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DTSTART:20260101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260610T103000
DTEND;TZID=Asia/Kolkata:20260610T120000
DTSTAMP:20260828T231309
CREATED:20260609T045550Z
LAST-MODIFIED:20260615T100351Z
UID:10000130-1781087400-1781092800@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Distributed Artificial Intelligence Technology for Robotic Swarms: An Interpretable Online Learning Perspective
DESCRIPTION:Robotic swarms offer immense potential for critical operations such as search and rescue\, surveillance\, and environmental monitoring\, owing to their distributed nature and redundancy. However\, the operational reliability of swarms heavily depends on a continuous\, closed-loop process: extracting high-fidelity or accurate collective situational awareness from distributed observation\, and subsequently utilizing that awareness for cooperative decision control in non-stationary environments. To achieve reliable operation across unstructured and dynamic domains\, the robotic swarm must maintain resilience when subjected to adverse situations. For instance\, in real-world target searching and surrounding\, environmental hazards can cause physical sensors to degrade or fail\, leading to significant prediction biases\, communication link drops\, or a complete loss of ground truth. Further\, robots operating in such dynamically evolving situations are frequently tasked with conflicting spatial objectives\, such as aggressively pursuing an agile target while safely navigating dense clutter\, requiring intelligent control to manage limited actuation and actuator velocity saturation limits. To address these demands\, this thesis develops an online learning based Distributed Artificial Intelligence Technology (DAITy) for robotic swarms\, which establishes a collective Situational Awareness – Decision Control (SA-DC) loop capable of executing resilient swarm cooperation and coordination across unstructured and non-stationary environments. \nThis thesis first focuses on extracting high-fidelity collective situational awareness from distributed observation under severe sensory biases and intermittent communication failures\, enabling the robots to accurately determine own-location and predict target behavior. The Distributed Learning-based Decentralized Cooperative Localization (DL-DCL) and Distributed Online learning-based Multi-Estimate (DOME) fusion frameworks are proposed. These supervised loss-driven online learning frameworks dynamically learn an information fusion strategy to combine pose estimates (or target position predictions) from onboard sensors (or prediction algorithms) and neighboring robots. To handle dynamically evolving situations and recover target trajectories despite severe environmental interference\, both frameworks incorporate periodic reset mechanisms to shed historical inertia alongside bounded loss functions to prevent explosive estimation errors from faulty sensors. Theoretically\, both frameworks establish the convergence of the fusion weights to the optimal local or social estimate/prediction; while DL-DCL’s theoretical analysis involves deterministic communication network\, DOME’s analysis involves random network. Quantitative evaluations demonstrate that DL-DCL improves own-pose estimation performance by approximately 40% under severe sensor faults\, while DOME achieves up to a 74% reduction in target position prediction loss compared to baselines that include both covariance-based and online learning methods. \nWhile supervised online learning is effective when landmarks or leaders are available\, swarms often operate in unstructured\, GPS-denied environments entirely lacking such ground-truth supervisors. To tackle this challenge\, the second contribution of this thesis introduces a reward-driven online learning framework based on concepts of independent learning or self-learning. The Autonomous Online Learning (AOL) framework enables resilient cooperative target monitoring by a reward-driven weighted information fusion process extracting accurate target location from limited\, intermittent exteroception among the robots in the swarm. Three variants are developed\, introducing a novel perturbation-greedy reward design that facilitates exploration-exploitation in the fusion weight space. The AOL framework empowers the swarm to isolate faulty robots and prioritize reliable information dynamically in adverse situations. Through rigorous convergence analysis\, the framework theoretically guarantees that the fusion weights converge to prioritize the most accurate information source. The top-performing variant\, AOL-1P\, demonstrates a 182.2% to 652% improvement in target detection scores and a 94.7% to 150.4% improvement in tracking closeness across varying swarm sizes over established baselines\, ensuring robust monitoring even when 50% of the total swarm population is undergoing permanent sensor failures. \nWith a high-fidelity situational awareness established\, the swarm must execute distributed decision control in non-stationary environments. Standard online optimization methods are often ineffective or inefficient on physical robotic swarms due to the dual challenge of simultaneous multi-objective balancing and actuator descent-step saturation\, particularly when target maneuvers force the swarm into dense clutter requiring seamless transitions between target tracking\, pursuit\, and collision avoidance. As the third contribution\, this thesis proposes the Softmax-Adaptive Objective Balancing in Multi-Objective Online Gradient Descent (SAO-MOOGD) framework. SAO-MOOGD utilizes a bounded loss signal to update objective weights using a softmax function\, enabling dynamic weighted averaging of the objective gradients. This enables simultaneous\, real-time balancing of competing goals\, such as decoupled collision avoidance versus target tracking. Theoretical analysis reveals dynamic regret bounds that explicitly quantify the error induced by physical velocity saturation\, showing that sub-linear regret growth can be guaranteed when proportional velocity controllers are appropriately tuned. Further\, theoretical analysis proves the exponential decay of the aggregation gap regret under non-degenerate loss margins. Complementing these theoretical guarantees\, the approach leverages the 1/2-Lipschitz continuity of the softmax operator to ensure smooth physical trajectory blending\, effectively eliminating heuristic limit-cycling. Across extensive ROS-Gazebo evaluations using TurtleBot3s\, SAO-MOOGD achieves improved multi-objective performance. Compared to high-tracking heuristic baselines\, it exhibits up to 5.5% lower target tracking accuracy while reducing collisions by up to 67% and lowering control effort by 30%. Further\, it demonstrates improved resilience\, incurring a reduction of less than 1% in tracking accuracy even under 40% communication packet drops and severe Gaussian sensory noise. \nDuring real-world deployments\, maintaining precise geometric configurations under physical disturbances is crucial for the Situational Awareness – Decision Control Loop. As the final contribution\, this thesis introduces the Topological Online Learning for Displacement-based (TOLD) formation control framework. Unlike conventional robust controllers that regulate node-level inputs without modifying the interaction topology\, TOLD performs real-time edge-level adaptation to preserve the swarm’s structural integrity in dynamically evolving situations. Two strategies are proposed: Online Gradient Flow (OGF) with unconstrained weights\, and Online Exponential Gradient Flow (OExpGF) with non-negative convex weights. Theoretical analysis proves that under directed communication topologies\, the convex OExpGF strategy drives single-integrator agents to asymptotic consensus\, whereas the unconstrained OGF approach guarantees a bounded structural distortion. Evaluated in both simulation and physical hardware experiments using Crazyflie 2.0 quadrotors\, TOLD significantly reduces formation distortion. OGF achieves a 62% reduction and OExpGF over a 31.4% reduction in median formation distortion compared to static interaction topologies in hardware experiments. \nOverall\, this thesis develops Distributed Artificial Intelligence Technology (DAITy) for robotic swarms from an interpretable online learning perspective\, seamlessly connecting collective information to decentralized situational awareness and decision control. Extensive evaluations across theoretical domains\, high-fidelity simulations\, and real-world hardware testbeds confirm the effectiveness and practical applicability of the proposed frameworks in unstructured and dynamically evolving situations. \nSpeaker: Shubhankar Gupta \nResearch Supervisor: Prof. Suresh Sundaram \n  \nTeams Meeting Link: Join: https://teams.microsoft.com/meet/48118742709693?p=5x8mXnmrvKS0j3tx9g\nMeeting ID: 481 187 427 096 93\nPasscode: 9JQ6Tg2d
URL:https://aero.iisc.ac.in/event/ph-d-engg-distributed-artificial-intelligence-technology-for-robotic-swarms-an-interpretable-online-learning-perspective/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/06/Shubhankar.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260623T110000
DTEND;TZID=Asia/Kolkata:20260623T130000
DTSTAMP:20260828T231309
CREATED:20260622T043524Z
LAST-MODIFIED:20260622T145229Z
UID:10000131-1782212400-1782219600@aero.iisc.ac.in
SUMMARY:AE Seminar by Dr Sri Prakash Sarathy\, Northrop Grumman
DESCRIPTION:AI in general and Agentic AI Frameworks in particular have begun to appear in safety critical and mission critical application of autonomous systems. Assurance of their behavior lags behind in terms of principles\, tools and engineering practice. In this presentation I will cover some emerging approaches that are both powerful and practical\, and easily understood and implemented by average engineering graduate. This is extremely important since assuring systems with AI requires a holistic approach starting from the systems design engineering all the way to implementation\, deployment and maintenance. I present some of the more advanced research methods applicable to autonomous aircraft systems.\n\nSpeaker: Dr. Prakash Sarathy\n\nBiography :\n\nDr. Prakash Sarathy is the Chief Engineer in the areas of advanced autonomy\, cyber assurance\, and systems engineering\, within the Research and Development division of NGAS. He has over 30 years of experience in various aspects of aerospace engineering\, providing technical and project/program management and oversight for advanced technology programs requiring accelerated risk burn down and rapid maturation. His technical expertise includes software for autonomous systems\, behavior assurance for safety and security of advanced vehicle configurations\, integration of hardware and software components in complex multi-physics application domains. This software engineering expertise coupled with his in-depth experience in linear and nonlinear dynamics of vehicle systems\, applied to guidance\, navigation and control of aircraft\, spacecraft and robots as well as of real-time and embedded simulations\, high fidelity modeling\, implementation\, VV&A and testing\, provide an excellent framework for the challenges of next generation autonomous aircraft systems and their assurance. He has provided technical and project/program management and oversight for advanced technology programs ( RTCF\, DARPA/OFW and USN/N-UCAS) requiring accelerated risk burn down and rapid maturation. He is experienced in many facets of hardware\, software and systems engineering process and practice as applied to R&D as well as production software across many application verticals. Expertise in SCM\, SQA\,  agile development\,  re-engineering and testing. He has deep expertise in linear and nonlinear dynamics of vehicle systems\, including flexible multi-vehicle interactions with particular emphasis to real-time simulation of vehicles.\, as well as guidance\, navigation and control of aircraft\, spacecraft and robots\, including flight mechanics\, handling qualities and aero-elasticity. He has spearheaded flight software safety in mixed critical domains under the AFRL MCAR program\, and  overseen software development under the DARPA/OFW (X-plane)\, DARPA/HURT and USN/UCAS-D programs.
URL:https://aero.iisc.ac.in/event/ae-seminar-by-dr-sri-prakash-sarathy-northrop-grumman/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/06/Dr-Sri-Prakash-Sarathy.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260624T113000
DTEND;TZID=Asia/Kolkata:20260624T130000
DTSTAMP:20260828T231309
CREATED:20260622T045426Z
LAST-MODIFIED:20260622T151648Z
UID:10000132-1782300600-1782306000@aero.iisc.ac.in
SUMMARY:From Pilot Workload to Adverse Couplings: Understanding Human–Vehicle Interactions in Challenging Rotorcraft Operations
DESCRIPTION:As civil and military aircraft evolve toward increasingly complex designs and intelligent systems\, understanding pilot–vehicle interactions and their impact on safety and performance remains essential. Rotorcraft shipboard landing is among the most demanding flight operations\, requiring pilots to contend with degraded and rapidly changing visual cues\, deck motion\, and environmental disturbances\, often resulting in elevated workload. Yet\, pilot workload is traditionally assessed using subjective rating scales that interrupt operations\, provide only post-task measures\, and offer limited insight into how pilot effort evolves during a mission. This seminar presents research on objective pilot workload assessment using signal processing of pilot inceptor activity\, with helicopter shipboard landing serving as a representative high-workload task. The talk also examines adverse aircraft/rotorcraft–pilot couplings\, including pilot-induced and pilot-assisted oscillations\, which are difficult to predict\, can arise from nonlinear pilot–vehicle interactions\, and have the potential to compromise mission completion and flight safety. Methods for identifying and characterizing such coupling phenomena using pilot inceptor activity are discussed\, together with their implications for aircraft dynamics and control\, pilot assistance technologies\, and autonomous aerial vehicles. \nSpeaker: Dr. Vinodhini Comandur \nBiography:\nVinodhini Comandur is an Assistant Teaching Professor at the University of Colorado Boulder. She completed her PhD in Aerospace Engineering at the Georgia Institute of Technology in 2025. Her research interests lie in flight dynamics and control\, handling qualities\, human factors engineering\, and the development of autonomy-enabled capabilities for rotorcraft applications. She received her B.Tech. (Hons.) in Mechanical Engineering from the IIT Kharagpur in 2014\, her M.Tech. in Aerospace Engineering from the IIT Kanpur in 2016\, and her M.S. in Computational Science and Engineering from the Georgia Institute of Technology in 2025.
URL:https://aero.iisc.ac.in/event/from-pilot-workload-to-adverse-couplings-understanding-human-vehicle-interactions-in-challenging-rotorcraft-operations/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/06/Vinodhini-Comandur.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260624T150000
DTEND;TZID=Asia/Kolkata:20260624T170000
DTSTAMP:20260828T231309
CREATED:20260623T083955Z
LAST-MODIFIED:20260712T055011Z
UID:10000133-1782313200-1782320400@aero.iisc.ac.in
SUMMARY:MTech(Res): Characterization of Turbulent Spots near the onset of Transition in a Flat-plate Boundary Layer
DESCRIPTION:Boundary layer (BL) transition to turbulence occurs through the inception\, growth\, and merging of turbulent spots. Understanding these spots is vital for predicting aerodynamic performance in disturbance-dominated environments like gas turbines.\n\nHowever\, conventional spot identification has been limited by subjective\, manual thresholding. The first phase of this work introduces a novel\, threshold-free demarcation scheme combining a Pre-Multiplied Wavelet Energy (PMWE) detector—scaled with BL thickness and log-transformed to establish an objective criterion for detection— along with a Gaussian Mixture Model (GMM) as a classifier. The framework generates wall-normal and spanwise variations of intermittency to a good accuracy and is validated across Direct Numerical Simulation (DNS) and wind-tunnel datasets for multiple transition scenarios.\n\n​Using this detection framework\, we track the precursors of spots (velocity spikes) upstream. Analysis of the instantaneous energetics of the pre-transitional region reveals that while stable streaks exhibit positive production within their cores and weak dissipation along their interfaces\, localized streak breakdown is consistently preceded by a distinct patch of negative turbulence production (a counter-gradient energy transfer back to the mean flow) co-located with intense dissipation. Crucially\, velocity spikes lacking this negative production signature fail to convert into downstream turbulent spots. Thus the presence of negative production appears to be a necessary precursor to spot inception.\n\n​Furthermore\, we evaluate the statistics near the transition front using a new intermittency-based conditioning method. While conventional conditional averaging at fixed streamwise locations obscures the physics by blending spots at different developmental stages\, conditioning along surfaces of constant local intermittency aligns spots at equivalent evolutionary stages much better. This approach reveals that as the transition onset is approached from downstream\, local turbulence production and dissipation increase manyfold. The sharp rise in these quantities signifies an abrupt\, highly localized energy transfer during the inception of spots\, occurring even while the corresponding skin friction coefficient remains close to laminar values.\n\nSpeaker : Yash Naiwar\n\nResearch Supervisor : Sourabh Suhas Diwan
URL:https://aero.iisc.ac.in/event/mtechres-characterization-of-turbulent-spots-near-the-onset-of-transition-in-a-flat-plate-boundary-layer/
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/07/Yash.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260706T093000
DTEND;TZID=Asia/Kolkata:20260706T180000
DTSTAMP:20260828T231309
CREATED:20260629T060709Z
LAST-MODIFIED:20260802T091747Z
UID:10000134-1783330200-1783360800@aero.iisc.ac.in
SUMMARY:Workshop on "Signal Processing for High-Precision Navigation and Surveillance"
DESCRIPTION:Dear All\, \nThe Dept. of Aerospace Engineering\, in collaboration with Centre for Continuing Education is conducting a one-week tutorial workshop on “Signal Processing for High-Precision Navigation and Surveillance”\, during 06 – 11 July 2026. \nBased on some requests\, the due date of Early Registration has been extended to 28-06-2026 (Sunday). \nMore details can be found here: https://cce.iisc.ac.in/self-support-courses/signal-processing-for-high-precision-navigation-and-surveillance/ \nLimited seats are still available on first come\, first serve basis. There is substantial reduction (60%) of course fee for IISc students and project staff (Note: Research Associates and Postdocs come under Professional category).
URL:https://aero.iisc.ac.in/event/workshop-on-signal-processing-for-high-precision-navigation-and-surveillance/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/06/ai.jpeg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260709T150000
DTEND;TZID=Asia/Kolkata:20260709T170000
DTSTAMP:20260828T231309
CREATED:20260707T091903Z
LAST-MODIFIED:20260712T062534Z
UID:10000135-1783609200-1783616400@aero.iisc.ac.in
SUMMARY:Characterizing Dynamic Response of Structures and Materials under Extreme Loading Environments
DESCRIPTION:Protective structures and vessels used in marine and defense applications are increasingly required to withstand extreme dynamic loading caused by explosions in air and underwater. Designing lightweight yet resilient structures demands a fundamental understanding of shock-wave interactions with materials\, structural geometry\, and the surrounding medium. This seminar presents a series of experimental investigations that progressively examine these aspects using advanced diagnostics.\nThe seminar begins with a comparative study of circular composite plates subjected to planar shock loading in air and underwater. The experiments reveal how the loading medium governs structural deformation\, vibration characteristics\, and cavitation-induced secondary loading\, providing insights into shock–structure interaction.\nNext\, the influence of structural geometry is examined through blast experiments on curved polymeric sandwich composite panels. The effects of curvature and boundary conditions on structural response are investigated\, demonstrating that geometric tailoring can significantly enhance blast resistance and modify damage mechanisms.\nThe seminar concludes by exploring the complex interaction between near-field underwater explosions and sandwich composite structures. Experimental observations capture the coupled effects of shock waves\, gas-bubble oscillations\, surface cavitation\, and structural deformation. The results highlight the influence of explosive stand-off distance and core density on impulse transfer\, cavitation dynamics\, and failure mechanisms\, providing valuable insights into fluid–structure interaction under extreme underwater loading.\nTogether\, these experimental studies advance the understanding of the dynamic response of composite structures under extreme loading and provide guidance for the design of resilient lightweight structures for naval\, offshore\, and protective engineering applications.\n\nSpeaker: Dr. Akshay Pandey\n\nBiography:\nDr. Akash Pandey is currently working as a Research Associate at the University of Cambridge. He previously worked at the Indian Space Research Organisation (ISRO) before earning his Ph.D. from the University of Rhode Island. His research focuses on the dynamic response of structures and materials subjected to extreme loading conditions\, including blast and impact
URL:https://aero.iisc.ac.in/event/characterizing-dynamic-response-of-structures-and-materials-under-extreme-loading-environments/
LOCATION:Online
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/07/Dr.-Akshay-Pandey.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260716T150000
DTEND;TZID=Asia/Kolkata:20260716T170000
DTSTAMP:20260828T231309
CREATED:20260708T083450Z
LAST-MODIFIED:20260712T064148Z
UID:10000136-1784214000-1784221200@aero.iisc.ac.in
SUMMARY:FROM MOTION PLANNING TO MULTI-ROBOT AUTONOMY IN CONSTRAINED AND DISCONNECTED ENVIRONMENTS
DESCRIPTION:Autonomous robots operating in challenging environments must make reliable decisions under geometric\, dynamic\, and environmental constraints. In such settings\, motion planning plays a central role in enabling robots to move safely and efficiently through cluttered\, narrow\, disconnected or uncertain spaces\, while balancing feasibility\, robustness\, and computational efficiency. \nThis talk will focus on motion planning for quadrotors flight through constrained regions such as narrow windows and cluttered spaces. In the later part of the talk\, I will briefly broaden the discussion to autonomy problems beyond single-robot flight\, including hierarchical coverage path planning in disconnected regions and terrain-aware balanced area allocation for heterogeneous multi-robot systems. Together\, these works highlight how planning methods must scale from vehicle-level motion generation to higher-level coordination and task allocation in challenging operational environments. \nSpeaker: Dr. Saurabh Upadhyay \nBiography: \nSaurabh Upadhyay received B.E. degree from SSGMCE\, Shegaon in 2009\, M.Tech. degree from IIT Guwahati in 2012\, and Ph.D. degree from IISc Bengaluru in 2018. He is a Lecturer in Space Engineering at Cranfield University\, UK. His research interests lie in mobile robots for extreme environments\, with special focus on low onboard resources decision making and ISRU-enabled robot design. He has received A.K. Rao best PhD thesis medal 2018 in Aerospace Engineering at IISc Bengaluru\, and he is endorsed as a potential leader/exceptional promise by Royal Academy of Engineering in 2021. He is an IEEE senior member\, lifetime AIAA Senior member\, and fellow of HEA.
URL:https://aero.iisc.ac.in/event/from-motion-planning-to-multi-robot-autonomy-in-constrained-and-disconnected-environments/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/07/Saurabh-Upadhyay-Talk.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260724T113000
DTEND;TZID=Asia/Kolkata:20260724T130000
DTSTAMP:20260828T231309
CREATED:20260723T070319Z
LAST-MODIFIED:20260802T100840Z
UID:10000139-1784892600-1784898000@aero.iisc.ac.in
SUMMARY:Modelling the response of Turbulent CH4-Air premixed flame using Resolvent Analysis
DESCRIPTION:An understanding of the flame transfer function (FTF) is essential for predicting the onset of combustion instabilities in gas turbine combustors\, where flow oscillations excited by acoustic forcing drive burning area and heat-release oscillations that can couple unfavourably with combustor acoustic modes. The heatrelease response is expensive to characterize directly through time resolved simulation\, motivating reduced order approaches that operate on a single time-averaged mean flow. In the present work\, we develop and critically assess a resolvent analysis (RA) based reduced order model for the FTF of a turbulent premixed methane air round jet flame (φ=0.8\, T_u=800 K\, Re≈1500)\, with the time-averaged base flow obtained from explicit-filtering large eddy simulation (EFLES) of the unforced flame. Two aspects of the RA formulation are examined systematically: the passive versus active treatment of the flame i.e.\, whether coherent reaction rate fluctuations are dropped or retained in the linearised species/energy equations and the choice of heatrelease rate closure across four models of increasing physical detail (a global Arrhenius model\, ARR-A; a Bayesian calibrated modified Arrhenius model with a cold-boundary correction\, ARR-B; and global and local Eddy Break-Up models\, EBUG and EBUL). RA-predicted FTF gain and phase are validated against harmonically forced LES over St=[0.2\,1.2]\, and the spatial structure of the leading RA response modes is compared against SPOD modes extracted from the same forced LES. FTF phase is recovered robustly by all four models up to St≈0.8\, since the leading velocity response mode and hence the convective phase speed governing flame surface wrinkling is set almost entirely by the mean vorticity and density field and shows weak dependence on the heatrelease closure. FTF gain is far more model dependent: the passive ARR-B model gives the best overall quantitative match to LES\, with excellent agreement at St=0.2 where non-linear flame tip pocket shedding is negligible\, while both EBU models underpredict gain across the full St range because their reaction rate is a function of progress variable and density alone\, giving identically zero sensitivity to temperature and fuel mass fraction fluctuations. The resolvent gain spectrum collapses toward strongly low rank behaviour with increasing St a single mode pair recovers 99% of the response for St≥0.6\, while three mode pairs are needed at St=0.2 and the Arrhenius-type models produce systematically higher gains than the EBU models owing to their spatially extended sensitivity field. Switching from the passive to the active formulation leaves the velocity response essentially unchanged but qualitatively alters the thermochemical response: temperature and species fluctuations\, which propagate downstream as undamped travelling waves in the passive case\, decay beyond the flame brush in the active case\, in closer qualitative agreement with the LES SPOD modes. This improved qualitative fidelity does not\, however\, translate into better FTF gain prediction the active formulation degrades gain agreement for every model examined\, a result traced to the single free parameter in each heatrelease closure being calibrated only against the mean heatrelease field\, with no constraint on the local dynamic sensitivities that the active formulation feeds back into the linear operator. The overall picture that emerges is that RA provides a reliable and computationally efficient framework for predicting FTF in axisymmetric premixed-flame configurations. The results further establish a clear pathway toward improved quantitative gain prediction through reaction-rate closures that represent the local dynamic sensitivities of the flame more faithfully\, enabling increasingly predictive low-order models from time-averaged base flows. Further work is needed to improve the active flame approach by developing reaction rate closures that capture both the mean heatrelease field and the local dynamic sensitivities governing flame response feedback. \n  \nSpeaker : SATYAM CHAUHAN \nResearch Supervisor :  Santosh Hemchandra
URL:https://aero.iisc.ac.in/event/modelling-the-response-of-turbulent-ch4-air-premixed-flame-using-resolvent-analysis/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/SATYAM.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260727T113000
DTEND;TZID=Asia/Kolkata:20260727T130000
DTSTAMP:20260828T231309
CREATED:20260723T053755Z
LAST-MODIFIED:20260802T095511Z
UID:10000138-1785151800-1785157200@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Wave Propagation in Small Scale Structure Modelled With Nonlocal Continuum Theory
DESCRIPTION:This thesis develops analytical and computational frameworks for studying static and dynamic behaviour in nonlocal elastic structures\, focusing on wave propagation\, stress localization\, and guided-wave phenomena at micro- and nano-scales\, where size-dependent effects fall outside classical continuum mechanics. Eringen’s differential nonlocal elasticity theory and higher-order continuum formulations are used to capture these small-scale interactions.\nThe work first examines plane-stress problems with geometric singularities (cracks\, circular and elliptical holes) using a finite element formulation based on a second-order stress-gradient nonlocal model. While the static displacement equation stays independent of the nonlocal length-scale parameter\, nonlocal effects become significant near large displacement gradients and stress concentrations. Unlike classical elasticity\, which predicts singular stresses at crack tips\, the nonlocal formulation produces bounded stress fields. Dynamically\, nonlocal interactions primarily affect inertia terms\, altering transient response rather than stiffness.\nTo handle high-frequency wave propagation efficiently\, a spectral super-element method combines wavenumber-frequency domain spectral elements with conventional finite elements\, enabling accurate modelling of cracks and holes while retaining exact wave representation in uniform regions. This eliminates classical stress singularities and supports applications such as MEMS analysis. A related hybrid spectral-finite element framework further restricts finite element use to defect regions\, cutting computational cost while accurately predicting stress concentration and intensity factors\, validated against commercial FE software for plates with holes and cracks.\nThe second major focus is guided-wave behaviour in elastic waveguides and plates under nonlocal constitutive laws. Analytical Lamb-wave dispersion relations are derived via Helmholtz decomposition with traction-free boundary conditions. Using Eringen’s second-order nonlocal model and strain-gradient theory\, the study reveals non-classical effects\, including wavenumber saturation\, modified cut-off frequencies\, and escape frequencies\, in symmetric and antisymmetric Lamb modes. Comparisons show that simpler one-dimensional models (Mindlin-Herrmann rod\, Timoshenko beam) can reproduce key guided-wave characteristics of the full two-dimensional nonlocal model.\nFinally\, a coupling framework uses local models away from defects and nonlocal elasticity near cracks. Since such coupling typically causes spurious reflections at domain interfaces\, a novel transition-zone strategy is proposed to suppress these artifacts. Implemented in a frequency-domain spectral element framework\, it is applied to waveguides with horizontal and vertical through-width cracks\, achieving accurate\, efficient\, and physically consistent wave analysis.\nOverall\, this thesis establishes a unified framework for nonlocal wave propagation and stress analysis in structures with discontinuities\, offering practical tools for wave-based sensing\, structural health monitoring\, ultrasonic nondestructive evaluation\, and micro- and nano-scale structural design. \n  \nSpeaker :  Ajeet Kumar Yadav \nResearch Supervisor : Prof S. Gopalakrishnan
URL:https://aero.iisc.ac.in/event/ph-d-engg-wave-propagation-in-small-scale-structure-modelled-with-nonlocal-continuum-theory/
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Ajeet.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260731T120000
DTEND;TZID=Asia/Kolkata:20260731T130000
DTSTAMP:20260828T231309
CREATED:20260724T101000Z
LAST-MODIFIED:20260802T104845Z
UID:10000140-1785499200-1785502800@aero.iisc.ac.in
SUMMARY:AstroNav: Autonomy for Navigating Deep Space and Beyond
DESCRIPTION:Autonomous navigation is becoming a critical capability for modern deep space exploration\, planetary defense\, and commercial space ventures. Traditional spacecraft navigation relies heavily on ground-based radio contact to collect two-way radiometric Doppler and range measurements. However\, this structural dependency introduces significant communication latency and places a heavy burden on oversubscribed ground antenna networks. For cutting-edge applications—such as navigating through the active plumes of Enceladus or executing precise planetary defense maneuvers like ion beam deflection and gravity tractoring—the turnaround time of ground-based loops is simply too slow. Furthermore\, legacy onboard solutions present severe limitations in modularity or applicability.\n\nThis talk addresses these challenges by highlighting the critical need for autonomous navigation within the rapidly expanding modern space economy. We begin with a historical review of autonomous deep space navigation\, tracking its evolution from the pioneering AutoNav software developed by NASA’s Jet Propulsion Laboratory (JPL) for Deep Space 1 through its critical successes on the Stardust and Deep Impact comet missions. The presentation then provides a comprehensive overview of AstroNav\, the next-generation successor designed to overcome legacy limitations. We will detail the specific architectural and algorithmic augmentations that advance AstroNav far beyond past technologies\, including its modular\, plug-and-play capability to ingest multi-source data. Finally\, we will present the concept of operations for AstroNav’s upcoming flight technology demonstration payload integrated onto the CAPSTONE-2 spacecraft\, scheduled for launch in mid-2027.\n\nSpeaker : Dr Swati Mohan\n\nBiography:\nDr Swati Mohan was born in Bengaluru\, India\, and emigrated to the United States of America with her parents when she was one year old. Dr. Mohan attended Cornell University and received her B.S. in 2004 in Mechanical and Aerospace Engineering.  After a brief stint working at NASA Jet Propulsion Laboratory on the Cassini mission\, in 2004-2005\, she went on to graduate school at Massachusetts Institute of Technology (MIT) in the Aeronautics/Astronautics department.  She rejoined NASA’s Jet Propulsion Laboratory in 2010 in the Guidance\, Navigation\, and Controls section.  Since then\, Swati has worked on a number of missions\, such as GRAIL\, OCO-3\, Mars 2020 Perseverance\, and Psyche. She is best known for being the voice of Entry\, Descent\, and Landing for Perseverance’s landing on February 18\, 2021.  She was the GNC lead and a Chief Engineer for the Psyche mission\, which launched on October 13\, 2023.  After launching Psyche\, Swati has transitioned to the Mars Sample Return mission.  She first served as Chief Engineer for the Mars Launch System\, then later as the Descent Command and Control Lead.  She is currently the Project Manager for AstroNav\, an autonomous celestial navigation payload.
URL:https://aero.iisc.ac.in/event/astronav-autonomy-for-navigating-deep-space-and-beyond/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Swati.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260804T150000
DTEND;TZID=Asia/Kolkata:20260804T170000
DTSTAMP:20260828T231309
CREATED:20260803T045933Z
LAST-MODIFIED:20260804T105424Z
UID:10000143-1785855600-1785862800@aero.iisc.ac.in
SUMMARY:Multiphase Reactive Flows: From Dust Explosions to Metal-Fueled Detonations
DESCRIPTION:. \nExplosions in coal mines\, metal-processing facilities\, and other industrial settings occur with alarming regularity\, while reactive metal particles are being considered for energy-storage and propulsion applications. Despite a long history of research and its importance to safety and propulsion applications\, the physical mechanisms that govern the ignition\, combustion\, and detonation of reactive particles remain relatively unknown. Basic questions such as “How do particle size and thermal radiation affect dust-explosion propagation?”\, “What mechanisms govern the ignition and combustion of shock-dispersed metal powders?”\, and “How can reactive particles modify or sustain detonation waves?” remain unanswered. This presentation will discuss an ongoing numerical simulation effort aimed at answering these and other fundamental questions. This problem is addressed by solving a set of equations that couples a fully compressible reacting gas to a granular multiphase model that accounts for particle motion\, interphase drag and heat transfer\, and particle combustion. The results of these simulations indicate that shock propagation\, particle dispersal\, ignition\, combustion\, and thermal radiation are tightly coupled in a highly dynamic process. Results discussing the influence of particle diameter and thermal radiation on layered coal-dust explosions and the ignition and combustion of TNT-dispersed aluminum powder will be discussed. The presentation will close by discussing recent work exploring hybrid aluminum–hydrogen–air detonations\, including the role of particle size in extending detonation limits and modifying detonation structure. \n  \nSpeaker: Dr. Guhathakurta \nBiography:  \nDr. Guhathakurta received an M.Sc. degree in Physics from the Indian Institute of Technology Delhi\, and M.S. and Ph.D. degrees in Aerospace Engineering from the University of Florida. He subsequently held a postdoctoral appointment at Eindhoven University of Technology in the Netherlands. Dr. Guhathakurta is currently an Assistant Professor in the Department of Aerospace Engineering at Texas A&M University. His research focuses on a wide range of topics in multiphase reactive flows\, combustion\, and numerical simulation\, including dust explosions\, hybrid detonations\, thermal-radiation effects\, metal-particle combustion\, and high-speed propulsion.
URL:https://aero.iisc.ac.in/event/multiphase-reactive-flows-from-dust-explosions-to-metal-fueled-detonations/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Dr-RD-Seminar-Aug-6.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260805T110000
DTEND;TZID=Asia/Kolkata:20260805T130000
DTSTAMP:20260828T231309
CREATED:20260728T061746Z
LAST-MODIFIED:20260802T102832Z
UID:10000141-1785927600-1785934800@aero.iisc.ac.in
SUMMARY:MTech(Res) : Design of an Ex-Situ Gas Sampling Layout with Various Probes and Their Performance Assessment for Accurate Emission Measurements
DESCRIPTION:Chemical kinetic mechanism development and validation require quantitative species data from canonical flames. Burner-stabilized pre -mixed flames provide a stationary post-flame region directly comparable to one-dimensional kinetic simulations. Ex-situ gas sampling delivers absolute CO and NO mole fractions from this region. The extraction step introduces two coupled biases. Reactions can continue inside the probe\, and the probe can perturb the flame upstream of the inlet. This thesis develops a coordinated ex-situ sampling framework for atmospheric McKenna burner-stabilized CH₄/air flames. The framework combines a sampling and dilution layout\, five sampling probes\, and a staged correction methodology. The measurements span fuel-lean to fuel-rich flames at three heights above the burner. The sampling and dilution layout is one of the principal contributions of the present work. The complete layout was designed and assembled in this work to adapt a portable gas analyzer (PG-350) for laboratory flame diagnostics. The PG-350 is built for stationary-source emissions monitoring rather than laboratory flame research. The design repurposes this industrial emissions instrument for high-precision species measurement in flames. The adapted instrument serves fundamental academic flame research. The layout delivers a conditioned\, metered\, and range-compatible sample to the analyzer. A vacuum pump extracts the sample using a sampling probe and drives it through the line. Two water-cooled drain separators\, designed and fabricated in this work\, remove the post-flame moisture. An Alicat mass flow meter measures the conditioned sample flow rate. A controlled N₂ dilution arrangement extends the CO measurement range beyond the analyzer’s full scale for the rich flames. Five sampling probes represent four reaction-quenching strategies. The aerodynamic-quench (AQ) probe was designed using a one-dimensional gas-dynamics model developed in this work. A brute-force screening selected its geometry against the pump and analyser constraints. The water-cooled (WC)\, pressure-quench (PQ)\, and uncooled probes were sized using non-reacting two-dimensional axisymmetric CFD. The uncooled-metal (UC-M) probe serves as a hot-wall reference. The uncooled-quartz (UC-Q) probe isolates the wall-material effect under the same geometry. Each probe was assessed experimentally and through two-dimensional probe-resolved reacting CFD in ANSYS Fluent. A residence-time method quantified the probe-induced upstream shift of the sampling location for the designed probes. A staged correction methodology recovers the sampled-gas composition from the conditioned analyzer reading. It corrects the mass flow meter reading for its gas-property mismatch. It then removes the imposed dilution and restores the moisture removed during conditioning. An independent route back-calculates the dilution ratio from paired CO₂ measurements. The methodology propagates the input uncertainties through the correction chain using the GUM framework. Reported values quote the expanded uncertainty on the corrected species. The corrected CO and NO were evaluated against a one-dimensional chemical kinetic simulation of the unperturbed flame. The comparison accounts for the probe-induced upstream shift of the sampling location. Each designed probe draws its sample from a location displaced toward the burner relative to its tip. The three designed probes were compared against the reference at their displaced sampling locations. The pressure-quench probe is the most consistent for both species. The water-cooled probe is a close alternative. The vacuum pump performance degraded due to moisture condensation in the pump head. Therefore\, it held the AQ suction above its design value throughout the campaign. The AQ probe is therefore off-design and cannot be ranked on equal terms. The uncooled-metal probe shows a large NO deficit in the rich flames from hot-wall surface reactions. The uncooled-quartz probe isolates the metal wall as the origin of this deficit. These rankings measure consistency with the kinetic reference rather than absolute accuracy. This work delivers outcomes of broader use to the combustion community. The framework offers documented guidelines to the community for ex-situ sampling experiments. It provides a comprehensive assessment of how each quenching strategy performs and which probe suits a given measurement. The corrected CO and NO data are suitable for chemical kinetic mechanism development and validation. Many detailed chemistry mechanisms exist\, yet reacting CFD of practical combustion devices requires reduced mechanisms that reproduce the target species profiles. The present setup allows reduced mechanisms to be validated quickly across flames spanning fuel-lean to fuel-rich conditions. A validated reduced mechanism can then support detailed CFD analysis of practical combustion systems. \n  \nSpeaker :  SARVAGYA SHARMA \nResearch Supervisor :  Irfan Ahmed Mulla
URL:https://aero.iisc.ac.in/event/mtechres-design-of-an-ex-situ-gas-sampling-layout-with-various-probes-and-their-performance-assessment-for-accurate-emission-measurements/
LOCATION:STC Conference Hall\, Ground Floor\, Department of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/SARVAGYA.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260806T113000
DTEND;TZID=Asia/Kolkata:20260806T130000
DTSTAMP:20260828T231309
CREATED:20260717T092701Z
LAST-MODIFIED:20260802T105215Z
UID:10000137-1786015800-1786021200@aero.iisc.ac.in
SUMMARY:Ph .D.(Engg.): Explicit Filtering LES of turbulent swirling flows and multi-regime hydrogen flames
DESCRIPTION:The need to decarbonize power generation and aviation has established hydrogen as a promising fuel for next generation gas turbine combustion systems. However\, its high chemical reactivity significantly increases the propensity for autoignition and flashback under lean premixed conditions commonly used in hydrocarbon combustion systems. New combustor concepts based on direct fuel injection address these problems but typically produce lifted flames. These types of flames exhibit multi-regime combustion\, in which premixed and non-premixed combustion regions co-exist within highly turbulent swirling flow fields. Accurate numerical prediction of such reacting flows remains a major challenge as traditional models developed for hydrocarbon flames often fail to reliably predict the stabilization and combustion characteristics of multi-regime hydrogen flames. This thesis proposes a regime-sensitive combustion model using the thickened flame approach to extend the explicit filtering large eddy simulation (EFLES) method for computations of high Reynolds number (Re) reacting flows. A combustion regime index (CI) is defined based on the alignment between the gradients of mixture fraction and oxygen mass fraction to distinguish between premixed and non-premixed regions. The flame thickening treatment is applied selectively in premixed regions only. The model is implemented within an in-house high-order finite-difference flow solver that employs structured multi-block overlapping meshes to represent complicated geometries encountered in practical combustion systems. The predictive capability of the overall numerical methodology is systematically assessed through a series of increasingly complex flow configurations relevant to swirl-stabilized hydrogen combustors. The first case corresponds to an isothermal (Re ~ 27000) flow in the PRECCINSTA single nozzle swirl combustor. EFLES solutions show excellent agreement with the experimental data for flow field statistics and shape of the vortex breakdown bubble. Spectral proper orthogonal decomposition applied on time resolved velocity fields confirms that the EFLES method accurately reproduces the broadband turbulence structures and the coherent\, narrow band\, self-excited precessing vortex core oscillation. The combustion model performance is then evaluated using a canonical lifted slot jet flame configuration\, comprising a nitrogen diluted hydrogen slot jet of Re=8000 at 400 K issuing into a co-flow of heated air at 850 K. Entrainment of air into the jet core results in a stratified rich premixed flame alongside the primary non-premixed flame branch. The LES predicted flame lift-off height and flow field statistics are in good agreement with companion direct numerical simulation (DNS) results. Differences between LES and DNS solutions are small in premixed flame regions but increase with mesh spacing in non-premixed flame regions. The CI field is shown to clearly distinguish the two flame branches. This result is further validated a-posteriori using chemically explosive mode analysis (CEMA). Combined with EFLES\, the combustion model accurately predicts mixture fraction conditioned thermochemical statistics\, combustion mode distributions and the downstream evolution of premixed and diffusion flame branches in the lifted slot jet hydrogen flame. Finally\, a turbulent lifted hydrogen flame in the dual-swirl HYLON burner is investigated as a practical test case. The time-averaged mean flame shape and liftoff height is well captured in the LES solution. Good agreement is obtained between LES predictions and experimental measurements for statistics of velocity\, temperature\, and major-species mole fractions. CEMA reveals that a partially premixed flame branch is formed along the inner shear layer due to entrainment of hydrogen into the high-velocity annular air stream. The central diffusion flame branch is located within the vortex breakdown bubble between the fuel jet and the recirculating lean combustion products. The distribution of key thermochemical variables in mixture fraction space is also analyzed to characterize the two flame branches. Overall\, the results demonstrate that the proposed multi-regime thickened flame model\, coupled with explicit filtering LES provides a robust framework for high-fidelity LES of turbulent hydrogen flames. The methodology reproduces turbulent flow features\, flame stabilization and mixed combustion regimes across canonical and practical configurations. These results make the case for evaluating the performance of EFLES at higher operating pressures towards realizing a reliable computational engineering method for the design and analysis of future hydrogen gas turbine combustors. \nSpeaker :  ANINDYA DATTA \nResearch supervisor : Santosh Hemchandra
URL:https://aero.iisc.ac.in/event/ph-dengg-colloquium/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/ANINDYA.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260807T110000
DTEND;TZID=Asia/Kolkata:20260807T130000
DTSTAMP:20260828T231309
CREATED:20260804T053733Z
LAST-MODIFIED:20260811T060311Z
UID:10000144-1786100400-1786107600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Aerodynamics and Stability of a Generic Tailless UAV in Ground Effect
DESCRIPTION:Tailless UAVs are stealthy\, high-subsonic configurations used for deep penetration into contested airspace. These configurations have wing with moderate leading edge sweep angle with no definite fuselage and lack both horizontal tail and vertical tail which makes the aerodynamics of these configurations very unique. The increase in autonomous UAVs in recent times have led to renewed interest in this class of configurations. Autonomous take-off and landing of tailless UAVs are complex technologies that require a detailed understanding of the underlying aerodynamic flow physics. The current literature on the ground effects focusses mainly on conventional configuration or high swept delta wings.  This work focusses on understanding the aerodynamic behavior of a typical tailless UAV near the ground and its influence on the stability characteristics. RANS CFD analysis is carried out at different ground heights\, angle of attack and side slip angle. Studies are also carried to understand the effect of roll orientation effect on the ground effects. The  effect of ground on the elevon behavior near the ground are also brought out. Unsteady CFD Analysis are conducted for different sink rates and pitch angles and compared with Static Ground Effects.\n The lift coefficient under Steady Ground Effects was observed to decrease near the ground at lower angle of attack and increase at high angle of attack. The region between the ground and aircraft acts like a venturi at low angle of attack. At high angle of attack\, ramming effect is observed due to increase in the pressure on the bottom surface. The drag coefficient does not change at lower angle of attack whereas significant reduction is observed at higher angle of attack due to the reduction in the induced drag.  The UAV shows a reduction in directional stability near the ground. The rolling moment due to side slip angle shows a stable behavior near the ground.  The roll orientation of the UAVs impacts the rolling moment behavior near the ground providing increased rolling moment near the ground which has a tendency to counter the direction of the roll.  Unsteady CFD Analysis is conducted for different sink rates and pitch angles and compared with Static Ground Effects which shows significant change especially at lower pitch angles. \n The aerodynamic changes introduced by the  presence of ground impacts the Stability of the UAV significantly.  The Stability  changes are particularly important for the tailless UAV as it is neutrally stable in the longitudinal and directional plane. A increase in Static Margin of 0.5% is observed at the lowest ground  height  (h/b = 0.15). There is also marginal increase in weather cock stability (Cnβ)  and roll stability (Clβ) at high angle of attack near the ground. The dynamics of the tailless UAV near the ground has interesting behavior near the ground. The short period mode has stabilizing behavior near the ground whereas the Dutch roll tends to be slightly unstable near the ground. The roll orientation of the UAV seems to impact the Dutch roll mode changing from slightly unstable to a slightly stable behavior.  The aerodynamics and stability aspects are highly coupled for tailless UAV. The understanding of tailless UAV near the ground will be key for development of control schemes for robust take-off and landing of these Configurations. \n  \nSpeaker :  B Saravanan \nResearch Supervisor :  N Balakrishnan \n 
URL:https://aero.iisc.ac.in/event/aerodynamics-and-stability-of-a-generic-tailless-uav-in-ground-effect/
LOCATION:AE Conference Room \, AE 003
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Saravanan.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260810T110000
DTEND;TZID=Asia/Kolkata:20260810T130000
DTSTAMP:20260828T231309
CREATED:20260808T055603Z
LAST-MODIFIED:20260811T060138Z
UID:10000145-1786359600-1786366800@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg):Tonal acoustic radiation from turbulent subsonic jets
DESCRIPTION:Acoustic tones in the near field of a Mach 0.9\, Reynolds number 10^6 round jet are investigated using large-eddy simulations (LES) performed with the explicit filtering LES (EFLES) approach. The jet is issued into the ambient through a cylindrical nozzle. Pressure spectra at observer locations in the upstream direction reveal the presence of tones which are 15–20 dB more intense than the background turbulent mixing noise. Spectral Proper Orthogonal Decomposition (SPOD) of the pressure field in the near-nozzle region reveals two distinct categories of tones. The first category comprises tones whose frequency corresponds to high order radial and azimuthal ductmodes of the nozzle. Their spatial amplitude distribution revealed by SPOD at these frequencies show significant support within the nozzle as expected for the natural hard-wall duct modes. These duct modes are scattered at the nozzle lip and radiate in the upstream direction and explain the tonal radiation observed in the LES at their corresponding frequencies. This mechanism has been extensively studied using Wiener-Hopf models applied to a cylindrical vortex sheet (Munt\, 1977; Rienstra\, 2003; Samanta and Freund\, 2008). The second category of tones observed have frequencies that are not hard wall duct mode frequencises. Their spatial amplitude distribution revelaed by SPOD for these frequencies is characterized by significant support within the jet potential core. Empirical dispersion relations constructed from the LES suggest that these tones arise from resonance in the potential core due to coupling between the upstream-propagating guided jet mode (GJM) and the upstream- and downstream-propagating duct-like modes (Schmidt et al.\, 2017; Towne et al.\, 2017) near the upper cut-off frequency of the guided jet mode (Bogey\, 2021). However\, the mechanism by which tones radiate from the potential core has not yet been established. This motivates the theoretical investigation in this thesis that focuses on the dynamics of the guided jet mode and its interaction with the nozzle lip leading to tonal upstream acoustic radiation. The interaction between the GJM and the nozzle lip is analyzed using a Wiener–Hopf formulation with the jet modelled as a semi-infinite cylindrical vortex sheet and the nozzle with a vanishingly-thin sharp edge. When the GJMs are cut-on\, these solutions show that an incident GJM is reflected as a downstream-traveling soft-duct mode\, a scattered Kelvin–Helmholtz (K–H) mode and a transmitted upstream-traveling hard-wall duct mode. The reflective efficiency of GJM increases with frequency and is greatest near their upper cut-off frequency. This explains why tones associated with potential core resonance occur near the upper cut-off frequency of the GJM. In addition\, the GJM is scattered as acoustic waves to the far field\, primarily in the upstream direction. The scattered wavefronts are most intense along the outer nozzle wall. The scattered waves propagate to the far field where they generate distinctive directivity patterns that show excellent agreement with the LES-computed far-field directivity reported by Bogey (2021). These results provide a mechanistic explanation for how tones generated by potential core resonance radiate to the far field through scattering of the guided jet mode at the nozzle lip. Acoustic tones in the near field of a Mach 0.9\, Reynolds number 10^6 round jet are investigated using large-eddy simulations (LES) performed with the explicit filtering LES (EFLES) approach. The jet is issued into the ambient through a cylindrical nozzle. Pressure spectra at observer locations in the upstream direction reveal the presence of tones which are 15–20 dB more intense than the background turbulent mixing noise. Spectral Proper Orthogonal Decomposition (SPOD) of the pressure field in the near-nozzle region reveals two distinct categories of tones. The first category comprises tones whose frequency corresponds to high order radial and azimuthal ductmodes of the nozzle. Their spatial amplitude distribution revealed by SPOD at these frequencies show significant support within the nozzle as expected for the natural hard-wall duct modes. These duct modes are scattered at the nozzle lip and radiate in the upstream direction and explain the tonal radiation observed in the LES at their corresponding frequencies. This mechanism has been extensively studied using Wiener-Hopf models applied to a cylindrical vortex sheet (Munt\, 1977; Rienstra\, 2003; Samanta and Freund\, 2008). The second category of tones observed have frequencies that are not hard wall duct mode frequencises. Their spatial amplitude distribution revealed by SPOD for these frequencies is characterized by significant support within the jet potential core. Empirical dispersion relations constructed from the LES suggest that these tones arise from resonance in the potential core due to coupling between the upstream-propagating guided jet mode (GJM) and the upstream- and downstream-propagating duct-like modes (Schmidt et al.\, 2017; Towne et al.\, 2017) near the upper cut-off frequency of the guided jet mode (Bogey\, 2021). However\, the mechanism by which tones radiate from the potential core has not yet been established. This motivates the theoretical investigation in this thesis that focuses on the dynamics of the guided jet mode and its interaction with the nozzle lip leading to tonal upstream acoustic radiation. The interaction between the GJM and the nozzle lip is analyzed using a Wiener–Hopf formulation with the jet modelled as a semi-infinite cylindrical vortex sheet and the nozzle with a vanishingly-thin sharp edge. When the GJMs are cut-on\, these solutions show that an incident GJM is reflected as a downstream-traveling soft-duct mode\, a scattered Kelvin–Helmholtz (K–H) mode and a transmitted upstream-traveling hard-wall duct mode. The reflective efficiency of GJM increases with frequency and is greatest near their upper cut-off frequency. This explains why tones associated with potential core resonance occur near the upper cut-off frequency of the GJM. In addition\, the GJM is scattered as acoustic waves to the far field\, primarily in the upstream direction. The scattered wavefronts are most intense along the outer nozzle wall. The scattered waves propagate to the far field where they generate distinctive directivity patterns that show excellent agreement with the LES-computed far-field directivity reported by Bogey (2021). These results provide a mechanistic explanation for how tones generated by potential core resonance radiate to the far field through scattering of the guided jet mode at the nozzle lip. Comparison of the Wiener–Hopf predictions with the LES-computed pressure spectra in the present investigation reveals excellent agreement at lower frequencies but deviations at higher frequencies. At lower frequencies\, the SPOD modes are qualitatively similar to the corresponding Wiener–Hopf solutions. In contrast\, at higher frequencies\, the scattered waves originating from the nozzle lip undergo secondary scattering at the slanted section of the outer nozzle wall\, causing them to lift away from the wall. The findings suggest two possible strategies for mitigating the tones generated by the potential core resonance: (i) modifying the nozzle-lip geometry and (ii) modifying the outer nozzle-wall geometry. \n  \nSpeaker: NAGA SARAS CHANDAN VEMPATI \nResearch Supervisor: Santosh Hemchandra
URL:https://aero.iisc.ac.in/event/ph-d-enggtonal-acoustic-radiation-from-turbulent-subsonic-jets/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/NAGA.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260814T110000
DTEND;TZID=Asia/Kolkata:20260814T133000
DTSTAMP:20260828T231309
CREATED:20260811T114531Z
LAST-MODIFIED:20260824T064859Z
UID:10000146-1786705200-1786714200@aero.iisc.ac.in
SUMMARY:MTech(res)  Parallel Particle Tracking for Turbulent Round Jets
DESCRIPTION:Particle tracking in turbulent jets is essential for an accurate Lagrangian understanding of jet flows. While parallel algorithms and numerical schemes to compute flow fields can be scaled to a large number of computing processes\, the same is not necessarily true for particle tracking. This thesis presents an analysis of the parallel efficiency of particle tracking in the specific context of round turbulent jets.\nA particle tracking module was developed and integrated with Xcompact3d – a well-established flow solver with strong and weak scaling up to 100\,000 processes. The module uses trilinear velocity interpolation scheme and a first-order Euler integration scheme with sub-stepping for particle advancement. Velocity data is exchanged via a halo API provided by 2DECOMP&FFT – the domain decomposition library that Xcompact3d builds upon. Particle data is exchanged via MPI collectives. Additional exchange algorithms that aim to avoid the scalability limitations of MPI collectives are available to the user. However\, the choice of algorithms for data exchange is often constrained by flow and simulation parameters. \nThe module is validated using an analytical velocity field and subsequently employed for DNS and LES of turbulent jets with particles. Particle concentration profiles are used to assess accuracy. The results demonstrate the capability of the integrated code to accurately track particles over multiple simulation runs. The particle numbers used for these simulations are comparable or higher than the number of grid points as opposed to most studies in the literature where particle numbers are much lower than the number of grid points. \nA detailed wall-time and particle-load analysis is done to assess the parallel efficiency and identify performance limitations. Particle tracking and exchange are the largest contributors to simulation time after flow field computation. The wall-time for particle tracking increases with the number of particles in the domain. A large difference is observed between the average wall-time and maximum wall-time across computing processes which is attributed to particle load imbalance. In contrast\, the particle exchange wall-time across computing processes is similar because of the MPI collectives being used for particle data exchange. However\, the number of particles\, and consequently\, the size of data being exchanged\, is a small fraction of the number of particles being tracked. A particle load-analysis reveals considerable variation in the number of particles being tracked by individual processes\, with the maximum difference in particle count amongst processes being as high as three orders of magnitude. \nThe results obtained highlight the challenges in implementing particle tracking at scale. While strategies to mitigate the impact of non-scalable collectives for particle exchange exist\, algorithms to mitigate the severe particle-load imbalance in the context of turbulent jets have not been adequately studied and are urgently required\, which is identified as the key area for future work. \n  \nSpeaker : Nikhil Jayswal \nResearch Supervisor: Prof. Joseph Mathew
URL:https://aero.iisc.ac.in/event/mtechres-parallel-particle-tracking-for-turbulent-round-jets/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Nikhil-Jayswal.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260901T140000
DTEND;TZID=Asia/Kolkata:20260901T170000
DTSTAMP:20260828T231309
CREATED:20260825T054145Z
LAST-MODIFIED:20260825T054307Z
UID:10000147-1788271200-1788282000@aero.iisc.ac.in
SUMMARY:Taming Turbulence
DESCRIPTION:Turbulence remains one of the outstanding problems of classical physics\, and one that has challenged physicists and engineers alike for decades\, even centuries. The fusion of classical approaches and tools of the modern day – theoretical analysis of the Navier-Stokes equations\, state-of-the-art experimental observations\, data-driven methods and machine learning – has led to substantial progress towards understanding the mechanisms sustaining turbulence\, developing predictive capabilities and achieving the potentially revolutionary goal of harnessing or taming turbulence in large-scale (high Reynolds number) practical settings. In this talk\, I will describe some fundamental challenges posed by turbulence near walls\, the impact of this phenomenon on many of the world’s pressing scientific concerns\, and some recent advances.\n\n \nSpeaker : Prof. Beverley McKeon\n\nbiography:\n\nBeverley J. McKeon is Professor of Mechanical Engineering at Stanford. She received her B.A.\, M.A. and M.Eng. from the University of Cambridge in the United Kingdom\, and an M.A. and Ph.D. in Mechanical and Aerospace Engineering from Princeton University. She completed postdoctoral research and a Royal Society Dorothy Hodgkin Fellowship at Imperial College London. Best known for her work pioneering resolvent analysis as an equation-driven tool to analyze and predict the dynamics of turbulent flow\, her research group has specialized in addressing its application to understand and modify wall turbulence in numerical data and via experiments with external forcing. Prof. McKeon is a Fellow of the APS and the AIAA and the recipient of a Vannevar Bush Faculty Fellowship from the DoD in 2017\, the Presidential Early Career Award (PECASE) in 2009 and an NSF CAREER Award in 2008 as well as Caltech’s Shair Program Diversity Award\, Graduate Student Council Excellence in Mentoring Award and Northrop Grumman Prize for Excellence in Teaching. She currently serves as co-Lead Editor of Physical Review Fluids and on the editorial board of the Annual Review of Fluid Mechanics.\n \nCoffee/tea will be served after the seminar at 3:30 pm.\n\nAt 4:00 pm\, Prof. McKeon will hold a special session on Physical Review Fluids\, one of the world’s leading research journals for fluid dynamics. Prof. McKeon is the co-Lead Editor of the journal. The session includes a short presentation on the journal’s history\, Q&A\, and a short tutorial on writing a successful submission.
URL:https://aero.iisc.ac.in/event/taming-turbulence/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/08/taming_turbulence_poster_16x9-4.png
END:VEVENT
END:VCALENDAR