高超声速边界层转捩高速纹影显示

Hypersonic Boundary Layer Transition Visualized by High-Speed Schlieren Technique

为建立适用于激波风洞边界层转捩测量的高速纹影显示技术,在Ma10条件下,采用高速纹影显示技术,研究了半锥角7°钝锥边界层中第二模态不稳定波的演变特性。试验在中国空气动力研究与发展中心超高速空气动力研究所(HAI)的FD-14激波风洞上进行。试验来流单位雷诺数为4. 9×106m-1、1. 6×107m-1,模型攻角0°,头部钝度有0. 2 mm、0. 5 mm和2 mm三种。通过对纹影图像灰度进行功率谱密度(PSD)分析得到了第二模态不稳定波的波长,对不稳定波纹影图像进行互相关分析计算了不稳定波的传播速度。基于纹影显示结果计算的第二模态波主频与PCB压力传感器测量结果符合较好,证明了纹影测量的可靠性。

Aiming at establishing a high-speed schlieren technique suitable for the boundary layer transition measurement in a shock tunnel,the development of second-mode instability within the boundary layer on a blunt cone with7°half-angle is investigated by using the high-speed schlieren technique at Mach 10.The tests are conducted in the FD-14 shock tunnel at CARDC Hypervelocity Aerodynamics Institute(HAI).The unit Reynolds numbers are 4.9×106 m-1 and1.6×107 m-1.The angle of attack is zero.The bluntness of the nosetip is 0.2 mm,0.5 mm and 2 mm.The wavelength of the second-mode waves is calculated by using the power spectral density(PSD)analysis for the gray scale of the schlieren images,while the propagation speed is estimated by the cross correlation method.The most amplified frequencies of the second-mode waves derived from the results of the schlieren visualizations compare favorably with the measurements of the PCB pressure sensors,which proves the reliability of the schlieren measurement.