摘要
Semi-periodic structures namely inclined wavy structures （IWS） are experimentally observed in compressible mixing layers at two convective Mach numbers （Mc = 0.11 and 0.47）. Flow structures are visualized by the laserinduced planar laser Mie scattering （PLMS） technique. Two methods are developed to investigate the spatial distribu- tion and geometry of IWS： （1） the dominant mode extrac- tion （DME） method, to extract the dominant modes of IWS from the streamwise gray-level fluctuation, and （2） the phase tracking （PT） method, to identify the shape of IWS. The re- sults suggest that pressure perturbations account for the for- marion of IWS in the initial mixing region and the joint effect of dilatation and coherent vortices enhances IWS in the well- developed region. The large transverse （cross-flow） scale of the IWS and their relation to coherent vortices （CV） indicate that the disturbance originated from CV in the mixing center propagates far into the free streams. The DME and the PT method are shown to be the effective tools to study the geometrical features of wavy structures in compressible shear flows.
Semi-periodic structures namely inclined wavy structures （IWS） are experimentally observed in compressible mixing layers at two convective Mach numbers （Mc = 0.11 and 0.47）. Flow structures are visualized by the laserinduced planar laser Mie scattering （PLMS） technique. Two methods are developed to investigate the spatial distribu- tion and geometry of IWS： （1） the dominant mode extrac- tion （DME） method, to extract the dominant modes of IWS from the streamwise gray-level fluctuation, and （2） the phase tracking （PT） method, to identify the shape of IWS. The re- sults suggest that pressure perturbations account for the for- marion of IWS in the initial mixing region and the joint effect of dilatation and coherent vortices enhances IWS in the well- developed region. The large transverse （cross-flow） scale of the IWS and their relation to coherent vortices （CV） indicate that the disturbance originated from CV in the mixing center propagates far into the free streams. The DME and the PT method are shown to be the effective tools to study the geometrical features of wavy structures in compressible shear flows.
基金
supported by National Nature Science Foundation of China(90716008,10572004,and 11172006)
by MOST 973 Project(2009CB724100)
