Impact force on downstream bed of weir by free overfall flow

Abstract

According to previous experimental studies on free overfall, the main influencing factors of the local scour downstream of a drop structure were found to be the impact position of the nappe flow and the force striking on the channel bed. In this study, the pressure transducers and strain amplifiers, which did not disturb the flow field, were set up to measure the pressure distributions along the streamwise direction downstream of the weir. The data were recorded through an A‐D converter and compared with the data collected by Moore (1943) and Rand (1955). Expressions for the impact position and impact force of the flow nappe derived from the experimental results and the theoretical analysis. The relationship among weir height h, impact position of free overfall Lp , and drop number D were put into the following equation: Lp/h = 1.82D 0.17.