基于流动显示的压缩拐角流动结构定量研究

Quantitative analysis of flow structures in compression ramp based on flow visualization

在Ma=3.0的超声速风洞中,采用NPLS技术对上游边界层为层流的25?压缩拐角进行了流动显示实验,获得了压缩拐角的精细流动结构,边界层、剪切层和激波等结构清晰可见.基于流动显示数据,采用间歇性、空间相关性和分形分析对流动结构进行了定量研究,计算了边界层和分离区的间歇因子分布,获取了边界层中拟序结构和结构角的大小,给出了边界层分形维数的分布,并与Ringuette和Bookey等的实验结果进行比较,阐述了压缩拐角流动结构的定量特征.

Flow visualization studies on the laminar boundary layer flows over a 25~ compression ramp are carried out via NPLS technique in a Mach 3.0 wind tunnel; fine flow structures such as boundary layer, shear layer, and shock waves may be visualized clearly. Based on the visualized data, quantitative analysis is conducted using intermittency, spatial correlations, and fractal theory. The intermittency function γ of the boundary layer and the interaction region is calculated, and the size of coherent structures and the structure angle θ for the boundary layer are obtained, so that the fractal dimension of the boundary layer in streamwise can be provided. Experimental data in the present paper have been compared with the results of Ringuette and Bookey, and the quantitative characteristics of flow structures are discussed in detail.