3-DIMENSIONAL MEASUREMENTS OF OPEN-CHANNEL FLOWS BY USING TWO-SETS OF LASER DOPPLER ANEMOMETERS

摘要

The Reynolds stresses are constituted by six components, i.e., - uu , -vv, - ww, -uv, -uw and - vw. However, the Reynolds shear stress ( - vw ) in open-channel flows has not been measured with high accuracy as yet. This is because such measurements of this stress are quite difficult. In this study, three-dimensional measurements in open-channel flows were conducted by the simultaneous use of two sets of laser Doppler anemometers(LDA). One is able to measure the U-V components, and the other is able to measure the U-W components. The Reynolds stress (- vw) could be first measured with high accuracy. The streamwise velocities which were measured by U-V measurements and U-W measurements were in a good agreement with each other. The third-order moments of the velocity fluctuations coincided well with the results of DNS(Direct Numerical Simulation). A new empirical formula, involving the van Driest damping function, expresses the distribution of the spanwise turbulence intensity in the inner region.