Hybrid particle-continuum simulations of nonequilibrium hypersonic blunt-body flowfields

Hypersonic blunt-body flowfields containing a mixture of continuum and nonequilibrium flow are investigated using a modular particle-continuum numerical method. The modular particle-continuum method solves the Navier-Stokes equations in near-equilibrium regions and uses the direct simulation Monte Carlo method in nonequilibrium regions. Hypersonic flow of nitrogen over a two-dimensional cylinder at a global Knudsen number of 0.01 is simulated for a range of Mach numbers using the modular particle-continuum method as well as full direct simulation Monte Carlo and full Navier-Stokes algorithms. For these conditions, Navier-Stokes simulations significantly overpredict the local shear stress and also overpredict the peak heating rate by 5-10% when compared with direct simulation Monte Carlo results. The direct simulation Monte Carlo method also predicts faster wake closure and 10-15% higher temperatures in the immediate wake region. The modular particle-continuum code is able to accurately reproduce the flowfield results, local velocity distributions, and surface properties obtained using the direct simulation Monte Carlo method up to 2.8 times faster. It is found that when using the modular particle-continuum method, particle simulation of the bow-shock interior is not necessary for accurate prediction of surface properties. However, particle simulation is required for the boundary-layer and near-wake regions.