Experimental evaluation of resistance of eroded bed in sediment laden open channel flow: Combined load transport case

Czech Technical University in Prague, Faculty of Civil Engineering, 166 29 Prague 6, Czech Republic

^* Corresponding author: v.matousek@fsv.cvut.cz

Published online: 4 July 2024

Abstract

A relation between the discharge and the flow depth in an open channel is quite sensitive to resistance (expressed by the friction coefficient) of the channel bottom. This relation is straightforward if the bottom is a fixed boundary, and the discharge is a result of one-phase (water) flow. The relation is considerably more complex if the channel bottom is an eroded mobile bed and the flow is solid-liquid flow. Sediment-transport experiments with various model lightweight sediments in a tilting flume of the Water Engineering Laboratory at Czech Technical University in Prague produced information suitable for an evaluation of the eroded bed resistance at conditions of intense bed load and intense combined load in the upper plane bed regime. An evaluation of the bed load condition has been published recently. This paper discusses a description and quantification of the bed resistance in the case of transported combined load, i.e., at the condition where a certain portion of the sediment is transported as bed load and the rest is transported as suspended load. The results show that the presence of transported sediment tends to increase the bed resistance and hence increases a flow depth for a certain discharge of water in an open channel with an eroded bed.