Effect of Boundary-Layer Development on the Water-Surface Fluctuations of Supercritical Flow below a Sluice Gate

Hydraulic structures with a sluice gate are commonly used for control of the flow. In supercritical flow below a sluice gate, an accurate estimation of the water depth and boundary layer thickness is important for the hydraulic design of a horizontal apron. The relation between water-surface fluctuations and boundary-layer development has not been clarified. The aim of this paper is to experimentally demonstrate the effect of boundary-layer development on water-surface fluctuations of supercritical flow below a sluice gate. It is shown that water surface begins to fluctuate slightly upstream of the critical point. The water-surface fluctuations and turbulence intensities downstream of the critical point are also obtained, which demonstrates the length required for the water-surface fluctuations and turbulence intensity distributions to nearly equal uniform open-channel flow