Shock-wave–boundary-layer interaction over an axisymmetric body

This study investigates the flow topology and unsteadiness induced by the interaction of an oblique shock and a supersonic boundary layer developing over an axisymmetric body, using implicit large-eddy simulations. The interaction produces highly three-dimensional flow features, including an open separation region, multiple vortex pairs and strong cross-flow, influenced by the surface curvature and the strong adverse pressure gradient. Three major vortex systems are identified: a primary vortex that detaches from the surface, a secondary vortex near the surface that dominates unsteadiness and a weaker tertiary vortex that dissipates downstream. Turbulence generation mechanisms vary in the azimuthal direction, with production being the dominant source on the windward plane, while turbulent transport contributes mostly in the leeward wake. Windward side unsteady dynamics is dominated by four major frequency bands: a very-low-frequency band ( italic St Subscript upper L Baseline tilde 0.03 St L ∼ 0.03 $ \textit{St}_{L} \sim 0.03$ , where upper S t S t $St$ is Strouhal number, upper S t Subscript upper L S t L $St_L$ is the Strouhal number with length of separation bubble as reference length) associated with bubble breathing, low-frequency shear-layer flapping at italic St Subscript upper L Baseline tilde 0.1 St L ∼ 0.1 $ \textit{St}_{L} \sim 0.1$ , Kelvin–Helmholtz shedding in the shear layer at italic St Subscript upper L Baseline tilde 1 St L ∼ 1 $ \textit{St}_{L} \sim 1$ and high-frequency content corresponding to fine-scale convection in the boundary layer. Leeward side dynamics is influenced by the coherent structures generated in the secondary and tertiary vortex pairs, resulting from short-wavelength elliptic instability, leading to vortex meandering. The primary vortex displays a ‘ V ’-shaped vertical oscillations corresponding to the very-low-frequency band, highlighting the impact of shock-wave/boundary-layer interaction bubble breathing on large-scale vortex oscillations. This low-frequency vortex dynamics has a significant impact on the aerodynamic loading on the cylinder.