Negative surge in open channel: physical, numerical and analytical modelling

Negative surges are caused by a sudden change in flow resulting from a decrease in water depth. New experiments were conducted in a horizontal channel (L = 12 m, W = 0.5 m) to record the unsteady water depth and turbulence in negative surges. The data were collected using video imagery, acoustic displacement meters and acoustic Doppler velocimetry (ADV). The experimental setup was designed to record data at two different locations within the channel under controlled flow conditions. The detailed results are compared with an analytical solution and a numerical solution of the Saint-Venant equation. The results derived from the analytical solution of the Saint-Venant equations compare well to the surface elevation data recorded from the physical experiments. The numerical solution of the Saint-Venant equations accounting for some friction compared not as well as the analytical solution implying that the effects of bed friction were small.