Turbulent boundary layer subjected to a sonic transverse jet in a supersonic flow

Abstract

Particle Image Velocimetry (PIV) technology, oil flow visualization and Nanoparticle-based Planar Laser Scattering (NPLS) technology are used to investigate the turbulent boundary layer (BL) of a sonic jet injected into a supersonic flow at Ma=2.95. Instantaneous and averaged NPLS images display detailed structures of the bow shock, the horseshoe vortex, separation zones and the collision shock. Root Mean Square (RMS) values of flow quantities calculated from NPLS images and PIV data reveal that turbulent fluctuations are suppressed downstream of the horseshoe separation zone in the jet lateral region and a 33%-35% reduction of the density fluctuation magnitude across the boundary layer is observed, while it is enhanced in the jet wake by 34%-50%. Further away from the wall, the influences of the λ shock system, the expansion process, and the reflected shock on turbulence intensity and velocities of the crossflow BL is weakened. A three-dimensional schematic diagram of the interaction between the sonic jet and the turbulent BL is presented, explaining the formation of the turbulence decay zone in the jet lateral region.