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(The top left panel illustrates the actual flow scenario encountered during launch, when the scramjet remains attached to the launch vehicle and the shroud is ejected. In this configuration, the flow passage between the SERN nozzle and the launch vehicle forms a cavity, while the scramjet isolator creates as a deeper sub-cavity. The high-speed flow passing over these regions produces complex aerodynamic interactions, including shock-wave formation, shear layer development and recirculation within the cavity and sub-cavity. These features strongly influence the pressure field and unsteady flow behaviour, as shown in the actual flow scenario. The right panel presents the reduced-order flow model adopted for the present study, where the complicated launch geometry is simplified into a rectangular cavity and sub-cavity while preserving the essential flow physics. This simplified configuration enables detailed investigation of pressure fluctuations, flow separation, and cavity-driven unsteadiness, providing a practical framework to understand the underlying mechanisms governing the real launch environment. The wind tunnel facility shown here is used to reproduce these flow conditions in a controlled environment and to study the associated pressure fluctuations and unsteady flow structures. The facility includes a high-pressure inlet, pressure regulation system, settling chamber, nozzle, test section, and diffuser, which together create a stable supersonic flow for testing.)
Experimental investigation of supersonic cavity flows for aerospace applications
A supersonic wind tunnel facility is used to investigate cavity-flow aeroacoustics under controlled high-speed conditions relevant to aerospace launch and propulsion systems. The experimental setup recreates simplified cavity and sub-cavity geometries to represent the essential flow features of the actual launch configuration, including a cavity formed between the scramjet and launch vehicle and a deep sub-cavity corresponding to the isolator region. Under supersonic flow, the shear layer separates at the cavity leading edge, spans the opening, and impinges at the trailing edge, generating recirculation, shock interactions, and unsteady pressure fluctuations. Diagnostics such as schlieren imaging, pressure measurements, and flow visualization are used to capture the flow evolution and identify dominant oscillation mechanisms. These experiments establish baseline capabilities and provide real-world proof for simulations and improving physical understanding of cavity-driven noise and instability. Such studies are essential because cavity oscillations can produce severe vibrations, structural fatigue, and performance losses in high-speed aerospace systems. By bridging lab data to practical designs, this research ensures safer, quieter high-speed systems.
Keywords: weapon bays, scramjet inlets, payload fairings
(a. Schematic of the existing blow-down facility and the proposed studies. Annotations: 1. Compressor, 2. Pipes, 3. Storage Tank, 4. Gate Valve, 5. Pressure Regulator, 6. Heater, 7. Settling Chamber, 8. Screens, 9. Total Pressure Monitor, 10. End Plate with Multiple Outlets, 11. Flexible Tubes, 12. Fast-Acting Valves, 13. Unsteady Load Cell, 14. Microphone Measurement Area, 15. Pressure Field Microphones, 16. Jet Visualization Area, 17. Clustered Aerospike Nozzle, and 18. Unsteady Pressure Sensors; (b) Geometry of the clustered aerospike nozzle configuration. b. Front view of the nozzle cluster showing the discrete nozzle defined as ψ_1-ψ_6. c. Reference aerospike geometry defining the total spike length L.)
Transient load generation and associated flow physics in a
clustered aerospike nozzle for thrust vectoring
This ongoing experimental research investigates the transient load generation and associated flow physics of clustered aerospike nozzles during dynamic thrust vectoring actuation. The study addresses a critical gap in understanding how rapid exhaust reorganization produces transient forces and moments that dominate structural and control responses. Utilizing a high-speed blow-down facility under cold-flow conditions, the project investigates a bounded operational envelope of nozzle pressure ratios (η) from 2 to 16. The methodology employs six fast-acting solenoid valves with a one-millisecond response time to achieve precise, asymmetric mass flow modulation. To correlate fluid-acoustic coupling, the research relies on synchronized, time-resolved diagnostics, including high-speed schlieren imaging, planar laser Rayleigh scattering, unsteady surface pressure monitoring, far-field microphone arrays, and six-axis force-moment measurements. These robust experimental datasets aim to define reliable operational thrust-vectoring envelopes for highly maneuverable aerospace vehicles.
Keywords: maneuverable air vehicles, non-gimbaled steering, dynamic trajectory control
(The left panel presents a purely computational three-dimensional transient thermal simulation, illustrating the evolution of internal temperature gradients and progressive material decomposition over an 11-second exposure period. The results highlight rapid surface heating, subsurface thermal response, and the onset of ablation under high-enthalpy plasma conditions, providing predictive insight into material behavior during severe thermal loading. The center panel shows time-resolved Schlieren visualization of the plasma plume, captured using a high-speed camera at 20,000 frames per second. The video reveals transient density gradients, and turbulent flow features within the high-enthalpy jet. The right panel shows experimental visualization of a high-velocity arc jet plasma operating in a free-jet configuration. The plasma plume expands into the ambient environment, exhibiting characteristic features such as jet spreading, and gradual thermal dissipation. This configuration provides insight into the intrinsic behavior of the plasma flow, including its stability, structure, and jet decay characteristics.)
Experimental diagnostics of arc jet plasma flows and high-temperature material response for thermal protection system applications
A 50 kW plasma torch facility with a 15 mm plasma jet is designed as a high-enthalpy experimental platform to simulate extreme thermal and erosive environments relevant to hypersonic and propulsion applications. The system generates a stable, high-temperature plasma jet (several thousand Kelvin) under controlled gas flow conditions, enabling precise regulation of heat flux, velocity, and exposure duration. The setup includes controlled atmosphere operation (inert or reactive), and diagnostics such as high-speed imaging, thermocouples, and possibly optical emission spectroscopy for plasma characterization. The planned tests focus on evaluating material response under severe thermo-mechanical loading, particularly erosion, ablation, and surface degradation. Candidate materials such as refractory alloys, coatings, or composites are exposed to the plasma jet to quantify mass loss, surface morphology evolution, and thermal resistance. These studies aim to generate data for nozzle throat materials, thermal protection systems, and high-temperature structural components, while also enabling validation of coupled thermal-fluid-material interaction models.
Keywords: ablation, thermal protection system (TPS), re-entry heating, plasma-material interaction
(The figure presents an overview of the light-gas gun system, projectile geometry, and flow visualization results. Schematic representations and a three-dimensional CAD model of the experimental setup highlight key components such as the gas supply cylinder, pressure plenum, pressure gauge, gate valve, nozzle block, barrel with the projectile, ballistic chronograph, and a sand-filled catcher box, along with labeled measurement locations. The hollow-base projectile geometry is illustrated through a 3D view and a 2D cross-sectional profile, detailing the rounded conical forebody and key dimensions. Shadowgraph and schlieren images capture the projectile in motion, revealing shock formation, density gradients, and wake development. Supplementary animations provide time-resolved visualizations of the projectile exiting the barrel, illustrating the evolution of shock structures and wake dynamics.)
Development of a low-cost light gas gun (Mk. I) for free-flight projectile testing
Kinetic energy weapons, or kinetic projectiles, rely on physical impact for effectiveness, with destructive capability stemming from the rapid conversion of kinetic energy into intense thermal and mechanical loads at the point of contact. Technical limitations on test-gas conditions favor accelerating models rather than the gas for high-speed aerodynamic studies, especially for capturing transient flow features. A compact, pressure-driven light-gas gun was developed using low-cost materials, employing a pressurized plenum and straight barrel to accelerate a lightweight projectile through rapid gas expansion. Experiments show that exit velocity depends on barrel-plenum sizing, travel distance, specific heat ratio, and pressure ratio. Increasing γ from 1.40 (air) to 1.66 (helium, He) nearly doubled velocity, while tripling barrel length (L_B) increased velocity by nearly twenty-three times. Direct shadowgraph and schlieren imaging captured compressible-flow features. The resulting system offers an economical method for generating repeatable supersonic ballistic trajectories suitable for free-flight aerodynamic studies.
Keywords: terminal ballistics, free flight testing, gas-gun
(The figure presents an overview of the detonation gun (D-Gun) system. Left image: Raw firing of the D-gun developed in-house using the Institute BUILD project fund. The conditions involve combusting the turbulently mixed 0.3 bar propane (C3H8) with 1.5 bar of oxygen (O2) using a carefully timed spark plug. Middle image: A typical streamwise apparent density gradient (line-of-sight light integration) showing the propogation of powerful wavefronts and the back reflecting sound waves from the surroundings at a framerate almost representing realtime capture. Right image: A slow motion capture of the high-speed events happening at the exit of the detonation gun barrel showing the shockwave propagation.)
Development of a detonation gun (D-Gun) for thermal sprays, PDEs, and RDEs.
Detonation-based systems utilize rapid, shock-coupled combustion to generate high-pressure and high-velocity gas flows, offering a compact means of producing extreme transient conditions for propulsion, flow physics, and materials-processing studies. A laboratory-scale pulsed detonation facility was developed using a propane–oxygen mixture, comprising a combustion chamber, a deflagration-to-detonation transition (DDT) section equipped with a Shchelkin spiral, and an extension tube. Independent solenoid valves enable controlled propellant injection, while spark ignition provides precise control over initiation timing. Schlieren imaging demonstrated repeatable formation and propagation of detonation waves, with measured wave Mach numbers reaching approximately 3.45. The facility also resolves complex transient phenomena including multi-shock detonation fronts, shock-induced autoignition, shock–reaction-front decoupling, and subsequent shock recombination. The system provides a versatile experimental platform for investigating detonation-wave dynamics, DDT, PDE, RDE and thermal sprays.
Keywords: pulsed detonation, detonation wave, thermal spray, D-Gun
(The figure presents an overview of the light-gas gun Mk2 system, projectile geometry, and impact-induced damage morphology results. (a) A schematic represents a three-dimensional CAD model of the new Mk2 experimental setup, highlighting key components such as the gas supply cylinder, pressure plenum, gate valve, nozzle block, pressure gauge, barrel, and cylinder mounting station. (b) carbon-steel, ogive-shaped armor-piercing projectile geometry and dimensions. (c) damage morphology of the Type 3 cylinder showing the front-face CFRP crater (𝐷_(𝑐,𝑎)), surface splits, and fiber breaks alongside the back-face aluminum crater (𝐷_(𝑐,𝑏)) with petal formation, and (d) damage morphology comparison for Type 4 cylinders (Cylinder no. 1 and Cylinder no. 2) showing craters (𝐷_(𝑐,1), 𝐷_(𝑐,2)), fiber breaks, and surface splits.)
Light gas gun Mk II: high-speed free-flight testing of projectiles and penetration/impact response
A compact light-gas-gun facility previously developed at IIT Hyderabad for supersonic free-flight testing has been upgraded into a high-speed impact or penetration test rig for certification (ISO 11192 and ISO 11439) testing of Composite Overwrapped Pressure Vessel (COPV) cylinders. The test rig was redesigned using metallic components to improve structural integrity during higher-energy experiments. 8 mm carbon-steel, ogive-shaped armour-piercing projectiles with a mass of 13 g were accelerated to an estimated velocity of approximately 850 m/s. Impact tests were conducted on both Type 3 and Type 4 COPV cylinders, extending the facility from an aerodynamic experimental setup to a broader certification-oriented test capability. High-resolution imaging was used to document impact-induced damage on the COPV catcher surfaces, including crater formation, surface splits, fibre breaks, and aluminium petalling. Calibrated image measurements were used to quantify crater dimensions and characterise the resulting damage morphology. The resulting system provides an economical method for conducting repeatable high-speed impact tests suitable for COPV certification and damage assessment.
Keywords: free-flight testing, high-speed impact, penetration test, damage characterization, crater morphology, light gas gun
(The figure presents a comparison of model geometries and experimental flow visualization results for slot-induced boundary-layer flow control under hypersonic freestream conditions (𝑀_∞=9.1, Argon gas, 𝑅𝑒=1.18×10^8/"m"). Left schematic: Detailed CAD schematics and isometric view of the test models illustrating the leading-edge nose radius (𝑅=0.50" mm"), ramp angles (30^∘ upper ramp, 5^∘lower expansion surface), and top-view slot orientations for Case (i) Baseline (smooth body), Case (ii) Streamwise slots (5 longitudinal channels), and Case (iii) Lateral slots (10 transverse channels). Right high-speed schlieren capture: High-speed time-resolved Z-type schlieren imagery (𝜕𝜌 ̅/𝜕𝑥) captured at 14,000" FPS "showcasing the flow topology across the three cases. Case (i) shows the baseline shock profile; Case (ii) highlights continuous suction along the upper surface with slight reduction in the primary shock angle and distributed lower surface mass ejection; Case (iii) shows discrete compression micro-shock trains generated along the upper surface and distinct jet-like mass ejection plumes along the lower surface.)
Experimental investigation of slot-induced boundary-layer suction and blowing in hypersonic external flow
Passive boundary-layer control techniques provide a self-sustaining approach for managing shock-wave/boundary-layer interactions, surface heating, and aerodynamic drag in hypersonic vehicles without requiring auxiliary power or complex active systems. This study experimentally investigates passive boundary-layer control through surface-slot-induced mass removal (suction) and internal pressure-driven mass ejection (blowing) under hypersonic external flow conditions in the HI-SEAL Hypersonic Ludwieg Tunnel at IIT Hyderabad. Experiments were conducted at a freestream Mach number of 𝑀_∞=9.1using Argon gas (𝛾=1.67, 𝑃_0=10" bar", 𝑇_0=300" K", 𝑅𝑒=1.18×10^8/"m") over an 8" ms" test duration. High-speed Z-type schlieren visualization utilizing twin parabolic mirrors (𝑓=1.2" m") and a Phantom VEO-L camera captured the time-resolved flow dynamics at 14,000" FPS"with a frame resolution of 832×600" pixels". Comparing a smooth baseline model with two slot orientations demonstrates significant modification of the primary shock structures and shear-layer behavior. Continuous mass removal along the upper ramp in the streamwise slot configuration lowers the primary shock angle and induces continuous spanwise disturbances, whereas the lateral slot configuration acts as discrete surface perturbations, generating a periodic sequence of repeated compression micro-shocks on the upper ramp alongside localized, jet-like mass ejection plumes along the lower expansion surface.
Keywords: hypersonic flow, boundary-layer suction/blowing, shock-structure modification, Ludwieg tunnel, schlieren visualization
(Figure (a) shows the schematic cross-sections of the nozzle without a cavity and with a cavity (c). Figure (b) presents the Schlieren flow visualization at an inlet stagnation pressure of (𝑝_𝑜 = 10) bar, comparing the cases without a cavity and with a cavity (d). Figure (e) shows the 3d printed model for doing the experiments, Annotations: 1. model cross-section, 2. Model, 3. Model mount. The flow under investigation is supersonic. In the case without a cavity, the jet exhibits relatively small-amplitude oscillations. In contrast, the presence of the cavity significantly enhances the jet oscillations, and the generated acoustic waves can be clearly observed propagating through the surrounding flow.)
Study of mixing augmentation using cavities (symmetric and asymmetric) & no cavities in the primary jet of a supersonic confined jet
Cavity and no-cavity configurations were analyzed to understand their influence on shock-cell structures, jet spreading, and overall flow stability under high Mach number conditions. An acoustic study was conducted to identifying screech phenomena, dominant frequency tones, and noise characteristics generated by different cavity geometries by varying the stagnation pressure 𝑝_𝑜. Future work will further examine how symmetric and asymmetric cavity arrangements affect shock interactions and acoustic feedback mechanisms. The designed cavity configurations have the potential to improve mixing efficiency while simultaneously reducing or, in some cases, amplifying unwanted noise levels. The overall objective is to develop an optimized supersonic jet configuration that achieves enhanced aerodynamic performance, stable flow behavior, and controlled acoustic emissions for industrial applications.
Keywords: supersonic confined jet, cavity flow, mixing augmentation, shock-cell structure
(The far-left schematics illustrate the primary flow features of a supersonic free jet (top) alongside a magnified view of the embedded upstream cavity geometry (bottom), defining the internal channel height (𝐻), cavity depth (𝐷), cavity length (𝐿), recirculation zones, and shock-cell wave structures. Spatial coordinates are non-dimensionalized with respect to the channel height (𝑥/𝐻,𝑦/𝐻) . Experimental Schlieren visualization on the middle panel captures density gradient fields for the baseline no-cavity jet, showing distinct diamond shock-cell patterns and constrained shear-layer spreading. The right panel presents the corresponding Schlieren visualization for the embedded cavity configuration, revealing strong acoustic wave emissions originating from shear-layer impingement at the cavity trailing edge. A side-by-side comparison highlights the role of the upstream cavity in perturbing the supersonic core jet, enhancing shear-layer instability, and promoting cross-stream fluidic mass exchange downstream of the exit plane.)
Study of supersonic free jet dynamics governed by embedded cavity configurations
This ongoing experimental research investigates the flow physics, structural shear-layer dynamics, and aeroacoustic feedback mechanisms of a supersonic free jet perturbed by an embedded channel cavity. The study addresses a critical gap in understanding how passive upstream geometric modifications disrupt compressibility-induced shear-layer suppression to enhance downstream fluidic mixing. The experimental methodology employs high-resolution, time-resolved Schlieren visualization to capture transient density gradient fields, shear-layer flapping, and acoustic wave radiation generated by cavity trailing-edge impingement. To correlate fluid-acoustic coupling and unsteadiness, the diagnostic suite integrates synchronized high-frame-rate optical imaging. These experimental datasets aim to characterize the fundamental acoustic mode switching, establish precise instability frequencies, and optimize passive cavity geometries for high-efficiency mixing in advanced aerospace propulsion systems.
Keywords: supersonic free jet, cavity flow, passive flow control, aeroacoustics, schlieren visualization
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