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以高时空分辨率的纳米平面激光散射(NPLS)实验技术为基础,在SML-1风洞中完成了超声速混合层的流动显示实验.相应的实验图像清晰地再现了层流、转捩及湍流区的流场结构,空间分辨率满足分形度量的要求.给出并比较了测量分形维数的两种常用方法,采用计盒维数法测量了超声速混合层转捩区和完全发展湍流区的分形维数.转捩区的分形维数随着湍流脉动的增强而增加.完全发展湍流区的分形维数并不会因为流场结构不同而有较大的变化,表面上杂乱无章的湍流界面具有基本相同的分形维数,体现了湍流流动的自相似性.
Based on the NPLS technique with high spatio-temporal resolution, flow-rate experiments of the supersonic mixing layer were completed in the SML-1 wind tunnel.The corresponding experimental images clearly reproduce the laminar flow, turbulent flow and turbulent flow The flow field structure and the spatial resolution of the area satisfy the requirement of fractal dimension.Two common methods of measuring fractal dimension are given and compared, and the box-fold method is used to measure the transition zone of supersonic mixing layer and the fully developed turbulent zone Fractal dimension.The transitional zone fractal dimension increased with turbulent pulsation increasing.The fractal dimension of fully developed turbulence zone did not change greatly due to the different flow field structure.The disordered turbulent interface on the surface had The same fractal dimension reflects the self-similarity of turbulent flow.