Extension of a Modular Particle-Continuum Method to Vibrationally Excited, Hypersonic Flows

摘要

A modular particle-continuum method is extended to include vibrationally excited energy modes to simulate hypersonic steady-state flows that exhibit small regions of translational nonequilibrium in a mainly continuum flow field. This method loosely couples an existing direct simulation Monte Carlo code to a Navier-Stokes solver (computational fluid dynamics) while allowing both time step and cell size to be completely decoupled between each method. A new information-transfer scheme that controls the inherently large statistical scatter of vibrational energies in low-temperature regions is described and tested. Two vibrational-relaxation models are implemented to test the sensitivity in agreement between direct simulation Monte Carlo and the modular particle-continuum method. By limiting the size of the direct simulation Monte Carlo region to only areas in translational nonequilibrium and maintaining consistent physical models in both computational fluid dynamics and direct simulation Monte Carlo modules, the modular particle-continuum method is able to reproduce full direct simulation Monte Carlo results for flow with global Knudsen number of 0.01 while decreasing the computational time required by a factor of about four.