Hypersonic flow over spherically blunted double cones

• Published in: Journal of fluid mechanics Vol. 896
• Main Authors: Hao, Jiaao, Wen, Chih-Yung
• Format: Journal Article
• Language: English
• Published: Cambridge Cambridge University Press 10.08.2020
• Subjects: Aerodynamics; Boundary layer interaction; Computational fluid dynamics; Computer simulation; Cones; Decks; Energy; Enthalpy; Equilibrium; Experiments; Fluid flow; Heat flux; Heat transfer; Hypersonic flow; Hypersonic shock; Impingement; Mach number; Nose; Pressure; Pressure gradients; Reynolds number; Separation; Shock waves; Simulation; Skin; Skin friction; Studies; Upstream; Vortices
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/jfm.2020.331

A hypersonic shock wave/laminar boundary-layer interaction over a canonical $25{-}55^{\circ }$ double-cone configuration is numerically investigated. A moderate-enthalpy flow of $5~\text{MJ}~\text{kg}^{-1}$ with a Mach number of 9.87 and a unit Reynolds number of $1.5\times 10^{5}~\text{m}^{-1}$ is considered. Special emphasis is given to the influence of leading-edge bluntness. The results indicate that the double-cone flow is insensitive to small bluntness in terms of shock structures, separation region sizes and surface pressure and heat flux distributions. A critical nose radius is observed, beyond which the separation bubble grows dramatically. The numerical data are analysed and interpreted based on a triple-deck formulation. It is shown that the sudden change in flow features is mainly caused by pressure overexpansion on the first cone due to leading-edge bluntness, such that the skin friction upstream of the separation is significantly reduced and the upstream pressure can no longer resist the large adverse pressure gradient induced by shock impingement. An estimation of the critical radius is established based on the pressure correlations of Blick & Francis ( AIAA J. , vol. 4 (3), 1966, pp. 547–549) for spherically blunted cones. Simulations at a higher enthalpy with the presence of both vibrational relaxation and air chemistry show a similar trend with increasing nose radius. The proposed criterion agrees well with the experimental observations.