Entrainment Mechanism Analysis of Oblique Shock-Wave/Boundary-Layer Interactions

The interaction between shock waves and boundary layers impacts hypersonic vehicles’ aerodynamic structure, internal turbulent mixing, and combustion processes. Direct numerical simulations (DNSs) of the hypersonic boundary layer have been performed to study the turbulent/non-turbulent interface (TNTI) entrainment mechanism and the impact of shock waves. Two cases are analyzed with and without the shock-wave and boundary layer interaction. A novel approach is proposed to identify TNTI by integrating the vorticity threshold and fuzzy clustering method. To account for the influence of increasing Reynolds number in the flow direction on the vorticity threshold analysis, vorticity is normalized using the local boundary layer thickness and friction velocity. Two entrainment mechanisms are quantitatively described and compared using TNTI local entrainment velocity and the mass conservation equation. The results demonstrate that the entrainment process within the hypersonic boundary layer TNTI is predominantly governed by large-scale engulfment, and under the influence of shock waves, the dominance of large-scale ingestion is notably enhanced.