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TZID:Asia/Kolkata
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DTSTART:20240101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241202T103000
DTEND;TZID=Asia/Kolkata:20241202T130000
DTSTAMP:20260418T124859
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
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241203T110000
DTEND;TZID=Asia/Kolkata:20241203T130000
DTSTAMP:20260418T124859
CREATED:20241126T095210Z
LAST-MODIFIED:20241129T054751Z
UID:10000033-1733223600-1733230800@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Aeroacoustic sources in twin turbulent jets
DESCRIPTION:An understanding of the aeroacoustics of twin turbulent jets is essential for applications involving noise reduction in dual engine aircrafts and launch vehicles. The aeroacoustic dynamics of these jets are influenced by the spacing between the shear layer of the two jets as well as the spatio-temporal nature of the structures arising from the interaction between the two jets. In the present work\, we construct reduced-order models of aeroacoustic sources for single and twin subsonic jets ($M_j=0.9$\, $Re=3600$)\, with the individual jets being replicas of a single jet\, with the goal of accurately recovering the far-field sound over a rather wide band of frequencies St=[0.07\,1.0] and directivity angles\, phi = [30 deg\,120 deg] within a subdecibel level accuracy. These models are designed as linear combinations of spatio-temporally coherent SPOD modes obtained in terms of the Lighthill’s stress tensor\, which in turn is computed through large-eddy simulations (LES) of the turbulent jets.  The present investigation involves two sets of twin subsonic jets of diameter D each\, with spacings of 0.1D and 1D\, where the jets merge upstream and downstream of breakdown\, respectively.  This is observed to alter the dynamics of twin jet evolution.  The closely spaced twin jet decays the slowest due to reduced turbulent stresses which are\, however\, more broadband due to early merging.  Such jets also show strong shielding in the plane of jets\, especially at shallow directivity angles where sound levels may drop below that of the single jet.  The farther spaced twin jets have dynamics that are more akin to the constituent single jet with turbulent fluctuations peaking here at St=0.34\, but showing very little shielding\, with their OASPL mostly linked to the nature of extra flow structures created during merging.  Three-dimensional\, energy-ranked\, coherent structures (SPOD modes) for twin jets exhibit rather poor low-rank behaviour\, especially\, at the far-field spectral peak St=0.14\, unlike that of the single jet\, which is indicative of spatio-temporally complicated structures arising from the merging of the turbulent merging of the twin jets.  At St > 0.3\, the SPOD wavepackets show strong visual coherence\, resembling Kelvin–Helmholtz instability modes upstream of breakdown\, while at the lower frequencies there is very little spatial coherence with wavepackets peaking downstream of breakdown.  Although the leading SPOD modes radiate poorly\, reduced-order models using a subset of them\, up to 45 SPOD modes per frequency\, show for the first time remarkable match (within 1 dB) against the LES-predicted sound over 0.1 < St < 0.5\, at all angles investigated\, including that for the peak sound. At other frequencies\, the error barely exceeds a decibel\, except for the closely spaced twin jet which due to its greater hierarchy of spatio-temporal structures\, show slower convergence at the shallower angles for St > 0.5. \n  \nSpeaker:  Nishanth Muthichur \nResearch Supervisor: Santosh Hemchandra
URL:https://aero.iisc.ac.in/event/ph-d-engg-aeroacoustic-sources-in-twin-turbulent-jets/
LOCATION:Online
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/11/nishant.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241205T103000
DTEND;TZID=Asia/Kolkata:20241205T123000
DTSTAMP:20260418T124859
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
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241205T110000
DTEND;TZID=Asia/Kolkata:20241205T130000
DTSTAMP:20260418T124859
CREATED:20241204T104533Z
LAST-MODIFIED:20241204T104533Z
UID:10000040-1733396400-1733403600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Control of Alternating Flow Phenomena in Transonic Shock Wave Boundary Layer Interactions Over Payload Region of a Generic Launch Vehicle Model
DESCRIPTION:The transonic Mach number regime is a critical phase in the atmospheric ascent of launch vehicles\, where aerodynamic loads peak due to the combined effects of high freestream dynamic pressure and angle of attack. Besides high steady loads\, launch vehicles experience very high levels of pressure fluctuations caused by interactions between the unsteady λ-shock system and the boundary layer – a phenomenon known as Shock Wave Boundary Layer Interaction (SWBLI). These interactions can induce buffet excitation over the payload region\, leading to structural failure as well as control issues. NASA recommends limiting the nose cone semi-angle to 15° to mitigate shock oscillations\, labelling such designs as “Buffet-Proof.” However\, practical constraints such as payload mass & volume\, rocket diameter\, launch-pad limitations\, etc. necessitate the use of larger nose cone angles which are buffet-prone. While SWBLI has been well understood for two-dimensional flows\, data for three-dimensional launch vehicle type configurations is sparse in the literature\, with regard to even the basic understanding of the phenomena. Hence\, there is a need to develop physics-based models to handle SWBLI in practical cases. \nWind tunnel experiments were conducted to evaluate the aerodynamic impact of increasing nose cone angles to 20° and 25° in the transonic Mach number range. These investigations revealed critical flow characteristics such as abrupt jumps in pitching moments at small angles of attack (±4°)\, very high levels of pressure fluctuations\, λ-shock system oscillations\, and the occurrence of destabilizing counter-rotating vortices\, intermittent supersonic and subsonic flows (termed alternating flow phenomena) at specific Mach numbers of 0.90 and 0.94. The present research explores two approaches towards controlling SWBLI. The first involves a passive device\, a front-mounted Aerodisc\, systematically evaluated for the effect of geometric parameters at critical Mach numbers of 0.9 and 0.94 in the range of angles of attack of ±4°. The optimized Aerodisc configuration achieved the maximum noise reduction of 22 dB (Overall Sound Pressure Level\, OASPL). The second approach involves an active flow control technique using a pneumatic counter-flow jet. The jet parameters were varied during the tests. Jets with exit diameters of 3 mm and 4 mm operating at a pressure ratio of 3.2 achieved the greatest suppression by nearly 20 dB. Both the passive and active techniques demonstrated that by energizing the boundary layer\, the oscillating shock waves were stabilized\, the counter-rotating vortices removed and the upstream travelling Kutta-Waves associated with the alternating flows completely suppressed. \nThis research clearly brings out the basic physics of SWBLI and its control for 3-dimensional launch vehicle type configurations at transonic Mach numbers\, highlighting that the energizing the boundary layer is the key to control the transonic flow over launch vehicles with large blunt nose-cones. Based on the understanding of the physics of the phenomena and control accomplished in the present research\, it is possible to design and develop digital-twin based systems for efficient control of the phenomena and thereby improve the payload capability of heavy lift launch vehicles. \n  \nSpeaker: Dheerendra Bahadur Singh \nResearch Supervisor: Gopalan jagadeesh
URL:https://aero.iisc.ac.in/event/ph-d-engg-control-of-alternating-flow-phenomena-in-transonic-shock-wave-boundary-layer-interactions-over-payload-region-of-a-generic-launch-vehicle-model/
LOCATION:Centre of Excellence in Hypersonics conference hall\, Room No.AE-239\,
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/Dheerendra-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241206T140000
DTEND;TZID=Asia/Kolkata:20241206T170000
DTSTAMP:20260418T124859
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
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241209T103000
DTEND;TZID=Asia/Kolkata:20241209T123000
DTSTAMP:20260418T124859
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
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241209T110000
DTEND;TZID=Asia/Kolkata:20241209T130000
DTSTAMP:20260418T124859
CREATED:20241209T043233Z
LAST-MODIFIED:20241209T052550Z
UID:10000042-1733742000-1733749200@aero.iisc.ac.in
SUMMARY:Boundary Layer Transition Experiment in a Supersonic Flight
DESCRIPTION:In fluid mechanics\, the boundary-layer transition is a very important phenomenon for high-speed flows because it severely affects the skin friction and heating rates on the model surface. The classical correlations for high-speed flows have been developed based on experimental observations in wind tunnels. When the experiments are performed\, they are mostly controlled by the flow Reynolds number because the maximum size of the model is fixed based on the size of the test section of a wind tunnel. In most cases\, artificial surface roughness is introduced to initiate a transition towards turbulence because of the restricted model size. The flow Reynolds number and Station number on the model surface are crucial non-dimensional indicative parameters that characterize the transition behaviour of the flow. A realistic approach to simulate the effect of model size for studying the boundary layer transition is to conduct a flight test. Against this backdrop\, a systematic procedure is adopted to design a generic ogive nose cone-cylinder payload module (0.7 m long) for a boundary-layer transition experiment in a supersonic flight. Nickel thin film gauges are used to infer heat transfer data on the payload module at various locations for 10s flight duration. The heat transfer data from the temperature history are obtained using two different techniques: one-dimensional semi-infinite heat conduction analysis and deconvolution method. The analysis from flight data indicates a peak Mach number of 2.018\, which is achieved after 1.157s of flight. The Reynolds number during the flight is of the order of 10 million \, which is an indication of completely turbulent flow during flight duration. It is also supported by heat transfer prediction through the Stanton number\, which falls in the range of 0.5 to 1.2. It is concluded that the length of the model is not sufficient to initiate a transition towards relaminarization because the Stanton number and Reynolds number variation do not show any drastic change at any of the gauge locations. However\, the promising surface temperature histories from nickel thin film gauges during flight are very useful to devise more realistic heat-transfer models for for higher time scales flow duration through inverse heat-conduction analysis and modern machine learning models.\n\n Speaker: Prof. Niranjan Sahoo\n\nBiography : \nProf. Sahoo’s research interests lie in high-speed aerodynamics\, ground test facilities\, measurements for forces and heat transfer\, shock waves\, and their applications in allied fields\, combustion\, energy \, hydrogen energy and storage. He has been awarded fellowships from DAAD Germany\, BOYCAST and Young Scientist Scheme from DSTHe has offered several online courses (Applied Thermodynamics\, Power Plant System Engineering\, Advanced Thermodynamics and Combustion\, Fundamentals of Compressible Flow) on NPTEL platform. He has over 115 Journal Publications\, 153 in conference proceedings and 11 Book Chapters.
URL:https://aero.iisc.ac.in/event/boundary-layer-transition-experiment-in-a-supersonic-flight/
LOCATION:AE Auditorium
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/Niranjan.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241209T110000
DTEND;TZID=Asia/Kolkata:20241209T130000
DTSTAMP:20260418T124859
CREATED:20241209T045719Z
LAST-MODIFIED:20241209T051859Z
UID:10000043-1733742000-1733749200@aero.iisc.ac.in
SUMMARY:The Dual Mesh Control Domain Method: A Marriage of the Finite Element and Finite Volume Methods
DESCRIPTION:The finite element method (FEM) and finite volume method (FVM) are widely used numerical techniques for solving differential equations\, with FEM mainly applied in solid mechanics and FVM in heat transfer and fluid dynamics. Both methods have drawbacks: FEM can lead to discontinuities at element interfaces unless C1-continuous approximations are used\, while FVM relies on ad-hoc techniques from finite difference methods\, lacking explicit approximations and concepts of duality. In 2019\, Reddy introduced the dual mesh control domain method (DMCDM)\, combining features of both FEM and FVM. DMCDM uses a primal mesh for dependent variable interpolation and a dual mesh for integral satisfaction of governing equations\, enhancing the methods’ effectiveness. This lecture discusses DMCDM’s key features and demonstrates its applications in various linear and nonlinear problems. \nSpeaker: Prof J N Reddy \nBiography:  \nDr. Reddy is a Distinguished Professor and Regents’ Professor at Texas A&M University\, holding the O’Donnell Foundation Chair IV in Mechanical Engineering. An ISI highly cited researcher\, he has authored 25 textbooks and over 800 journal papers\, making significant contributions to applied mechanics\, particularly through his shear deformation theories\, including the Reddy third-order plate theory and Reddy layerwise theory. These theories have influenced commercial finite element software like ABAQUS and NISA. Recently\, his research has focused on locking-free shell finite elements and nonlocal continuum mechanics related to architected materials and structural failures. Dr. Reddy has received numerous prestigious awards\, including the 2023 Leonardo da Vinci Award\, the 2023 Michael Païdoussis Medal\, and the 2019 SP Timoshenko Medal\, among others. He is a member of eight national academies\, including the U.S. National\nAcademy of Engineering\, and a foreign fellow of several international engineering academies.
URL:https://aero.iisc.ac.in/event/the-dual-mesh-control-domain-method-a-marriage-of-the-finite-element-and-finite-volume-methods/
LOCATION:Auditorium\, Department of Physics\, IISc
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/reddy1.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241218T110000
DTEND;TZID=Asia/Kolkata:20241218T123000
DTSTAMP:20260418T124859
CREATED:20241217T044151Z
LAST-MODIFIED:20241217T044151Z
UID:10000044-1734519600-1734525000@aero.iisc.ac.in
SUMMARY:Phase Transformations in Multifunctional Materials
DESCRIPTION:Phase transformation materials are characterized by their ability to rapidly and reversibly switch between distinct properties\, such as insulating and conducting\, paramagnetic and ferromagnetic\, or Li-rich and Li-poor. These transformations\, however\, are accompanied by abrupt structural changes in the crystal lattices\, which can nucleate defects\, accumulate strain energy\, and accelerate material decay. We investigate these transformations in multifunctional materials from the viewpoint of Ericksen’s multiple energy wells. By doing so\, we identify important links between material constants\, crystallographic microstructures\, and macroscopic properties. This approach to understanding material behavior from the perspective of energy landscapes may suggest new ways to design materials with improved properties and lifespans. In this talk\, I will present our findings on phase transformations in battery electrodes (intercalation compounds) and soft magnetic alloys.\n\n Speaker: Ananya Balakrishna\n\nBiography:\nAnanya Renuka Balakrishna is an Assistant Professor in the Materials Department at the University of California Santa Barbara. She received her B.Tech degree in Mechanical Engineering from the National Institute of Technology Karnataka and her Ph.D. in Solid Mechanics and Materials Engineering from the University of Oxford. Before her current appointment\, she was a Lindemann Postdoctoral Fellow at MIT and the University of Minnesota and joined the faculty in the Department of Aerospace & Mechanical Engineering at the University of Southern California in 2020. Her research group develops theoretical models to understand the interplay between fundamental material constants and microstructural instabilities\, and how they collectively shape the physical response of a material.
URL:https://aero.iisc.ac.in/event/phase-transformations-in-multifunctional-materials/
LOCATION:AE Auditorium
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/Ananya-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241219T090000
DTEND;TZID=Asia/Kolkata:20241220T173000
DTSTAMP:20260418T124859
CREATED:20241219T044539Z
LAST-MODIFIED:20241219T044539Z
UID:10000045-1734598800-1734715800@aero.iisc.ac.in
SUMMARY:Two-Day Short Course on Mathematics and Computing of Risk\, Reliability and Resilience in Network and Enterprise Systems
DESCRIPTION:This course is designed to familiarize the students with the mathematical concepts and computational techniques in quantifying the risk\, reliability and resilience (RRR) of large\, complex systems\, in the presence of multiple types of uncertainty. Often the information available for RRR analysis is heterogeneous\, coming from multiple sources (models\, tests\, experts) and in multiple formats. The use of Bayesian methods to integrate heterogeneous information will be presented. The use of RRR quantification results in various types of decisions will be discussed\, such as system design\, manufacturing\, operations\, and sustainment. The concept and use of digital twins that continuously update the system model with incoming data to maintain high levels of system performance and resilience will be presented. Application examples from engineering systems (e.g.\, aircraft\, buildings)\, business enterprise systems (e.g.\, manufacturing and distribution supply chains)\, and civil infrastructure systems (e.g.\, power grid\, transportation) will be used to illustrate the RRR techniques for large complex systems. For more information\, please visit our website https://abcmc.iisc.ac.in/events/ \n  \nSpeaker: Dr. Sankaran Mahadevan \n  \nBiograpgy:  \nProfessor Sankaran Mahadevan has thirty-six years of research and teaching experience in reliability and risk methods\, uncertainty quantification\, model validation\, system health and risk management\, and optimization under uncertainty. His research has been extensively funded by NSF\, NASA\, FAA\, DOE\, DOD\, DOT\, NIST\, General Motors\, Chrysler\, Union Pacific\, American Railroad Association\, and Sandia\, Idaho\, Los Alamos and Oak Ridge national laboratories. His research contributions are documented in more than 700 publications\, including two textbooks on reliability methods and 350 journal papers. He is one of the world’s highest cited researchers in the field of uncertainty and risk analysis (Google Scholar h-index 90). He has directed 56 Ph.D. dissertations and 24 M. S. theses and has taught many industry and university short courses on the mathematics and computing of uncertainty and reliability analysis. Professor Mahadevan is a Fellow of AIAA\, Fellow of the Engineering Mechanics Institute (ASCE)\, and Fellow of Prognostics and Health Management Society (PHM). He is the winner of several prestigious awards including the Senior Distinguished Research Award from the International Association of Structural Safety and Reliability\, NASA Next Generation Design Tools award\, SAE Distinguished Probabilistic Methods Educator Award\, and best paper awards in several international conferences. He recently completed his service as President of the ASCE Engineering Mechanics Institute and Managing Editor of ASCE-ASME Journal of Risk and Uncertainty (Part B: Mechanical Engineering). He is currently Chair of the ASME VVUQ50 Committee on Advanced Manufacturing.
URL:https://aero.iisc.ac.in/event/two-day-short-course-on-mathematics-and-computing-of-risk-reliability-and-resilience-in-network-and-enterprise-systems/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/TwoDay.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241227T110000
DTEND;TZID=Asia/Kolkata:20241227T130000
DTSTAMP:20260418T124859
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
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END:VCALENDAR