Kegerise Michael A, Rufer Shann J
Flow Physics and Control Branch, NASA Langley Research Center, Hampton, VA 23681, USA.
Aerothermodynamics Branch, NASA Langley Research Center, Hampton, VA 23681, USA.
Exp Fluids. 2016;57. doi: 10.1007/s00348-016-2214-9. Epub 2016 Jul 28.
In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.
在本文中，我们报告了原子层热电堆（ALTP）热流传感器在高超声速平板边界层层流到湍流转变测量中的应用。平板模型的中心线配备了沿流向排列的ALTP传感器，并且平板模型在一系列单位雷诺数下暴露于马赫数为6的自由流中。在此，我们观察到与平板表面形成的层流边界层中的第二模态不稳定波相关的不稳定频率带。这些不稳定波的测量频率、群速度、相速度和波长与文献中先前报道的数据一致。热流时间序列及其Morlet小波变换揭示了第二模态不稳定波的波包性质。此外，使用基于激光的辐射加热系统来测量风洞试验中使用的ALTP传感器的频率响应函数（FRF）。这些测量用于评估传感器FRF随时间的稳定性，并校正由有限传感器带宽引起的任何衰减的频谱估计。
