An iterative method for temperature gradient measurements in two-dimensional thermal boundary layer flows by speckle photography

摘要

An iterative method for measuring two-dimensional refractive index fields induced by convective heat transfer phenomena is presented. Starting from the so-called correction parabola, this reconstruction technique takes into account the local second derivative variation of the refractive index field. The efficiency of the method is analytically defined as a function of non-dimensional parameter and numerically investigated using a ray-tracing code for different classic index profiles and a thermal boundary layer case. Finally, as an implementation test, this algorithm is applied to an impinging jet heat transfer experiment using speckle photography measurement data set. The results show a relative dispersion of 20% compared to the parabola reconstruction when the refractive index gradient becomes more severe.