Nonequilibrium thermohydrodynamic effects on the Rayleigh-Taylor instability in compressible flows

Abstract

The effects of compressibility on Rayleigh-Taylor instability (RTI) are investigated by inspecting the interplay between thermodynamic and hydrodynamic nonequilibrium phenomena (TNE, HNE, respectively) via a discrete Boltzmann model. Two effective approaches are presented, one tracking the evolution of the local TNE effects and the other focusing on the evolution of the mean temperature of the fluid, to track the complex interfaces separating the bubble and the spike regions of the flow. It is found that both the compressibility effects and the global TNE intensity show opposite trends in the initial and the later stages of the RTI. Compressibility delays the initial stage of RTI and accelerates the later stage. Meanwhile, the TNE characteristics are generally enhanced by the compressibility, especially in the later stage. The global or mean thermodynamic nonequilibrium indicators provide physical criteria to discriminate between the two stages of the RTI.

Discrete Boltzmann modeling of Rayleigh-Taylor instability in two-component compressible flows

“…Some new observations made by the DBM, for example, the fine physical structures of shock waves [46], have been confirmed and supplemented by molecular dynamics simulations [51][52][53]. In 2016, Lai et al [10] adopted the DBM to probe the effects of compressibility on RTI by inspecting the interplay between HNE and TNE phenomena. Almost at the same time, Chen et al [11] utilized a multiple-relaxation-time DBM to investigate the viscosity, heat conductivity, and Prandtl number effects from macroscopic and nonequilibrium viewpoints.…”

“…In fact, it covers a wide range of applications, from microscopic to macroscopic levels, such as inertial confinement fusion, astrophysics, atmospheric science, oceanography, combustion, etc. Extensive efforts have been devoted to theoretical [4][5][6], experimental [7], and computational studies of the phenomena [8][9][10][11].…”

“…At present, it is still an open subject with many challenging issues, especially those relevant to hydrodynamic nonequilibrium (HNE) and thermodynamic nonequilibrium (TNE) phenomena [10][11][12]. To investigate those complex nonequilibrium manifestations, a rigorous approach is to employ the Boltzmann equation [13][14][15][16][17][18][19][20] which describes the evolution of nonequilibrium statistical physical systems.…”

“…In addition to a better characterization of nonequilibrium flow state, the study on the TNE is helpful for understanding the nonlinear constitutive relation which significantly influences the physical accuracy of the hydrodynamic model. To this end, we resort to a variant of the traditional LBM which is named the discrete Boltzmann model (DBM) [10,11,[46][47][48][49][50]. The DBM has been used to investigate various complex flows.…”

“…Almost at the same time, Chen et al [11] utilized a multiple-relaxation-time DBM to investigate the viscosity, heat conductivity, and Prandtl number effects from macroscopic and nonequilibrium viewpoints. The two DBMs [10,11] are only applicable to single component fluids where heavy (light) medium has low (high) temperature. For the sake of investigating the RTI in more common situations, we extend the DBM to compressible two-component systems in a force field.…”