AN EXPERIMENTAL INVESTIGATION ON MIXING-ENHANCED COMPRESSIBLE SHEAR LAYERS

摘要

Two-dimensional, instantaneous velocity fields of mixing-enhanced compressible, planar shear layers are measured via the particle image velocimetry (PIV) at a convective Mach number, M_c, of 0.62 in order to investigate the mechanism of mixing enhancement by sub-boundary layer triangular disturbances. Flow visualization by the planar laser Mie scattering (PLMS) technique is also conducted. The PLMS results reveal the present mixing enhancement technique increases shear layer growth rate by about 50%. The results of PIV show that in the mixing enhanced case, the streamwise velocity profile across the shear layer has triple inflection points. A pair of counter-rotating streamwise vortices due to the disturbances are observed. It is found that the enhanced case shows higher turbulent intensity and Reynolds stress than no-disturbance case, suggesting mixing enhancement effects through a large momentum transport, and also reveals lower anisotropy.