Modeling of the high altitude portion of reentry vehicle trajectories with DSMC or statistical BGK solvers requires accurate evaluation of the boundary conditions at the ablating TPS surface. Presented in this article is a model which takes into account the complex ablation physics including the production of pyrolysis gases, and chemistry at the TPS surface. Since the ablation process is time ...

Electron-acoustic waves have strong linear Landau damping, but are observed as nonlinear BGK modes in experiments with pure electron plasmas. The waves have phase velocity vφ ≈ 1.3v̄, in agreement with theory, and the longest wavelength BGK states exhibit only relatively weak damping. Shorter wavelength modes exhibit a strong decay instability which can be experimentally controlled.

In this study, we employ physics-informed neural networks (PINNs) to solve forward and inverse problems via the Boltzmann-BGK formulation (PINN-BGK), enabling PINNs model flows in both continuum rarefied regimes. particular, PINN-BGK is composed of three sub-networks, i.e., first for approximating equilibrium distribution function, second non-equilibrium third one encoding equation as well corr...

This paper presents an improved gas-kinetic scheme based on the Bhatnagar-Gross-Krook (BGK) model for the compressible Navier-Stokes equations. The current method extends the previous gaskinetic Navier-Stokes solver developed by Xu and Prendergast by implementing a general nonequilibrium state to represent the gas distribution function at the beginning of each time step. As a result, the requir...

Coherent bipolar electric field structures with negative unipolar potentials are widely observed in space plasmas. These often found to be ion Bernstein Greene Kruskal (BGK) modes or holes. Most theoretical models of holes assume them stationary respect the background plasma that follows either Maxwellian kappa-type distribution. In this paper, we present a new model where non-stationary, and e...

Following van Leer's MUSCL idea, a numerical scheme can be regarded as consisting of two key steps: a reconstruction step followed by a gas evolution step. We present a gas-kinetic method based on the collisional BGK model which provides an alternative to Riemann solvers for the gas evolution step. An advanced BGKscheme is derived under quite general assumptions on the initial conditions. The n...

We study the BGK approximation to first-order scalar conservation laws with a flux which is discontinuous in the space variable. We show that the Cauchy Problem for the BGK approximation is well-posed and that, as the relaxation parameter tends to 0, it converges to the (entropy) solution of the limit problem.