【摘要】 利用纹影成像技术,在新近研制的超声速剪切风洞中测出了可压缩剪切层的厚度增长率曲线,并捕获了其中的瞬时涡结构。实验对流马赫数分别为0.26,0.43,0.50,0.66,纹影光源曝光时间为200μs和10ns。纹影照片显示,随着对流马赫数增加,可压缩剪切层正则化厚度增长率显著降低,当Mc>0.66时,趋近于0.2。Mc=0.26和0 43时,可压缩剪切层中大尺度结构是二维展向涡,Mc=0.5和0.66时,大尺度结构呈现三维性而且不规则。更多还原

【Abstract】 An experiment is conducted at a new facility to study the characteristics of compressible shear flow behind a flat plate. Four cases are studied in which the free-stream Mach numbers range from 0.25 to 2.0, and the convective Mach numbers range from 0.26 to 0.66. Schlieren photograph is employed to get the photographs of shear layer.The schlieren photograph of 200μs exposure time reveals very low spreading rates and the schlieren photograph of 10ns exposure time reveals the characteristics of compressible shear respectively. A compressible-effect parameter (Mc) is used to correlate and unify the spreading rates.The major results of this experiment are as follows:(1) The normalized growth rate ,which is unity for incompressible flow ,decreases rapidly with increasing convective Mach number, reaching an asymptotic value of about 0.2 for Mc>0.66.(2) Compressible shear layer is dominated by spanwise rollers at Mc=0.26 and 0.42,but much more three dimensional and unorganized structures at Mc=0.5 and Mc=0.66.更多还原