高超声速钝头体边界层转捩试验

为研究高超声钝头体边界层转捩以及头部钝度对转捩的影响，在FD-14和FD-14A两座激波风洞中开展了热流、压力扰动和高速纹影显示等综合测量。试验结果表明，转捩雷诺数关于钝度雷诺数的变化显示出转捩反转的趋势。压力扰动的功率谱密度（PSD）分析结果以流向离散分布云图形式显示，边界层高速纹影图像显示了第二模态波的发展、湍流的生成和熵层对边界层结构的显著影响。大头部钝度带来的强熵梯度熵层流动对边界层压力扰动频谱特性和流动结构影响显著，在转捩反转机理中起到重要作用。此外，马赫数对转捩的影响不容忽视。

Hypersonic boundary layer transition over blunt nosetipped bodies:Experiment

To investigate hypersonic boundary layer transition and the effect of nosetip bluntness on transition, this study carries out experiments in both FD-14 and FD-14A shock tunnels. Integrated measurements including heat flux measurement, pressure disturbances measurement, and high-speed schlieren visualization are conducted. Results show that the transition Reynolds number as a function of Reynolds number based on nosetip bluntness exhibits a trend of transition-reversal. Power Spectral Density (PSD) analysis of pressure disturbances in the boundary layer is shown in the form of discrete contour maps in a streamwise direction. Development of second-mode waves, generation of turbulence and effect of the entropy layer on the boundary layer structure are visualized in images of high-speed schlieren. The entropy layer with an intense entropy gradient derived from large nosetip bluntness shows significant influence on the frequency spectral of pressure disturbances and flow structures of the boundary layer, playing an important role in the mechanism of transition-reversal. In addition, the effect of the Mach number should not be ignored.