Free-Surface Profiles, Velocity and Pressure Distributions on a Broad-Crested Weir: A Physical Study

Basic experiments were conducted on a large-size broad-crested weir with a rounded corner. Detailed free-surface, velocity, and pressure measurements were performed for a range of flow conditions. The results showed the rapid flow distribution at the upstream end of the weir and next to the weir brink at large flow rates. The flow properties above the crest were analyzed taking into account the nonuniform velocity and nonhydrostatic pressure distributions. Introducing some velocity and pressure correction coefficients, it is shown that critical flow conditions were achieved above the weir crest for 0.1 < x=Lcrest < 1. The velocity measurements highlighted a developing boundary layer. The data differed from the smooth turbulent boundary layer theory, although the present results were consistent with earlier studies. On average, the boundary stress was approximately τo=ðρ × g ×H1Þ 0.0015–0.0025. DOI: 10.1061/(ASCE)IR.1943-4774.0000515. © 2012 American Society of Civil Engineers. CE Database subject headings: Weirs; Velocity; Boundary layers; Pressure distribution; Irrigation.