Numerical studies of hypersonic binary gas-mixture flows near a sphere

Diffusion processes have a significant effect on the structure of a low-density gas mixture flow near blunt bodies [1], [2]. The effect of abnormal increasing of the temperature recovery factor at the stagnation point of a blunt body in the rarefied gas mixture flow was studied experimentally by Maise and Fenn [3]. The structure of rarefied gas mixture flows about a sphere was analyzed by Molodtsov and Riabov [4], [5] using numerical solutions of the Navier-Stokes equations. The normal shock wave structure in binary gas mixture was studied by Center [6] and Harnet and Muntz [7]. Direct Simulation Monte-Carlo (DSMC) technique was used by Bird [8], [9] and Plotnikov and Rebrov [10] to study the flow. In the present study, diffusive effects in hypersonic flows of binary gas-mixtures near a sphere are studied using the DSMC method [9], [11] and numerical solutions of the Navier-Stokes equations [4]. The range of applicability of these techniques is estimated using the comparison of the results with experimental data [2] for N2-H2 and air-He mixtures. It is found that the diffusion and rarefaction affect the shock-wave width, allocation and width of high-pressure areas far from the surface, adiabatic temperature, pressure at the stagnation point, heat transfer, and the effectiveness of species separation and injected-gas penetration in the flow. These features are illustrated by numerical results for N2-H2 mixture flow (fN2,∞ = 0.1) near a sphere for different regimes at Reynolds numbers 6 ≤ Re 0,R ≤ 100 or Knudsen numbers 0.257 ≥ Kn∞,R ≥ 0.015. Compared to a mono-component gas, the shock layer thickness increases, the mixture enrichment with heavy particles occurs in high pressure regions, and the adiabatic wall temperature rises. The Mach number contours in the flow at M∞ = 6.6 past a sphere are shown in Fig. 1. At Kn∞,R ≥ 0.1, the regime of the fully merged layer [12] is characterized by relatively smooth changing of the flow parameters in the flow-field (see Fig. 1 (left )). Under