mechanical Engineering\, Tel Aviv University\, Israel. He obtained his PhD in Theoretical Condensed Matter Physics from the Institute of Physics\, Bhubaneswar\, India\, in 2022. His research is interdisciplinary\, integrating theoretical physics and engineering to emulate complex analogue quantum and high-energy phenomena using lab-scale platforms. One key finding includes the proposal and simulation of analogue gravitational lensing and Hawking radiation using mechanical networks. These studies provide accessible routes to investigate phenomena that are otherwise difficult to observe directly in the universe. Another major research direction focuses on non-Hermitian systems\, where non-conservation of energy gives rise to intriguing dynamics and interplay with topology and nonlinearity. Realizations in active metamaterials reveal novel wave phenomena and control mechanisms\, with significant potential for advanced wave manipulation and energy technologies.
URL:https://aero.iisc.ac.in/event/taming-waves-through-non-hermiticity-from-invisible-tunneling-to-unidirectional-nonlinear-pulses/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/10/Sayan.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250723T110000
DTEND;TZID=Asia/Kolkata:20250723T130000
DTSTAMP:20260415T080237
CREATED:20250723T033046Z
LAST-MODIFIED:20250824T142259Z
UID:10000085-1753268400-1753275600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Development of Approaches for Optimal Shared Utilization of Spatially Distributed Resources Under Sparse Connectivity in Energy Internet
DESCRIPTION:The global shift towards sustainable power generation has led to a significant rise in distributed energy resources (DERs)\, particularly from renewable sources. These localized generation systems\, when combined with energy storage\, form microgrids—self-contained units capable of managing generation and consumption. While energy storage enables time-shifted usage of intermittent renewable power\, limitations in storage capacity and dynamic load variations still result in curtailment of generated energy. Peer-to-Peer (P2P) power trading among geographically adjacent prosumers offers a more energy-efficient and cost-effective alternative to grid feed-in. P2P trading enhances local energy utilization\, optimizes resource use\, and improves resilience in interconnected communities of microgrids. However\, achieving full connectivity among all peers is infrastructure-intensive\, while relying on sparse connectivity with indirect power exchange through intermediaries—facilitated via an Energy Internet (EI)—presents a scalable and feasible alternative. Within this context\, the challenge becomes the optimal utilization of spatially distributed generation under connectivity constraints.\nThis thesis addresses this challenge by modelling realistic microgrid behaviour using multiple real-world electrical load datasets. Initially\, internal power scheduling within a grid connected microgrid equipped with solar generation and storage is formulated as a mixed integer nonlinear optimization problem\, later relaxed to a mixed-integer linear formulation to reduce computational complexity. Predictive scheduling is employed to enable time-shifted energy usage. The resulting surplus and deficit data form the basis for simulating P2P power exchange within a connected community. To evaluate trading under constrained infrastructure\, the thesis introduces the Connectivity and Preference-constrained Hop-regulated P2P Trading (CPHPT) approach. CPHPT models P2P trading as a linear optimization problem that schedules energy exchange along shortest paths while respecting capacity and predefined hop limits. The internal microgrid scheduling and inter-microgrid trading are coordinated using a distributed control architecture\, enhancing scalability and preserving data privacy. Graph theory is leveraged to avoid explicit route computation during hop-constrained scheduling. Theoretical analysis demonstrates that while full connectivity maximizes P2P power transfer\, increasing the allowable hop count in sparsely connected communities enables near-optimal performance\, albeit with higher routing complexity.\nBuilding on this\, the Optimal Multi-Path Power Routing (OMPR) algorithm is developed. OMPR uses graph-theoretic principles to determine the connectivity structure and identifies all feasible routes between peers deterministically. The power scheduling among the routes is formulated and solved as both a linear and nonlinear multi-path power scheduling optimization problem. The OMPR approach divides each multi-hop P2P exchange into multiple individual hop exchanges and solves each step-by-step. While routing multiple concurrent P2P exchanges\, the order in which each P2P exchange is routed affects the optimal solution\, as each route increases the power flow routing constraints. To overcome this limitation\, a Hop Optimized Multi-Exchange Routing and Scheduling (HOMERS) algorithm that solves all concurrent multi-hop P2P exchanges simultaneously to obtain the optimal routing paths has been developed. HOMERS formulates the routing and scheduling of all concurrent P2P exchanges into a single-step mixed-integer nonlinear programming optimization problem. This approach efficiently identifies all feasible routes and schedules each power exchange\, ensuring conflict-free power flow from the source to the destination in the predetermined number of hops.\nRecognizing the limitations of assuming uniform node distribution and connectivity in the CPHPT and random connectivity for OMPR\, and HOMERS models—the thesis proposes a more realistic framework named as a Spatial and Renewable resource Distribution Informed Network for Energy exchange (SRDINE). SRDINE accounts for non-homogeneous node spacing and variable power generation capabilities across the community. It identifies optimal connectivity topologies based on geographic and resource distribution\, yielding improved connectivity efficiency. The resulting community specific connectivity model from SRDINE is shown to have better connectivity utilization and has improved efficiency compared to the ideal full connectivity. Through the development of CPHPT\, OMPR\, HOMERS\, and STRIDE\, this thesis makes substantial contributions to the field of distributed energy systems and P2P power trading. The integration of predictive scheduling\, hop-constrained routing\, and spatial-connectivity modelling offers a comprehensive and scalable framework for the future deployment of Energy Internet architectures. The research establishes a practical and theoretically grounded foundation for resilient\, intelligent\, and energy-efficient microgrid communities.\nSpeaker :  Neethu M \nResearch Supervisor : Prof Suresh Sundaram
URL:https://aero.iisc.ac.in/event/ph-d-engg-development-of-approaches-for-optimal-shared-utilization-of-spatially-distributed-resources-under-sparse-connectivity-in-energy-internet/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/07/Neethu-M.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250718T150000
DTEND;TZID=Asia/Kolkata:20250718T170000
DTSTAMP:20260415T080237
CREATED:20250715T045641Z
LAST-MODIFIED:20250715T045641Z
UID:10000084-1752850800-1752858000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): ON HIGH-SPEED CURVED COMPRESSION RAMP AIR INTAKES
DESCRIPTION:A scramjet\, i.e.\, a supersonic combustion ramjet\, is an air-breathing engine that enables sustained atmospheric flight in the hypersonic regime. It consists broadly of four key components: the air intake\, isolator\, combustor\, and nozzle. The air intake and the isolator collectively comprise the compression system\, which captures and conditions the freestream flow to suit the operational requirements of the combustor positioned downstream. The general set of attributes sought in a high-speed air intake is: low structural weight; low drag; low aero-thermal loads; started flow with high thermodynamic efficiency and high compression ratio; operational robustness to back-pressure fluctuations arising from the combustor; and stable engine operation over a wide flight envelope. The intake flow characteristics and performance are primarily governed by its geometric shape. High-speed air intakes with a curved compression ramp (CCR) are a class of rectangular intakes wherein the compression ramp comprises a curved surface followed by a planar surface tangential to the trailing end of the curved surface. A CCR intake compresses the flow through a combination of a curved ramp shock wave and a series of compression waves. These intake geometries can provide improvements in compression ratio\, pressure recovery\, and allow for a shorter length intake section in comparison to conventional multi-step intake geometries.\nThe present effort consists of the development of a novel analytical framework to model the CCR intake flow and estimate the intake performance parameters at design and off-design operating conditions\, and wind tunnel experiments with a model CCR air intake at Mach 6 to obtain a detailed understanding of the flow dynamics. The analytical framework builds on the principles of mass conservation and the compressible flow theory to model the inviscid flow structure in the intake without any empiricism. A modified Kantrowitz criterion is proposed to examine the ability of a given fixed-geometry CCR intake to spontaneously self-start at the design Mach number. The framework provides a simple\, fast\, and low-cost tool to develop an effective first-cut design of a self-starting hypersonic CCR air intake for any specified set of operating conditions and performance parameters of interest\, such as the startability\, compression efficiency\, and compression ratio. Inviscid flow numerical experiments of intake starting were carried out to preliminarily verify the starting characteristics predicted by the analytical model.\nThe analytical framework was then employed to identify a suitable geometric design point for the experimental CCR air intake model. A self-starting intake test model was designed following the strong shock design principle\, and built for experimentation in the Roddam Narasimha Hypersonic Wind Tunnel at Mach 6 freestream flow conditions. Time-resolved pressure measurements and high-speed schlieren flow visualization were conducted to understand in detail the flow features internal and external to the intake model\, including the dynamics of shock-shock and shock-boundary layer interactions at the cowl and inside the isolator. Performance assessment at design operating conditions involved evaluating the intake’s ability to spontaneously self-start\, in addition to examining pressure recovery and compression ratio of the started intake. At off-design operating conditions\, the intake dynamics were studied by experimentally varying two parameters: intake back-pressure and angle-of-attack (𝛼). In order to mimic combustor-induced isolator back-pressure variations\, a sliding plate was introduced at the isolator exit; the motion of the sliding plate varies the isolator exit area (blockage) and thereby changes the back-pressure. Experimental results showed that the intake auto-reverts to the started state on realizing suitable pressure values at the isolator exit. Coherent flow oscillations with certain characteristic frequencies were observed in the isolator section during the intermediate state of operation (between started and unstarted states). The angle-of-attack (AoA) studies\, in the 𝛼 range of -70 to 20.70\, show that the relatively gradual distribution of adverse pressure along the compression ramp mitigates the risk of large-scale boundary layer separation\, even at very large AoAs. The model intake was found to satisfy shock-on-lip condition and operate in the started state between 𝛼 = 00 and 𝛼 = 100\, and supersonic flow was sustained in the isolator section up to 𝛼 = 20.70. Overall\, the experimental results were found to validate predictions made by the analytical model. The experiments also allowed for a careful examination of flow during various stages of intake operation\, including intake unstart and restart\, and quantification of operational margins (in terms of pressure) for the model intake. In addition to aiding performance assessment\, these results can also form the basis for the design of a practical early-warning system for preventing engine unstart.\nIn summary\, this work offers a clear experimental demonstration of the advantages offered by CCR air intakes\, and an analytical framework that serves as a good starting point for a design exercise. In practical terms\, this work exhibits the promise held by CCR air intake in providing a wide flight envelope for an air-breathing hypersonic flight vehicle. \nSpeaker : Sushmitha Janakiram \nResearch Supervisor : Duvvuri Subrahmanyam
URL:https://aero.iisc.ac.in/event/ph-d-engg-on-high-speed-curved-compression-ramp-air-intakes/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/07/Sushmitha-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250716T110000
DTEND;TZID=Asia/Kolkata:20250716T130000
DTSTAMP:20260415T080237
CREATED:20250715T041029Z
LAST-MODIFIED:20250715T041029Z
UID:10000083-1752663600-1752670800@aero.iisc.ac.in
SUMMARY:Investigation of flow instabilities in high-speed impinging jets using dual-time velocity measurements
DESCRIPTION:Motivated by applications in the aerospace propulsion industry as well as other energy systems\, the fundamental study of phase-locked shear-layer instabilities in high-speed impinging jets\, has been of research interest for a long time.  The study of instabilities is usually conducted with time derivatives of velocity field. However\, time-resolved experimental data acquisition using particle image velocimetry (PIV) techniques has its challenges for high-speed flows due to the requirements of high spatial and temporal resolution. In this talk\, I will introduce an alternate approach of utilizing time-unresolved dual-time PIV measurements for investigation of the flow instabilities in supersonic impinging jets and illustrate the valuable information about the flow dynamics that can be extracted using the same. \nSpeaker : Dr. Tushar Sikroria \nBiography: \nTushar Sikroria obtained his B.Tech.-M.Tech. Dual Degree in Aerospace Engineering from IIT Kanpur\, Uttar Pradesh\, India\, in 2013. Then he worked for more than two years in John F. Welch Technology Centre\, General Electric (GE)\, Bangalore\, India. Thereafter\, he carried out research work as a Project Engineer in Propulsion Laboratory\, IIT Kanpur\, in 2016\, and later went to pursue his doctoral study from the University of Melbourne\, Australia. He was awarded PhD in Mechanical Engineering from the University of Melbourne\, in December 2021. He pursued post-doctoral research in the Turbomachinery & Propulsion Department\, von Karman Institute\, Belgium and then joined IIT Kanpur as an Assistant Professor in the Department of Mechanical Engineering in January 2024.
URL:https://aero.iisc.ac.in/event/investigation-of-flow-instabilities-in-high-speed-impinging-jets-using-dual-time-velocity-measurements/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/07/Tushar.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250603T113000
DTEND;TZID=Asia/Kolkata:20250603T130000
DTSTAMP:20260415T080237
CREATED:20250527T091724Z
LAST-MODIFIED:20250527T091724Z
UID:10000077-1748950200-1748955600@aero.iisc.ac.in
SUMMARY:Space Domain Awareness in the Artemis Era
DESCRIPTION:Since the Apollo era\, space has become an increasingly valuable domain for national security due to diplomatic\, informational\, and economic reasons. The last few years have seen exponential growth in the launch of space objects and there is an increased interest in having a permanent cislunar presence through the Artemis program. The understanding of motion of a spacecraft in multi-body environment is essential to transit between different regions in the cislunar space and to forecast and track objects in the cislunar space. The perturbed two-body restrictive framework has led to extensive modeling\, analysis\, and analytical solutions to study spacecraft motion in orbits around the Earth. However\, beyond GEO (XGEO) the dynamical environment shifts\, and the structure of fundamental behaviors can be radically different. The primary challenge that limits the transferability of tools and techniques from the GEO to XGEO region is non-Keplerian dynamics\, data sparsity from limited coverage and availability of sensors. The process of orbit determination and forecasting the path for an object based on short time arc observations is not trivial. This talk will introduce novel tools to track spacecraft motion in cislunar space and transfers between different regions in cislunar space. These tools make use of dynamical system theory in combination with advances in optimal control theory to provide a better understanding of transport mechanisms in cislunar space. Local orbit elements will be discussed to characterize the trajectories in the cislunar space.\n\nSpeaker : Dr. Puneet Singla\n\nBiography:\n\nDr. Puneet Singla is a Harry and Arlene Schell Professor of the Aerospace engineering at the Pennsylvania State University (PSU). Dr. Singla’s research focus pertains to uncertainty propagation through nonlinear systems\, data driven modelling and control of autonomous systems. His research related honours include the IEEE AESS’s Judith A. Resnik Award\, NSF CAREER award\, the AFOSR Young Investigator award\, the University at Buffalo’s “Exceptional Scholar” Young Investigator Award and the Texas A&M University’s Young Aerospace Engineering Distinguished Alumni Award in recognition of his scholarly activities. He is a fellow of American Astronautical Society (AAS) and an associate fellow of American Institute of Aeronautics and Astronautics (AIAA).
URL:https://aero.iisc.ac.in/event/space-domain-awareness-in-the-artemis-era/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/05/Puneet-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250416T153000
DTEND;TZID=Asia/Kolkata:20250416T170000
DTSTAMP:20260415T080237
CREATED:20250416T051419Z
LAST-MODIFIED:20250416T051419Z
UID:10000070-1744817400-1744822800@aero.iisc.ac.in
SUMMARY:Miniaturised technologies for potential applications in space research
DESCRIPTION:Miniaturised technologies\, due to their portability\, rapid responses\, low powers and ability of multi-component integration\, have received an ever-growing interest in areas like healthcare\, air quality\, and space research. This talk will provide an overview of my research in 3 domains of miniaturised technologies: a) microfluidics\, b) MEMS sensors and c) nanoaerosol instruments. I will also highlight areas of space research where this work is potentially relevant. \nI will begin my talk with my work in microfluidic particle enrichment and gene therapy devices. Enrichment devices\, when integrated with a downstream sensor for target particle detection\, can significantly improve the sensor sensitivity. I will cover my work in developing enrichment devices and mitigation of some undesirable effects that can limit their reliability. I will also introduce my work in commercial-scale microfluidic mixers for gene therapy. The work in this theme is highly relevant to healthcare in manned space missions and CubeSats to understand in-space behaviour of bio-species. \nI will next cover my work in thin film MEMS mass sensors\, which offer several advantages over conventional sensors like QCMs thanks to their portability\, high sensitivities and excellent compatibility with semiconductor technology. This talk will cover my work towards enhancing their capabilities in areas of biosensing and simultaneous detection of multiple parameters. This work has a promising applicability in controlling ambient conditions inside spacecrafts\, and healthcare in manned space missions. \nI will conclude with my work in 2 miniaturised nano-aerosol technologies\, namely a) an instrument that can produce a constant number concentration of charged nanoaerosols\, a need unmet in aerosol instrumentation until now\, and b) a sensor that can both count and map the global distribution of airborne ultrafine particles\, a requirement crucial for the upcoming WHO air quality guidelines. The work in this theme has enormous significance in simulating cosmic dust conditions and satellite-based remote sensing of particulate matter distribution near the earth’s surface. \n  \nSpeaker: Dr. Akshay Shridhar Kale \nBiography: \nDr. Akshay Shridhar Kale is a senior postdoctoral affiliate at Trinity College and a teaching assistant at the Department of Engineering at the University of Cambridge\, UK. He is also an Honorary Adjunct Professor at the Department of Mechanical Engineering at COEP Technological University in Pune. His research interests lie in the development of miniaturised technologies and possesses a track record in the areas of microfluidic devices\, MEMS / acoustic devices and nanoaerosol instrumentation. He is also highly active in industry-oriented research and has completed several industrial consultancy projects in his areas of interest. His recent work on integration of miniaturisation principles with nanoaerosol instruments has won him grant funding awards that have partially supported the early stages of commercialisation of a portable nanoaerosol counter in collaboration with a spin-out company from his research group. At COEP\, he is actively involved in developing microfluidics research programs and a proposed centre of excellence in micro- and nano- manufacturing. Along with research and development\, he regularly teaches thermal and fluid science courses at Trinity College\, and has co-guided several undergraduate and Masters students through his research projects across Cambridge and COEP. Dr. Kale earned his B.Tech. in Mechanical Engineering at COEP\, followed by an MS and a PhD in thermal and fluid systems from Clemson University\, USA
URL:https://aero.iisc.ac.in/event/miniaturised-technologies-for-potential-applications-in-space-research/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/04/Akshay-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250327T150000
DTEND;TZID=Asia/Kolkata:20250327T163000
DTSTAMP:20260415T080237
CREATED:20250327T063920Z
LAST-MODIFIED:20250327T063920Z
UID:10000065-1743087600-1743093000@aero.iisc.ac.in
SUMMARY:Laser Beam Control Through Atmospheric Turbulence
DESCRIPTION:Laser beam is highly affected by prevailing atmospheric conditions and limit the system performance for various applications. The talk mainly covers the cause of optical turbulence\, its effects on laser beam and further discuss the technologies for controlling the beam for enhancing the effectiveness. Two main techniques namely the Tip-tilt correction for maintaining the beam at same position and adaptive optics technology for controlling the phase distortions and thus enhancing the signal strength on the receiver plane will be discussed. The experimental results for long range propagation will also be presented and discussed. \n  \nSpeaker: Dr. Amit Pratap\, Sc F\, CHESS (DRDO)
URL:https://aero.iisc.ac.in/event/laser-beam-control-through-atmospheric-turbulence/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Amit.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250318T110000
DTEND;TZID=Asia/Kolkata:20250318T130000
DTSTAMP:20260415T080237
CREATED:20250311T060827Z
LAST-MODIFIED:20250311T060827Z
UID:10000060-1742295600-1742302800@aero.iisc.ac.in
SUMMARY:Ph.D.(Engg): Investigations on Hypersonic Laminar to Turbulent Boundary Layer Transition in a Shock Tunnel.
DESCRIPTION:The laminar to turbulent boundary layer transition onset has perplexed fluid dynamics community irrespective of the flow regime under which the phenomenon is probed. The complexity of the problem is compounded in high-speed compressible flows where in the transition onset location is a strong function of many subtle factors like freestream quality\, surface roughness\, wall temperature etc. The transitional and turbulent boundary layers bring their typical characteristics\, like an increase in skin friction\, heat transfer\, fluid dynamic parameters fluctuations\, mixing characteristics\, potential to negotiate adverse pressure gradient\, along with them. These typical characteristics of transitional and turbulent boundary layers can be both detrimental and advantageous to a given facet of an aerodynamic vehicle design. Hence the boundary layer transition onset location is one of the key design inputs in the development of aerodynamic vehicles operating in subsonic\, supersonic and hypersonic freestream environment. A plethora of work has been conducted to investigate the transition onset phenomena in supersonic and hypersonic flow regime since the beginning of space age and the inception of the idea of an air breathing hypersonic cruise vehicle. The outcomes of these investigations and studies on high-speed boundary layer transition onset although led to the development of several techniques and correlations to estimate the transition onset location\, applicable usually to a particular test model and freestream condition\, very few studies targeted the characterization of transitional boundary layer in hypersonic flow regime. The earlier and contemporary work on roughness induced transition onset focused on the effect of the said roughness element on transition onset location but the features associated with the instabilities thus generated by these roughness elements have seldom been reported in the open literature. Hence characterization of transitional boundary layer and the instabilities associated with the same was one of the primary objectives of the present work.\nThe present work on hypersonic boundary layer transition was conducted in a shock tunnel HST4 by employing generic test models like flat plate\, cone and elliptic cone. The work began with the design\, development and deployment of a new contoured nozzle\, with a nominal Mach number of 6.0\, for HST4. Before embarking on the boundary layer transition studies\, dedicated efforts were made to characterize the freestream noise environment of the test section of HST4 by employing experimental and numerical methods. A two-dimensional finite difference Navier-Stokes solver was developed in order to numerically compute the transfer functions required to retrieve freestream pressure fluctuations from the experimental measurements. The RMS of pressure fluctuations in the test section of HST4 was found to be 4.32% for the freestream Reynolds number of 4.5 million/m with major contribution of low frequency fluctuations (<50 kHz) towards the aforementioned RMS magnitude. The transitional boundary layer on smooth surface of a flat plate and an axisymmetric cone were characterized by experimentally measuring the intermittency associated with such boundary layers. The intermittent nature of the transitional boundary layer results from the convection of the turbulent spots along the boundary layer. The leading edge and trailing edge velocities associated with these turbulent spots as well as their generation rates were experimentally measured and computed. The second mode instabilities\, a typical characteristic of high Mach number boundary layers\, were also measured in terms of pressure fluctuations and the bandwidth of these instabilities was found to be in the range of 240-480 kHz. The wavelengths associated with these instabilities were found to be 2.5 times the local boundary layer thickness. Transition onset due to the presence of an isolated roughness element\, either a protrusion or a three-dimensional shoe box cavity\, was also investigated as part of the present campaign. Both isolated protrusion and cavity led to an early onset of transition when compared to the smooth test models with no isolated roughness element. In the case of transition onset due to an isolated cubic protrusion\, the Shuttle Orbiter correlations were found to be inadequate in estimating the transition onset and correlations based on the present dataset were formulated. A single frequency oscillation with a narrow bandwidth centered around 23 kHz corresponding to hair pin vortices in the wake of roughness element was found in the present work. It was also found that while the protrusion suppressed the second mode instabilities\, the cavity aided in the development of high frequency instabilities akin to second mode. Finally initial findings of the transition onset due to cross flow instabilities in an elliptic cone were also discussed in the present work. \n  \nSpeaker : Ankit Bajpai \n  \nResearch Supervisor : Prof. Gopalan Jagadeesh
URL:https://aero.iisc.ac.in/event/ph-d-engg-investigations-on-hypersonic-laminar-to-turbulent-boundary-layer-transition-in-a-shock-tunnel/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Ankit-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250317T110000
DTEND;TZID=Asia/Kolkata:20250317T130000
DTSTAMP:20260415T080237
CREATED:20250311T111336Z
LAST-MODIFIED:20250311T111336Z
UID:10000062-1742209200-1742216400@aero.iisc.ac.in
SUMMARY:The longest known insect migration: Fusing Biology with Aerospace Engineering for innovative solutions
DESCRIPTION:The intriguing annual migration of the dragonfly species\, Pantala flavescens\, was reported a century ago.\nThe multi-generational\, transoceanic migration circuit spanning 14000-18000 kms\, from India to Africa is an\n astonishing feat for an insect few cms in size. Wind\, precipitation\, fuel\, breeding\, and the life cycle affect\n the migration\, yet understanding of their collective role in the migration remains elusive. We identify the\n transoceanic migration route by imposing a time constraint emerging from energetics on Dijkstra’s\npath-planning algorithm. Energetics calculations reveal Pantala flavescens can endure 90 hours of steady\n flight at 4.5m/s. We incorporate active wind compensation in Dijkstra’s algorithm to compute the migration\n route from years 2002 to 2007. The prevailing winds play a pivotal role; a direct crossing of the Indian Ocean\n from Africa to India is feasible with the Somali Jet\, whereas the return requires stopovers in Maldives and Seychelles.\n The migration timing\, identified using monthly-successful trajectories\, life cycle\, and precipitation data\,\ncorroborates reported observations. While working on this problem my mind ventured into many different\n applications of engineering\, which are all connected to the transoceanic migration of dragonflies.\nThe applications range from designing airfoils/wings\, sports aerodynamics and wind turbines to developing\n novel spectral accuracy algorithms for numerical simulations. Hence the ideas vary from simple mimicking\n of dragonflies to more complex abstractions arising from the need to understand their flying behaviour.\n\nSpeaker: Dr Sandeep Saha\n\nBiography :\n\nDr Sandeep Saha is an Associate Professor in the Department of Aerospace Engineering\, IIT Kharagpur.\nHe obtained his bachelors and masters degrees in Mechanical Engineering from IIT Kharagpur.\nHe completed his PhD in Mechanical Engineering from Imperial College London. He thereafter worked as  a\nMarie-Curie Experienced Researcher\, CNRS (Laboratoire FAST)\, Orsay\, France. Thereafter he worked as\n an Aerodynamics Engineer\, ALSTOM Power (now GE)\, Rugby\, UK; then as Research Scientist (Fluids)\,\nSchlumberger Gould Research\, Cambridge\, UK; and then as Academic Staff member\, Mechanical Engineering\,\nUniversity of Duisburg-Essen\, Germany (in collaboration with SIEMENS AG). He has worked on a range of\n problems in fluid mechanics and in recent years has focused on Low Reynolds number Aerodynamics\n ranging a broad spectrum of problems like insect flight\, extraterrestrial flight\, respiratory flows and\nwaste heat recovery and sports aerodynamics.
URL:https://aero.iisc.ac.in/event/the-longest-known-insect-migration-fusing-biology-with-aerospace-engineering-for-innovative-solutions/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Sandeep.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250312T150000
DTEND;TZID=Asia/Kolkata:20250312T170000
DTSTAMP:20260415T080237
CREATED:20250307T064034Z
LAST-MODIFIED:20250307T064034Z
UID:10000059-1741791600-1741798800@aero.iisc.ac.in
SUMMARY:Ph.D.(Engg) : Multi-Agent Pursuit-Evasion and Coverage Strategies
DESCRIPTION:Autonomous agents are increasingly being used to solve many tasks\, deemed complex by humans\, with ease and effectiveness. Two such applications are in defense scenarios and in coverage. This thesis\, therefore\, is devoted towards study of motion planning strategies for autonomous agents in the context of pursuit-evasion problems as well as different coverage problems. The thesis comprises two parts. In the first part\, pursuit-evasion is considered between an evader and one or more pursuers\, all the agents being non-holonomic having turn radius constraints. A partial information setting is considered wherein the agents (evader and pursuer) know about each others’ speed and position but not about their turning capability. The objective in these problems\, where the pursuer is of higher speed but less agile\, is to obtain an evasive strategy. A two-phase evasive strategy is proposed as an effective solution against the pursuers. It is a proximity based strategy. In the first phase\, when the pursuer is beyond a critical distance from the evader\, the latter assumes the worst that the pursuer is holonomic and solves for the best response strategy. This phase is called the Worst Case Scenario Planning (WCSP). When the evader is within the critical range from the pursuer\, the former attempts sharp maneuvers to sidestep the pursuer and extend time of capture. This phase is called the Proximity Based Maneuver (PBM). Dynamic programming is used to solve for the WCSP strategy. In case of multiple pursuers\, the concept of dominance regions is used to obtain the WCSP strategy. Additionally\, the pursuit-evasion problem is extended to a reach-avoid problem where the evader has the dual objective of avoiding the pursuer and reaching a target. This thesis considers the problem of reaching a moving but non-maneuvering target by a turn radius constrained evader in the shortest time. The evader is modeled as a Dubins vehicle and the reaching strategy is deduced by studying the time-to-go properties for different strategies and chronologically checking simple conditions at crossover points. The proposed two-phase evasive strategy is used for avoiding the pursuer. The reaching strategy and the avoiding strategy are linearly combined to obtain the net reach-avoid strategy. Extensive simulation results are provided to corroborate the effectiveness of both the evasive and the reach-avoid strategies. In the second part of the thesis static and dynamic coverage problems are discussed. Inspiration from flocking principles with substantial modifications is used to design a static coverage strategy. This ensures that the covering agents are spread uniformly around the structure while avoiding collision among themselves and with obstacles in the environment. Coverage is addressed for convex and non-convex shapes in 2D and 3D. For dynamic coverage\, concept of Lissajous curves is used to achieve coverage. Dynamic coverage is split into two chapters: coverage of planar regions and coverage of 3D structures. For planar regions\, the boundary of the region is approximated using Fourier series and radial Lissajous curves are generated within the boundary as reference coverage paths. The optimal field-of-view size is analytically determined along with the upper-bound on the time taken for complete coverage. Various extensions of the strategy such as preferential coverage and simultaneous coverage are also discussed. For 3D structures\, an enclosing volume is considered and Lissajous curves are generated on the surface of the enclosing volume. Conditions for complete coverage as well as collision free coverage in case of multiple agents are determined analytically. Artificial potential fields are used to obtain coverage by conforming to shape of the structure. A variety of enclosing volumes are discussed along with diverse applications such as patch coverage\, waypoint coverage\, and coverage of moving structures. Performance metrics are proposed for both static and dynamic coverage problems that helps in ascertaining the quality of coverage. \n  \nSpeaker : Suryadeep Nath    \nResearch Supervisor: Debasish Ghose
URL:https://aero.iisc.ac.in/event/ph-d-engg-multi-agent-pursuit-evasion-and-coverage-strategies/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/SURYADEEP-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250307T110000
DTEND;TZID=Asia/Kolkata:20250307T130000
DTSTAMP:20260415T080237
CREATED:20250304T093656Z
LAST-MODIFIED:20250304T093656Z
UID:10000057-1741345200-1741352400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Studies on Fluid Structure Interactions in Hypersonic Flow
DESCRIPTION:The global thrust towards the development of hypersonic cruise systems for various applications is leading towards slender configurations with lifting and control surfaces which are thin and complaint and face a hypersonic flow. Hypersonic flows are characterized by large flow kinetic energy and momentum\, which manifests into strong shocks\, high temperatures\, and associated effects that can cause coupling between the flow\, structure\, and thermal effects. Therefore\, understanding Fluid-Structure Interactions (FSI) in hypersonic flow gains significance\, and its predictive modelling is necessary to avoid adverse effects in flight. The majority of literature in supersonic and hypersonic FSI  consider low-fidelity modelling using piston theory\, two-dimensional FSI  computations\, and a limited number of experiments on mainly fully clamped flat panels subjected to aerodynamic loads\, including shock-boundary layer interactions at supersonic Mach numbers. Studies on cantilevered panels\, which are template shapes of control surfaces\, at hypersonic Mach numbers are few\, and there is a significant need to obtain experimental data to aid physical understanding\, validate computational tools and methodology and model the hypersonic FSI  phenomena.\n This motivated the study of three different template flat plate experimental models in the hypersonic shock tunnel HST-2 in the Ludwieg  Mode of Operation\, which has 35 ms of test time. The freestream Mach number of M=6.6 is incident upon a) a cantilevered panel placed along the direction of the flow\, b) a cantilevered panel with an impinging shock\, and c) a trapezoidal wing-like shape fixed at the root and placed transverse to the flow. High-speed schlieren imaging and static pressure measurements at specific locations yield information on the flow characteristics. Image tracking methods are used to extract structural deformation\, and accelerometers measure the oscillatory structural response in the presence of hypersonic flow. Complementary two-dimensional numerical simulations in a fully coupled format are conducted for a limited number of cases. Parametric studies are conducted by varying the panel thickness\, angle of attack\, and mass ratio for plain panels and the impinging shock characteristics for the panel with shock impingement. Natural\, free vibration experiments using an impact hammer excitation are first carried out to evaluate the natural structural modal frequencies.\n Great care is taken in designing all experimental models so that the FSI  response can be captured during the short test time. Oscillatory response is captured successfully using the different diagnostic tools.   For a plain cantilevered panel placed at the Angle of Attack of 20 degrees\,  the FSI response is dominantly near the first structural bending mode at a frequency of 89.65 Hz\, which is higher in comparison to the natural frequency of 75.82 Hz. Multiple diagnostic tools and Dynamic Mode  Decomposition analysis confirm these observations. The angle of attack and mass ratio affect the amplitude of oscillations. Varying thickness changes the structural stiffness\, and accordingly\, the oscillations occur at higher frequencies. Higher downstream pressures on the top surface of the panel due to forebody shock first cause the panel to bend away from the flow\, which leads to the formation of expansion fans\,  releasing the pressure and causing the elastic restoring force to bring it back. Complementary two-dimensional FSI simulations showed good agreement with the experiments\, though the magnitude of amplitude was higher due to the 2D nature of the simulation. Shock Boundary Layer  Interaction is significantly affected by the panel’s compliance. There is a 29.6% reduction of the SBLI separation bubble size on a complaint cantilevered panel. The twin effects of a relaxation in pressure gradient and the existence of wall-normal velocities due to a vibrating panel can be attributed to the observed effect. The trapezoidal wing shape exhibited significantly higher magnitudes in the second structural mode.\nThe studies have laid the foundations for deeper investigations using field imaging techniques like 3D-Digital Image Correlation in the future. The experimental database can be used to develop predictive modelling approaches and data-driven modelling.\n\nSpeaker: Ms. Kartika Ahuja \n\nResearch Supervisor: Prof. Srisha Rao M V
URL:https://aero.iisc.ac.in/event/ph-d-engg-studies-on-fluid-structure-interactions-in-hypersonic-flow/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Kartika.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250224T160000
DTEND;TZID=Asia/Kolkata:20250224T170000
DTSTAMP:20260415T080237
CREATED:20250221T055800Z
LAST-MODIFIED:20250221T055800Z
UID:10000054-1740412800-1740416400@aero.iisc.ac.in
SUMMARY:MTech(Res): Adjoint-Based Aerodynamic Shape and Mesh Optimization with High-order Discontinuous Galerkin Methods
DESCRIPTION:The aerodynamic shape of an aircraft plays a critical role in its performance. Aerodynamic Shape Optimization (ASO) modifies the shape to achieve desired performance metrics\, such as reduced drag or increased lift. ASO integrates numerical optimization techniques with Computational Fluid Dynamics (CFD). Gradient-based optimization techniques are widely employed for ASO. The adjoint solution enables the accurate and efficient computation of the gradients of the performance metrics with respect to the shape parameters. Performance metrics are derived from CFD solutions\, which inherently contain inaccuracies. These inaccuracies can affect the reliability of the optimization process. High-order methods\, like Discontinuous Galerkin (DG)\, offer improved accuracy for a computational cost comparable to Finite Volume methods in compressible flows\, making them well-suited for ASO. Adaptive mesh refinement can further improve the accuracy of simulations. The adjoint solution used for computing gradients also finds application in mesh adaptation. Combining adjoint-based mesh adaptation with gradient-based ASO provides better control over the inaccuracies during optimization. \nTowards this\, the present work performs ASO using high-order DG methods and devises strategies for incorporating adaptive mesh refinement. The shape is defined using smooth splines\, and the Free Form Deformation (FFD) method controls shape changes. With changes in the geometry\, the mesh needs to move to be consistent with the modified shape. A mesh deformation strategy ensures that the mesh evolves smoothly with geometry. A gradient-based method employing the Sequential Quadratic Programming (SQP) algorithm is used for optimization. The adjoint solution computes the gradients and passes them to the optimization algorithm. Optimization for a set of drag minimization problems\, including benchmark Aerodynamic Design Optimization Discussion Group (ADODG) test case 1 and inverse design problems\, is performed on non-adapted meshes. \nFurthermore\, a strategy is formulated to incorporate adjoint-based mesh adaptation within the optimization process. Based on the value of adjoint-based error estimates\, the strategy decides on instances of the optimization process that require control of the errors and\, thus\, mesh adaptation. Such a strategy leads to automated control of errors in the performance metrics\, thus improving the reliability and efficiency of the optimization process. \n  \nSpeaker : Pandya Kush Tusharbhai \nResearch Supervisor : Aravind Balan
URL:https://aero.iisc.ac.in/event/mtechres-adjoint-based-aerodynamic-shape-and-mesh-optimization-with-high-order-discontinuous-galerkin-methods-2/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/02/Slide3.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241227T110000
DTEND;TZID=Asia/Kolkata:20241227T130000
DTSTAMP:20260415T080237
CREATED:20241224T090743Z
LAST-MODIFIED:20241224T090743Z
UID:10000046-1735297200-1735304400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Effect of Surface Roughness on Mechanical Strength of Adhesively Bonded CFRP Joints – Experimental and Numerical Studies
DESCRIPTION:This dissertation focuses on surface preparation and its effect on the shear strength of adhesively bonded Single Lap Joints (SLJs) in Carbon Fiber Reinforced Polymer (CFRP)\, their fracture properties\, and the associated Non-Destructive Evaluation (NDE) parameters. The surface preparation was carried out using different grades of emery paper so that the interfaces of different roughness were available for bonding. The morphology of the interfaces before bonding was captured with the light interferometry [Micro-System Analyzer (MSA)]. Then\, roughness parameters were characterized by contact-based measurements. The correlations of the contact angle between the droplet of liquid and the bonding interface with varied surface roughness and the increase in area with respect to the smoothest surface were established. CFRP\, one of the most preferred composite materials in the aerospace industry\, has been chosen in this study. \nA band of NDE techniques was utilized to evaluate the effects of surface roughness in ABJs of CFRP adherends. This included Ultrasonic Testing (UT)\, Infra-Red Thermography (IRT)\, Acoustic Wave Propagation (AWP)\, Acoustic Emission Testing (AET)\, X-ray Radiography Testing (XRT)\, and Digital Image Correlation (DIC). \nIn the FEA model it is difficult to model micro-roughness on the adherend of mesoscale. Hence\, an approach was presented to model the fracture in rough interfaces. Modelling of joints with varied roughness was considered\, and fracture properties were implemented in the commercial FEA software Abaqus. The surface-to-surface interactions were modelled for each interface. The interaction was based on the Cohesive Zone Model (CZM). Traction separation laws were derived from experimental fracture energies. \n  \nSpeaker: Laxmikant Mane Sarjerao \nResearch Supervisor: Prof Bhat M Ramachandra
URL:https://aero.iisc.ac.in/event/ph-d-engg-effect-of-surface-roughness-on-mechanical-strength-of-adhesively-bonded-cfrp-joints-experimental-and-numerical-studies/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/Laxmikant-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241209T103000
DTEND;TZID=Asia/Kolkata:20241209T123000
DTSTAMP:20260415T080237
CREATED:20241202T071527Z
LAST-MODIFIED:20241202T071527Z
UID:10000038-1733740200-1733747400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): "Design and Development of Novel Quadcopters for Reliable Operations in Cluttered Environments"
DESCRIPTION:The quadcopters are increasingly used in cluttered environments as rapid advancements are made in the development of lightweight sensors and payloads. Intelligence Surveillance Reconnaissance (ISR) missions\,  crack detection on the interior surface of a pipe/tunnel\, and close inspection in tropical forest environments are a handful of examples where quadcopters are being deployed. Safe operation in these cluttered environments is challenging mainly due to the proximity of obstacles to the spinning propellers. The complete loss of the propeller makes it impossible to have full-attitude stability on traditional quadcopters. After the propeller failure\, the existing literature relies upon reduced-attitude control\, where the control authority about yaw is sacrificed. To maintain reduced attitude control\, the quadcopter must continuously spin rapidly about the yaw axis. Such a maneuver is risky\, and the quadcopter may not continue the mission after the actuator fails completely. \nFor reliable operation in a cluttered environment\, the quadcopter should also be able to reduce its span mid-flight to minimize the risk of the propeller collision with the obstacles. The quadcopter should remain fully controllable for all spans to enhance usability and applicability. The degree of span reduction should be controllable between the nominal and extreme states. Ideally\, the quadcopter should also be tolerant to the complete failure of the additional “span-reducing” actuator (not to be confused with primary rotor-based actuators). For the broader range of applications\, the concept or the mechanism of span-reducing should be weight-scalable.  The effective execution of an indoor cluttered environment mission may also require a mid-flight flipping quadcopter for gaining the perception of the environment along both nadir and zenith directions with respect to the payload.  Traditional quadcopters cannot sustain the inverted flight and thus lack the maneuverability and reliability to operate safely and effectively in a cluttered environment. Enhancements to the fundamental principles governing quadcopter dynamics are required to facilitate challenging operations in cluttered environments. \nThe first half of the presentation consists of the design and development of a morphing quadcopter called Scissorbot. Scissorbot is a novel mid-flight reconfigurable geometry quadcopter that reduces its lateral span using a single servo-motor coupled with a compact bevel differential gearbox. Scissorbot possesses unique practical features\, including weight-scalability\, geometrical symmetricity\, and fault tolerance to the servo-motor. Scissorbot achieves significant lateral-span reduction without the risk of propeller tip collision by positioning adjacent propellers in different planes. The maximum lateral-span reduction is 88% of its nominal value (highest reported in the literature). This work derives a detailed attitude dynamics model and analyzes the gearbox theoretically. Attitude control is accomplished by implementing a Sliding Mode Controller (SMC) that exhibits robustness to parametric uncertainties such as the moment of inertia and aerodynamic disturbances due to the overlapping of the propellers. The control allocation loop is parametrized with respect to the morphing angle to adapt to the reconfiguration process.  The performance of the Scissorbot is validated using simulations\, test-benches as well as real-world free-flight experiments. \nThe other half presents the design and development of a novel Variable-Pitch-Propeller (VPP) quadcopter called Heliquad. The cambered airfoil propeller-equipped Heliquad generates significantly more torque than its symmetrical airfoil counterpart\, ensuring full-attitude hover equilibrium on only three of its working actuators. VPPs can generate reverse thrust\, enabling mid-flight flip and sustained inverted flight on Heliquad. A unified control architecture ensures the tractability of the Heliquad. Furthermore\, a Neural-Network (NN) based control allocation method is proposed to address the non-linearities in the actuator dynamics. The control allocation is reconfigurable based on the index of the faulty actuator. For the experimental validation\, a prototype of  Heliquad is built. The design and analysis of the VPP mechanism installed on the Heliquad prototype are also presented. The performance of Heliquad is validated using simulations\, test-benches\, and real-world free-flight experiments. The safe recovery of a quadcopter architecture (Heliquad) with full attitude control after the complete failure of an actuator is demonstrated for the first time in the literature. \nSpeaker:  Kulkarni Eeshan Prashant \nResearch Supervisor: Prof Suresh Sundaram
URL:https://aero.iisc.ac.in/event/ph-d-engg-design-and-development-of-novel-quadcopters-for-reliable-operations-in-cluttered-environments/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/Eeshan.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241206T140000
DTEND;TZID=Asia/Kolkata:20241206T170000
DTSTAMP:20260415T080237
CREATED:20241204T101223Z
LAST-MODIFIED:20241204T101223Z
UID:10000039-1733493600-1733504400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Multiscale modelling and design of multifunctional composites for microwave absorption applications
DESCRIPTION:Microwave absorption materials (MAMs) are crucial for both long-standing aeronautical and emerging space security applications\, with carbon-based materials traditionally dominating the field due to their exceptional strength and lightweight nature. In recent years\, other ceramic-based materials have emerged as promising alternatives\, due to their superior resistance to thermal detection\, due in turn to their low thermal conductivity and inertness to oxidation at high temperatures. However\, such ceramics by themselves often lack the mechanical flexibility and lightweight characteristics essential for aircraft. Combining such ceramics with carbon-based materials renders the achievement of an optimal balance of electromagnetic and mechanical (specific strength\, stiffness\, stability) performances\, possible. Traditional experimental approaches to designing MAMs are resource-intensive\, given the multidimensional parametric space that must be explored. This research adopts a multiscale computational framework\, leveraging minimal self-generated experimental data to efficiently design ceramic-carbon hybrid materials for broadband microwave absorption\, ensuring durability and low observability in extreme environments.\nThe initial phase investigates the microwave absorption capabilities of ceramic-based auxetic metamaterials with four distinct topologies: star\, re-entrant\, anti-tetrachiral\, and cross-chiral. These structures were chosen to analyse their reflection loss (RL) performance under transverse electric (TE) and transverse magnetic (TM) polarised electromagnetic (EM) waves. An in-house computationally-efficient homogenisation tool\, based on the Variational Asymptotic Method (VAM)\, was employed to derive the effective EM properties. These properties were then used to compute RL spectra by evaluating the scattering matrices. Interestingly\, the star and cross-chiral auxetic structures demonstrated identical absorption capabilities despite their architectural differences\, achieving a maximum absorption of 99.99% (RL of -40 dB) with a thickness of 3.5 mm under TM-polarised EM waves. These absorbers maintained RL < -10 dB for incidence angles up to 700. However\, TE-polarised EM waves led to more reflection (RL > -6 dB)\, highlighting a significant performance gap.\nLater\, to overcome the limitations observed with auxetic metamaterials\, a novel sandwich composite structure was proposed to achieve broadband RL under both TE and TM polarisations. This sandwich panel integrates ceramic-coated graphite fibre-reinforced polymer (C-GFRP) composite as the face sheet with a ceramic-based star auxetic metamaterial as the core. Representative volume elements (RVEs) of C-GFRP composites are generated using the in-house tool\, and the effective properties of the unidirectional C-GFRP face sheets were computed using the in-house homogenisation tool and validated with experimental results from the literature. A detailed parametric study of 300 analyses was conducted using the in-house transfer matrix method (TMM) tool to identify the optimal designs. Two configurations thus identified from the analysis are (a) Vf = 15% (uncoated) and (b) Vf = 20% with a ceramic coating volume fraction (Cf) of 70%. Configuration (a) achieved RL < -10 dB up to an incidence angle of 400\, while configuration (b) extended this performance up to 600. Both configurations attained broadband RL performance\, covering the entire X-band frequency range.\nThe final phase of the study experimentally validates the multiscale computational framework. For this purpose\, multiphase nanocomposites comprising carbon-based nanoparticles (MWCNTs) and other ceramic inclusions (BaTiO₃\, CoFe₂O₄) are fabricated and tested for broadband RL capabilities. Comprehensive characterisation techniques such as SEM\, TGA\, and X-ray computed tomography were employed to confirm nanoparticle morphology\, volume fractions\, and distribution. Reflection and transmission measurements using a two-port vector network analyser (VNA) provided scattering parameters within the X-band. Effective EM properties were derived using the Nicolson-Ross-Weir (NRW) algorithm. At the same time\, an in-house optimisation tool\, based on Nelder-Mead and L-BFGS-B methods\, was employed to extract the individual inclusion properties. Parametric studies revealed that composites with high BaTiO₃ or MWCNTs content exhibited surface impedance mismatches\, leading to EM wave reflection rather than absorption. In contrast\, CoFe₂O₄ dominant composites demonstrated superior broadband RL (< -10 dB) for different thickness samples\, attributed to improved surface impedance matching. Additionally\, the influence of incident angle and polarisation was assessed. TM-polarised EM waves provided broadband RL for incidence angles up to 800\, while TE-polarised EM waves were effective only up to 400 due to distinct field interaction mechanisms. The study demonstrates a versatile framework for designing novel nanocomposites tailored to broadband or frequency-selective microwave absorption applications\, addressing the limitations of traditional approaches.\n\nSpeaker: Attada Phanendra Kumar\nResearch Supervisor: Prof. Dineshkumar Harursampath
URL:https://aero.iisc.ac.in/event/ph-d-engg-multiscale-modelling-and-design-of-multifunctional-composites-for-microwave-absorption-applications/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/Attada-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241205T103000
DTEND;TZID=Asia/Kolkata:20241205T123000
DTSTAMP:20260415T080237
CREATED:20241129T112328Z
LAST-MODIFIED:20241129T112328Z
UID:10000037-1733394600-1733401800@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Development of Scalable UAV Swarm-based Cooperative Search and Mitigation Approaches for Wildfire Management
DESCRIPTION:Climate change has significantly exacerbated the wildfire seasons\, increasing their frequency\, duration\, and scale of destruction. Globally\, wildfires destroy approximately 400 million hectares of land annually\, resulting in significant biodiversity loss\, degradation of soil nutrients\, and other ecological consequences. The fire locations are often inaccessible for ground-based interventions due to the challenging terrain\, and current human-centered firefighting strategies are both dangerous and unreliable\, primarily due to limited situational awareness of evolving wildfire scenarios. Additionally\, wildfire scenarios frequently involve rapidly spreading clusters of fires that surpass available resources. The wildfire scenarios also have large fires that require simultaneous action from multiple resources for mitigation. Unmanned Aerial Vehicles (UAVs) have emerged as an effective solution for enhancing situational awareness and facilitating interventions during wildfires. This thesis develops UAV swarm-based strategies for wildfire detection\, monitoring\, and mitigation in resource-constrained and dynamic environments.\nThe thesis first focuses on the early mitigation of clustered fires by assigning and scheduling firefighting UAVs under resource limitations. The objective is to reduce biodiversity loss through early mitigation of fires as Single UAV Tasks (SUTs) before they escalate into complex multi-UAV coordination tasks. The problem is reformulated as a shortest-schedule-route optimization and solved using two centralized approaches: Genetic Algorithm-based Routing and Scheduling with Time Constraints (GARST) and Hybrid Particle Swarm Optimization-based Routing and Scheduling with Time Constraints (HPSO-RST). GARST and HPSO-RST evaluated on homogeneous and heterogeneous UAV teams under full observability conditions show that HPSO-RST outperforms GARST\, with a higher success rate\, reduced mean fitness values\, and minimized burned areas. However\, the centralized nature of GARST and HPSO-RST limits scalability and convergence in dynamic environments with continuously evolving task demands. These challenges are further compounded in real-world firefighting scenarios by partial observability\, limited UAV sensor capabilities\, and physical constraints of UAVs related to payload and endurance. \nNext\, the complexities of non-stationary wildfire scenarios\, including growing fires\, emerging new fires\, partial observability\, and heterogeneous temporal and physical constraints\, are addressed in the SUT mitigation. The problem is reformulated into a sequential spatiotemporal task assignment framework with non-stationary cost functions under partial observability. The Conflict-aware Resource-Efficient Decentralized Sequential planner (CREDS) is developed to address the challenges for early wildfire suppression using heterogeneous UAV teams. CREDS employs a three-phase approach: fire detection using a search algorithm\, local trajectory generation with an auction-based Resource-Efficient Decentralized Sequential planner (REDS) incorporating a novel Deadline-Prioritized Mitigation Cost (DPMC) function\, and a conflict-aware consensus algorithm to establish global trajectories for mitigation. CREDS achieves high success rates under various conditions\, handling diverse fire-to-UAV ratios with scalability and robustness. The CREDS is robust against physical constraints\, managing resource limitations through increased UAV capacity\, additional UAVs\, and efficient refueling strategies. In resource-constrained wildfire scenarios\, the evolving nature of the wildfire may result in multiple spatially distributed larger fires\, which require simultaneous and coordinated mitigation efforts from multiple UAVs. The single swarm mission with a decentralized approach has less likelihood of multiple UAVs detecting the same target. The multi-swarm missions with distributed solutions lead to the collective action of swarm members in the search and mitigation of larger fires in large unknown areas. \nFinally\, the thesis develops the Multi-Swarm Cooperative Information-Driven Search and Divide-and-Conquer Mitigation Control (MSCIDC) approach for large-scale wildfire scenarios. This methodology employs cooperative UAV swarms to enhance fire detection and mitigation efficiency. A two-stage search process combines exploration and exploitation\, guided by thermal sensor data\, for rapid identification of fire locations. Dynamic swarm behaviors\, including regulative repulsion and merging\, minimize detection and mitigation times\, while local attraction accelerates the response of non-detector UAVs. The divide-and-conquer strategy ensures effective\, non-overlapping sector allocation for fire mitigation. The simulations for a pine forest environment show that MSCIDC reduces the average burned area and mission time considerably compared to existing multi-UAV methods\, providing faster and more efficient wildfire management. \nOverall\, the thesis presents scalable UAV swarm-based solutions to address clustered and large-scale wildfire management challenges. The UAV swarm-based solutions integrate decentralized spatiotemporal task assignment and multi-swarm strategies to effectively minimize ecological damage and provide robust solutions for real-world disaster management applications. \nSpeaker: Josy John \nResearch Supervisor: Dr. Suresh Sundaram
URL:https://aero.iisc.ac.in/event/ph-d-engg-development-of-scalable-uav-swarm-based-cooperative-search-and-mitigation-approaches-for-wildfire-management/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/11/john.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241202T103000
DTEND;TZID=Asia/Kolkata:20241202T130000
DTSTAMP:20260415T080237
CREATED:20241128T095209Z
LAST-MODIFIED:20241202T054246Z
UID:10000036-1733135400-1733144400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Experimental Study of Isolator Shock Trains in Confined Co-Flowing Supersonic Streams
DESCRIPTION:Futuristic high Mach number flight systems using advanced air-breathing propulsion technologies typically have multiple flow paths with supersonic flows that merge before exiting the vehicle. The supersonic-supersonic co-flow configuration is a canonical model used to study the fundamental aerodynamics of these interactions. A pseudo-shock is a composite gas-dynamic feature produced in viscous-dominated internal flows due to shock-boundary layer interaction. It consists of a series of shocks (shock train) and a mixing region. The terms pseudo-shock and shock train are often used interchangeably. The isolator is a finite-length\, constant-area duct that contains the shock train across a wide range of operating conditions. Understanding and predicting the length\, adverse pressure handling capacity\, and instability of the shock train in the isolator is crucial for designing weight-critical aerospace systems. Most research on shock trains in isolators involves configurations without a co-flowing supersonic stream\, where the adverse pressure ratio is imposed mechanically. Fluidic throttling\, however\, establishes the isolator shock train in a supersonic-supersonic co-flow configuration\, which differs fundamentally from mechanical throttling\, which necessitates separate investigations. The limited literature on shock trains in supersonic-supersonic co-flow configurations shows the shock train in a narrow operating regime\, either in the overexpanded regime or with combustion in the mixed stream producing back pressure. These studies\, conducted in opaque tubular ducts\, relied on pressure measurements to infer shock train characteristics. Empirical relations of the shock train pressure distribution and length were not in consensus. This thesis aims to understand the shock train in a supersonic-supersonic co-flow configuration using an optically accessible test section that provides simultaneous time-resolved schlieren imaging and static pressure measurement. A wide range of operating conditions is achieved by converting an existing blowdown supersonic jet facility to a pressure-vacuum-driven system. A new modular supersonic-supersonic co-flow test section is established with independent control over Mach number\, isolator length\, and stagnation conditions of the separate streams\, offering a larger parameter space than previous studies. The flow topology and morphology of 158 shock train cases are studied experimentally\, leading to several key insights. Novel image analysis techniques and static pressure profile analysis enabled the extraction of the last shock in the shock train\, correctly identifying the number of shocks and separating the mixing region. The maximum number of shocks for the supersonic-supersonic co-flow configuration ranges from 6 to 8\, and the maximum length of the shock train in the pseudo-shock occupies an average of 6 to 6.5 times the isolator duct height. A major outcome is the revelation of a secondary shock at the isolator duct exit due to local entrainment effects of the supersonic co-flow. This secondary shock can significantly contribute to about 20% to 25% of the overall adverse pressure ratio of the isolator. Consequently\, the addition of the secondary shock increases the overall adverse pressure-handling capacity of the isolator to 85% to 90% of the normal shock pressure ratio corresponding to the isolator entrance Mach number. Four transition points are identified based on significant changes in shock train topology. Across various operating conditions and geometries\, the normalized adverse pressure ratio (normalized with respect to the normal shock pressure ratio for the isolator entrance Mach number) ranges between 0.4 and 0.85. The flow topology in cases where the core flow is overexpanded is notably different due to the absence of the secondary shock in the shock train and the core flow’s contribution to the overall adverse pressure ratio. A comparative study between fluidic and mechanical throttling is conducted by implementing a mechanical flap module in the same setup. In the mechanically throttled case\, the shock train system has a lower adverse pressure ratio than the fluidically throttled case and a higher number of shocks\, with a maximum of about 10 to 11. The large dataset produced in this study allows a critical evaluation of well-known empirical correlations for shock trains\, leading to a new prediction algorithm to address gaps in their predictive ability. A regression-based correlation is developed to estimate the imposed adverse pressure ratio for the given Mach number and stagnation pressure combinations of both flows. An adaptive pressure increase factor for estimating the shock train leading edge is obtained using a linear regression model for cases with available wall static pressure data. The ratio of the imposed adverse pressure ratio to the incipient pressure ratio for a turbulent boundary layer is used to estimate the initiation of large amplitude oscillations of the shock train leading edge\, with an average factor of 2. Spectral analysis of the STLE oscillations using wall static pressure fluctuations and data-driven analysis of schlieren image datasets showed a broad-band spectrum without distinguishable tones\, with a spread of less than 200 Hz. \n  \nSpeaker: A Balaji Himakar \nResearch Supervisor: Srisha Rao M V
URL:https://aero.iisc.ac.in/event/ph-d-engg-experimental-study-of-isolator-shock-trains-in-confined-co-flowing-supersonic-streams/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/11/Balaji-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241129T150000
DTEND;TZID=Asia/Kolkata:20241129T170000
DTSTAMP:20260415T080237
CREATED:20241126T093642Z
LAST-MODIFIED:20241126T093642Z
UID:10000031-1732892400-1732899600@aero.iisc.ac.in
SUMMARY:MTech(Res): Adjoint-Based Aerodynamic Shape and Mesh Optimization with High-order Discontinuous Galerkin Methods
DESCRIPTION:The aerodynamic shape of an aircraft plays a critical role in its performance. Aerodynamic Shape Optimization (ASO) modifies the shape to achieve desired performance metrics\, such as reduced drag or increased lift. ASO integrates numerical optimization techniques with Computational Fluid Dynamics (CFD). Gradient-based optimization techniques are widely employed for ASO. The adjoint solution enables the accurate and efficient computation of the gradients of the performance metrics with respect to the shape parameters. Performance metrics are derived from CFD solutions\, which inherently contain inaccuracies. These inaccuracies can affect the reliability of the optimization process. High-order methods\, like Discontinuous Galerkin (DG)\, offer improved accuracy for a computational cost comparable to Finite Volume methods in compressible flows\, making them well-suited for ASO. Adaptive mesh refinement can further improve the accuracy of simulations. The adjoint solution used for computing gradients also finds application in mesh adaptation. Combining adjoint-based mesh adaptation with gradient-based ASO provides better control over the inaccuracies during optimization.\n\nTowards this\, the present work performs ASO using high-order DG methods and devises strategies for incorporating adaptive mesh refinement. The shape is defined using smooth splines\, and the Free Form Deformation (FFD) method controls shape changes. With changes in the geometry\, the mesh needs to move to be consistent with the modified shape. A mesh deformation strategy ensures that the mesh evolves smoothly with geometry. A gradient-based method employing the Sequential Quadratic Programming (SQP) algorithm is used for optimization. The adjoint solution computes the gradients and passes them to the optimization algorithm. Optimization for a set of drag minimization problems\, including benchmark Aerodynamic Design Optimization Discussion Group (ADODG) test case 1 and inverse design problems\, is performed on non-adapted meshes.\n\nFurthermore\, a strategy is formulated to incorporate adjoint-based mesh adaptation within the optimization process. Based on the value of adjoint-based error estimates\, the strategy decides on instances of the optimization process that require control of the errors and\, thus\, mesh adaptation. Such a strategy leads to automated control of errors in the performance metrics\, thus improving the reliability and efficiency of the optimization process.\n\n\nSpeaker: Pandya Kush Tusharbhai\n\nResearch Supervisor: Aravind Balan
URL:https://aero.iisc.ac.in/event/mtechres-adjoint-based-aerodynamic-shape-and-mesh-optimization-with-high-order-discontinuous-galerkin-methods/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/11/pandya.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241114T140000
DTEND;TZID=Asia/Kolkata:20241114T170000
DTSTAMP:20260415T080237
CREATED:20241114T083023Z
LAST-MODIFIED:20241126T093958Z
UID:10000030-1731592800-1731603600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Asymptotic Modelling of Carbon Nanotube (CNT) and CNT-Reinforced Composite Structures Using Strain Gradient Formulations
DESCRIPTION:Carbon nanotubes (CNTs) have garnered attention for their remarkable mechanical\, thermal\, and electrical properties\, making them valuable in various applications. CNTs are particularly advantageous in aerospace structures as reinforcements in polymer matrix composites\, enhancing structural performance while reducing weight. Furthermore\, they offer the potential for multifunctionality\, integrating structural\, thermal\, and electrical functionalities within components like wings. However\, accurately modelling CNT behaviour poses challenges\, especially considering their application in larger-scale aerospace structures. While accurate\, molecular dynamics and molecular structural mechanics are computationally intensive and limited in length scale. In this context\, the present research proposes reduced-order continuum structural models using the Variational Asymptotic Method (VAM) to study CNT and its composite structures while incorporating length-scale effects using strain-gradient formulations. \nUsing VAM\, single-walled CNTs (SWCNTs) were first analysed by considering them as straight\, hollow\, circular tubes in a local continuum framework. This tube model accounts for the geometrically-nonlinear behaviour of standalone CNT when subjected to bending and buckling loads. Cross-sectional ovalisation leading to nonlinear bending and buckling behaviour has been studied. Combined loading cases of bending and compression; torsion and compression; & bending and torsion have been examined. The study aims to provide insights into the 3-D nonlinear deformation behaviour of SWCNTs\, offering a more efficient approach for evaluating CNTs in aerospace composite applications. \nIn the next step\, recognising the significance of the structure’s small size (such as used in MEMS\, NEMS\, and sensors)\, non-classical theories\, such as the Modified Strain Gradient Theory\, which account for the size effect in the material\, have been employed to develop a pioneering beam and plate models tailored for CNT-reinforced composite structures. Emphasising the critical nature of size effects\, characterised by length-scale parameters\, this study delves into the nuances of the length-scale effects in nanoscale structures. To develop the asymptotically-correct strain-gradient beam model\, a prismatic beam with a rectangular cross section has been considered to derive zeroth-order and subsequent higher-order models while capturing the strain-gradient effects. Notably\, this work is the first application of non-classical theories in developing VAM-based beam models. Different orders for length-scale parameters have been considered\, and the validity of each choice is scrutinised\, followed by guidance on the appropriate choice of the length-scale parameters. \nFollowing the development of the strain-gradient beam model\, a modified strain gradient theory-based plate model has also been developed using VAM\, which is again a first-of-its-kind work in the context of VAM and reduced-order structural models. Using the variational methods\, fourth-order differential equations were obtained for the non-classical case\, and similarly\, an additional set of boundary conditions (non-classical) were also derived. The warping solutions and the plate stiffnesses are obtained by solving this boundary value problem. It was noted that the material length-scale parameters appear only in the bending and twist stiffness terms. Further\, the classical results can be derived by setting the material length-scale parameters to zero. Zeroth- and first-order approximations have been derived\, followed by detailed validation of the results with literature for bending and buckling load cases. Parametric studies involving variations in thickness and plate width have been conducted to assess their influence on mechanical behaviour. The developed plate model is then applied to CNT-reinforced composites\, and their bending and buckling studies have been carried out. The parametric studies have also considered evaluating all influencing parameters like CNT volume fraction\, material length-scale parameter\, plate thickness and width. \n  \nSpeaker: Renuka Sahu \nResearch advisor: Prof Dineshkumar Harursampath
URL:https://aero.iisc.ac.in/event/asymptotic-modelling-of-carbon-nanotube-cnt-and-cnt-reinforced-composite-structures-using-strain-gradient-formulations-2/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/11/renuka.jpg
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END:VCALENDAR