Visualization of shock-free compression/laminar boundary layer interaction caused by a curved fin in supersonic flow

The laminar boundary layer interacting with a curved fin is visualized in a Mach 2.95 flow. The nanoparticle-based planar laser scattering (NPLS) method, which has a high spatiotemporal resolution, is used to obtain the fine flow structures of the shock-free compression/laminar boundary layer interaction. A curved fin of a 20-degree total turn produces shock-free compression in the investigated region. The visualization results reveal the separation of the boundary layer flow and the downwards flowing of the high-momentum mainstream. The flowfield is divided into three regions. The disturbance of the vortexes shed from the fin combined with the pressure gradients attributed to the transition of the boundary layer. The vortexes with variable scales, generated from the flow on the fin, shed from the upstream flow on the fin and developed from the boundary layer, respectively, spread over the downstream convergence region.