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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 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
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