Dynamics of Axisymmetric Shockwave-Boundary Layer Interactions

This study investigates the flow topology and unsteadiness of a Mach 2 oblique shock impinging on a laminar boundary layer (Re = 35,800) over a cylinder using high-fidelity Implicit Large Eddy Simulations (I-LES). The impinging shock wraps around the cylinder, inducing a complex three-dimensional separation zone, before reflecting as a conical shock. A primary separation forms a vortex pair that detaches from the surface, while a secondary separation remains closer to the surface, meandering as it moves toward the leeward plane, inducing additional vortices. These flow features, in conjunction with strong cross flow, driven by pressure gradients from the shock and surface curvature, introduce significant azimuthal variations in wall loading. On the windward plane, unsteadiness similar to 2D shock-boundary layer interactions (SWBLI) is observed, including low-frequency bubble breathing, mid-frequency shear layer shedding, and shock oscillations, along with high-frequency boundary layer instabilities. Spatial eigenmodes extracted using Spectral Proper Orthogonal Decomposition (SPOD) shows strong evidence of this similarity. Across other azimuthal planes, the dominant unsteadiness arises from vortex breakdown and turbulence associated with the separation regions.