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TZID:Asia/Kolkata
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TZOFFSETFROM:+0530
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DTSTART:20260101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260804T150000
DTEND;TZID=Asia/Kolkata:20260804T170000
DTSTAMP:20261010T050659
CREATED:20260803T045933Z
LAST-MODIFIED:20260804T105424Z
UID:10000143-1785855600-1785862800@aero.iisc.ac.in
SUMMARY:Multiphase Reactive Flows: From Dust Explosions to Metal-Fueled Detonations
DESCRIPTION:. \nExplosions in coal mines\, metal-processing facilities\, and other industrial settings occur with alarming regularity\, while reactive metal particles are being considered for energy-storage and propulsion applications. Despite a long history of research and its importance to safety and propulsion applications\, the physical mechanisms that govern the ignition\, combustion\, and detonation of reactive particles remain relatively unknown. Basic questions such as “How do particle size and thermal radiation affect dust-explosion propagation?”\, “What mechanisms govern the ignition and combustion of shock-dispersed metal powders?”\, and “How can reactive particles modify or sustain detonation waves?” remain unanswered. This presentation will discuss an ongoing numerical simulation effort aimed at answering these and other fundamental questions. This problem is addressed by solving a set of equations that couples a fully compressible reacting gas to a granular multiphase model that accounts for particle motion\, interphase drag and heat transfer\, and particle combustion. The results of these simulations indicate that shock propagation\, particle dispersal\, ignition\, combustion\, and thermal radiation are tightly coupled in a highly dynamic process. Results discussing the influence of particle diameter and thermal radiation on layered coal-dust explosions and the ignition and combustion of TNT-dispersed aluminum powder will be discussed. The presentation will close by discussing recent work exploring hybrid aluminum–hydrogen–air detonations\, including the role of particle size in extending detonation limits and modifying detonation structure. \n  \nSpeaker: Dr. Guhathakurta \nBiography:  \nDr. Guhathakurta received an M.Sc. degree in Physics from the Indian Institute of Technology Delhi\, and M.S. and Ph.D. degrees in Aerospace Engineering from the University of Florida. He subsequently held a postdoctoral appointment at Eindhoven University of Technology in the Netherlands. Dr. Guhathakurta is currently an Assistant Professor in the Department of Aerospace Engineering at Texas A&M University. His research focuses on a wide range of topics in multiphase reactive flows\, combustion\, and numerical simulation\, including dust explosions\, hybrid detonations\, thermal-radiation effects\, metal-particle combustion\, and high-speed propulsion.
URL:https://aero.iisc.ac.in/event/multiphase-reactive-flows-from-dust-explosions-to-metal-fueled-detonations/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Dr-RD-Seminar-Aug-6.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260805T110000
DTEND;TZID=Asia/Kolkata:20260805T130000
DTSTAMP:20261010T050659
CREATED:20260728T061746Z
LAST-MODIFIED:20260802T102832Z
UID:10000141-1785927600-1785934800@aero.iisc.ac.in
SUMMARY:MTech(Res) : Design of an Ex-Situ Gas Sampling Layout with Various Probes and Their Performance Assessment for Accurate Emission Measurements
DESCRIPTION:Chemical kinetic mechanism development and validation require quantitative species data from canonical flames. Burner-stabilized pre -mixed flames provide a stationary post-flame region directly comparable to one-dimensional kinetic simulations. Ex-situ gas sampling delivers absolute CO and NO mole fractions from this region. The extraction step introduces two coupled biases. Reactions can continue inside the probe\, and the probe can perturb the flame upstream of the inlet. This thesis develops a coordinated ex-situ sampling framework for atmospheric McKenna burner-stabilized CH₄/air flames. The framework combines a sampling and dilution layout\, five sampling probes\, and a staged correction methodology. The measurements span fuel-lean to fuel-rich flames at three heights above the burner. The sampling and dilution layout is one of the principal contributions of the present work. The complete layout was designed and assembled in this work to adapt a portable gas analyzer (PG-350) for laboratory flame diagnostics. The PG-350 is built for stationary-source emissions monitoring rather than laboratory flame research. The design repurposes this industrial emissions instrument for high-precision species measurement in flames. The adapted instrument serves fundamental academic flame research. The layout delivers a conditioned\, metered\, and range-compatible sample to the analyzer. A vacuum pump extracts the sample using a sampling probe and drives it through the line. Two water-cooled drain separators\, designed and fabricated in this work\, remove the post-flame moisture. An Alicat mass flow meter measures the conditioned sample flow rate. A controlled N₂ dilution arrangement extends the CO measurement range beyond the analyzer’s full scale for the rich flames. Five sampling probes represent four reaction-quenching strategies. The aerodynamic-quench (AQ) probe was designed using a one-dimensional gas-dynamics model developed in this work. A brute-force screening selected its geometry against the pump and analyser constraints. The water-cooled (WC)\, pressure-quench (PQ)\, and uncooled probes were sized using non-reacting two-dimensional axisymmetric CFD. The uncooled-metal (UC-M) probe serves as a hot-wall reference. The uncooled-quartz (UC-Q) probe isolates the wall-material effect under the same geometry. Each probe was assessed experimentally and through two-dimensional probe-resolved reacting CFD in ANSYS Fluent. A residence-time method quantified the probe-induced upstream shift of the sampling location for the designed probes. A staged correction methodology recovers the sampled-gas composition from the conditioned analyzer reading. It corrects the mass flow meter reading for its gas-property mismatch. It then removes the imposed dilution and restores the moisture removed during conditioning. An independent route back-calculates the dilution ratio from paired CO₂ measurements. The methodology propagates the input uncertainties through the correction chain using the GUM framework. Reported values quote the expanded uncertainty on the corrected species. The corrected CO and NO were evaluated against a one-dimensional chemical kinetic simulation of the unperturbed flame. The comparison accounts for the probe-induced upstream shift of the sampling location. Each designed probe draws its sample from a location displaced toward the burner relative to its tip. The three designed probes were compared against the reference at their displaced sampling locations. The pressure-quench probe is the most consistent for both species. The water-cooled probe is a close alternative. The vacuum pump performance degraded due to moisture condensation in the pump head. Therefore\, it held the AQ suction above its design value throughout the campaign. The AQ probe is therefore off-design and cannot be ranked on equal terms. The uncooled-metal probe shows a large NO deficit in the rich flames from hot-wall surface reactions. The uncooled-quartz probe isolates the metal wall as the origin of this deficit. These rankings measure consistency with the kinetic reference rather than absolute accuracy. This work delivers outcomes of broader use to the combustion community. The framework offers documented guidelines to the community for ex-situ sampling experiments. It provides a comprehensive assessment of how each quenching strategy performs and which probe suits a given measurement. The corrected CO and NO data are suitable for chemical kinetic mechanism development and validation. Many detailed chemistry mechanisms exist\, yet reacting CFD of practical combustion devices requires reduced mechanisms that reproduce the target species profiles. The present setup allows reduced mechanisms to be validated quickly across flames spanning fuel-lean to fuel-rich conditions. A validated reduced mechanism can then support detailed CFD analysis of practical combustion systems. \n  \nSpeaker :  SARVAGYA SHARMA \nResearch Supervisor :  Irfan Ahmed Mulla
URL:https://aero.iisc.ac.in/event/mtechres-design-of-an-ex-situ-gas-sampling-layout-with-various-probes-and-their-performance-assessment-for-accurate-emission-measurements/
LOCATION:STC Conference Hall\, Ground Floor\, Department of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/SARVAGYA.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260806T113000
DTEND;TZID=Asia/Kolkata:20260806T130000
DTSTAMP:20261010T050659
CREATED:20260717T092701Z
LAST-MODIFIED:20260802T105215Z
UID:10000137-1786015800-1786021200@aero.iisc.ac.in
SUMMARY:Ph .D.(Engg.): Explicit Filtering LES of turbulent swirling flows and multi-regime hydrogen flames
DESCRIPTION:The need to decarbonize power generation and aviation has established hydrogen as a promising fuel for next generation gas turbine combustion systems. However\, its high chemical reactivity significantly increases the propensity for autoignition and flashback under lean premixed conditions commonly used in hydrocarbon combustion systems. New combustor concepts based on direct fuel injection address these problems but typically produce lifted flames. These types of flames exhibit multi-regime combustion\, in which premixed and non-premixed combustion regions co-exist within highly turbulent swirling flow fields. Accurate numerical prediction of such reacting flows remains a major challenge as traditional models developed for hydrocarbon flames often fail to reliably predict the stabilization and combustion characteristics of multi-regime hydrogen flames. This thesis proposes a regime-sensitive combustion model using the thickened flame approach to extend the explicit filtering large eddy simulation (EFLES) method for computations of high Reynolds number (Re) reacting flows. A combustion regime index (CI) is defined based on the alignment between the gradients of mixture fraction and oxygen mass fraction to distinguish between premixed and non-premixed regions. The flame thickening treatment is applied selectively in premixed regions only. The model is implemented within an in-house high-order finite-difference flow solver that employs structured multi-block overlapping meshes to represent complicated geometries encountered in practical combustion systems. The predictive capability of the overall numerical methodology is systematically assessed through a series of increasingly complex flow configurations relevant to swirl-stabilized hydrogen combustors. The first case corresponds to an isothermal (Re ~ 27000) flow in the PRECCINSTA single nozzle swirl combustor. EFLES solutions show excellent agreement with the experimental data for flow field statistics and shape of the vortex breakdown bubble. Spectral proper orthogonal decomposition applied on time resolved velocity fields confirms that the EFLES method accurately reproduces the broadband turbulence structures and the coherent\, narrow band\, self-excited precessing vortex core oscillation. The combustion model performance is then evaluated using a canonical lifted slot jet flame configuration\, comprising a nitrogen diluted hydrogen slot jet of Re=8000 at 400 K issuing into a co-flow of heated air at 850 K. Entrainment of air into the jet core results in a stratified rich premixed flame alongside the primary non-premixed flame branch. The LES predicted flame lift-off height and flow field statistics are in good agreement with companion direct numerical simulation (DNS) results. Differences between LES and DNS solutions are small in premixed flame regions but increase with mesh spacing in non-premixed flame regions. The CI field is shown to clearly distinguish the two flame branches. This result is further validated a-posteriori using chemically explosive mode analysis (CEMA). Combined with EFLES\, the combustion model accurately predicts mixture fraction conditioned thermochemical statistics\, combustion mode distributions and the downstream evolution of premixed and diffusion flame branches in the lifted slot jet hydrogen flame. Finally\, a turbulent lifted hydrogen flame in the dual-swirl HYLON burner is investigated as a practical test case. The time-averaged mean flame shape and liftoff height is well captured in the LES solution. Good agreement is obtained between LES predictions and experimental measurements for statistics of velocity\, temperature\, and major-species mole fractions. CEMA reveals that a partially premixed flame branch is formed along the inner shear layer due to entrainment of hydrogen into the high-velocity annular air stream. The central diffusion flame branch is located within the vortex breakdown bubble between the fuel jet and the recirculating lean combustion products. The distribution of key thermochemical variables in mixture fraction space is also analyzed to characterize the two flame branches. Overall\, the results demonstrate that the proposed multi-regime thickened flame model\, coupled with explicit filtering LES provides a robust framework for high-fidelity LES of turbulent hydrogen flames. The methodology reproduces turbulent flow features\, flame stabilization and mixed combustion regimes across canonical and practical configurations. These results make the case for evaluating the performance of EFLES at higher operating pressures towards realizing a reliable computational engineering method for the design and analysis of future hydrogen gas turbine combustors. \nSpeaker :  ANINDYA DATTA \nResearch supervisor : Santosh Hemchandra
URL:https://aero.iisc.ac.in/event/ph-dengg-colloquium/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/ANINDYA.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260807T110000
DTEND;TZID=Asia/Kolkata:20260807T130000
DTSTAMP:20261010T050659
CREATED:20260804T053733Z
LAST-MODIFIED:20260811T060311Z
UID:10000144-1786100400-1786107600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Aerodynamics and Stability of a Generic Tailless UAV in Ground Effect
DESCRIPTION:Tailless UAVs are stealthy\, high-subsonic configurations used for deep penetration into contested airspace. These configurations have wing with moderate leading edge sweep angle with no definite fuselage and lack both horizontal tail and vertical tail which makes the aerodynamics of these configurations very unique. The increase in autonomous UAVs in recent times have led to renewed interest in this class of configurations. Autonomous take-off and landing of tailless UAVs are complex technologies that require a detailed understanding of the underlying aerodynamic flow physics. The current literature on the ground effects focusses mainly on conventional configuration or high swept delta wings.  This work focusses on understanding the aerodynamic behavior of a typical tailless UAV near the ground and its influence on the stability characteristics. RANS CFD analysis is carried out at different ground heights\, angle of attack and side slip angle. Studies are also carried to understand the effect of roll orientation effect on the ground effects. The  effect of ground on the elevon behavior near the ground are also brought out. Unsteady CFD Analysis are conducted for different sink rates and pitch angles and compared with Static Ground Effects.\n The lift coefficient under Steady Ground Effects was observed to decrease near the ground at lower angle of attack and increase at high angle of attack. The region between the ground and aircraft acts like a venturi at low angle of attack. At high angle of attack\, ramming effect is observed due to increase in the pressure on the bottom surface. The drag coefficient does not change at lower angle of attack whereas significant reduction is observed at higher angle of attack due to the reduction in the induced drag.  The UAV shows a reduction in directional stability near the ground. The rolling moment due to side slip angle shows a stable behavior near the ground.  The roll orientation of the UAVs impacts the rolling moment behavior near the ground providing increased rolling moment near the ground which has a tendency to counter the direction of the roll.  Unsteady CFD Analysis is conducted for different sink rates and pitch angles and compared with Static Ground Effects which shows significant change especially at lower pitch angles. \n The aerodynamic changes introduced by the  presence of ground impacts the Stability of the UAV significantly.  The Stability  changes are particularly important for the tailless UAV as it is neutrally stable in the longitudinal and directional plane. A increase in Static Margin of 0.5% is observed at the lowest ground  height  (h/b = 0.15). There is also marginal increase in weather cock stability (Cnβ)  and roll stability (Clβ) at high angle of attack near the ground. The dynamics of the tailless UAV near the ground has interesting behavior near the ground. The short period mode has stabilizing behavior near the ground whereas the Dutch roll tends to be slightly unstable near the ground. The roll orientation of the UAV seems to impact the Dutch roll mode changing from slightly unstable to a slightly stable behavior.  The aerodynamics and stability aspects are highly coupled for tailless UAV. The understanding of tailless UAV near the ground will be key for development of control schemes for robust take-off and landing of these Configurations. \n  \nSpeaker :  B Saravanan \nResearch Supervisor :  N Balakrishnan \n 
URL:https://aero.iisc.ac.in/event/aerodynamics-and-stability-of-a-generic-tailless-uav-in-ground-effect/
LOCATION:AE Conference Room \, AE 003
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Saravanan.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260810T110000
DTEND;TZID=Asia/Kolkata:20260810T130000
DTSTAMP:20261010T050659
CREATED:20260808T055603Z
LAST-MODIFIED:20260811T060138Z
UID:10000145-1786359600-1786366800@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg):Tonal acoustic radiation from turbulent subsonic jets
DESCRIPTION:Acoustic tones in the near field of a Mach 0.9\, Reynolds number 10^6 round jet are investigated using large-eddy simulations (LES) performed with the explicit filtering LES (EFLES) approach. The jet is issued into the ambient through a cylindrical nozzle. Pressure spectra at observer locations in the upstream direction reveal the presence of tones which are 15–20 dB more intense than the background turbulent mixing noise. Spectral Proper Orthogonal Decomposition (SPOD) of the pressure field in the near-nozzle region reveals two distinct categories of tones. The first category comprises tones whose frequency corresponds to high order radial and azimuthal ductmodes of the nozzle. Their spatial amplitude distribution revealed by SPOD at these frequencies show significant support within the nozzle as expected for the natural hard-wall duct modes. These duct modes are scattered at the nozzle lip and radiate in the upstream direction and explain the tonal radiation observed in the LES at their corresponding frequencies. This mechanism has been extensively studied using Wiener-Hopf models applied to a cylindrical vortex sheet (Munt\, 1977; Rienstra\, 2003; Samanta and Freund\, 2008). The second category of tones observed have frequencies that are not hard wall duct mode frequencises. Their spatial amplitude distribution revelaed by SPOD for these frequencies is characterized by significant support within the jet potential core. Empirical dispersion relations constructed from the LES suggest that these tones arise from resonance in the potential core due to coupling between the upstream-propagating guided jet mode (GJM) and the upstream- and downstream-propagating duct-like modes (Schmidt et al.\, 2017; Towne et al.\, 2017) near the upper cut-off frequency of the guided jet mode (Bogey\, 2021). However\, the mechanism by which tones radiate from the potential core has not yet been established. This motivates the theoretical investigation in this thesis that focuses on the dynamics of the guided jet mode and its interaction with the nozzle lip leading to tonal upstream acoustic radiation. The interaction between the GJM and the nozzle lip is analyzed using a Wiener–Hopf formulation with the jet modelled as a semi-infinite cylindrical vortex sheet and the nozzle with a vanishingly-thin sharp edge. When the GJMs are cut-on\, these solutions show that an incident GJM is reflected as a downstream-traveling soft-duct mode\, a scattered Kelvin–Helmholtz (K–H) mode and a transmitted upstream-traveling hard-wall duct mode. The reflective efficiency of GJM increases with frequency and is greatest near their upper cut-off frequency. This explains why tones associated with potential core resonance occur near the upper cut-off frequency of the GJM. In addition\, the GJM is scattered as acoustic waves to the far field\, primarily in the upstream direction. The scattered wavefronts are most intense along the outer nozzle wall. The scattered waves propagate to the far field where they generate distinctive directivity patterns that show excellent agreement with the LES-computed far-field directivity reported by Bogey (2021). These results provide a mechanistic explanation for how tones generated by potential core resonance radiate to the far field through scattering of the guided jet mode at the nozzle lip. Acoustic tones in the near field of a Mach 0.9\, Reynolds number 10^6 round jet are investigated using large-eddy simulations (LES) performed with the explicit filtering LES (EFLES) approach. The jet is issued into the ambient through a cylindrical nozzle. Pressure spectra at observer locations in the upstream direction reveal the presence of tones which are 15–20 dB more intense than the background turbulent mixing noise. Spectral Proper Orthogonal Decomposition (SPOD) of the pressure field in the near-nozzle region reveals two distinct categories of tones. The first category comprises tones whose frequency corresponds to high order radial and azimuthal ductmodes of the nozzle. Their spatial amplitude distribution revealed by SPOD at these frequencies show significant support within the nozzle as expected for the natural hard-wall duct modes. These duct modes are scattered at the nozzle lip and radiate in the upstream direction and explain the tonal radiation observed in the LES at their corresponding frequencies. This mechanism has been extensively studied using Wiener-Hopf models applied to a cylindrical vortex sheet (Munt\, 1977; Rienstra\, 2003; Samanta and Freund\, 2008). The second category of tones observed have frequencies that are not hard wall duct mode frequencises. Their spatial amplitude distribution revealed by SPOD for these frequencies is characterized by significant support within the jet potential core. Empirical dispersion relations constructed from the LES suggest that these tones arise from resonance in the potential core due to coupling between the upstream-propagating guided jet mode (GJM) and the upstream- and downstream-propagating duct-like modes (Schmidt et al.\, 2017; Towne et al.\, 2017) near the upper cut-off frequency of the guided jet mode (Bogey\, 2021). However\, the mechanism by which tones radiate from the potential core has not yet been established. This motivates the theoretical investigation in this thesis that focuses on the dynamics of the guided jet mode and its interaction with the nozzle lip leading to tonal upstream acoustic radiation. The interaction between the GJM and the nozzle lip is analyzed using a Wiener–Hopf formulation with the jet modelled as a semi-infinite cylindrical vortex sheet and the nozzle with a vanishingly-thin sharp edge. When the GJMs are cut-on\, these solutions show that an incident GJM is reflected as a downstream-traveling soft-duct mode\, a scattered Kelvin–Helmholtz (K–H) mode and a transmitted upstream-traveling hard-wall duct mode. The reflective efficiency of GJM increases with frequency and is greatest near their upper cut-off frequency. This explains why tones associated with potential core resonance occur near the upper cut-off frequency of the GJM. In addition\, the GJM is scattered as acoustic waves to the far field\, primarily in the upstream direction. The scattered wavefronts are most intense along the outer nozzle wall. The scattered waves propagate to the far field where they generate distinctive directivity patterns that show excellent agreement with the LES-computed far-field directivity reported by Bogey (2021). These results provide a mechanistic explanation for how tones generated by potential core resonance radiate to the far field through scattering of the guided jet mode at the nozzle lip. Comparison of the Wiener–Hopf predictions with the LES-computed pressure spectra in the present investigation reveals excellent agreement at lower frequencies but deviations at higher frequencies. At lower frequencies\, the SPOD modes are qualitatively similar to the corresponding Wiener–Hopf solutions. In contrast\, at higher frequencies\, the scattered waves originating from the nozzle lip undergo secondary scattering at the slanted section of the outer nozzle wall\, causing them to lift away from the wall. The findings suggest two possible strategies for mitigating the tones generated by the potential core resonance: (i) modifying the nozzle-lip geometry and (ii) modifying the outer nozzle-wall geometry. \n  \nSpeaker: NAGA SARAS CHANDAN VEMPATI \nResearch Supervisor: Santosh Hemchandra
URL:https://aero.iisc.ac.in/event/ph-d-enggtonal-acoustic-radiation-from-turbulent-subsonic-jets/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/NAGA.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260814T110000
DTEND;TZID=Asia/Kolkata:20260814T133000
DTSTAMP:20261010T050659
CREATED:20260811T114531Z
LAST-MODIFIED:20260824T064859Z
UID:10000146-1786705200-1786714200@aero.iisc.ac.in
SUMMARY:MTech(res)  Parallel Particle Tracking for Turbulent Round Jets
DESCRIPTION:Particle tracking in turbulent jets is essential for an accurate Lagrangian understanding of jet flows. While parallel algorithms and numerical schemes to compute flow fields can be scaled to a large number of computing processes\, the same is not necessarily true for particle tracking. This thesis presents an analysis of the parallel efficiency of particle tracking in the specific context of round turbulent jets.\nA particle tracking module was developed and integrated with Xcompact3d – a well-established flow solver with strong and weak scaling up to 100\,000 processes. The module uses trilinear velocity interpolation scheme and a first-order Euler integration scheme with sub-stepping for particle advancement. Velocity data is exchanged via a halo API provided by 2DECOMP&FFT – the domain decomposition library that Xcompact3d builds upon. Particle data is exchanged via MPI collectives. Additional exchange algorithms that aim to avoid the scalability limitations of MPI collectives are available to the user. However\, the choice of algorithms for data exchange is often constrained by flow and simulation parameters. \nThe module is validated using an analytical velocity field and subsequently employed for DNS and LES of turbulent jets with particles. Particle concentration profiles are used to assess accuracy. The results demonstrate the capability of the integrated code to accurately track particles over multiple simulation runs. The particle numbers used for these simulations are comparable or higher than the number of grid points as opposed to most studies in the literature where particle numbers are much lower than the number of grid points. \nA detailed wall-time and particle-load analysis is done to assess the parallel efficiency and identify performance limitations. Particle tracking and exchange are the largest contributors to simulation time after flow field computation. The wall-time for particle tracking increases with the number of particles in the domain. A large difference is observed between the average wall-time and maximum wall-time across computing processes which is attributed to particle load imbalance. In contrast\, the particle exchange wall-time across computing processes is similar because of the MPI collectives being used for particle data exchange. However\, the number of particles\, and consequently\, the size of data being exchanged\, is a small fraction of the number of particles being tracked. A particle load-analysis reveals considerable variation in the number of particles being tracked by individual processes\, with the maximum difference in particle count amongst processes being as high as three orders of magnitude. \nThe results obtained highlight the challenges in implementing particle tracking at scale. While strategies to mitigate the impact of non-scalable collectives for particle exchange exist\, algorithms to mitigate the severe particle-load imbalance in the context of turbulent jets have not been adequately studied and are urgently required\, which is identified as the key area for future work. \n  \nSpeaker : Nikhil Jayswal \nResearch Supervisor: Prof. Joseph Mathew
URL:https://aero.iisc.ac.in/event/mtechres-parallel-particle-tracking-for-turbulent-round-jets/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/08/Nikhil-Jayswal.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260901T110000
DTEND;TZID=Asia/Kolkata:20260901T130000
DTSTAMP:20261010T050659
CREATED:20260831T045301Z
LAST-MODIFIED:20260904T050250Z
UID:10000148-1788260400-1788267600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg):Effect of rotation on the flow organisation and instability of a slender spinning body across quiescent\, axial and compressible regimes
DESCRIPTION:A body of revolution spinning in a fluid drives an inherently three-dimensional boundary layer\, in which a centrifugally driven secondary circulation lifts the layer off the surface and a centrifugal instability carries it into transition. Most of what is known about this flow comes from single geometries (the rotating disk\, the isolated cone or cylinder) in an unbounded fluid\, and from diagnostics that resolve neither the secondary meridional circulation nor the three-component velocity of the vortices. This work instead resolves the rotation-driven layer with whole-field measurements on a composite\, finite cone–cylinder (half-cone angle 15°)\, and follows it across the settings in which such a layer arises in practice\, of relevance to spin-stabilised flight and rotating machinery: a still fluid with and without confining walls\, the transient establishment from rest\, an imposed axial stream\, and\, as a bounding case\, a compressible free stream.\nCombining planar (two-component) and time-resolved stereoscopic (three-component) particle image velocimetry in the meridional plane with a phase-locked acquisition and a proper-orthogonal decomposition of the fluctuating field\, the study shows how confinement changes the transition from a sharp two-branch switch to a smooth downstream migration coupled to a growing separation bubble; how the layer establishes advectively from rest in a single turnover\, some fifty times faster than viscous diffusion; and how the base rotation ratio Sᵇ = ωR/U∞ organises transition under axial inflow\, with onset at Sᵇ of order unity. As a bounding case\, a slender cone spun in a Mach 2 stream leaves the shock-dominated mean flow and the surface topology essentially unchanged\, adding only broadband unsteadiness with no tonal lock-in\, so that the rotation-driven layer\, though real\, is masked at supersonic speed. Taken together\, the studies trace a single rotation-driven\, centrifugally unstable boundary layer\, with its meridional lift-up and counter-rotating vortices\, reshaped in turn by confinement\, start-up\, axial inflow and compressibility. \nSpeaker : Rajkamal Sah \nResearch Supervisor : Prof. Gopalan Jagadeesh
URL:https://aero.iisc.ac.in/event/ph-d-enggeffect-of-rotation-on-the-flow-organisation-and-instability-of-a-slender-spinning-body-across-quiescent-axial-and-compressible-regimes/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/09/Rajkamal-Sah.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260901T140000
DTEND;TZID=Asia/Kolkata:20260901T170000
DTSTAMP:20261010T050659
CREATED:20260825T054145Z
LAST-MODIFIED:20260825T054307Z
UID:10000147-1788271200-1788282000@aero.iisc.ac.in
SUMMARY:Taming Turbulence
DESCRIPTION:Turbulence remains one of the outstanding problems of classical physics\, and one that has challenged physicists and engineers alike for decades\, even centuries. The fusion of classical approaches and tools of the modern day – theoretical analysis of the Navier-Stokes equations\, state-of-the-art experimental observations\, data-driven methods and machine learning – has led to substantial progress towards understanding the mechanisms sustaining turbulence\, developing predictive capabilities and achieving the potentially revolutionary goal of harnessing or taming turbulence in large-scale (high Reynolds number) practical settings. In this talk\, I will describe some fundamental challenges posed by turbulence near walls\, the impact of this phenomenon on many of the world’s pressing scientific concerns\, and some recent advances.\n\n \nSpeaker : Prof. Beverley McKeon\n\nbiography:\n\nBeverley J. McKeon is Professor of Mechanical Engineering at Stanford. She received her B.A.\, M.A. and M.Eng. from the University of Cambridge in the United Kingdom\, and an M.A. and Ph.D. in Mechanical and Aerospace Engineering from Princeton University. She completed postdoctoral research and a Royal Society Dorothy Hodgkin Fellowship at Imperial College London. Best known for her work pioneering resolvent analysis as an equation-driven tool to analyze and predict the dynamics of turbulent flow\, her research group has specialized in addressing its application to understand and modify wall turbulence in numerical data and via experiments with external forcing. Prof. McKeon is a Fellow of the APS and the AIAA and the recipient of a Vannevar Bush Faculty Fellowship from the DoD in 2017\, the Presidential Early Career Award (PECASE) in 2009 and an NSF CAREER Award in 2008 as well as Caltech’s Shair Program Diversity Award\, Graduate Student Council Excellence in Mentoring Award and Northrop Grumman Prize for Excellence in Teaching. She currently serves as co-Lead Editor of Physical Review Fluids and on the editorial board of the Annual Review of Fluid Mechanics.\n \nCoffee/tea will be served after the seminar at 3:30 pm.\n\nAt 4:00 pm\, Prof. McKeon will hold a special session on Physical Review Fluids\, one of the world’s leading research journals for fluid dynamics. Prof. McKeon is the co-Lead Editor of the journal. The session includes a short presentation on the journal’s history\, Q&A\, and a short tutorial on writing a successful submission.
URL:https://aero.iisc.ac.in/event/taming-turbulence/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/08/taming_turbulence_poster_16x9-4.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260915T110000
DTEND;TZID=Asia/Kolkata:20260915T130000
DTSTAMP:20261010T050659
CREATED:20260909T051218Z
LAST-MODIFIED:20260915T051721Z
UID:10000149-1789470000-1789477200@aero.iisc.ac.in
SUMMARY:Invited Talk on the Occasion of the Engineer's Day - From MV to Spaceflight: Satellite Re-entry and the Future of Space Sustainability
DESCRIPTION:National Engineers’ Day commemorates the legacy of Sir M. Visvesvaraya\, whose vision and engineering leadership helped lay foundations for India’s technological development. From civil infrastructure and water resource management to advanced aerospace systems\, India’s engineering journey has been characterised by the pursuit of innovation that delivers enduring societal value. As India extends its capabilities in space exploration\, satellite services\, human spaceflight\, and a growing commercial space sector\, attention is increasingly turning to the sustainability of space activities across the entire lifecycle of a spacecraft\, including its final return to Earth.\nThis seminar examines the end-of-life phase of satellites\, focusing on the competing concepts of design for demise and design for recovery during atmospheric re-entry. While these approaches have traditionally been evaluated in terms of ground safety and debris mitigation\, recent studies have raised important questions regarding the introduction of metallic oxides and other compounds into atmospheric regions where they are not normally present. Drawing on observations of spacecraft re-entries and current research into demise physics\, material response\, and environmental impacts\, the presentation will explore the challenges and opportunities associated with sustainable spacecraft disposal. In doing so\, it considers how future spacecraft design and operations may contribute to a responsible and enduring spacefaring future for India and the global community. \nSpeaker : Prof. David Buttsworth \nBiography ::\nProfessor David Buttsworth is Professor of Thermofluids Engineering at the University of Southern Queensland\, where he leads the Hypersonics and Rocketry Group within the Institute for Space\, Defence and Advanced Technologies. He is also an Honorary Professor at the University of Queensland\, from which he holds a BE (Hons) and a PhD on shock-induced mixing and combustion in scramjets. He designed and built the TUSQ hypersonic wind tunnel\, a key Australian facility for re-entry and hypersonic ground testing\, and has led airborne optical observation campaigns of spacecraft re-entry\, including the Hayabusa capsule return. He currently leads Australian Research Council-funded research on the dispersion and demise of spacecraft components during atmospheric re-entry. He is a Senior Member of the American Institute of Aeronautics and Astronautics. Prof. Buttsworth is a Fellow of the Society for Shock Wave Research
URL:https://aero.iisc.ac.in/event/invited-talk-on-the-occasion-of-the-engineers-day-from-mv-to-spaceflight-satellite-re-entry-and-the-future-of-space-sustainability/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/09/Slide1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260921T110000
DTEND;TZID=Asia/Kolkata:20260921T130000
DTSTAMP:20261010T050659
CREATED:20260917T113043Z
LAST-MODIFIED:20260923T090942Z
UID:10000151-1789988400-1789995600@aero.iisc.ac.in
SUMMARY:Illuminating Complex Flows: Optical Diagnostics for Aerospace Applications
DESCRIPTION:Hypersonic flight represents a major frontier in aerospace engineering\, with its realization requiring a fundamental understanding of coupled chemical and fluid dynamic processes across multiple environments. Of particular importance are the reacting flows within the propulsion systems that enable sustained hypersonic flight and the high-temperature\, chemically reacting flows that develop near vehicle surfaces at extreme speeds. Understanding the complex and strongly coupled phenomena governing these environments requires a synergistic combination of high-fidelity computation and carefully designed experiments. Experimental investigations\, however\, are inherently challenging\, often relying on sophisticated ground-based facilities equipped with advanced diagnostic capabilities to generate meaningful\, high-resolution data. Among these\, optical diagnostics have emerged as a powerful class of measurement tools\, offering significant advantages over conventional techniques. Their non-intrusive nature\, high temporal resolution\, and robustness under extreme conditions make them uniquely suited for probing high-speed\, high-enthalpy flows. Continued advances in optical diagnostics have enabled transformative progress across multiple domains of aerospace research\, including chemical kinetics\, aerodynamics\, and active flow control.\nThis talk will focus on a specific application of advanced optical diagnostics: elucidating the chemical kinetics of complex fuels such as jet fuels\, gasoline surrogates\, and rocket propellants under engine-relevant conditions. Particular emphasis will be placed on the role of advanced laser-based diagnostics\, coupled with shock tube reactors\, in uncovering fundamental insights into the behavior of large hydrocarbons and their mixtures at elevated temperatures and pressures. These insights have enabled the development of the Low-Temperature Hybrid Chemistry (LT-HyChem) framework\, a methodology for constructing compact\, fuel-specific chemical kinetic models that remain valid across the full range of operating conditions relevant to modern and next-generation propulsion systems. The LT-HyChem approach is fuel-agnostic and produces models that are over two orders of magnitude more compact than those generated using conventional methodologies\, while simultaneously reducing predictive uncertainties by more than an order of magnitude. This combination of compactness and accuracy facilitates integration with computational fluid dynamics solvers\, significantly reducing the computational cost associated with combustor design\, analysis\, and optimization. The talk will conclude with a discussion of the broader implications of this work for rapid screening of sustainable aviation fuels and potential extensions to solid fuel systems.\n\nSpeaker: Dr. Rishav Choudhary\n\nBiography:\nDr. Rishav Choudhary received his B.Tech. in Aerospace Engineering from IIT Kanpur and his M.S. and Ph.D. in Mechanical Engineering from Stanford University. His doctoral research focused on absorption-spectroscopy-based diagnostics for chemical kinetics under extreme conditions relevant to engine combustion\, hypersonic re-entry\, and other high-temperature environments. He subsequently worked as a Postdoctoral Researcher in Aerospace Engineering at the University of Michigan\, developing optical diagnostics for high-speed density fluctuations\, velocity measurements in supersonic flows\, and electron-density measurements in plasmas. He is currently an Engineer at Lam Research Corporation\, where his work involves optical diagnostics applied to multiphase flows and plasmas relevant to semiconductor manufacturing.\n\nNote: Dr. Rishav Choudhary is a faculty candidate in the Propulsion stream in the Department of Aerospace Engineering\, IISc. Faculty members are encouraged to attend the talk and interact with the candidate.\n\n\n\n\n\n 
URL:https://aero.iisc.ac.in/event/illuminating-complex-flows-optical-diagnostics-for-aerospace-applications/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/09/Dr.-Rishav-.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260922T103000
DTEND;TZID=Asia/Kolkata:20260922T123000
DTSTAMP:20261010T050659
CREATED:20260921T133040Z
LAST-MODIFIED:20260923T094114Z
UID:10000152-1790073000-1790080200@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Development of Learning-based Strategies for Reconnaissance with Multi-Robot Systems
DESCRIPTION:Reconnaissance is the contest for information about a territory: one side tries to observe an asset or a guarded area\, the other tries to deny it. Low-cost drones have made this contest cheap and constant\, and protecting critical infrastructure against it is now a crucial problem\, because an intruder no longer needs to strike a target to threaten it. This thesis develops learning-based strategies for multi-robot reconnaissance from both of its perspectives. In the defense perspective\, a team of defenders must deny reconnaissance of a protected territory by intercepting intruders before they cross its perimeter. In the adversarial perspective\, an agent inside a guarded region must escape to a safe area with the information it has gathered before it is neutralized. Both are hard for the same real-world reasons: opponents arrive from any direction at any time\, so the environment is non-stationary; each robot senses only a limited range\, so the state is partially observed; communication may be unavailable; and the opponent’s numbers and strategy are unknown. Classical game-theoretic and assignment-based methods assume away one or more of these conditions\, which motivates strategies that learn from local observations.\nFor the defense perspective\, the thesis first formulates perimeter defense as a decentralized assignment learning problem and develops the Context-aware Deep Assignment Network (CDAN). Each defender encodes its limited field of view as a spatio-temporal context map of past observations\, the present\, and a predicted future with position uncertainty; pseudo-values around each intruder counter the sparsity of this map and allow a 3D convolutional network\, trained by imitating a centralized solution\, to converge and to be reused by the whole team. CDAN captures about 6% more intruders than the best decentralized baseline (73.4% against 67.5%) and generalizes over team size\, perimeter length\, and intruder speed and maneuvers. Because assignment quality inherits the reliability of the communication channel\, the second contribution\, CARE (Communication-free planning using Adaptive Regions of Engagement)\, resolves the assignment from each defender’s own observations: a defender senses over its full detection radius but commits only within an engagement region set by the distance to its nearest observed teammate\, and drifts its rest position toward the arrival directions it has itself observed. Without a single message\, CARE matches or exceeds communicating baselines over about 200 scenarios and 38\,600 seed-paired episodes\, and is demonstrated on a Crazyflie quadrotor team.\nFor the adversarial perspective\, the third contribution gives the first reinforcement learning formulation of the confinement escape problem\, with a constant-size LiDAR-based state that is independent of the number of pursuers and the shape of the region\, and proposes Scaffolding Reflection based Reinforcement Learning (SR2L)\, in which a simple motion-planner scaffold guides the learner only when its suggestion is clearly better\, so that it can accelerate learning but never damage it. SR2L converges in about half the episodes of standalone actor-critic methods and escapes faster against three pursuit strategies\, with the lowest variance in every case.\nBecause no single learned policy is best under all conditions\, the fourth contribution fuses a pool of pre-trained policies online in a non-stationary environment. Standard multiplicative-weights fusion collapses onto one policy and performs worse than doing nothing. Regularized Reward-aware Online LEarning (ROLE) adapts the fusion weights from the reward of the executed action alone\, without ground truth\, and bounds every weight with an anti-collapse cap. ROLE raises perfect escape runs from 41% for the best single policy to 68% on healthy pools and degrades gracefully when rogue policies contaminate the pool.\nTogether\, these contributions treat reconnaissance in multi-robot systems as one problem seen from two perspectives\, and show that learning from local observations\, with minimal or no information exchange\, can both deny reconnaissance of a protected territory and accomplish it from inside a guarded one. \nSpeaker : Vignesh Gurumurthy \nResearch Supervisor: Prof. Suresh Sundaram \n 
URL:https://aero.iisc.ac.in/event/ph-d-engg-development-of-learning-based-strategies-for-reconnaissance-with-multi-robot-systems/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/09/Vignesh-Gurumurthy.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260925T150000
DTEND;TZID=Asia/Kolkata:20260925T170000
DTSTAMP:20261010T050659
CREATED:20260915T052755Z
LAST-MODIFIED:20260915T052755Z
UID:10000150-1790348400-1790355600@aero.iisc.ac.in
SUMMARY:Magneto-Active Solids for Adaptive Structures: Can Magnetic Fields Control Elastic Waves?
DESCRIPTION:Magneto-active solids couple their mechanical response to externally applied magnetic fields\, providing a promising route toward remotely tunable materials and structures. Such functionality is particularly attractive for aerospace applications involving vibration isolation\, adaptive structures\, sensing\, and elastic-wave control. However\, exploiting this coupling requires understanding a fundamental question: when does a magnetic field actually modify elastic-wave propagation\, and which wave modes are affected?\n\nIn this seminar\, Prof. Galich will present recent theoretical and experimental work on elastic waves in magneto-active solids. Starting from the incremental theory of nonlinear magnetoelasticity\, he will introduce the generalized acoustic tensor governing small-amplitude waves superimposed on a magnetically biased state. For compressible isotropic magneto-active polymers\, magnetic tunability is shown to be strongly dependent on wave polarization. In an undeformed material subjected to a magnetic field transverse to the propagation direction\, the shear wave polarized along the magnetic field is directly field-sensitive\, whereas the pressure wave and the orthogonally polarized shear wave remain essentially unaffected. These theoretical predictions are supported by ultrasonic experiments on 3D-printed iron-filled polymers.\n\nThe discussion will then extend from bulk waves to Rayleigh surface waves\, where the coupling between mechanics and magnetism introduces additional questions concerning constitutive modeling and stability. In particular\, physically consistent selection of magnetoelastic material parameters is essential: models that reproduce the magnetic permeability but violate the corresponding Maxwell-stress condition can predict artificially strong wave-speed changes and even surface instabilities.\n\nFinally\, the seminar will cover periodic magneto-active solids\, where magnetic fields\, finite deformation\, and material architecture can be combined to control elastic-wave dispersion and phononic bandgaps. These results illustrate both the opportunities and fundamental limitations of magnetic-field control of elastic waves and provide guidelines for the development of adaptive materials and structures for vibration manipulation.\n\nSpeaker :  Prof. Pavel I. Galich\n\nBiography:\n\nProf. Pavel I. Galich has been an Assistant Professor at The Stephen B. Klein Faculty of Aerospace Engineering\, Technion\, since 2020. He earned his Ph.D. in Aerospace Engineering from the Technion in 2018 and served as a Postdoctoral Research Associate in the Department of Materials Science & NanoEngineering (MSNE) at Rice University from 2018 to 2020.
URL:https://aero.iisc.ac.in/event/magneto-active-solids-for-adaptive-structures-can-magnetic-fields-control-elastic-waves/
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/png:https://aero.iisc.ac.in/wp-content/uploads/2026/09/Prof.-Pavel-I.-Galich.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260926T160000
DTEND;TZID=Asia/Kolkata:20260926T170000
DTSTAMP:20261010T050659
CREATED:20260923T060556Z
LAST-MODIFIED:20260923T102930Z
UID:10000153-1790438400-1790442000@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): A Slotted Wing Configuration for STOL Applications
DESCRIPTION:The rapid development of Urban Air Mobility (UAM) has led to the emergence of electric vertical take-off and landing (eVTOL) aircraft\, with many current concepts relying on tilt-rotor or other complex propulsion-conversion mechanisms to achieve vertical take-off and landing followed by efficient forward flight. While these configurations provide the required operational flexibility\, the mechanical complexity associated with tilting propulsion systems can introduce challenges related to durability\, power efficiency\, system integration\, and flight stability. This thesis explores an alternative approach based on short take-off and landing (STOL) capability\, with the objective of developing a compact\, mechanically simple\, and aerodynamically efficient wing configuration that can reduce the dependence on such complex mechanisms. The proposed design is CFD based and the required computations have been carried out using the CFD solver HiFUN. All computations have been performed using standard SA turbulence model. The propellers are simulated using varying levels of fidelity available in the solver\, such as the Blade Element Method and sliding mesh simulations. Moving mesh capability available in the solver is made use of in simulating synthetic jets.\nA novel fixed-wing configuration is developed specifically for STOL operation in the context of urban air mobility. Instead of relying on conventional high-lift devices\, the proposed configuration combines a highly cambered wing\, distributed propulsion\, and active flow control to achieve the high lift required during take-off and landing. A NACA four-digit formulation is used to define the airfoil\, with an unconventionally high camber and a slot introduced at the location of maximum camber. To maintain vehicle compactness while improving aerodynamic efficiency\, a low aspect-ratio wing with optimized end plates is employed. The influence of end-plate size on the aerodynamic performance is investigated\, showing a progressive reduction in trailing-vortex strength and associated induced effects on lift and drag with increasing end-plate size. Based on the investigated configurations\, an end plate with a width equal to 20% of the wing aerodynamic chord is selected.\nDistributed propulsion is subsequently integrated into the wing configuration to exploit propeller slipstream effects during STOL operation. An enhanced actuator-disc model\, coupled with blade-element analysis\, is used to represent the propellers\, with a NACA 640 four-bladed propeller selected for the study. The propeller thrust requirements are determined from the take-off drag of the unpowered wing and distributed among four equally spaced propellers. The interaction between an individual propeller and the wing is first investigated to determine the optimum propeller location. The resulting slipstream–wing interaction substantially increases the wing lift\, thereby reducing the required take-off velocity. The complete powered configuration is then investigated using high-fidelity sliding-mesh simulations with counter-rotating propellers arranged on either side of the wing. \nThe high camber required to achieve the desired lift characteristics introduces a separation bubble in the rear portion of the wing downstream of the slot. To address this limitation without introducing conventional high-lift mechanisms\, a zero-net-mass-flux active flow-control system based on synthetic jets is incorporated. A dynamic-mesh methodology is first validated against the NASA Langley Research Center standard hump test case with oscillatory control. The validated methodology is then used to establish the actuator momentum coefficient and excitation frequency. To reduce the computational cost of the full-wing simulations\, an unsteady boundary-condition model is developed and validated and subsequently employed to investigate the effectiveness of synthetic-jet actuation in suppressing the separation bubble and improving the aerodynamic performance of the wing. Discrete synthetic-jet slits are positioned between the propeller slipstreams\, allowing flow control to be concentrated in regions outside the primary propeller wakes while reducing the additional power requirement.\nOverall\, the thesis demonstrates the feasibility of combining fixed-wing STOL aerodynamics\, distributed propulsion\, and localized active flow control as an alternative pathway for compact urban air-mobility vehicles. \n  \nSpeaker : S Amsha \nResearch Supervisor : N. Balakrishnan
URL:https://aero.iisc.ac.in/event/ph-d-engg-a-slotted-wing-configuration-for-stol-applications/
LOCATION:Online
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/09/S-Amsha.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20261001T113000
DTEND;TZID=Asia/Kolkata:20261001T130000
DTSTAMP:20261010T050659
CREATED:20260928T090723Z
LAST-MODIFIED:20260929T095847Z
UID:10000154-1790854200-1790859600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg): Splashing of impacting drops on rigid and flexible superhydrophobic surfaces
DESCRIPTION:Understanding droplet impact dynamics on superhydrophobic (SHP) surfaces is crucial for exploiting their exceptional liquid-repellent properties in various industrial applications. Studies on high-velocity droplet impacts on SHP surfaces\, particularly under splashing conditions\, are of significant importance for applications such as anti-icing and erosion protection of turbine blades. This thesis presents an experimental investigation of splashing of impacting drops on flexible cantilever and rigid superhydrophobic (SHP) surfaces. The SHP surfaces are prepared by spray-coating plastic polymer films (overhead projector sheets) with commercially available NeverWet hydrophobic solution. For the flexible cantilever SHP surfaces\, the coated film is cut into rectangular beams\, with one end of the beam is firmly fixed on an aluminium support. For the rigid SHP surface\, the entire coated film is firmly fixed to the aluminium support. In this study\, four cantilever beams of different lengths are considered to study the effect of beam stiffness on the drop impact dynamics. Three different droplet liquids – water (W)\, 20% glycerine and 80% water (G20)\, and 50% glycerine and 50% water (G50) – varying mainly in their dynamic viscosity are considered.\nWater droplet impact on the rigid superhydrophobic (R-SHP) surface exhibits five regimes with increasing Weber number\, We\, from complete rebound to prompt splashing\, and is mapped on a We–Re chart alongside reported SHP surfaces. The various parameters of droplet impact such as maximum spread factor (βmax)\, spreading time\, contact time\, maximum retraction rate\, and coefficient of restitution (COR) are characterized as functions of We. The splashing of impacting water drops on the R-SHP surface is studied and an additional regime (sixth regime) of prompt splashing with hole nucleation is documented. Quantitative measurements of the temporal variation of lamella diameter\, number of holes formed\, time at which the first hole nucleates\, critical impact velocity at which the hole-nucleation begins\, and contact time are extracted. These measurements clearly show that the contact time reduction of splashing droplets decreases with increase in droplet viscosity. Moreover\, the number of holes formed in the lamella film scales with the number of micro-bumps underneath the droplet at its maximum spreading which\, in turn\, decreases with increase in droplet viscosity. The time instant at which the first hole nucleates on the lamella film is seen to be independent of the droplet viscosity. A modified model is proposed to describe the effects of droplet viscosity and surface micro-characteristics (height and pitch of surface micro-bumps) on the critical velocity for hole nucleation\, Uc\,h. The predictions from this modified model seem to explain the experimental observations on Uc\,h in the current study as well as in the literature.\nDroplet impacts on the flexible superhydrophobic (F-SHP) surface follow the same sequence of regimes as the R-SHP surface\, but the regime boundaries are shifted to higher We due to partial energy transfer from the droplet into beam bending. For a given We\, the maximum spread factor\, receding velocity\, and maximum rebound height are all reduced relative to that of the R-SHP surface. A modified Weber number\, We#\, which accounts for the elastic bending energy stored in the beam during the drop impact dynamics is proposed\, and the variation of F-SHP data with We# collapses with the corresponding data recorded on the R-SHP surface for both spreading and receding dynamics. The beam oscillation response\, including deflection\, oscillation amplitude\, and the effect of droplet re-impact on the oscillation cycle\, is also characterized. Splashing dynamics of impacting drops on the F-SHP surface shows regime transitions comparable to those on the R-SHP surface but shifted to higher We and Re. Hole nucleation on the F-SHP surface is delayed relative to the R-SHP surface. The recorded value of Uc\,h increases from 1.75 to 2.00 m/s (14.3%) for W and from 2.35 to 2.53 m/s (7.7%) for G20 drops\, and the number of holes is lower for both liquids at a given We\, attributed to part of the impact kinetic energy being stored as strain energy in the beam. For G50 drops\, no holes are formed on both surfaces within the tested We range. Before the hole nucleation\, the contact time is unaffected by the surface flexibility\, and while beyond Uc\,h\, the recorded contact time is longer on the F-SHP surface by about 10% for W and 8% for G20 drops. The surface flexibility therefore affects the contact time only indirectly\, by delaying and suppressing hole nucleation.\nThe effect of beam stiffness on droplet impact dynamics is studied by carrying out water drop impacts on four F-SHP surfaces. The maximum spread factor follows βmax = α(We)0.25\, with the empirical constant α decreasing systematically from 1.012 for the stiffest beam to 0.899 for the most flexible beam\, reflecting greater energy loss to beam bending as stiffness decreases. The variation of βmax with We# collapses the data across all the F-SHP and R-SHP surfaces into a single trend\, established in the present study as βmax = α#(We#)0.25 with α# estimated as 1.00 ± 0.07 for both the R-SHP and F-SHP surfaces. Similarly\, the receding velocity decreases with decreasing beam stiffness but collapses across all surfaces when plotted against We#. The contact time is found to be largely unaffected by the beam flexibility. The maximum rebound height of the bouncing drop on the F-SHP surfaces decreases with decreasing beam stiffness. Since the pinched-off droplet formed in the rebounding process carries 6 to 14% of the impacting droplet mass\, the COR is redefined in the present study using an effective rebound velocity that accounts for both droplets\, and the modified COR decreases with increasing beam length at a given We. The maximum beam tip deflection of the F-SHP surfaces increases with both We and beam length\, L\, and is well predicted by spring-mass model incorporating the impact force and beam natural frequency\, fb. Finally\, a theoretical model is proposed to predict COR on the F-SHP surfaces. The proposed model predicts the experimental COR across all F-SHP and the R-SHP surfaces with errors of 5.0 – 15.2% and also captures the dependence of COR on the beam length.\n\nSpeaker : Kumar Gaurav   \n\nResearch Supervisor : D. Sivakumar
URL:https://aero.iisc.ac.in/event/ph-d-engg-splashing-of-impacting-drops-on-rigid-and-flexible-superhydrophobic-surfaces/
LOCATION:STC Seminar Hall\, Dept. of Aerospace Engineering
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/09/Kumar.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20261006T143000
DTEND;TZID=Asia/Kolkata:20261006T170000
DTSTAMP:20261010T050659
CREATED:20261005T050831Z
LAST-MODIFIED:20261005T101944Z
UID:10000155-1791297000-1791306000@aero.iisc.ac.in
SUMMARY:M.Tech (Res): Direct Numerical Simulation of Turbulent Aerosol Transport in Human Respiratory Flows
DESCRIPTION:Airborne transmission of respiratory diseases is governed by the coupled dynamics of the exhaled turbulent flow and the transport of pathogen-laden aerosols and droplets. This thesis studies two representative respiratory activities\, speech and cough\, and quantifies the infection probability using Direct Numerical Simulations. The incompressible Boussinesq Navier-Stokes equations are solved using Megha-5 solver\, including the required scalar and dispersed-phase transport equations. Speech flow is studied for a repeated plosive-rich utterance at soft\, normal and loud levels. Aerosol exposure is quantified from the instantaneous and time-integrated flux through a face-sized region representing a silent listener at different streamwise separations. Normal and loud speech develop from individual puffs into a jet-like mean flow\, whereas soft speech remains comparatively underdeveloped. The centreline exposure increases in the approximate ratio 1:5.4:18.4\, governed mainly by the source conditions. At a separation of 1 m\, the infection probabilities are approximately 12%\, 28% and 63% for soft\, normal and loud speech\, respectively. For cough flow\, the existing variable-timescale model is compared with a variable-number-density closure based on the Direct Quadrature Method of Moments. The latter transports droplet number density and total surface area as Eulerian fields and captures strong spatial non-uniformity\, particularly within the toroidal vortex at the puff head. It increases the centreline infection probability by 10-30%\, while a laterally displaced breathing zone produces a non-monotonic variation with distance. The results show that infection risk cannot be described by separation distance alone. The framework provides distance-resolved inputs for room-scale and epidemiological transmission models. \n  \nSpeaker : SUBBA REDDY GARI SHASHANK REDDY \nResearch Supervisor : Sourabh Suhas Diwan
URL:https://aero.iisc.ac.in/event/m-tech-res-direct-numerical-simulation-of-turbulent-aerosol-transport-in-human-respiratory-flows/
LOCATION:AE Conference Room \, AE 003
CATEGORIES:Thesis Colloquium / Defence
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/10/SUBBA.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20261009T150000
DTEND;TZID=Asia/Kolkata:20261009T170000
DTSTAMP:20261010T050659
CREATED:20261005T102527Z
LAST-MODIFIED:20261005T102527Z
UID:10000156-1791558000-1791565200@aero.iisc.ac.in
SUMMARY:How important are differential and preferential diffusion effects for hydrogen combustion?
DESCRIPTION:Hydrogen is coming to the forefront as a potential energy carrier to achieve decarbonisation goals and objectives. It is well known that hydrogen is a light molecule diffusing quicker than other molecules and thermal energy in the fuel-air mixture of hydrogen combustion systems. Critical evaluations of these effects have been studied for many decades\, suggesting that they can be ignored while modelling combustion using the RANS approach. However\, recent DNS studies of hydrogen-air turbulent combustion show that these effects ought to be considered.\nTheir importance for practical systems is still an open question\, and finding an unequivocal answer will be the focus of this talk. Specifically\, the aim is to show these effects\, their roles and importance systematically using a priori analysis and a posteriori testing. The findings will highlight the answer\, which is beneficial for numerical modelling and simulations of hydrogen-air partially premixed combustion under practical conditions.\n\nSpeaker: Prof. N. Swaminathan\n\nBiography:\n\nSwaminathan is a professor of mechanical engineering at Cambridge University Engineering Department. His research interests span from candle flames to aero gas turbine combustion and tropical cyclones to bio-acoustics. He explores these multi-scale and multi-physics problems using numerical simulations with the aim to understand the physical mechanisms and to build simple mathematical models for practical use. He has published more than 200 papers and has co-edited two books on turbulent combustion and one on application of machine learning to turbulent combustion. He is a Fellow of Royal Academy of Engineering\, ASME\, IMechE\, Royal Aeronautical Society\, Combustion Institute and Cambridge Philosophical Society.
URL:https://aero.iisc.ac.in/event/how-important-are-differential-and-preferential-diffusion-effects-for-hydrogen-combustion/
LOCATION:Auditorium (AE 005)\, Department of Aerospace Engineering
CATEGORIES:AE Seminar
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/10/9th-Oct-Seminat-.jpg
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