Shock Structure Solution by Hybrid Flowfield Methods

A hybrid kinetic-based code, the Unified Flow Solver, is called on to investigate the internal structure of a normal shock wave for a Mach range of 1.55 to 9.0 for Argon, and 1.53 to 3.8 for diatomic Nitrogen. Reciprocal shock thickness, density, temperature, heat flux, and the partially-integrated velocity distribution function are calculated for a one-dimensional shock wave and compared with experimental data and Direct Simulation Monte Carlo results. The models used in the Unified Flow Solver include the Euler, Navier-Stokes, Bhatnagar-Gross-Krook, and the three-temperature Bhatnagar-Gross-Krook schemes. In particular, hybrid results of coupled kinetic-based solvers (Bhatnagar-Gross-Krook with Navier-Stokes, and three-temperature Bhatnagar-Gross-Krook with Euler) are compared with uncoupled kinetic models (Bhatnagar-Gross-Krook and three-temperature Bhatnagar-Gross-Krook). To correctly couple the solvers near a shock wave at moderate Knudsen numbers, a relevant switching parameter is chosen. Hybrid solvers are here shown to be attractive alternatives to uncoupled methods because they can produce almost identical results with lower computational costs. On average, the Argon and Nitrogen hybrid simulations are 1.8 and 1.3 times faster, respectively.