Abstract
Turbulence measurements in open-channel flows with strong unsteadiness were conducted with a two component laser Doppler anemometer (LDA). The water-surface fluctuations at three points were measured by making use of 3 sets of ultrasonic wave gauges. It was found that the Karman constant κ can be dealt with as a universal constant (κ=0.41) in the case that the unsteadiness parameter α is smaller than 0.002. In contrast, the integration constant A of the log-law changes in a complicated manner. The time-dependent property of each term in the momentum equation (4) was examined on the basis of experimental data. The gravity term is smaller than the pressure and acceleration terms. The pressure term has an effect of increase upon the bed-shear stress τb in the rising stage, and vise versa in the falling stage. On the other hand, the unsteady term has the opposite effect to the pressure term.
