Study on Oil-Film Interferometry Measurement Technique of Hypersonic Boundary Layer Transition

高超声速边界层转捩的油膜干涉测量技术研究

Received: 22 January 2018

Abstract

Prediction of boundary layer transition is important for the design of hypersonic aircrafts. The study of boundary layer transition of hypersonic flow around a flat plate using oil-film interferometry was investigated at Φ500mm traditional hypersonic wind tunnel. In order to measure the skin friction fast and precisely on the hypersonic wind tunnel, the traditional oil-film interferometry technique is improved. A high-speed camera is used to capture the images of fringes and the viscosity of the silicon oil is modified according to the wall temperature measured by thermocouples during the test. The skin frictions of smooth surface and the surface with single square roughness element were measured. For the smooth surface, the boundary layer is laminar. However, the boundary layer transition is promoted by wake vortices induced by the roughness element. Both the results of skin friction with and without the roughness element are in good agreement with the simulation results correspondingly, indicating high accuracy of the oil film interferometry technique.

摘要

高超声速边界层转捩预测对于飞行器的设计十分重要。在Φ500 mm常规高超声速风洞中开展了高超声速平板边界层转捩的油膜干涉测量技术研究。为了快速、准确地测量表面摩擦阻力因数，针对高超声速风洞的运行特点，对常规油膜干涉测量技术进行了改进，采用高速相机记录干涉条纹图像，并在实验中采用热电偶实时测量模型表面温度变化来修正硅油黏度因数。实验测量了光滑表面平板和布置单个方形粗糙元平板的表面摩擦阻力因数。光滑表面平板的边界层为层流流动状态；增加方形粗糙元后，粗糙元在其后方产生的尾涡促进了边界层流动转捩为湍流状态。并且实验测量的不同状态下的表面摩擦阻力因数与数值计算的结果相吻合，表明该实验方法具有较高的精度。