Hybrid Particle-Continuum Simulations of Hypersonic Flow Over a Hollow-Cylinder-Flare Geometry

Abstract

A modular particle-continuum numerical method is used to simulate steady-state hypersonic flow over a hollowcylinder-flare geometry. The resulting flowfield involves a mixture of rarefied nonequilibrium flow and high-density continuum flow. The hybrid particle-continuum method loosely couples direct simulation Monte Carlo and NavierStokes methods, which operate in different regions, use different mesh densities, and are updated using differentsized time steps. Hybrid numerical results are compared with full particle and full continuum simulations as well as with experimental data. The hybrid particle-continuum simulations are demonstrated to reproduce experimental and full particle simulation results for surface and flowfield properties including velocity slip, temperature jump, thermal nonequilibrium, heating rates, and pressure distributions with high accuracy. The hybrid method, which uses particle simulation next to the surface, is also shown to predict accurate heating rates even when a highly dissipative numerical scheme is used for the continuum solver. For this particular flow, a hybrid simulation is obtained with modest computational savings over full particle simulation. NomenclatureBr cutoff = cutoff value of the continuum-breakdown parameter

Hybrid simulations of rarefied supersonic gas flows in micro-nozzles

“…Indeed, it has been shown that the use of a Chapman-Enskog distribution leads to somewhat higher accuracy as compared to a Maxwellian distribution in hybrid DSMC-Navier Stokes simulations of a Couette flow, which is an extreme example of a strongly non-equilibrium flow driven purely by gradient effects [58]. Based on these findings, many recent papers on hybrid DSMC-Navier Stokes simulations have applied a Chapman-Enskog distribution [29,31,61,20,63,62]. Other authors, on the other hand, have chosen to apply a Maxwellian distribution in hybrid DSMC-Navier Stokes simulations, arguing that the use of a Chapman-Enskog distribution leads to a small improvement in accuracy [59,65] which does not justify the largely increased computational costs [60], or because of the fact that the Chapman-Enskog distribution becomes negative with deviation from the Maxwellian distribution [59], or because of the observation that for specific flows a greater mismatch at the interface between Navier Stokes and DSMC was observed for a ChapmanEnskog distribution as compared to a Maxwellian distribution [64].…”

Heat flux correlation for high-speed flow in the transitional regime

“…It is noted that Wang et al (2010) recently proposed the opposite trend, using similar Burnett-order analysis to that presented in § 2.3 above, where such a comparison predicted a higher heat flux compared with continuum analysis. However, the trend of lower heat flux in the transition regime, compared with continuum predictions, has been verified in a number of articles (for example Lofthouse et al 2007;Schwartzentruber, Scalabrin & Boyd 2008a;Schwartzentruber et al 2008b,c;Holman & Boyd 2009 in which DSMC calculations have been compared with matching CFD calculations where both codes used highly consistent physical models. Figure 4 shows that the correlation proposed by Brandis & Johnston (2014) (2009) together with free-molecular results, we determine the constants in our expression as α = −0.476, C 2 = 1.10, C 3 = 1.8.…”

Computational Strategies for Micro‐ and Nanofluid Dynamics

“…This distribution has been used primarily in hybrid simulations of dilute gases. 78,81,[101][102][103] The Chapman-Enskog distribution is a perturbed Maxwell-Boltzmann distribution 104 with the probability density given by…”