Adaptive criterion and modification of wave-particle decomposition in UGKWP method for high-speed flow simulation

TL;DR

This paper introduces an adaptive criterion and modifications to the wave-particle decomposition in the UGKWP method, improving high-speed flow simulations by better handling scale variations and reducing computational costs.

Contribution

The study develops a scale adaptive criterion based on space, time, and gradient criteria, and modifies flux evolution in UGKWP for enhanced efficiency and accuracy in high-speed flow simulations.

Findings

Improved wave-particle decomposition efficiency.

Enhanced accuracy in hypersonic flow simulations.

Validated performance across multiple complex test cases.

Abstract

Benefitting from the direct modeling of physical laws in a discretized space and the automatic decomposition of hydrodynamic waves and particles, the unified gas-kinetic wave-particle (UGKWP) method offers notable advantages in various multiscale physics, such as hypersonic flow, plasma transport and radiation transport. Aiming at achieving a more suitable and efficient wave-particle decomposition in high-speed flow simulation and enhancing the performance in the drastic scale variation region, in this work, the scale adaptive criterion is studied and the flux evolution of UGKWP method is modified. Specifically, besides the perspective of time which is naturally considered in the time-dependent distribution function of UGKWP method, two more criteria from views of space and gradient are utilized to identify the local scale, and to reduce the computational consumption of particles on describing the near-equilibrium microscopic gas distribution function. Moreover, corresponding to the coefficients in the time integration flux of unified gas-kinetic scheme (UGKS), the evolution of hydrodynamic wave is modified to be more consistent with particles, which is essential when the scale changes intensely in different cells. A variety of test cases are conducted to validate the performance of the adaptive UGKWP method, including hypersonic flows around a cylinder at multiple inflow Knudsen numbers, hypersonic flow over a slender cavity, side-jet impingement on hypersonic flow and three-dimensional hypersonic flows over a $70^{\circ}$ blunted cone with a cylindrical sting.