Experimental investigation of interactions between laminar or turbulent boundary layer and shock wave

Abstract

Investigation on the interactions between laminar or turbulent layer and shock wave is performed in a Mach 3.4 supersonic wind tunnel, based on nanoparticle-tracer based planar laser scattering (NPLS) system and supersonic particle image velocimetry (PIV) system. The model geometry in this experiment is composed of two flats with different positions in the test section which can provide the flat with different kinds of boundary layer, and a shock wave generator–a 12° wedge. Boundary layer separation/attachment, induced suppression waves, induced shock wave and expansion fan were clearly presented by NPLS images, velocity field and vorticity field were given by PIV results. Instantaneous flow structures and temporal evolution of two different flow conditions were analysised and compared according to both NPLS and PIV results. The experimental results show that: the separation zone in the turbulent boundary layer is long and narrow, but it’s quite different in the turbulent boundary layer where it is oval-shaped; upstream of the oblique shock wave, a serious of suppression waves can be observed outside of the laminar boundary layer and they will focus into a unsteady induced shock wave, but in contrast, only a focused shock wave can be found outside of the turbulent boundary layer and it’s quite stable; the expansion fan downstream of the oblique shock wave is small in the laminar boundary layer, leading to a sufficient acceleration of the flow, and the attachment shock wave behind the expansion fan is extremely weak, however it is a totally different condition in the turbulent boundary layer with a wide expansion fan and a strong attachment shock wave.