Abstract
Near-wall region which consists of viscous sublayer and buffer layer in unsteadyopen-channel flows was measured accurately by making use of a two-component threebeam LDA system; the effects of pressure gradient produced by the time-variation of water surface and discharge were revealed experimentally. Friction velocities evaluated from linear formula and log-law formula coincided well with each other. However, the van Driest damping factor B which indicates the thickness of sublayer varied in the decelerating flows, whereas it showed an opposite manner in the accelerating flows.The von Karman constant K is nearly universal one even in strong unsteady flows. The normalized turbulence intensity was affected by the pressure gradient. The Reynolds stress and other statistical quantities were also changed from their universal distribution of zero pressure-gradient flows.
