Influence of Rarefaction Degree and Aft-Body Geometry on Supersonic Flows

• Published in: AIAA journal 2024-10, p.1-21
• Main Authors: Toussaint, Damien, Noubel, Hugo, Baranger, Céline, Braeunig, Jean-Philippe, Lago, Viviana
• Format: Article
• Language: English
• ISSN: 0001-1452; 1533-385X
• DOI: 10.2514/1.J063798

During atmospheric entry, super-/hypersonic vehicles cross distinct atmospheric layers characterized by large density variations and thus experience different flow regimes ranging from free molecular, transition, slip, to continuous regimes. Due to the distinct modeling strategy between these regimes and complex physical phenomena appearing near the vehicles (boundary-layer/shock interaction, base-flow recirculation, etc.), assessing their aerodynamic properties may be difficult. The present work focuses on supersonic flows around sharp-base geometries in both continuous and slip-flow regimes and aims at highlighting the influence of both rarefaction degree and base geometry on the vehicles’ aerodynamic features. For this purpose, three axisymmetric cone-cylinder geometries with right-angled, rounded, or flared rear parts are considered. Flow visualization, pressure, and drag measurements are carried out at Mach number [Formula: see text] and Knudsen numbers ranging from [Formula: see text] to [Formula: see text] in the supersonic rarefied MARHy wind tunnel. The experimental data are compared with numerical results of simulations performed with a continuous-flow Navier–Stokes ([Formula: see text]) solver and two rarefied flows codes: a discrete-ordinate Bhatnagar–Gross–Krook ([Formula: see text]) solver and a direct simulation Monte Carlo (SPARTA) solver. While the [Formula: see text] solver overestimates frictional drag as [Formula: see text] rises, the rarefied [Formula: see text] and SPARTA results show satisfactory agreement with experimental data. The latter numerical results highlight the main effects of rarefaction: as [Formula: see text] increases, shocks become more diffuse, skin friction strengthens (leading to a significant increase in drag coefficients), and the extent of the base-recirculation decreases. Regarding the aft-body geometry, its influence on the base recirculation vanishes with increasing [Formula: see text].