Computational Research Work

(The computational study presents non-dimensional pressure contours with particle visualization of a generic supersonic cavity with multiple geometric configurations, including a baseline cavity with a sub-cavity (C1), a cavity with four chamfered edges (C2), a cavity with a step-up trailing edge (C3), and a cavity with a step-down trailing edge (C4). The model analysis illustrates the overall fluid-dynamic mechanism, where the incoming supersonic stream separates at the leading edge, forms a shear layer across the cavity, and interacts with the recirculation region and impinge on trailing edge. The particle-visualization video further highlights the unsteady nature of the flow, showing vortical structures traveling through the domain, impinging on cavity walls, and generating pressure disturbances. In the baseline case, strong pressure peaks appear near the shear layer and trailing edge due to vortex shedding and acoustic feedback. In the modified geometries, the flow response changes noticeably: chamfering smooths the pressure variation, the step-up configuration disrupts the natural shear-layer path, the step-down case stabilizes the exit region, and the ventilated sub-cavity allows part of the disturbance energy to escape. Together, these results provide insight into the mechanisms governing resonance and the effectiveness of passive control strategies.)

Suppressing Cavity Noise in Supersonic Flows

The Computational Lab at IIT Hyderabad uses advanced CFD simulations to investigate different models and control aeroacoustics in high-speed flows. The study focuses on how an external high-speed stream separates at the cavity leading edge, forms a shear layer across the opening, and interacts with the recirculation region to generate Rossiter-mode oscillations through a self-sustaining acoustic feedback loop. To capture these flow mechanisms, the simulations include non-dimensional pressure contours, streamline and particle visualization, numerical schlieren, spectrogram analysis, and spatial pressure mapping for multiple cavity configurations, passive control optimization at Mach 2.5. The results show that geometry modification can significantly reduce cavity noise and pressure amplification. In particular, the step-down design reduces end-wall pressure fluctuations by up to 70%, chamfered edges lower fluctuations by about 32%, and ventilated sub-cavities suppress them by nearly 40%, based on comparison with pressure and schlieren data. This research is important because cavity-induced oscillations can lead to vibrations, structural fatigue, and performance loss in high-speed aerospace systems. By understanding the flow physics and testing passive control strategies, the computational study supports the design of quieter and safer supersonic vehicles.

Keywords: Weapon bays, scramjet flameholders, launch vehicle interfaces

(The left panel illustrates the non-dimensionalized cavity geometry (scaled with cavity depth, D) along with the incoming flow direction. A detailed visualization of flow entrainment into both the cavity and the sub-cavity, captured at a microscopic level using particle-based imaging techniques. Schlieren-based density gradient contours effectively distinguish high-energy regions within the control volume, introducing clear identification of compressibility effects and shear layer dynamics. the vorticity contours elucidate the role of controlled mass injection in stabilizing cavity-induced oscillations and mitigating the formation of high-energy eddies. A comparative assessment from left to right across the vorticity fields highlights the progressive impact of optimized injection rates, demonstrating their significance in enhancing flow stability under high-speed aerodynamic conditions.)

Numerical investigation of supersonic flow over open cavity
with deep sub-cavity under steady mass injection

A two-dimensional numerical investigation is conducted to examine supersonic flow over an open cavity with a deep sub-cavity, employing steady mass injection as an active flow control technique. The study is motivated by the need to suppress pressure oscillations and shear-layer instabilities commonly encountered in high-speed aerospace configurations, including weapon bays, scramjet flame holders, and landing gear cavities. Simulations are performed at a freestream Mach number of 2.5 using a hybrid turbulence modeling approach to accurately capture both large-scale unsteadiness and near-wall effects. The analysis systematically explores a range of mass injection ratios to identify an optimal regime for flow stabilization. Results indicate that moderate injection levels effectively attenuate the shear layer–acoustic feedback loop, leading to a significant reduction in pressure fluctuations and overall flow unsteadiness. In contrast, insufficient injections fail to disrupt the instability mechanisms, while excessive injections introduce additional disturbances due to localized fluid accumulation and enhanced mixing. The study focusses on the critical role of controlled mass injection in modulating cavity flow dynamics and demonstrates that careful optimization of injection parameters is essential for achieving stable and efficient flow behavior in supersonic regimes.

Keywords: unsteady flow, cavity flow, flow control, DES

(The present computational simulation elucidates the complex thermofluidic behaviour within an arc jet plasma torch under steady-state conditions operating at a discharge current of 50 A. As the working gas enters from the inlet and flows through the inter-electrode region between the central cathode and the surrounding anode, it undergoes intense Joule heating. The resulting temperature distribution, as shown by contour analysis (left panel), reveals the formation of a highly concentrated thermal core originating at the cathode tip, where plasma temperatures reach peak values on the order of 13,823 K. This high-enthalpy plasma plume extends downstream beyond the nozzle exit, gradually dissipating thermal energy into the surrounding environment. In addition to thermal expansion effects, the velocity field (right panel) demonstrates significant acceleration influenced by electromagnetic forces. Specifically, the interaction between the electric current and the self-induced magnetic field generates a Lorentz force, which contributes to further acceleration of the plasma. The velocity contours indicate the formation of a high-velocity jet, with peak velocities in the core region immediately downstream of the cathode tip.)

Multiphysics Modelling of an Arc Jet Plasma flow

The physics of the arc-jet plasma is governed by a strong coupling between fluid flow, heat transfer, and electromagnetics. When a high voltage is applied between the cathode and anode, the working gas undergoes electrical breakdown and becomes ionized, forming plasma. This plasma behaves as an electrically conducting fluid. The electric current flowing through the plasma leads to Joule heating, which significantly raises the temperature. As the temperature increases, the degree of ionization also increases, which in turn enhances the electrical conductivity of the plasma. This creates a feedback mechanism where higher conductivity allows more current to pass, further increasing the temperature. At the same time, the interaction between the electric current and the induced magnetic field generates a Lorentz force. This force acts on the plasma and contributes to its acceleration, influencing the flow field. The high temperature of the plasma results in large pressure gradients, which drive the flow from the torch exit into the surrounding environment. The plasma also transfers energy through convection as it moves, and through conduction within the flow. Additionally, at such high temperatures, radiation becomes significant. The plasma emits energy in the form of electromagnetic radiation, which contributes to overall energy loss. All these phenomena Joule heating, Lorentz force, fluid flow, heat transfer, and radiation are interdependent. The temperature affects conductivity, conductivity affects current flow, current affects heating and magnetic fields, and these in turn influence the velocity and energy transport.

Keywords: Arc jet plasma flow, High-enthalpy flow, Magnetohydrodynamics (MHD)