Turbulent structures of shock-wave diffraction over 90° convex corner

Abstract

The turbulent structures and long-time flow dynamics of shock diffraction over 90 ○ convex corner associated with an incident shock Mach number Ms = 1.5 are investigated by large eddy simulation (LES). The average evolution of the core of the primary vortex is in agreement with the previous two dimensional studies. The Type-N wall shock structure is found to be in excellent agreement with the previous experimental data. The turbulent structures are well resolved and resemble those observed in the experimental findings. Subgrid scale dissipation and subgrid scale activity parameter are quantified to demonstrate the effectiveness of the LES. An analysis based on turbulent-nonturbulent interface reveals that locally incompressible regions exhibit the universal teardrop shape of the joint probability density function of the second and third invariants of the velocity gradient tensor. Stable focus stretching (SFS) structures dominate throughout the evolution in these regions. Stable node/saddle/saddle structures are found to be predominant at the early stage in locally compressed regions, and the flow structures evolve to more SFS structures at later stages. On the other hand, the locally expanded regions show a mostly unstable nature. From the turbulent kinetic energy, we found that the pressure dilatation remains important at the early stage, while turbulent diffusion becomes important at the later stage. Furthermore, the analysis of the resolved vorticity transport equation reveals that the stretching of vorticity due to compressibility and stretching of vorticity due to velocity gradients plays an important role compared to diffusion of vorticity due to viscosity as well as the baroclinic term.

Diffraction of shock waves through a non-quiescent medium

“…Several numerical studies have been undertaken on shock diffraction in quiescent media covering a broad range of topics including vortices generated during diffraction (Murugan et al 2012;Reeves & Skews 2012;Dora et al 2014), turbulent structures (Soni et al 2019) and vorticity production (Sivier et al 1992;Tseng & Yang 2006). On numerous occasions, it has been demonstrated that viscous contributions may be neglected and many of the significant flow features associated with shock diffraction are sufficiently captured (Hillier 1991;Sun & Takayama 1997;Ripley, Lien & Yovanovich 2006).…”

“…2014), turbulent structures (Soni et al. 2019) and vorticity production (Sivier et al. 1992; Tseng & Yang 2006).…”

On Shock Propagation through Double-Bend Ducts by Entropy-Generation-Based Artificial Viscosity Method

“…In this regard, Chaudhuri et al [ 34 ] reported the stable shock capturing capabilities of explicit high-order DSEM in conjunction with entropy-generation-based artificial viscosity (AV) method. Although inviscid simulations quite accurately predict the shock wave diffraction wave patterns over different geometrical shapes, it is evident that viscous effects are important for resolving long-time behavior of shock-vortex evolution, shock-shear layer and shock-boundary layer interactions [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. These issues are also discussed in the recent works [ 42 , 43 ] using high-order DSEM with AV method.…”