ANALYSIS OF THE FLOW IN A SEDIMENT BYPASS TUNNEL WITH A LARGE FLUCTUATION IN SEDIMENT LOADING

Abstract

A numerical method has been constructed that computes the flow and the sediment transport in a sediment bypass tunnel that is being planned for installation at various dam sites. In these tunnels, sediment loads change abruptly due to the mechanism at the intake area. Existing methods of predicting sediments in rivers cannot be applied directly and unsteadiness and variation along the tunnel must be taken into account. The present method that considers these aspects can predict the flow and the sediment transport well compared with the model experiments. In the calculation, the transport is somewhat slower near the upstream end of the sediment deposition area. This, however, is due to the low friction on the smooth bottom wall of the model tunnel and will not be a problem in the application to the real sediment bypass tunnel, which will have a rough bed.