Arnab Roy

Shock–bubble interaction constitutes a canonical problem in compressible turbulence, governed by the interplay of compressive and vortical dynamics. Numerical simulations are employed to examine light (He) and heavy (R22) bubbles using dynamic mode decomposition and Favre-weighted turbulent kinetic energy spectra. The flow initially displays steep, shock-dominated spectra consistent with Burgers-type scaling. Following shock passage, the light bubble generates coherent jet-driven vortices and a hierarchical energy cascade, producing departures from k−2 scaling. In contrast, the heavy bubble suppresses large-scale coherence and dissipates energy rapidly. These findings highlight that spectral evolution is dictated by the competition among baroclinic vorticity generation, compressibility, and shear-driven turbulence. Although the numerical analysis clarifies the persistence of k−2 spectral scaling in shock–bubble interactions, its applicability is limited by the two-dimensional inviscid framework adopted for incident shocks at Mach 1.22 and Mach 1.8. Extrapolation to fully three-dimensional flows requires caution, as additional dissipative and vortical mechanisms may modify the scaling behavior.

Film cooling is one of the most efficient external cooling methods used to ensure the proper functionality of modern gas turbine engines. The use of sweeping jets as a coolant stream is a recent addition to the field of film cooling, gaining popularity due to its improvement in performance over steady jets. With an increasing abundance of investigations on the topic, surprisingly, sweeping jets are rarely explored for the leading-edge film cooling. In this study, numerical investigations were performed to study the effects of various blowing configurations on the multihole sweeping jet film cooling at the leading edge of an HP turbine nozzle guide vanes (NGV). Three sweeping jets were studied with transitional periodicity, and the blowing ratio was varied as BR = 0.5, 0.75, and 1.0 in two configurations. When the BR of the middle hole was increased, keeping others the same, it was termed as “jet focusing,” and when the BR of all the holes was increased, it was termed as “straight blowing.” A detailed discussion of the heat transfer augmentation results is presented along with the unsteady aerodynamics and thermal fields produced by a row of sweeping jets. It was observed that sweeping jets placed in a row interact in a nonsynchronized and highly unpredictable manner. This results in an asymmetrical distribution of coolant over the target surface. A new feature of reversed hole configuration was found where the coolant stream comes out of the cooling hole in the form of lumps of cold fluid. This phenomenon was termed “blobbing.” The results also showed that jet focusing may result in a 9% reduction in heat transfer augmentation without affecting the film cooling effectiveness in the leading edge region. Increasing the coolant flow rate with straight blowing proves to be detrimental to leading-edge film cooling.

In the present investigation, a supernova remnant (SNR) propagation inside the interstellar medium (ISM) is numerically simulated by solving the compressible magneto-hydrodynamic equations, employing a high-order finite volume methodology as implemented in the PLUTO solver. Flow features associated with the SNR propagated inside non-uniform ISM, is discussed thoroughly. The vortical coherent modes, identified through dynamic mode decomposition during the propagation of a SNR through a non-uniform ISM exhibit spatio-temporal decay behavior due to strong dissipation induced by the reverse shock and forward shock, respectively.

In this article, the numerical simulation of a three-dimensional hydrodynamic relativistic jet issuing from an active galactic nucleus and its propagation inside a low radio-shift cluster has been performed by solving relativistic hydrodynamic equations using the computer code PLUTO [Mignone et al., “PLUTO: A numerical code for computational astrophysics,” Astrophys. J. Suppl. Ser. 170, 228 (2007)], which is based on the higher-order finite volume method. The detailed flow physics associated with relativistic jet propagation inside both uniform medium and low radio-shift clusters has been discussed thoroughly. Furthermore, the invariants (P, Q, and R) of the velocity gradient tensor (∂ui∂xj) have been analyzed using numerical simulation data to identify the local flow topology [Chong et al., “A general classification of three-dimensional flow fields,” Phys. Fluids A 2, 765–777 (1990); Suman and Girimaji, “Velocity gradient invariants and local flow-field topology in compressible turbulence,” J. Turbul. 11, N2 (2010); Thaker et al., “Invariants of the velocity gradient tensor in a spatially developing compressible round jet,” J. Fluid Mech. 971, A18 (2023)] and thereby shock–turbulence interaction. The joint probability density function of Q–R obtained from numerical data, depicts the presence of turbulent sheet-like structures during the propagation of this relativistic jet through both uniform medium and low radio-shift cluster environments. Eventually, the study reveals that the occurrence of sheet-like structures is more dominant in the uniform medium due to strong shock–turbulence amplification inside the cocoon of the uniform medium over the low radio-shift cluster environment.