FREE-SURFACE PROFILES, VELOCITY AND PRESSURE DISTRIBUTIONS ON A BROAD-CRESTED WEIR

Abstract: 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, as well as next to the weir brink at large flow rates. The flow properties above the crest were analysed taking into account the non-uniform velocity and non-hydrostatic 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 about o/(×g×H1) ~ 0.0015 to 0.0025