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DTSTART:20240101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251215T110000
DTEND;TZID=Asia/Kolkata:20251215T120000
DTSTAMP:20260619T065354
CREATED:20251210T103048Z
LAST-MODIFIED:20251213T093321Z
UID:10000100-1765796400-1765800000@aero.iisc.ac.in
SUMMARY:Flow-Aware Simulation Technique (FAST) for AI-Enabled\, Physics-Integrated Turbulence Computations
DESCRIPTION:Data-driven approaches have generated tremendous excitement in turbulence modeling\, but enthusiasm has often outpaced scientific rigor. Many current AI/ML turbulence models lack physical interpretability\, exhibit limited generalizability across flow regimes\, and do not reflect the true dynamical nature of turbulence. A new strategy is needed—one that leverages AI while remaining fully compliant with the physics of flow evolution. This talk proposes a flow-aware AI paradigm that integrates data-driven learning with physical constraints and local flow-regime awareness. Recognizing that turbulence spans a wide spectrum of coherent and stochastic behaviors\, we propose an adaptive framework that allows AI to dynamically select modeling pathways—switching between physics-based closures and selective scale resolution as conditions demand. This approach improves robustness in complex flow regimes\, enabling AI to enhance rather than replace traditional models. The presentation will clarify the limitations of current ML methods and illustrate how physics-aware hybridization can accelerate accurate and efficient turbulence simulations. The goal is not to abandon classical turbulence modeling\, but to augment it with AI-enabled predictive insight\, producing simulations that are consistently reliable\, interpretable\, and deployment-ready in unseen flows.  \nSpeaker : Prof. Sharath Girimaji \nBiography: \nDr. Sharath S. Girimaji is a Professor of Aerospace Engineering and Department Head of Ocean Engineering at Texas A&M University\, where he holds the Wofford Cain Chair position. His research expertise spans turbulence modeling\, computational fluid dynamics\, compressible and high-speed flows\, and complex fluid dynamics. Dr. Girimaji received his B.Tech from Indian Institute of Technology Madras (1983) and his M.S. and Ph.D. from Cornell University (1990). Before joining academia\, he spent nine years as a research scientist at NASA Langley Research Center. He has graduated 25 PhD students to date. He is a Fellow of the American Physical Society (APS) and an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA).
URL:https://aero.iisc.ac.in/event/flow-aware-simulation-technique-fast-for-ai-enabled-physics-integrated-turbulence-computations/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/12/Sharath.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251201T110000
DTEND;TZID=Asia/Kolkata:20251201T130000
DTSTAMP:20260619T065354
CREATED:20251201T040004Z
LAST-MODIFIED:20251201T040004Z
UID:10000097-1764586800-1764594000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Autorotation of Single-Winged Spinning Samaras
DESCRIPTION:Nature has consistently served as a powerful source of innovation\, offering elegant and sustainable solutions to complex engineering problems. Among these\, the spinning samara seed stands out as a biologically efficient system for passive aerial transport. Samaras\, such as those from mahogany and Buddha coconut trees\, exhibit stable autorotative descent\, making them strong candidates for biomimicry in aerial delivery systems. Understanding and replicating the flight mechanics of samaras requires accurate analytical modelling. The dynamics of a single-winged spinning samara can be described using Newton’s laws and Euler’s rigid‐body equations\, while the aerodynamic forces acting on the wing can be derived from the Navier–Stokes equations or using Blade Element Momentum Theory (BEMT). Together\, these frameworks provide a foundation for predicting its motion\, thrust generation\, and stability in samara-inspired designs. Building on this theoretical basis\, the present thesis delivers a comprehensive experimental study on the bioinspired engineering of single-winged spinning samaras\, focusing on their aerodynamic behavior\, kinematic characteristics\, structural morphology\, and wake dynamics. To investigate the kinematics\, a custom-designed drop rig was developed to capture high-resolution visual data of the steady-state descent. Parameters such as descent velocity\, coning angle\, wingtip trajectory\, and precession were extracted and analyzed. The results revealed a complex motion involving coupled coning and precession\, challenging simplified theoretical models that typically assume a steady\, non-precessing descent. Parallel morphological studies using high-resolution 3D scanning of natural samaras highlighted spanwise variations in chord length\, camber\, and sweep\, which contribute significantly to aerodynamic performance. Five 3D printed models incorporating geometric variations were fabricated to evaluate their aerodynamic efficiency. Experimental observations showed that models featuring variable chord\, sweep\, and anhedral/dihedral configurations achieved the lowest descent velocities\, underscoring the importance of structural morphology in enhancing autorotative performance. To examine local flow physics in detail\, a custom low-Reynolds-number vertical wind tunnel was developed and characterized. Flat-plate airfoils were studied using Particle Image Velocimetry (PIV) across a wide range of angles of attack and Reynolds numbers\, revealing flow regimes ranging from steady attached flow to unsteady vortex shedding. Wake flow physics of samaras were further captured within a transparent glass chamber using seeded PIV\, revealing stable wingtip vortices extending several diameters downstream and confirming the presence of a windmill-brake state analogous to helicopter autorotation. Induced velocities computed using Momentum Theory showed close agreement with theoretical predictions. To evaluate practical feasibility\, a bioinspired delivery system was designed and tested through drone-based release experiments. Six models (FR01 to FR06) were fabricated and deployed under varying payloads and wind conditions. All models demonstrated successful autorotation and stable descent\, confirming the viability of samara-inspired mechanisms for passive aerial delivery. This research advances the understanding of samara aerodynamics and opens pathways for bioinspired applications in unmanned aerial systems. Future work should explore 3D motion capture\, high-fidelity simulations\, and optimization of geometries and materials. The insights from this thesis provide a strong foundation for future innovations in samara-inspired flight technologies. \nSpeaker :  G.YOGESHWARAN \n  \nResearch Supervisor: Gopalan Jagadeesh \nCo-Research Supervisor: Srisha Rao M V
URL:https://aero.iisc.ac.in/event/ph-d-engg-autorotation-of-single-winged-spinning-samaras/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/12/YOGESHWARAN.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20251027T110000
DTEND;TZID=Asia/Kolkata:20251027T130000
DTSTAMP:20260619T065354
CREATED:20251015T064811Z
LAST-MODIFIED:20251015T064811Z
UID:10000088-1761562800-1761570000@aero.iisc.ac.in
SUMMARY:Taming Waves through Non-Hermiticity: From Invisible Tunneling to Unidirectional Nonlinear Pulses
DESCRIPTION:Non-Hermitian wave dynamics challenge our conventional understanding of wave propagation\, revealing transport behaviors inaccessible in Hermitian systems. In this seminar\, I will present a few intriguing phenomena arising from these dynamics. In the first part\, I will show a counterintuitive tunneling effect at the interface of a non-Hermitian system sandwiched between two Hermitian ones. Here\, the non-Hermitian skin effect creates barriers at the boundaries\, yet under the right conditions\, a wave can tunnel through as if the interface were invisible. This phenomenon is explored in both quantum and classical regimes\, with experimental demonstrations using an active electric circuit platform. In the second part\, I turn focus to nonlinear systems\, addressing generation of unidirectional\, narrow pulses (solitons) that propagate without distortion in active mechanical setups. I present a theoretical model for generating stable unidirectional solitons by carefully balancing nonlinearity and nonreciprocity\, and show how these pulses are realized experimentally\, supported by analytical results and numerical simulations. \nReferences: \nInvisible tunneling through non-Hermitian barriers in nonreciprocal lattices. Sayan Jana\, Lea Sirota\, Physical Review B (Letter) 111 (10)\, L100301\, (2025).\nHarnessing Nonlinearity to Tame Wave Dynamics in Nonreciprocal Active Systems\, Sayan Jana et al.\, arXiv:2502.16216 (2025). \n  \nSpeaker :  Dr. Sayan Jana \nBiography:  \nDr. Sayan Jana is a Postdoctoral Researcher at the Department of Mechanical Engineering\, Tel Aviv University\, Israel. He obtained his PhD in Theoretical Condensed Matter Physics from the Institute of Physics\, Bhubaneswar\, India\, in 2022. His research is interdisciplinary\, integrating theoretical physics and engineering to emulate complex analogue quantum and high-energy phenomena using lab-scale platforms. One key finding includes the proposal and simulation of analogue gravitational lensing and Hawking radiation using mechanical networks. These studies provide accessible routes to investigate phenomena that are otherwise difficult to observe directly in the universe. Another major research direction focuses on non-Hermitian systems\, where non-conservation of energy gives rise to intriguing dynamics and interplay with topology and nonlinearity. Realizations in active metamaterials reveal novel wave phenomena and control mechanisms\, with significant potential for advanced wave manipulation and energy technologies.
URL:https://aero.iisc.ac.in/event/taming-waves-through-non-hermiticity-from-invisible-tunneling-to-unidirectional-nonlinear-pulses/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/10/Sayan.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250723T110000
DTEND;TZID=Asia/Kolkata:20250723T130000
DTSTAMP:20260619T065354
CREATED:20250723T033046Z
LAST-MODIFIED:20250824T142259Z
UID:10000085-1753268400-1753275600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Development of Approaches for Optimal Shared Utilization of Spatially Distributed Resources Under Sparse Connectivity in Energy Internet
DESCRIPTION:The global shift towards sustainable power generation has led to a significant rise in distributed energy resources (DERs)\, particularly from renewable sources. These localized generation systems\, when combined with energy storage\, form microgrids—self-contained units capable of managing generation and consumption. While energy storage enables time-shifted usage of intermittent renewable power\, limitations in storage capacity and dynamic load variations still result in curtailment of generated energy. Peer-to-Peer (P2P) power trading among geographically adjacent prosumers offers a more energy-efficient and cost-effective alternative to grid feed-in. P2P trading enhances local energy utilization\, optimizes resource use\, and improves resilience in interconnected communities of microgrids. However\, achieving full connectivity among all peers is infrastructure-intensive\, while relying on sparse connectivity with indirect power exchange through intermediaries—facilitated via an Energy Internet (EI)—presents a scalable and feasible alternative. Within this context\, the challenge becomes the optimal utilization of spatially distributed generation under connectivity constraints.\nThis thesis addresses this challenge by modelling realistic microgrid behaviour using multiple real-world electrical load datasets. Initially\, internal power scheduling within a grid connected microgrid equipped with solar generation and storage is formulated as a mixed integer nonlinear optimization problem\, later relaxed to a mixed-integer linear formulation to reduce computational complexity. Predictive scheduling is employed to enable time-shifted energy usage. The resulting surplus and deficit data form the basis for simulating P2P power exchange within a connected community. To evaluate trading under constrained infrastructure\, the thesis introduces the Connectivity and Preference-constrained Hop-regulated P2P Trading (CPHPT) approach. CPHPT models P2P trading as a linear optimization problem that schedules energy exchange along shortest paths while respecting capacity and predefined hop limits. The internal microgrid scheduling and inter-microgrid trading are coordinated using a distributed control architecture\, enhancing scalability and preserving data privacy. Graph theory is leveraged to avoid explicit route computation during hop-constrained scheduling. Theoretical analysis demonstrates that while full connectivity maximizes P2P power transfer\, increasing the allowable hop count in sparsely connected communities enables near-optimal performance\, albeit with higher routing complexity.\nBuilding on this\, the Optimal Multi-Path Power Routing (OMPR) algorithm is developed. OMPR uses graph-theoretic principles to determine the connectivity structure and identifies all feasible routes between peers deterministically. The power scheduling among the routes is formulated and solved as both a linear and nonlinear multi-path power scheduling optimization problem. The OMPR approach divides each multi-hop P2P exchange into multiple individual hop exchanges and solves each step-by-step. While routing multiple concurrent P2P exchanges\, the order in which each P2P exchange is routed affects the optimal solution\, as each route increases the power flow routing constraints. To overcome this limitation\, a Hop Optimized Multi-Exchange Routing and Scheduling (HOMERS) algorithm that solves all concurrent multi-hop P2P exchanges simultaneously to obtain the optimal routing paths has been developed. HOMERS formulates the routing and scheduling of all concurrent P2P exchanges into a single-step mixed-integer nonlinear programming optimization problem. This approach efficiently identifies all feasible routes and schedules each power exchange\, ensuring conflict-free power flow from the source to the destination in the predetermined number of hops.\nRecognizing the limitations of assuming uniform node distribution and connectivity in the CPHPT and random connectivity for OMPR\, and HOMERS models—the thesis proposes a more realistic framework named as a Spatial and Renewable resource Distribution Informed Network for Energy exchange (SRDINE). SRDINE accounts for non-homogeneous node spacing and variable power generation capabilities across the community. It identifies optimal connectivity topologies based on geographic and resource distribution\, yielding improved connectivity efficiency. The resulting community specific connectivity model from SRDINE is shown to have better connectivity utilization and has improved efficiency compared to the ideal full connectivity. Through the development of CPHPT\, OMPR\, HOMERS\, and STRIDE\, this thesis makes substantial contributions to the field of distributed energy systems and P2P power trading. The integration of predictive scheduling\, hop-constrained routing\, and spatial-connectivity modelling offers a comprehensive and scalable framework for the future deployment of Energy Internet architectures. The research establishes a practical and theoretically grounded foundation for resilient\, intelligent\, and energy-efficient microgrid communities.\nSpeaker :  Neethu M \nResearch Supervisor : Prof Suresh Sundaram
URL:https://aero.iisc.ac.in/event/ph-d-engg-development-of-approaches-for-optimal-shared-utilization-of-spatially-distributed-resources-under-sparse-connectivity-in-energy-internet/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/07/Neethu-M.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250718T150000
DTEND;TZID=Asia/Kolkata:20250718T170000
DTSTAMP:20260619T065354
CREATED:20250715T045641Z
LAST-MODIFIED:20250715T045641Z
UID:10000084-1752850800-1752858000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): ON HIGH-SPEED CURVED COMPRESSION RAMP AIR INTAKES
DESCRIPTION:A scramjet\, i.e.\, a supersonic combustion ramjet\, is an air-breathing engine that enables sustained atmospheric flight in the hypersonic regime. It consists broadly of four key components: the air intake\, isolator\, combustor\, and nozzle. The air intake and the isolator collectively comprise the compression system\, which captures and conditions the freestream flow to suit the operational requirements of the combustor positioned downstream. The general set of attributes sought in a high-speed air intake is: low structural weight; low drag; low aero-thermal loads; started flow with high thermodynamic efficiency and high compression ratio; operational robustness to back-pressure fluctuations arising from the combustor; and stable engine operation over a wide flight envelope. The intake flow characteristics and performance are primarily governed by its geometric shape. High-speed air intakes with a curved compression ramp (CCR) are a class of rectangular intakes wherein the compression ramp comprises a curved surface followed by a planar surface tangential to the trailing end of the curved surface. A CCR intake compresses the flow through a combination of a curved ramp shock wave and a series of compression waves. These intake geometries can provide improvements in compression ratio\, pressure recovery\, and allow for a shorter length intake section in comparison to conventional multi-step intake geometries.\nThe present effort consists of the development of a novel analytical framework to model the CCR intake flow and estimate the intake performance parameters at design and off-design operating conditions\, and wind tunnel experiments with a model CCR air intake at Mach 6 to obtain a detailed understanding of the flow dynamics. The analytical framework builds on the principles of mass conservation and the compressible flow theory to model the inviscid flow structure in the intake without any empiricism. A modified Kantrowitz criterion is proposed to examine the ability of a given fixed-geometry CCR intake to spontaneously self-start at the design Mach number. The framework provides a simple\, fast\, and low-cost tool to develop an effective first-cut design of a self-starting hypersonic CCR air intake for any specified set of operating conditions and performance parameters of interest\, such as the startability\, compression efficiency\, and compression ratio. Inviscid flow numerical experiments of intake starting were carried out to preliminarily verify the starting characteristics predicted by the analytical model.\nThe analytical framework was then employed to identify a suitable geometric design point for the experimental CCR air intake model. A self-starting intake test model was designed following the strong shock design principle\, and built for experimentation in the Roddam Narasimha Hypersonic Wind Tunnel at Mach 6 freestream flow conditions. Time-resolved pressure measurements and high-speed schlieren flow visualization were conducted to understand in detail the flow features internal and external to the intake model\, including the dynamics of shock-shock and shock-boundary layer interactions at the cowl and inside the isolator. Performance assessment at design operating conditions involved evaluating the intake’s ability to spontaneously self-start\, in addition to examining pressure recovery and compression ratio of the started intake. At off-design operating conditions\, the intake dynamics were studied by experimentally varying two parameters: intake back-pressure and angle-of-attack (𝛼). In order to mimic combustor-induced isolator back-pressure variations\, a sliding plate was introduced at the isolator exit; the motion of the sliding plate varies the isolator exit area (blockage) and thereby changes the back-pressure. Experimental results showed that the intake auto-reverts to the started state on realizing suitable pressure values at the isolator exit. Coherent flow oscillations with certain characteristic frequencies were observed in the isolator section during the intermediate state of operation (between started and unstarted states). The angle-of-attack (AoA) studies\, in the 𝛼 range of -70 to 20.70\, show that the relatively gradual distribution of adverse pressure along the compression ramp mitigates the risk of large-scale boundary layer separation\, even at very large AoAs. The model intake was found to satisfy shock-on-lip condition and operate in the started state between 𝛼 = 00 and 𝛼 = 100\, and supersonic flow was sustained in the isolator section up to 𝛼 = 20.70. Overall\, the experimental results were found to validate predictions made by the analytical model. The experiments also allowed for a careful examination of flow during various stages of intake operation\, including intake unstart and restart\, and quantification of operational margins (in terms of pressure) for the model intake. In addition to aiding performance assessment\, these results can also form the basis for the design of a practical early-warning system for preventing engine unstart.\nIn summary\, this work offers a clear experimental demonstration of the advantages offered by CCR air intakes\, and an analytical framework that serves as a good starting point for a design exercise. In practical terms\, this work exhibits the promise held by CCR air intake in providing a wide flight envelope for an air-breathing hypersonic flight vehicle. \nSpeaker : Sushmitha Janakiram \nResearch Supervisor : Duvvuri Subrahmanyam
URL:https://aero.iisc.ac.in/event/ph-d-engg-on-high-speed-curved-compression-ramp-air-intakes/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/07/Sushmitha-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250716T110000
DTEND;TZID=Asia/Kolkata:20250716T130000
DTSTAMP:20260619T065354
CREATED:20250715T041029Z
LAST-MODIFIED:20250715T041029Z
UID:10000083-1752663600-1752670800@aero.iisc.ac.in
SUMMARY:Investigation of flow instabilities in high-speed impinging jets using dual-time velocity measurements
DESCRIPTION:Motivated by applications in the aerospace propulsion industry as well as other energy systems\, the fundamental study of phase-locked shear-layer instabilities in high-speed impinging jets\, has been of research interest for a long time.  The study of instabilities is usually conducted with time derivatives of velocity field. However\, time-resolved experimental data acquisition using particle image velocimetry (PIV) techniques has its challenges for high-speed flows due to the requirements of high spatial and temporal resolution. In this talk\, I will introduce an alternate approach of utilizing time-unresolved dual-time PIV measurements for investigation of the flow instabilities in supersonic impinging jets and illustrate the valuable information about the flow dynamics that can be extracted using the same. \nSpeaker : Dr. Tushar Sikroria \nBiography: \nTushar Sikroria obtained his B.Tech.-M.Tech. Dual Degree in Aerospace Engineering from IIT Kanpur\, Uttar Pradesh\, India\, in 2013. Then he worked for more than two years in John F. Welch Technology Centre\, General Electric (GE)\, Bangalore\, India. Thereafter\, he carried out research work as a Project Engineer in Propulsion Laboratory\, IIT Kanpur\, in 2016\, and later went to pursue his doctoral study from the University of Melbourne\, Australia. He was awarded PhD in Mechanical Engineering from the University of Melbourne\, in December 2021. He pursued post-doctoral research in the Turbomachinery & Propulsion Department\, von Karman Institute\, Belgium and then joined IIT Kanpur as an Assistant Professor in the Department of Mechanical Engineering in January 2024.
URL:https://aero.iisc.ac.in/event/investigation-of-flow-instabilities-in-high-speed-impinging-jets-using-dual-time-velocity-measurements/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/07/Tushar.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250603T113000
DTEND;TZID=Asia/Kolkata:20250603T130000
DTSTAMP:20260619T065354
CREATED:20250527T091724Z
LAST-MODIFIED:20250527T091724Z
UID:10000077-1748950200-1748955600@aero.iisc.ac.in
SUMMARY:Space Domain Awareness in the Artemis Era
DESCRIPTION:Since the Apollo era\, space has become an increasingly valuable domain for national security due to diplomatic\, informational\, and economic reasons. The last few years have seen exponential growth in the launch of space objects and there is an increased interest in having a permanent cislunar presence through the Artemis program. The understanding of motion of a spacecraft in multi-body environment is essential to transit between different regions in the cislunar space and to forecast and track objects in the cislunar space. The perturbed two-body restrictive framework has led to extensive modeling\, analysis\, and analytical solutions to study spacecraft motion in orbits around the Earth. However\, beyond GEO (XGEO) the dynamical environment shifts\, and the structure of fundamental behaviors can be radically different. The primary challenge that limits the transferability of tools and techniques from the GEO to XGEO region is non-Keplerian dynamics\, data sparsity from limited coverage and availability of sensors. The process of orbit determination and forecasting the path for an object based on short time arc observations is not trivial. This talk will introduce novel tools to track spacecraft motion in cislunar space and transfers between different regions in cislunar space. These tools make use of dynamical system theory in combination with advances in optimal control theory to provide a better understanding of transport mechanisms in cislunar space. Local orbit elements will be discussed to characterize the trajectories in the cislunar space.\n\nSpeaker : Dr. Puneet Singla\n\nBiography:\n\nDr. Puneet Singla is a Harry and Arlene Schell Professor of the Aerospace engineering at the Pennsylvania State University (PSU). Dr. Singla’s research focus pertains to uncertainty propagation through nonlinear systems\, data driven modelling and control of autonomous systems. His research related honours include the IEEE AESS’s Judith A. Resnik Award\, NSF CAREER award\, the AFOSR Young Investigator award\, the University at Buffalo’s “Exceptional Scholar” Young Investigator Award and the Texas A&M University’s Young Aerospace Engineering Distinguished Alumni Award in recognition of his scholarly activities. He is a fellow of American Astronautical Society (AAS) and an associate fellow of American Institute of Aeronautics and Astronautics (AIAA).
URL:https://aero.iisc.ac.in/event/space-domain-awareness-in-the-artemis-era/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/05/Puneet-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250416T153000
DTEND;TZID=Asia/Kolkata:20250416T170000
DTSTAMP:20260619T065354
CREATED:20250416T051419Z
LAST-MODIFIED:20250416T051419Z
UID:10000070-1744817400-1744822800@aero.iisc.ac.in
SUMMARY:Miniaturised technologies for potential applications in space research
DESCRIPTION:Miniaturised technologies\, due to their portability\, rapid responses\, low powers and ability of multi-component integration\, have received an ever-growing interest in areas like healthcare\, air quality\, and space research. This talk will provide an overview of my research in 3 domains of miniaturised technologies: a) microfluidics\, b) MEMS sensors and c) nanoaerosol instruments. I will also highlight areas of space research where this work is potentially relevant. \nI will begin my talk with my work in microfluidic particle enrichment and gene therapy devices. Enrichment devices\, when integrated with a downstream sensor for target particle detection\, can significantly improve the sensor sensitivity. I will cover my work in developing enrichment devices and mitigation of some undesirable effects that can limit their reliability. I will also introduce my work in commercial-scale microfluidic mixers for gene therapy. The work in this theme is highly relevant to healthcare in manned space missions and CubeSats to understand in-space behaviour of bio-species. \nI will next cover my work in thin film MEMS mass sensors\, which offer several advantages over conventional sensors like QCMs thanks to their portability\, high sensitivities and excellent compatibility with semiconductor technology. This talk will cover my work towards enhancing their capabilities in areas of biosensing and simultaneous detection of multiple parameters. This work has a promising applicability in controlling ambient conditions inside spacecrafts\, and healthcare in manned space missions. \nI will conclude with my work in 2 miniaturised nano-aerosol technologies\, namely a) an instrument that can produce a constant number concentration of charged nanoaerosols\, a need unmet in aerosol instrumentation until now\, and b) a sensor that can both count and map the global distribution of airborne ultrafine particles\, a requirement crucial for the upcoming WHO air quality guidelines. The work in this theme has enormous significance in simulating cosmic dust conditions and satellite-based remote sensing of particulate matter distribution near the earth’s surface. \n  \nSpeaker: Dr. Akshay Shridhar Kale \nBiography: \nDr. Akshay Shridhar Kale is a senior postdoctoral affiliate at Trinity College and a teaching assistant at the Department of Engineering at the University of Cambridge\, UK. He is also an Honorary Adjunct Professor at the Department of Mechanical Engineering at COEP Technological University in Pune. His research interests lie in the development of miniaturised technologies and possesses a track record in the areas of microfluidic devices\, MEMS / acoustic devices and nanoaerosol instrumentation. He is also highly active in industry-oriented research and has completed several industrial consultancy projects in his areas of interest. His recent work on integration of miniaturisation principles with nanoaerosol instruments has won him grant funding awards that have partially supported the early stages of commercialisation of a portable nanoaerosol counter in collaboration with a spin-out company from his research group. At COEP\, he is actively involved in developing microfluidics research programs and a proposed centre of excellence in micro- and nano- manufacturing. Along with research and development\, he regularly teaches thermal and fluid science courses at Trinity College\, and has co-guided several undergraduate and Masters students through his research projects across Cambridge and COEP. Dr. Kale earned his B.Tech. in Mechanical Engineering at COEP\, followed by an MS and a PhD in thermal and fluid systems from Clemson University\, USA
URL:https://aero.iisc.ac.in/event/miniaturised-technologies-for-potential-applications-in-space-research/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/04/Akshay-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250327T150000
DTEND;TZID=Asia/Kolkata:20250327T163000
DTSTAMP:20260619T065354
CREATED:20250327T063920Z
LAST-MODIFIED:20250327T063920Z
UID:10000065-1743087600-1743093000@aero.iisc.ac.in
SUMMARY:Laser Beam Control Through Atmospheric Turbulence
DESCRIPTION:Laser beam is highly affected by prevailing atmospheric conditions and limit the system performance for various applications. The talk mainly covers the cause of optical turbulence\, its effects on laser beam and further discuss the technologies for controlling the beam for enhancing the effectiveness. Two main techniques namely the Tip-tilt correction for maintaining the beam at same position and adaptive optics technology for controlling the phase distortions and thus enhancing the signal strength on the receiver plane will be discussed. The experimental results for long range propagation will also be presented and discussed. \n  \nSpeaker: Dr. Amit Pratap\, Sc F\, CHESS (DRDO)
URL:https://aero.iisc.ac.in/event/laser-beam-control-through-atmospheric-turbulence/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Amit.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250318T110000
DTEND;TZID=Asia/Kolkata:20250318T130000
DTSTAMP:20260619T065354
CREATED:20250311T060827Z
LAST-MODIFIED:20250311T060827Z
UID:10000060-1742295600-1742302800@aero.iisc.ac.in
SUMMARY:Ph.D.(Engg): Investigations on Hypersonic Laminar to Turbulent Boundary Layer Transition in a Shock Tunnel.
DESCRIPTION:The laminar to turbulent boundary layer transition onset has perplexed fluid dynamics community irrespective of the flow regime under which the phenomenon is probed. The complexity of the problem is compounded in high-speed compressible flows where in the transition onset location is a strong function of many subtle factors like freestream quality\, surface roughness\, wall temperature etc. The transitional and turbulent boundary layers bring their typical characteristics\, like an increase in skin friction\, heat transfer\, fluid dynamic parameters fluctuations\, mixing characteristics\, potential to negotiate adverse pressure gradient\, along with them. These typical characteristics of transitional and turbulent boundary layers can be both detrimental and advantageous to a given facet of an aerodynamic vehicle design. Hence the boundary layer transition onset location is one of the key design inputs in the development of aerodynamic vehicles operating in subsonic\, supersonic and hypersonic freestream environment. A plethora of work has been conducted to investigate the transition onset phenomena in supersonic and hypersonic flow regime since the beginning of space age and the inception of the idea of an air breathing hypersonic cruise vehicle. The outcomes of these investigations and studies on high-speed boundary layer transition onset although led to the development of several techniques and correlations to estimate the transition onset location\, applicable usually to a particular test model and freestream condition\, very few studies targeted the characterization of transitional boundary layer in hypersonic flow regime. The earlier and contemporary work on roughness induced transition onset focused on the effect of the said roughness element on transition onset location but the features associated with the instabilities thus generated by these roughness elements have seldom been reported in the open literature. Hence characterization of transitional boundary layer and the instabilities associated with the same was one of the primary objectives of the present work.\nThe present work on hypersonic boundary layer transition was conducted in a shock tunnel HST4 by employing generic test models like flat plate\, cone and elliptic cone. The work began with the design\, development and deployment of a new contoured nozzle\, with a nominal Mach number of 6.0\, for HST4. Before embarking on the boundary layer transition studies\, dedicated efforts were made to characterize the freestream noise environment of the test section of HST4 by employing experimental and numerical methods. A two-dimensional finite difference Navier-Stokes solver was developed in order to numerically compute the transfer functions required to retrieve freestream pressure fluctuations from the experimental measurements. The RMS of pressure fluctuations in the test section of HST4 was found to be 4.32% for the freestream Reynolds number of 4.5 million/m with major contribution of low frequency fluctuations (<50 kHz) towards the aforementioned RMS magnitude. The transitional boundary layer on smooth surface of a flat plate and an axisymmetric cone were characterized by experimentally measuring the intermittency associated with such boundary layers. The intermittent nature of the transitional boundary layer results from the convection of the turbulent spots along the boundary layer. The leading edge and trailing edge velocities associated with these turbulent spots as well as their generation rates were experimentally measured and computed. The second mode instabilities\, a typical characteristic of high Mach number boundary layers\, were also measured in terms of pressure fluctuations and the bandwidth of these instabilities was found to be in the range of 240-480 kHz. The wavelengths associated with these instabilities were found to be 2.5 times the local boundary layer thickness. Transition onset due to the presence of an isolated roughness element\, either a protrusion or a three-dimensional shoe box cavity\, was also investigated as part of the present campaign. Both isolated protrusion and cavity led to an early onset of transition when compared to the smooth test models with no isolated roughness element. In the case of transition onset due to an isolated cubic protrusion\, the Shuttle Orbiter correlations were found to be inadequate in estimating the transition onset and correlations based on the present dataset were formulated. A single frequency oscillation with a narrow bandwidth centered around 23 kHz corresponding to hair pin vortices in the wake of roughness element was found in the present work. It was also found that while the protrusion suppressed the second mode instabilities\, the cavity aided in the development of high frequency instabilities akin to second mode. Finally initial findings of the transition onset due to cross flow instabilities in an elliptic cone were also discussed in the present work. \n  \nSpeaker : Ankit Bajpai \n  \nResearch Supervisor : Prof. Gopalan Jagadeesh
URL:https://aero.iisc.ac.in/event/ph-d-engg-investigations-on-hypersonic-laminar-to-turbulent-boundary-layer-transition-in-a-shock-tunnel/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Ankit-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250317T110000
DTEND;TZID=Asia/Kolkata:20250317T130000
DTSTAMP:20260619T065354
CREATED:20250311T111336Z
LAST-MODIFIED:20250311T111336Z
UID:10000062-1742209200-1742216400@aero.iisc.ac.in
SUMMARY:The longest known insect migration: Fusing Biology with Aerospace Engineering for innovative solutions
DESCRIPTION:The intriguing annual migration of the dragonfly species\, Pantala flavescens\, was reported a century ago.\nThe multi-generational\, transoceanic migration circuit spanning 14000-18000 kms\, from India to Africa is an\n astonishing feat for an insect few cms in size. Wind\, precipitation\, fuel\, breeding\, and the life cycle affect\n the migration\, yet understanding of their collective role in the migration remains elusive. We identify the\n transoceanic migration route by imposing a time constraint emerging from energetics on Dijkstra’s\npath-planning algorithm. Energetics calculations reveal Pantala flavescens can endure 90 hours of steady\n flight at 4.5m/s. We incorporate active wind compensation in Dijkstra’s algorithm to compute the migration\n route from years 2002 to 2007. The prevailing winds play a pivotal role; a direct crossing of the Indian Ocean\n from Africa to India is feasible with the Somali Jet\, whereas the return requires stopovers in Maldives and Seychelles.\n The migration timing\, identified using monthly-successful trajectories\, life cycle\, and precipitation data\,\ncorroborates reported observations. While working on this problem my mind ventured into many different\n applications of engineering\, which are all connected to the transoceanic migration of dragonflies.\nThe applications range from designing airfoils/wings\, sports aerodynamics and wind turbines to developing\n novel spectral accuracy algorithms for numerical simulations. Hence the ideas vary from simple mimicking\n of dragonflies to more complex abstractions arising from the need to understand their flying behaviour.\n\nSpeaker: Dr Sandeep Saha\n\nBiography :\n\nDr Sandeep Saha is an Associate Professor in the Department of Aerospace Engineering\, IIT Kharagpur.\nHe obtained his bachelors and masters degrees in Mechanical Engineering from IIT Kharagpur.\nHe completed his PhD in Mechanical Engineering from Imperial College London. He thereafter worked as  a\nMarie-Curie Experienced Researcher\, CNRS (Laboratoire FAST)\, Orsay\, France. Thereafter he worked as\n an Aerodynamics Engineer\, ALSTOM Power (now GE)\, Rugby\, UK; then as Research Scientist (Fluids)\,\nSchlumberger Gould Research\, Cambridge\, UK; and then as Academic Staff member\, Mechanical Engineering\,\nUniversity of Duisburg-Essen\, Germany (in collaboration with SIEMENS AG). He has worked on a range of\n problems in fluid mechanics and in recent years has focused on Low Reynolds number Aerodynamics\n ranging a broad spectrum of problems like insect flight\, extraterrestrial flight\, respiratory flows and\nwaste heat recovery and sports aerodynamics.
URL:https://aero.iisc.ac.in/event/the-longest-known-insect-migration-fusing-biology-with-aerospace-engineering-for-innovative-solutions/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Sandeep.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250312T150000
DTEND;TZID=Asia/Kolkata:20250312T170000
DTSTAMP:20260619T065354
CREATED:20250307T064034Z
LAST-MODIFIED:20250307T064034Z
UID:10000059-1741791600-1741798800@aero.iisc.ac.in
SUMMARY:Ph.D.(Engg) : Multi-Agent Pursuit-Evasion and Coverage Strategies
DESCRIPTION:Autonomous agents are increasingly being used to solve many tasks\, deemed complex by humans\, with ease and effectiveness. Two such applications are in defense scenarios and in coverage. This thesis\, therefore\, is devoted towards study of motion planning strategies for autonomous agents in the context of pursuit-evasion problems as well as different coverage problems. The thesis comprises two parts. In the first part\, pursuit-evasion is considered between an evader and one or more pursuers\, all the agents being non-holonomic having turn radius constraints. A partial information setting is considered wherein the agents (evader and pursuer) know about each others’ speed and position but not about their turning capability. The objective in these problems\, where the pursuer is of higher speed but less agile\, is to obtain an evasive strategy. A two-phase evasive strategy is proposed as an effective solution against the pursuers. It is a proximity based strategy. In the first phase\, when the pursuer is beyond a critical distance from the evader\, the latter assumes the worst that the pursuer is holonomic and solves for the best response strategy. This phase is called the Worst Case Scenario Planning (WCSP). When the evader is within the critical range from the pursuer\, the former attempts sharp maneuvers to sidestep the pursuer and extend time of capture. This phase is called the Proximity Based Maneuver (PBM). Dynamic programming is used to solve for the WCSP strategy. In case of multiple pursuers\, the concept of dominance regions is used to obtain the WCSP strategy. Additionally\, the pursuit-evasion problem is extended to a reach-avoid problem where the evader has the dual objective of avoiding the pursuer and reaching a target. This thesis considers the problem of reaching a moving but non-maneuvering target by a turn radius constrained evader in the shortest time. The evader is modeled as a Dubins vehicle and the reaching strategy is deduced by studying the time-to-go properties for different strategies and chronologically checking simple conditions at crossover points. The proposed two-phase evasive strategy is used for avoiding the pursuer. The reaching strategy and the avoiding strategy are linearly combined to obtain the net reach-avoid strategy. Extensive simulation results are provided to corroborate the effectiveness of both the evasive and the reach-avoid strategies. In the second part of the thesis static and dynamic coverage problems are discussed. Inspiration from flocking principles with substantial modifications is used to design a static coverage strategy. This ensures that the covering agents are spread uniformly around the structure while avoiding collision among themselves and with obstacles in the environment. Coverage is addressed for convex and non-convex shapes in 2D and 3D. For dynamic coverage\, concept of Lissajous curves is used to achieve coverage. Dynamic coverage is split into two chapters: coverage of planar regions and coverage of 3D structures. For planar regions\, the boundary of the region is approximated using Fourier series and radial Lissajous curves are generated within the boundary as reference coverage paths. The optimal field-of-view size is analytically determined along with the upper-bound on the time taken for complete coverage. Various extensions of the strategy such as preferential coverage and simultaneous coverage are also discussed. For 3D structures\, an enclosing volume is considered and Lissajous curves are generated on the surface of the enclosing volume. Conditions for complete coverage as well as collision free coverage in case of multiple agents are determined analytically. Artificial potential fields are used to obtain coverage by conforming to shape of the structure. A variety of enclosing volumes are discussed along with diverse applications such as patch coverage\, waypoint coverage\, and coverage of moving structures. Performance metrics are proposed for both static and dynamic coverage problems that helps in ascertaining the quality of coverage. \n  \nSpeaker : Suryadeep Nath    \nResearch Supervisor: Debasish Ghose
URL:https://aero.iisc.ac.in/event/ph-d-engg-multi-agent-pursuit-evasion-and-coverage-strategies/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/SURYADEEP-.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250307T110000
DTEND;TZID=Asia/Kolkata:20250307T130000
DTSTAMP:20260619T065354
CREATED:20250304T093656Z
LAST-MODIFIED:20250304T093656Z
UID:10000057-1741345200-1741352400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Studies on Fluid Structure Interactions in Hypersonic Flow
DESCRIPTION:The global thrust towards the development of hypersonic cruise systems for various applications is leading towards slender configurations with lifting and control surfaces which are thin and complaint and face a hypersonic flow. Hypersonic flows are characterized by large flow kinetic energy and momentum\, which manifests into strong shocks\, high temperatures\, and associated effects that can cause coupling between the flow\, structure\, and thermal effects. Therefore\, understanding Fluid-Structure Interactions (FSI) in hypersonic flow gains significance\, and its predictive modelling is necessary to avoid adverse effects in flight. The majority of literature in supersonic and hypersonic FSI  consider low-fidelity modelling using piston theory\, two-dimensional FSI  computations\, and a limited number of experiments on mainly fully clamped flat panels subjected to aerodynamic loads\, including shock-boundary layer interactions at supersonic Mach numbers. Studies on cantilevered panels\, which are template shapes of control surfaces\, at hypersonic Mach numbers are few\, and there is a significant need to obtain experimental data to aid physical understanding\, validate computational tools and methodology and model the hypersonic FSI  phenomena.\n This motivated the study of three different template flat plate experimental models in the hypersonic shock tunnel HST-2 in the Ludwieg  Mode of Operation\, which has 35 ms of test time. The freestream Mach number of M=6.6 is incident upon a) a cantilevered panel placed along the direction of the flow\, b) a cantilevered panel with an impinging shock\, and c) a trapezoidal wing-like shape fixed at the root and placed transverse to the flow. High-speed schlieren imaging and static pressure measurements at specific locations yield information on the flow characteristics. Image tracking methods are used to extract structural deformation\, and accelerometers measure the oscillatory structural response in the presence of hypersonic flow. Complementary two-dimensional numerical simulations in a fully coupled format are conducted for a limited number of cases. Parametric studies are conducted by varying the panel thickness\, angle of attack\, and mass ratio for plain panels and the impinging shock characteristics for the panel with shock impingement. Natural\, free vibration experiments using an impact hammer excitation are first carried out to evaluate the natural structural modal frequencies.\n Great care is taken in designing all experimental models so that the FSI  response can be captured during the short test time. Oscillatory response is captured successfully using the different diagnostic tools.   For a plain cantilevered panel placed at the Angle of Attack of 20 degrees\,  the FSI response is dominantly near the first structural bending mode at a frequency of 89.65 Hz\, which is higher in comparison to the natural frequency of 75.82 Hz. Multiple diagnostic tools and Dynamic Mode  Decomposition analysis confirm these observations. The angle of attack and mass ratio affect the amplitude of oscillations. Varying thickness changes the structural stiffness\, and accordingly\, the oscillations occur at higher frequencies. Higher downstream pressures on the top surface of the panel due to forebody shock first cause the panel to bend away from the flow\, which leads to the formation of expansion fans\,  releasing the pressure and causing the elastic restoring force to bring it back. Complementary two-dimensional FSI simulations showed good agreement with the experiments\, though the magnitude of amplitude was higher due to the 2D nature of the simulation. Shock Boundary Layer  Interaction is significantly affected by the panel’s compliance. There is a 29.6% reduction of the SBLI separation bubble size on a complaint cantilevered panel. The twin effects of a relaxation in pressure gradient and the existence of wall-normal velocities due to a vibrating panel can be attributed to the observed effect. The trapezoidal wing shape exhibited significantly higher magnitudes in the second structural mode.\nThe studies have laid the foundations for deeper investigations using field imaging techniques like 3D-Digital Image Correlation in the future. The experimental database can be used to develop predictive modelling approaches and data-driven modelling.\n\nSpeaker: Ms. Kartika Ahuja \n\nResearch Supervisor: Prof. Srisha Rao M V
URL:https://aero.iisc.ac.in/event/ph-d-engg-studies-on-fluid-structure-interactions-in-hypersonic-flow/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/03/Kartika.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20250224T160000
DTEND;TZID=Asia/Kolkata:20250224T170000
DTSTAMP:20260619T065354
CREATED:20250221T055800Z
LAST-MODIFIED:20250221T055800Z
UID:10000054-1740412800-1740416400@aero.iisc.ac.in
SUMMARY:MTech(Res): Adjoint-Based Aerodynamic Shape and Mesh Optimization with High-order Discontinuous Galerkin Methods
DESCRIPTION:The aerodynamic shape of an aircraft plays a critical role in its performance. Aerodynamic Shape Optimization (ASO) modifies the shape to achieve desired performance metrics\, such as reduced drag or increased lift. ASO integrates numerical optimization techniques with Computational Fluid Dynamics (CFD). Gradient-based optimization techniques are widely employed for ASO. The adjoint solution enables the accurate and efficient computation of the gradients of the performance metrics with respect to the shape parameters. Performance metrics are derived from CFD solutions\, which inherently contain inaccuracies. These inaccuracies can affect the reliability of the optimization process. High-order methods\, like Discontinuous Galerkin (DG)\, offer improved accuracy for a computational cost comparable to Finite Volume methods in compressible flows\, making them well-suited for ASO. Adaptive mesh refinement can further improve the accuracy of simulations. The adjoint solution used for computing gradients also finds application in mesh adaptation. Combining adjoint-based mesh adaptation with gradient-based ASO provides better control over the inaccuracies during optimization. \nTowards this\, the present work performs ASO using high-order DG methods and devises strategies for incorporating adaptive mesh refinement. The shape is defined using smooth splines\, and the Free Form Deformation (FFD) method controls shape changes. With changes in the geometry\, the mesh needs to move to be consistent with the modified shape. A mesh deformation strategy ensures that the mesh evolves smoothly with geometry. A gradient-based method employing the Sequential Quadratic Programming (SQP) algorithm is used for optimization. The adjoint solution computes the gradients and passes them to the optimization algorithm. Optimization for a set of drag minimization problems\, including benchmark Aerodynamic Design Optimization Discussion Group (ADODG) test case 1 and inverse design problems\, is performed on non-adapted meshes. \nFurthermore\, a strategy is formulated to incorporate adjoint-based mesh adaptation within the optimization process. Based on the value of adjoint-based error estimates\, the strategy decides on instances of the optimization process that require control of the errors and\, thus\, mesh adaptation. Such a strategy leads to automated control of errors in the performance metrics\, thus improving the reliability and efficiency of the optimization process. \n  \nSpeaker : Pandya Kush Tusharbhai \nResearch Supervisor : Aravind Balan
URL:https://aero.iisc.ac.in/event/mtechres-adjoint-based-aerodynamic-shape-and-mesh-optimization-with-high-order-discontinuous-galerkin-methods-2/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2025/02/Slide3.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241227T110000
DTEND;TZID=Asia/Kolkata:20241227T130000
DTSTAMP:20260619T065354
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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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241209T103000
DTEND;TZID=Asia/Kolkata:20241209T123000
DTSTAMP:20260619T065354
CREATED:20241202T071527Z
LAST-MODIFIED:20241202T071527Z
UID:10000038-1733740200-1733747400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): "Design and Development of Novel Quadcopters for Reliable Operations in Cluttered Environments"
DESCRIPTION:The quadcopters are increasingly used in cluttered environments as rapid advancements are made in the development of lightweight sensors and payloads. Intelligence Surveillance Reconnaissance (ISR) missions\,  crack detection on the interior surface of a pipe/tunnel\, and close inspection in tropical forest environments are a handful of examples where quadcopters are being deployed. Safe operation in these cluttered environments is challenging mainly due to the proximity of obstacles to the spinning propellers. The complete loss of the propeller makes it impossible to have full-attitude stability on traditional quadcopters. After the propeller failure\, the existing literature relies upon reduced-attitude control\, where the control authority about yaw is sacrificed. To maintain reduced attitude control\, the quadcopter must continuously spin rapidly about the yaw axis. Such a maneuver is risky\, and the quadcopter may not continue the mission after the actuator fails completely. \nFor reliable operation in a cluttered environment\, the quadcopter should also be able to reduce its span mid-flight to minimize the risk of the propeller collision with the obstacles. The quadcopter should remain fully controllable for all spans to enhance usability and applicability. The degree of span reduction should be controllable between the nominal and extreme states. Ideally\, the quadcopter should also be tolerant to the complete failure of the additional “span-reducing” actuator (not to be confused with primary rotor-based actuators). For the broader range of applications\, the concept or the mechanism of span-reducing should be weight-scalable.  The effective execution of an indoor cluttered environment mission may also require a mid-flight flipping quadcopter for gaining the perception of the environment along both nadir and zenith directions with respect to the payload.  Traditional quadcopters cannot sustain the inverted flight and thus lack the maneuverability and reliability to operate safely and effectively in a cluttered environment. Enhancements to the fundamental principles governing quadcopter dynamics are required to facilitate challenging operations in cluttered environments. \nThe first half of the presentation consists of the design and development of a morphing quadcopter called Scissorbot. Scissorbot is a novel mid-flight reconfigurable geometry quadcopter that reduces its lateral span using a single servo-motor coupled with a compact bevel differential gearbox. Scissorbot possesses unique practical features\, including weight-scalability\, geometrical symmetricity\, and fault tolerance to the servo-motor. Scissorbot achieves significant lateral-span reduction without the risk of propeller tip collision by positioning adjacent propellers in different planes. The maximum lateral-span reduction is 88% of its nominal value (highest reported in the literature). This work derives a detailed attitude dynamics model and analyzes the gearbox theoretically. Attitude control is accomplished by implementing a Sliding Mode Controller (SMC) that exhibits robustness to parametric uncertainties such as the moment of inertia and aerodynamic disturbances due to the overlapping of the propellers. The control allocation loop is parametrized with respect to the morphing angle to adapt to the reconfiguration process.  The performance of the Scissorbot is validated using simulations\, test-benches as well as real-world free-flight experiments. \nThe other half presents the design and development of a novel Variable-Pitch-Propeller (VPP) quadcopter called Heliquad. The cambered airfoil propeller-equipped Heliquad generates significantly more torque than its symmetrical airfoil counterpart\, ensuring full-attitude hover equilibrium on only three of its working actuators. VPPs can generate reverse thrust\, enabling mid-flight flip and sustained inverted flight on Heliquad. A unified control architecture ensures the tractability of the Heliquad. Furthermore\, a Neural-Network (NN) based control allocation method is proposed to address the non-linearities in the actuator dynamics. The control allocation is reconfigurable based on the index of the faulty actuator. For the experimental validation\, a prototype of  Heliquad is built. The design and analysis of the VPP mechanism installed on the Heliquad prototype are also presented. The performance of Heliquad is validated using simulations\, test-benches\, and real-world free-flight experiments. The safe recovery of a quadcopter architecture (Heliquad) with full attitude control after the complete failure of an actuator is demonstrated for the first time in the literature. \nSpeaker:  Kulkarni Eeshan Prashant \nResearch Supervisor: Prof Suresh Sundaram
URL:https://aero.iisc.ac.in/event/ph-d-engg-design-and-development-of-novel-quadcopters-for-reliable-operations-in-cluttered-environments/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/12/Eeshan.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241206T140000
DTEND;TZID=Asia/Kolkata:20241206T170000
DTSTAMP:20260619T065354
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:20241205T103000
DTEND;TZID=Asia/Kolkata:20241205T123000
DTSTAMP:20260619T065354
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:20241202T103000
DTEND;TZID=Asia/Kolkata:20241202T130000
DTSTAMP:20260619T065354
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:20241129T150000
DTEND;TZID=Asia/Kolkata:20241129T170000
DTSTAMP:20260619T065354
CREATED:20241126T093642Z
LAST-MODIFIED:20241126T093642Z
UID:10000031-1732892400-1732899600@aero.iisc.ac.in
SUMMARY:MTech(Res): Adjoint-Based Aerodynamic Shape and Mesh Optimization with High-order Discontinuous Galerkin Methods
DESCRIPTION:The aerodynamic shape of an aircraft plays a critical role in its performance. Aerodynamic Shape Optimization (ASO) modifies the shape to achieve desired performance metrics\, such as reduced drag or increased lift. ASO integrates numerical optimization techniques with Computational Fluid Dynamics (CFD). Gradient-based optimization techniques are widely employed for ASO. The adjoint solution enables the accurate and efficient computation of the gradients of the performance metrics with respect to the shape parameters. Performance metrics are derived from CFD solutions\, which inherently contain inaccuracies. These inaccuracies can affect the reliability of the optimization process. High-order methods\, like Discontinuous Galerkin (DG)\, offer improved accuracy for a computational cost comparable to Finite Volume methods in compressible flows\, making them well-suited for ASO. Adaptive mesh refinement can further improve the accuracy of simulations. The adjoint solution used for computing gradients also finds application in mesh adaptation. Combining adjoint-based mesh adaptation with gradient-based ASO provides better control over the inaccuracies during optimization.\n\nTowards this\, the present work performs ASO using high-order DG methods and devises strategies for incorporating adaptive mesh refinement. The shape is defined using smooth splines\, and the Free Form Deformation (FFD) method controls shape changes. With changes in the geometry\, the mesh needs to move to be consistent with the modified shape. A mesh deformation strategy ensures that the mesh evolves smoothly with geometry. A gradient-based method employing the Sequential Quadratic Programming (SQP) algorithm is used for optimization. The adjoint solution computes the gradients and passes them to the optimization algorithm. Optimization for a set of drag minimization problems\, including benchmark Aerodynamic Design Optimization Discussion Group (ADODG) test case 1 and inverse design problems\, is performed on non-adapted meshes.\n\nFurthermore\, a strategy is formulated to incorporate adjoint-based mesh adaptation within the optimization process. Based on the value of adjoint-based error estimates\, the strategy decides on instances of the optimization process that require control of the errors and\, thus\, mesh adaptation. Such a strategy leads to automated control of errors in the performance metrics\, thus improving the reliability and efficiency of the optimization process.\n\n\nSpeaker: Pandya Kush Tusharbhai\n\nResearch Supervisor: Aravind Balan
URL:https://aero.iisc.ac.in/event/mtechres-adjoint-based-aerodynamic-shape-and-mesh-optimization-with-high-order-discontinuous-galerkin-methods/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/11/pandya.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241114T140000
DTEND;TZID=Asia/Kolkata:20241114T170000
DTSTAMP:20260619T065354
CREATED:20241114T083023Z
LAST-MODIFIED:20241126T093958Z
UID:10000030-1731592800-1731603600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Asymptotic Modelling of Carbon Nanotube (CNT) and CNT-Reinforced Composite Structures Using Strain Gradient Formulations
DESCRIPTION:Carbon nanotubes (CNTs) have garnered attention for their remarkable mechanical\, thermal\, and electrical properties\, making them valuable in various applications. CNTs are particularly advantageous in aerospace structures as reinforcements in polymer matrix composites\, enhancing structural performance while reducing weight. Furthermore\, they offer the potential for multifunctionality\, integrating structural\, thermal\, and electrical functionalities within components like wings. However\, accurately modelling CNT behaviour poses challenges\, especially considering their application in larger-scale aerospace structures. While accurate\, molecular dynamics and molecular structural mechanics are computationally intensive and limited in length scale. In this context\, the present research proposes reduced-order continuum structural models using the Variational Asymptotic Method (VAM) to study CNT and its composite structures while incorporating length-scale effects using strain-gradient formulations. \nUsing VAM\, single-walled CNTs (SWCNTs) were first analysed by considering them as straight\, hollow\, circular tubes in a local continuum framework. This tube model accounts for the geometrically-nonlinear behaviour of standalone CNT when subjected to bending and buckling loads. Cross-sectional ovalisation leading to nonlinear bending and buckling behaviour has been studied. Combined loading cases of bending and compression; torsion and compression; & bending and torsion have been examined. The study aims to provide insights into the 3-D nonlinear deformation behaviour of SWCNTs\, offering a more efficient approach for evaluating CNTs in aerospace composite applications. \nIn the next step\, recognising the significance of the structure’s small size (such as used in MEMS\, NEMS\, and sensors)\, non-classical theories\, such as the Modified Strain Gradient Theory\, which account for the size effect in the material\, have been employed to develop a pioneering beam and plate models tailored for CNT-reinforced composite structures. Emphasising the critical nature of size effects\, characterised by length-scale parameters\, this study delves into the nuances of the length-scale effects in nanoscale structures. To develop the asymptotically-correct strain-gradient beam model\, a prismatic beam with a rectangular cross section has been considered to derive zeroth-order and subsequent higher-order models while capturing the strain-gradient effects. Notably\, this work is the first application of non-classical theories in developing VAM-based beam models. Different orders for length-scale parameters have been considered\, and the validity of each choice is scrutinised\, followed by guidance on the appropriate choice of the length-scale parameters. \nFollowing the development of the strain-gradient beam model\, a modified strain gradient theory-based plate model has also been developed using VAM\, which is again a first-of-its-kind work in the context of VAM and reduced-order structural models. Using the variational methods\, fourth-order differential equations were obtained for the non-classical case\, and similarly\, an additional set of boundary conditions (non-classical) were also derived. The warping solutions and the plate stiffnesses are obtained by solving this boundary value problem. It was noted that the material length-scale parameters appear only in the bending and twist stiffness terms. Further\, the classical results can be derived by setting the material length-scale parameters to zero. Zeroth- and first-order approximations have been derived\, followed by detailed validation of the results with literature for bending and buckling load cases. Parametric studies involving variations in thickness and plate width have been conducted to assess their influence on mechanical behaviour. The developed plate model is then applied to CNT-reinforced composites\, and their bending and buckling studies have been carried out. The parametric studies have also considered evaluating all influencing parameters like CNT volume fraction\, material length-scale parameter\, plate thickness and width. \n  \nSpeaker: Renuka Sahu \nResearch advisor: Prof Dineshkumar Harursampath
URL:https://aero.iisc.ac.in/event/asymptotic-modelling-of-carbon-nanotube-cnt-and-cnt-reinforced-composite-structures-using-strain-gradient-formulations-2/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/11/renuka.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241108T150000
DTEND;TZID=Asia/Kolkata:20241108T170000
DTSTAMP:20260619T065354
CREATED:20241108T093028Z
LAST-MODIFIED:20241126T093831Z
UID:10000029-1731078000-1731085200@aero.iisc.ac.in
SUMMARY:MTech(Res): Deformation-based Topological Lattices and their Edge States
DESCRIPTION:Topological elastic metamaterials (TEMs) represent a novel class of elastic materials known for their unique ability to localize vibration energy at boundaries\, maintaining robustness against system disorders. These unconventional properties make TEMs highly attractive for applications in vibration isolation\, energy harvesting\, mechanical sensing\, and waveguiding. \nSpring-mass models are fundamental in designing TEMs\, capturing essential physics due to their structure of periodically repeating unit cells with lumped masses. The elastic coupling of these unit cells gives rise to unique wave propagation properties within the bulk material. Traditionally\, TEMs have been analyzed using mass displacements as degrees of freedom. However\, recent discoveries have shown that analyzing these models through the lens of spring deformations as degrees of freedom opens up new design possibilities for TEMs. \nIn this study\, we generalize the deformation framework in one dimension (1D). We introduce a novel 1D TEM that employs spinners with alternating moments of inertia coupled to their nearest neighbors through various types of spring connections. These connections result in different spring deformations\, thereby extending the deformation framework. Notably\, different localization profiles of boundary states emerge at opposite ends of the finite model\, explained by hidden chiral symmetry in the deformation framework. The results are validated experimentally using Laser Doppler Vibrometry. We further extend the deformation framework to two dimensions (2D) using a quasi-1D approach\, demonstrating the robustness of boundary waves against disorder. \nWe then explore the mathematical foundations of the deformation framework for a general 1D lattice\, emphasizing an underlying rank deficiency in the local stiffness matrices of spring-mass models. This leads to a special factorization of the global stiffness matrix that involves trapezoidal matrices\, thereby allowing the model to be represented in the deformation framework as an isospectral partner. We illustrate the utility of this approach with examples of disordered topological models\, generating a family of isospectral partners exhibiting boundary states and bandgaps. \nOur study introduces a non-standard approach to expressing the dynamics of spring-mass models of TEMs\, unlocking numerous research opportunities to construct periodic and aperiodic topological systems with a broader range of boundary conditions. Additionally\, the insights gained from this work can be extended to other classical domains\, such as acoustic\, photonic\, and electrical systems. \n  \nSpeaker: Udbhav Vishwakarma \nResearch Supervisor: Rajesh Chaunsali
URL:https://aero.iisc.ac.in/event/deformation-based-topological-lattices-and-their-edge-states/
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/Udbhav-Vishwakarma1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20241030T150000
DTEND;TZID=Asia/Kolkata:20241030T170000
DTSTAMP:20260619T065354
CREATED:20241030T093004Z
LAST-MODIFIED:20241126T093945Z
UID:10000028-1730300400-1730307600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Intersection Planning in Multilane Aerial Corridors for UAVs
DESCRIPTION:Uncrewed aerial vehicles (UAVs) are revolutionizing traditional aviation markets by opening the airspace to new participants and expanding multimodal applications\, increasing the UAVs’ participation in the uncontrolled low-altitude class G airspace. Therefore\, having a UAV Traffic Management (UTM) system is of great importance in designing structured traffic rules for UAV paths in the airspace (corridors) and intersections. This work addresses the problem of intersection planning in the context of UTM. We consider a multilane multi-UAV traffic management framework\, CORRIDRONE. In this setup\, an intersection volume is defined when two or more multilane corridors merge in the airspace. Unlike road intersection scenarios\, an aerial intersection has a virtual\, non-visible boundary. Hence\, resolving conflicts is challenging without a traffic light. In this thesis\, we develop algorithms to manage intersections and resolve conflicts in pre-flight and in-flight modes. In the first part of the thesis\, we consider that only one UAV is assigned per corridor. Hence\, intersection volumes are created by intersecting two lanes. Here\, we present an algorithm that exploits the relative geometry between the UAVs and schedules the speed of one UAV relative to the other for multiple intersections. Next\, we extend this methodology to pre-plan a UAV trajectory also to include UAV accelerations while scheduling. This method utilizes the time taken for the UAVs involved in the conflict to enter and exit an intersection formed owing to their corridor paths. For corridors with multiple lanes\, we define an intersection volume free of lanes\, such that the lane boundaries are valid only till the intersection boundaries. We then present a lane-changing approach to resolve conflicts by changing the initially intended path connecting two lanes. We further added security to the UAVs in conflict-laden scenarios by creating a dronecage\, which is an amalgamation of multiple geofences intersecting at multiple points (intercrosses). The UAVs travel inside these geofences to change lanes or corridors and reach their destination safely. We propose an algorithm that uses an approach vector-based strategy to navigate this dronecage. We show the effectiveness of the algorithms developed with numerical simulations and hardware tests. The motivation behind the thesis lies in providing the complete conflict resolution architecture for UTM to be used if and when needed in real-life scenarios. \nSpeaker: Samiksha Rajkumar Nagrare \nResearch Supervisor: Debasish Ghose
URL:https://aero.iisc.ac.in/event/intersection-planning-in-multilane-aerial-corridors-for-uavs/
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/samiksha.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240801T103000
DTEND;TZID=Asia/Kolkata:20240801T113000
DTSTAMP:20260619T065354
CREATED:20240801T054703Z
LAST-MODIFIED:20240803T054737Z
UID:10000011-1722508200-1722511800@aero.iisc.ac.in
SUMMARY:[PhD Colloquium] Development of Generalizable Spiking Neural Network-based Learning Frameworks for Solving Perimeter Defense Problem
DESCRIPTION:Spiking Neural Networks (SNNs) are third-generation neural networks that can process information in a more biologically realistic way compared to other neural networks such as sigmoidal networks. They process the information in terms of spike which is considered as a discrete event in time. Due to their high energy efficiency\, SNNs are used in various applications such as classification\, prediction\, assignment\, recognition\, etc. In this thesis\, the capability of SNNs to solve the SpatioTemporal MultiTask Assignment (STMTA) problem which is formulated from a Perimeter Defense Problem (PDP) is explored. \nDue to the efficiency of SNNs in handling spatiotemporal data\, they are used to develop learning-based frameworks to solve the PDP. Initially\, a time-varying weight SNN for decentralized assignment learning for a critical PDP is presented in this thesis. A Decentralized sequential Assignment Learning with Spiking neural networks (abbreviated as DeALS) approach is proposed for the PDP which can approximate the relation between intruder velocity\, shape of the territory\, size of the defender team\, and protection area. In DeALS\, a multitask assignment SNN is developed for each defender to protect the perimeter. This time-varying weight multitask assignment SNN is trained in a supervised manner to approximate the ground truth obtained from the existing external solution for PDP. To reduce the usage of external ground truth algorithms the greedy assignment learning-based frameworks are developed to solve PDP in a decentralized manner. Due to the decentralized training of SNN\, conflicts are found in the final defender assignments. Therefore to resolve this conflicts an additional conflict-free trajectory generation algorithm is used. Further\, in the thesis to reduce the usage of a conflict-free trajectory generation algorithm an SNN which can generate conflict-free assignments is developed to solve PDP. A centralized greedy assignment learning solution is developed for PDP using the aforementioned conflict-free assignment SNN. These conflict-free assignments are obtained with the help of inhibitory connections among the assignment neurons in the SNN. \nFurther\, the inhibitory connections are used to develop efficient deep SNNs for classification purposes. The inhibitory connections are motivated by biology. These inhibitory connections make sure that the first spiking neurons in a layer acquire knowledge efficiently about the input by inhibiting the response of other neurons in the same layer. A Distributed Coding SNN (DC-SNN) architecture with inhibitory connections in the hidden layer is developed for solving classification problems. With the help of Temporal Separation Modulated Spike Timing Dependent Plasticity (TSM-STDP) learning it is demonstrated that a DC-SNN is suitable for early interruption which helps in faster classification. Eventually\, in this thesis\, SNN classifiers with time-varying weights without hidden layers are developed which are capable of inherent interpretations. The time-varying weights are modeled using random Gaussian mixtures spread across the simulation interval.  By establishing relationships between the amplitudes of time-varying weights and the spike patterns of the neurons in the architecture\, the decisions of these spiking neural classifiers are interpreted. \n  \nSpeaker: P. Mohammed Thousif
URL:https://aero.iisc.ac.in/event/phd-colloquium-development-of-generalizable-spiking-neural-network-based-learning-frameworks-for-solving-perimeter-defense-problem/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/04/Thesis-Colloquium-Defence.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240731T150000
DTEND;TZID=Asia/Kolkata:20240731T160000
DTSTAMP:20260619T065354
CREATED:20240731T054804Z
LAST-MODIFIED:20240822T084630Z
UID:10000012-1722438000-1722441600@aero.iisc.ac.in
SUMMARY:[MTech(Res) Colloquium] Deformation-based Topological Lattices and their Edge States
DESCRIPTION:Topological elastic metamaterials (TEMs) represent a novel class of elastic materials known for their unique ability to localize vibration energy at boundaries\, maintaining robustness against system disorders. These unconventional properties make TEMs highly attractive for applications in vibration isolation\, energy harvesting\, mechanical sensing\, and waveguiding.\n\n\nSpring-mass models are fundamental in designing TEMs\, capturing essential physics due to their structure of periodically repeating unit cells with lumped masses. The elastic coupling of these unit cells gives rise to unique wave propagation properties within the bulk material. Traditionally\, TEMs have been analyzed using mass displacements as degrees of freedom. However\, recent discoveries have shown that analyzing these models through the lens of spring deformations as degrees of freedom opens up new design possibilities for TEMs.\n\n\nIn this study\, we generalize the deformation framework in one dimension (1D). We introduce a novel 1D TEM that employs spinners with alternating moments of inertia coupled to their nearest neighbors through various types of spring connections. These connections result in different spring deformations\, thereby extending the deformation framework. Notably\, different localization profiles of boundary states emerge at opposite ends of the finite model\, explained by hidden chiral symmetry in the deformation framework. The results are validated experimentally using Laser Doppler Vibrometry. We further extend the deformation framework to two dimensions (2D) using a quasi-1D approach\, demonstrating the robustness of boundary waves against disorder.\n\n\nWe then explore the mathematical foundations of the deformation framework for a general 1D lattice\, revealing an underlying rank deficiency in the local stiffness matrices of spring-mass models. This leads to a unique factorization of the global stiffness matrix\, allowing the model to be represented in the deformation framework as an isospectral partner. We illustrate the utility of this approach with examples of spring-mass models for bars and beams\, generating a family of isospectral partners exhibiting disorder and boundary states.\n\n\nOur study introduces a non-standard approach to expressing the dynamics of spring-mass models of TEMs\, unlocking numerous research opportunities to construct periodic and aperiodic topological systems with a broader range of boundary conditions. Additionally\, the insights gained from this work can be extended to other classical domains\, such as acoustic\, photonic\, and electrical systems.\n  \n  \n\nSpeaker: UDBHAV VISHWAKARMA
URL:https://aero.iisc.ac.in/event/mtechres-colloquium-deformation-based-topological-lattices-and-their-edge-states/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/04/Thesis-Colloquium-Defence.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240719T103000
DTEND;TZID=Asia/Kolkata:20240719T233000
DTSTAMP:20260619T065354
CREATED:20240719T061638Z
LAST-MODIFIED:20240803T061806Z
UID:10000016-1721385000-1721431800@aero.iisc.ac.in
SUMMARY:On mathematical analysis of biomembrane structures
DESCRIPTION:During the cellular processes\, membrane instabilities play a crucial role across the several domains of life. In many cases\, this is aided by evolutionary molecular complexes. For example\, the complex contains protein monomers that adhere to the cell membrane and polymerize into thin filaments\, which proceed to form a helical constricting bundle\, eventually leading to the cleavage of the neck during cell division; the exact mechanism by which the helical filament induces curvature in the membrane is poorly understood. Recently\, we explored the mechanics of membrane and filament coupling through a continuum model for both structures and presented computational strategies to solve the highly nonlinear model. In an ongoing work\, we model a similar phenomenon associated with particles and use linear stability analysis to predict the onset of certain instabilities in the case when proteins are modeled as embedded particles. A part of this research is under current investigation using both numerical techniques as well as tools of local nonlinear analysis of bifurcating branches. \nSpeaker: Prof. Basant Lal Sharma \nBiography: Prof. Basant Lal Sharma received a Bachelor of Technology in Mechanical Engineering from the Indian Institute of Technology Bombay\, Powai\, Mumbai\, India\, in 1999. In 2004\, he received a Ph.D. in Mechanics (P. Rosakis) from Cornell University\, Ithaca\, NY\, USA. After post-doctoral positions at Cornell University (S.H. Strogatz) and École Polytechnique\, Palaiseau\, Paris\, France (L. Truskinovsky)\, he joined the Department of Mechanical Engineering\, Indian Institute of Technology Kanpur in January 2007 as a Faculty member.
URL:https://aero.iisc.ac.in/event/on-mathematical-analysis-of-biomembrane-structures/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/04/AE-Seminar.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240716T160000
DTEND;TZID=Asia/Kolkata:20240716T170000
DTSTAMP:20260619T065354
CREATED:20240716T061914Z
LAST-MODIFIED:20240803T062047Z
UID:10000017-1721145600-1721149200@aero.iisc.ac.in
SUMMARY:[PhD Defense] Bearings-Only Quadrotor Guidance in Gap Traversal Scenarios
DESCRIPTION:In autonomous missions\, quadrotors are often required to safely fly through gaps or openings. Designing traversal guidance strategies becomes crucial in such scenarios\, especially when the quadrotor relies on the information obtained through onboard sensors. Lightweight and passive vision-based sensors can readily provide bearing information of the gaps using image features. This thesis addresses the quadrotor guidance problem of traversing gaps using only the relative bearing information. Specifically\, the work considers three scenarios: planar flight through gaps\, window traversal\, and moving gap traversal for lane transition in air corridors. \nThe first part of the thesis presents a planar gap traversal guidance law using bearings-only information. The main contribution in this part is a novel guidance method governing quadrotor heading direction using bearing information of the gap opening. The proposed heading direction is designed using an elliptic shaping angle derived from the angular bisector orientation of the gap-bearing angles. The stability of the resulting closed-loop kinematics is ascertained using Lyapunov’s direct method. Additionally\, a phase plane analysis is carried out to visualize the safe traversal characteristics of the proposed method considering all possible initial conditions around the gap. Combined with a tracking controller\, the proposed guidance strategy is applied to a six-degree-of-freedom (6-DOF) quadrotor model\, ensuring convergence towards the prescribed trajectory. The effectiveness of the proposed guidance method is validated with numerical simulations considering several initial conditions\, noisy bearing measurements\, and dynamic vehicle constraints. \nMoving beyond planar scenarios\, a three-dimensional window traversal problem is considered in the next part of the thesis and a guidance solution is proposed using bearing information of window extremities. The guidance logic governs the commanded flight path angle and heading angle of the vehicle. Again\, these commands comprise an angular bisector component with a shaping angle\, facilitating traversal along a direction normal to the window plane and passing through the centroid. A detailed stability analysis ascertains the convergence of vehicle trajectories to the desired traversal path. Simulation studies consider a 6-DOF quadrotor model\, dynamic attitude constraints\, and noise in bearing information. The robustness of the proposed method is demonstrated through a Monte-Carlo simulation study\, considering various initial conditions and noisy measurements. \nNext\, a new lane transition guidance method for a quadrotor flying in an air corridor system is introduced. Utilizing the bearing information of the neighboring vehicles\, the guidance method directs the quadrotor for a safe transition between two lanes. Comprising three sequential guidance phases\, the method includes discerning guidance for determining neighboring vehicle velocity\, longitudinal guidance to identify suitable gaps in the destination lane\, and transit guidance to maneuver the quadrotor into the desired gap. A detailed analysis deduces\, in closed-form\, the time duration for each of the three guidance phases. Additionally\, local asymptotic stability is ascertained for the proposed guidance phases. Simulation results and Monte-Carlo studies demonstrate the proposed method’s feasibility\, effectiveness\, and robustness for safe autonomous lane transition. \nOverall\, the proposed guidance methods present simple\, easily computable and closed-form analytic guidance inputs using only the passive bearing information. Further\, deterministic performance guarantees provide a sound theoretical foundation for the novel guidance solutions. The thesis also includes representative experimental studies using an indoor motion capture system and Crazyflie quadrotor platform. \n  \n  \nSpeaker: Midhun E K
URL:https://aero.iisc.ac.in/event/phd-defense-bearings-only-quadrotor-guidance-in-gap-traversal-scenarios/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/04/Thesis-Colloquium-Defence.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240705T163000
DTEND;TZID=Asia/Kolkata:20240705T173000
DTSTAMP:20260619T065354
CREATED:20240705T061014Z
LAST-MODIFIED:20240803T061218Z
UID:10000014-1720197000-1720200600@aero.iisc.ac.in
SUMMARY:[PhD Defense] Wave Propagation in Bio-Inspired Inhomogeneous waveguides for Impact  Mitigation Applications
DESCRIPTION:Decades of research aim to shield structures and people from impact and  shock\, mitigating damage and traumatic brain injuries. The development  of novel structures to absorb energy and reduce stress waves in  structures is indispensable. This thesis derives inspiration from the  biological structure of the woodpecker beak. The woodpecker pecking  generates very high amplitude impact loads causing stress waves to  propagate in its inhomogeneous beak structure\, without sustaining any  brain injury. The main aim of this thesis is to mimic such inhomogeneous  structures in the critical mechanical systems that require impact  mitigation. This dissertation focuses on comprehensive investigation of  computational and experimental wave propagation analysis in such  bio-inspired inhomogeneous structures\, which are often periodic\,  symmetric or anti-symmetric about the midplane\, while exhibiting both  the elastic and viscoelastic material behaviour. Importantly\, the goal  of these new bio-inspired designs is to control the wave propagation in  terms of increased attenuation\, reduction of group speeds and increase  in dispersion. \nFirstly\, the superconvergent finite elements (FE) for longitudinal and  flexural wave propagation analysis in the symmetrical sinusoidally  corrugated bio-inspired structures considering both elastic and  viscoelastic material models are developed\, whose accuracy is validated  using Abaqus. In addition to the wave propagation studies\, static and  free vibration analyses are also carried out in such structures. Next\,  the governing differential equations and the superconvergent FE are  derived for the wave propagation analysis in the shear-deformable  waveguides with anti-symmetric sinusoidal corrugations that introduce  coupling between the wave modes\, and it is validated using the  conventional FE. The study resulted in the development of the  methodology to easily manipulate wave propagation characteristics. Thus\,  a few optimised waveguide configurations that can reduce both group  speeds and wave amplitudes are presented. \nDue to the advantage of modeling viscoelasticity in the frequency  domain\, the frequency domain finite elements based on the spectral FE  are developed for both elastic and viscoelastic structures. Exploiting  the periodicity of the bio-inspired structures\, the dispersion plots are  obtained using the Floquet-Bloch theorem and the transfer matrix method.  The spectral FE and Bloch theorem-eigenvector methods are then used to  obtain the time-history responses in the semi-infinite as well as finite  structures. For dynamic and wave propagation analysis of viscoelastic  structures in the time domain\, a new direct time integration scheme is  also proposed. The stability analysis of the proposed scheme is carried  out using the spectral technique as well as the von Neumann stability  criteria. The responses obtained using the proposed time integration  scheme for various structures are validated with a commercial finite  element code. \nBased on the conducted research\, facesheets for honeycomb sandwich  structures as a practical application for blast wave mitigation are  developed. The suture structures in the facesheets are obtained with the  multi-objective structural optimization method using genetic algorithm  (NSGA-II)\, wherein the developed viscoelastic FE formulation is used.  The performance of this optimized suture-based face sheet is  experimentally tested in a vertical shock tube to validate the results  obtained using Abaqus.\nIn summary\, this thesis offers a multidisciplinary approach in  investigating and understanding wave propagation in the bio-inspired  inhomogeneous structures and its relevance to impact mitigation. \n  \n  \nSpeaker: Manish Suresh Raut
URL:https://aero.iisc.ac.in/event/phd-defense-wave-propagation-in-bio-inspired-inhomogeneous-waveguides-for-impact-mitigation-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/2024/04/Thesis-Colloquium-Defence.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240627T153000
DTEND;TZID=Asia/Kolkata:20240627T163000
DTSTAMP:20260619T065354
CREATED:20240627T053941Z
LAST-MODIFIED:20240803T060152Z
UID:10000010-1719502200-1719505800@aero.iisc.ac.in
SUMMARY:[MTech(Res) Colloquium] Sub-mesoscale modeling of woven fabrics using VAM-based geometrically-exact beam model
DESCRIPTION:In this work\, a sub-mesoscale model of a woven fabric is developed using finite element methods. The yarns are modeled as beam elements that move freely in space and undergo large deformations and rotations. The geometrically-exact beam theory (GEBT) used to model composite beams of arbitrary cross sections is considered to model the yarns. The variational asymptotic method (VAM) offers the advantage of modeling beams of arbitrary cross sections. A surface-to-surface contact model is developed\, considering that the contact occurs at a point on the surface. The robustness of the contact model is tested by designing a patch test. The mesoscale model is validated using experimental results of biaxial tests performed on a plain glass weave woven fabric. The biaxial simulation is performed by varying the number of yarns in the mesoscale model to study the behavior of the model and demonstrate a representative volume element (RVE). The yarns are made up of fibers twisted together. An isotropic model is an approximation that works well on the mesoscale\, but a more general model is needed to include fiber-level information. Most microscale models use technologically expensive micro-CT scans. There are powerful homogenization techniques\, such as variational asymptotic homogenization (VAH)\, that can be leveraged to develop homogenized properties of the yarn by including fiber-level information. The use of VAH includes more physics into the model with minimal effort. A novel alternative model to a woven fabric is developed using VAM to include microscale information. The tools like cross-sectional analysis\, GEBT\, and VAH are used to study the behavior of woven fabrics with different coatings. The model can be extended by introducing friction between yarns in the contact. Further\, the uncertainty in the input parameters can be quantified by propagating the uncertainty through the system using uncertainty quantification (UQ) techniques. \n  \n\nSpeaker: R ADHITHYA
URL:https://aero.iisc.ac.in/event/mtechres-colloquium-sub-mesoscale-modeling-of-woven-fabrics-using-vam-based-geometrically-exact-beam-model/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/04/Thesis-Colloquium-Defence.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20240614T160000
DTEND;TZID=Asia/Kolkata:20240614T170000
DTSTAMP:20260619T065354
CREATED:20240614T061338Z
LAST-MODIFIED:20240803T061531Z
UID:10000015-1718380800-1718384400@aero.iisc.ac.in
SUMMARY:Design and characterization of periodic scatterers for noise insulation
DESCRIPTION:The array of periodic scatterers is known as sonic crystal at present and sonic crystal is the most cost-effective solution for a “noise barrier” because of its acoustic attenuation due to size\, geometry\, and periodic arrangement of scatterers. Porous materials that are commonly used for sound absorption have poor sound insulation capability. In this work\, rigid scatterers are installed periodically inside porous materials to improve their transmission loss (TL) with the Bragg diffraction. The Delany-Bazley impedance model is used to model the porous material and the transfer matrix method is adopted to calculate the TL of the mixed structure in a duct. Simulation results with a different number of scatterers and porous materials with different airflow resistivity show that the TL of porous materials can be increased significantly with periodically arranged scatterers. The decoupled analysis reveals that the TL of the mixed structure is larger than the sum of the TL of individual components in most frequency bands\, except that around the first Bragg resonance frequency. Afterwards\, the insertion loss (IL) of two types of finite size structures constructed by installing two parallel porous sheets within rows of periodic scatterers is investigated in free field. Next\, the free field insertion loss (IL) and echo reduction (ER) are calculated for finite size periodic scatterers via time domain simulations in a room environment where the walls of the room are acoustically reflective. A spectrally dense short pulse is used as a sound source and the time domain pulse separation technique is devised to calculate the IL and ER of finite size periodic scatterers. The key discovery of the research is that the calculated IL and ER of periodic cylindrical scatterers in a room environment agree to results obtained from the free field simulations which are also imitable experimentally. Next\, the experiments are conducted in a room environment with periodic cylindrical scatterers. A loudspeaker is used as a sound source. The signal synthesis technique is demonstrated to generate the desired short pulse from a loudspeaker for measurement in given environment followed by measurements which agree to simulation results. \n  \nSpeaker: Dr. Dibya Prakash Jena \nBiography: Dr. Dibya Prakash Jena is an expert in artificial metamaterials\, condition monitoring\, and acoustics\, vibration and noise control having wide experience in industry and academia. He has been awarded the DIN Young Visiting Fellowship 2022 and the Honorary Research Fellow of the University of Technology Sydney. He has over 32 journal publications\, 4 patents\, 2 book chapters and 12 conference publications.
URL:https://aero.iisc.ac.in/event/design-and-characterization-of-periodic-scatterers-for-noise-insulation/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2024/04/AE-Seminar.jpg
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END:VCALENDAR