Study of shock wave/boundary layer interaction from the perspective of nonequilibrium effects

Abstract

Shock wave/boundary layer interaction (SWBLI) is a widespread phenomenon in supersonic flows and has received extensive attention. The boundary layer is generated due to viscous stress, which is a kind of macroscopic manifestation of molecular nonequilibrium motion, namely, nonequilibrium effects. In this paper, an investigation is conducted on SWBLI from the perspective of nonequilibrium effects. A method is proposed for studying nonequilibrium effects based on the Navier–Stokes (NS) equations and the Reynolds-averaged NS (RANS) equations. The SWBLI at Mach 2 and Mach 6 is concerned. The results show that nonequilibrium effects associated with the incident shock wave are weaker than that in the boundary layer for a Mach 2 incoming flow. Neither the separation shock wave nor the incident shock wave has an obvious interaction with nonequilibrium effects in the boundary layer. However, the nonequilibrium effects of the incident shock wave are stronger for a Mach 6 incoming flow, and it has an obvious interaction with the nonequilibrium effect in the boundary layer. We also discuss the relation between nonequilibrium effects and energy conversion in the boundary layer. The analysis reveals that changes in the gradients of total energy-related nonequilibrium effects contribute to the change in total energy by influencing the gradient of the heat flux and the power of viscous stress. Thus, this work provides the flow characteristics of boundary layer separation and energy conversion mechanism of SWBLI from the perspective of nonequilibrium effects, as well as the interaction of nonequilibrium effects between the shock wave and boundary layer.

Mesoscopic Kinetic Approach of Nonequilibrium Effects for Shock Waves

“…Research on hypersonic flow using LBM mainly focuses on exploring more optimal physical models. Faced with numerical stability issues in solving hypersonic flows with shock waves and boundary layers using LBM, BAO took a different approach and proposed a macroscopic-equation-based method for studying nonequilibrium effects related to SWBLI [ 45 ]. This method solves the macroscopic equations to analyze the flow field disturbed by shock waves and boundary layers, and then utilizes the obtained macroscopic quantities to derive corresponding nonequilibrium quantities.…”

“…Then, they further analyzed the flow characteristics of separation shocks, incident shocks, and reattachment regions based on the clue of the speed-of-sound lines that shock waves can reach within the boundary layer. The distribution of nonequilibrium quantities at these positions is illustrated in Figure 22 , and specific analysis can be found in reference [ 45 ].…”

Investigation of viscous supersonic laminar flows around F-16 airfoil: experimental, numerical, and analytical approaches

“…Similarly, phenomena like bow shocks or the sonic bubble, where the flow turns subsonic and becomes rotational, dominate this region. These intricate flow structures are challenging to predict analytically due to their highly non-linear nature and dependence on many factors, Gülçat (2010), Bao et al (2022).…”

Discrete Boltzmann multi-scale modelling of non-equilibrium multiphase flows

“…2020, 2021; Bao et al. 2022). Kinetic features, such as the unbalancing and mutual conversion of internal energy at different degrees of freedom, provide appropriate criteria for determining whether or not higher-order TNE effects should be considered in the modelling, and which level of DBM should be adopted (Lin et al.…”

“…a specific form of coarse-graining as applied to the physics of fluids beyond the hydrodynamic level. Specifically, the THNE effects presented by the DBM have permitted us to recover the main features of the distribution function (Lin et al 2014;Su & Lin 2022), to capture various interfacial phenomena (Lin et al 2014;Lai et al 2016;Gan et al 2019), to investigate entropy-increasing mechanisms and their relative importance (Zhang et al 2016(Zhang et al , 2019, and to clarify some of the fundamental mechanisms of the fine structures of shock waves, contact discontinuities and rarefaction waves beyond the reach of molecular dynamics (Gan et al 2018;Qiu et al 2020Qiu et al , 2021Bao et al 2022). Kinetic features, such as the unbalancing and mutual conversion of internal energy at different degrees of freedom, provide appropriate criteria for determining whether or not higher-order TNE effects should be considered in the modelling, and which level of DBM should be adopted (Lin et al 2014;Gan et al 2015Gan et al , 2018.…”