Abstract
Wall pressure measurements were conducted for a 90 degree elbow of which the axis curvature coincided with its inner diameter (125 mm). Reynolds numbers examined were 3.2 X 105 and 5.0 X 105. Results showed that distributions of fluctuating normalized pressures obtained here and those made by Shiraishi et al. for the Reynolds number of 3.25 X 106 [1] coincided within 0.02 of the dynamic pressure. Power spectral density functions of fluctuating pressures mostly exhibited the slope of the minus seven-third law at large frequencies. The peak spectrum with the Strouhal number of 0.5 could be found in the curvature inside downstream of the elbow. They corresponded to the vortex shedding from the boundary layer developed in the inner and aft part of the elbow. The peak intensity having the Strouhal number of 0.5 quantitatively was in accordance with that of the data obtained in the experimental setup that Shiraishi et al. used [2], suggesting that the law of dynamical similarity could be applied with regard to this oscillation.
