BOUNDARY-LAYER-TRANSITION DETECTION WITH INFRARED IMAGING EMPHASIZING CRYOGENIC APPLICATIONS
BOUNDARY-LAYER-TRANSITION DETECTION WITH INFRARED IMAGING EMPHASIZING CRYOGENIC APPLICATIONS
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DOI：
10.2514/3.12186
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发表时间：
1994-09-01
期刊：
影响因子：
2.5
通讯作者：
WRIGHT, RE
中科院分区：
文献类型：
--
作者：
GARTENBURG, E;WRIGHT, RE
本文回顾了利用红外 (IR) 成像进行边界层转变检测的技术，重点介绍了低温风洞测试。 除了低温对红外辐射的影响外，讨论还与传统风洞和飞行测试相关。 在低温下，红外成像会遇到整个红外光谱中辐射能量的减少，同时大部分辐射会转向更长的波长。 由于其固定波段灵敏度，这种辐射行为会影响红外成像系统的最小可分辨温差 (MRTD)。 在缺乏商业长波长红外成像系统（工作波长超过 13 μm）的情况下，可以采取一些措施来缓解 MRTD 限制造成的问题。 可以通过允许风洞流的小幅且受控的温度升高来增强转变的热特征，从而引起向模型的瞬态热传递。 与层流状态相比，该行为通过其更高的加热速率暂时揭示了湍流状态下的模型区域。 暴露于两种状态的区域之间的对比度可以通过减去热分析图（瞬态热分析图的平衡热分析图）来增强。 通过阴影拉伸或二元着色可以进一步改善视觉效果。
This paper reviews the technique of boundary-layer transition detection using infrared (IR) imaging, emphasizing cryogenic wind-tunnel testing. With the exception of the low-temperature effects on the IR radiation, the discussion is relevant to conventional wind-tunnel and flight testing as well. At low temperatures, IR imaging encounters a reduction in the radiated energy throughout the IR spectrum, combined with a shift to longer wavelengths of the bulk of the radiation. This radiation behavior affects the minimum resolvable temperature difference (MRTD) of the IR imaging system because of its fixed wave band sensitivity. In the absence of commercial long wavelength IR imaging systems, operating at wavelengths longer than 13 mum, some measures can be taken to alleviate the problem caused by the MRTD limitation. The thermal signature of transition can be enhanced by allowing a small and controlled temperature increase of the wind-tunnel flow that induces a transient heat transfer to the model. This action temporarily reveals the model area under the turbulent regime through its higher heating rate compared with the laminar regime. The contrast between the areas exposed to the two regimes can be enhanced by subtraction of thermograms (the equilibrium thermogram from the transient thermogram). Further visual improvement can be obtained through shade stretching or binary shading.