Simultaneous Measurements of Flow and Temperature Fields by Laser Induced Fluorescence and Correlation Techniques

点击翻译按钮获取中文摘要

An image processing velocimeter and thermometer using the Digital Particle Image Velocimetry (DPIV) and the Laser Induced Fluorescence (LIF) technique has been applied to measurements of a thermally stratified pipe flow and an impinging jet. The velocity and temperature data measured by the system were transferred to an EWS and analyzed by a visualization software. The results reveal the mechansm of the turbulent mixing and the turbulent heat transfer.Two-dimensional time-dependent velocity and temperature fields of a stable thermally stratified pipe flow was measured by using a DPIV and LIF to capture the instantaneous structure of turbulent mixing accompanied by the heat and momentum transfer. One thousand instantaneous velocity and temperature distributions were obtained successively. The vorticity, Reynolds stress and heat flux vectors were estimated. The instantaneous distribution of the heat vectors and temporal variations of the Reynolds stress showed the strong exchange of heat and momentum occur through the coherent structure.Velocity and temperature in the stagnation region of a plane impinging jet were simultaneously measured by DPIV and LIF.Instantaneous thermal flow field and spatial correlation of the vorticity and turbulent heat flux showed that a streamwise vortex pair in the stagnation region swept cold fluid toward the wall and ejected high-temperature fluid toward the outer region. The weighted PDF of the turbulent heat flux indicated that the free-jet region and the vorticity was amplified by the mean strain in the vicinity the wall.