The paper introduces hidden grid background oriented schlieren for quantitative study and visualization of natural convection heat transfer. In this technique, the refractive index variation, induced by the temperature gradient, is encoded in the recorded signal phase through the distortion of a background pattern. The background (undistorted) pattern is implicit (or hidden) in the light source. Quantitative estimation of the phase map is obtained by windowed Fourier transform. This method offers localized processing of the signal using joint space-frequency representation. The performance of hidden grid background oriented schlieren is practically demonstrated by investigating natural convective flow, a demanding task due to its comparatively small heat transfer.

中文翻译：

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面向隐藏网格背景的纹影的定量流动可视化

本文介绍了面向隐藏网格背景的纹影，用于自然对流换热的定量研究和可视化。在这种技术中，由温度梯度引起的折射率变化通过背景图案的失真被编码在记录的信号相位中。背景（未失真）图案在光源中是隐含的（或隐藏的）。相位图的定量估计是通过加窗傅里叶变换获得的。该方法使用联合空间频率表示提供信号的局部处理。通过研究自然对流实际上证明了面向隐藏网格背景的纹影的性能，由于其相对较小的热传递，这是一项艰巨的任务。