Author(s): Kejun Yang; Shuyou Cao; Xingnian Liu
Keywords: Compound channels; Momentum transfer; Transverse kinetic energy correction coefficient; Kinetic energy loss rate; Shapes of cross section; Relative depth
Abstract: In a compound channel, the intense momentum transfer on the vertical interface between main channel and flood plain, makes its conveyance capacity decrease. For steady, uniform and turbulent flows, two new concepts, transverse kinetic energy correction coefficient (TKECC) and kinetic energy loss rate (KELR), are put forward in the paper. By theoretical analysis, a conclusion is drawn that TKECC is larger than 1 and KELR is larger than 0 in compound channels. By analyzing a large number of experimental data from Science and Engineering Research Council Flood Channel Facility (SERC-FCF), it is found that TKECC and KELR are both related to shapes of cross section and relative depth (Dr). For a given relative depth, kinetic energy loss becomes weaker with main channel side slope factor increasing and becomes stronger with the width ratio of main channel and flood plain increasing; kinetic energy loss in a symmetric compound channel is stronger than in an asymmetric one. For all shapes of the cross section, kinetic energy loss increases with the relative depth increasing; after it reaches the largest value, it decreases with Dr increasing, and the compound channel ultimately shows a characteristic of a single channel. But the relative depths in compound channels with different shapes of cross section are different, when kinetic energy loss in them reaches maximum value.