Simultaneous Measurement of Flow and Thermal Fluctuations near Reattachment Point over a Backward Facing Step

Abstract

In this study, the mechanism of heat transfer enhancement near the reattachment point behind a backward facing step is experimentally investigated at Reynolds number of 5400. The unsteady fluctuations of the velocity and temperature are simultaneously measured by using 2 dimensions and 3 components (2D-3C) Particle Image Velocimetry (PIV) and the high-speed infrared (IR) thermography. In order to discuss the temporal-spatio characteristic of the velocity and the heat transfer fluctuations, 3 components of the velocity and the heat transfer coefficient are calculated. Also, these time history data are analyzed by using continuous wavelet transform and the fluidic and thermal structures are visualized. As a result, the characteristic frequency of the velocity and heat transfer coefficient appears at the non-dimensional frequency of 0.06 and 0.2. These frequencies have relationship to the fluctuations of the streamwise vortex and the reverse region.