Effect of sediment supply on the flow characteristics in a meandering channel

Abstract

Meandering channels are common in natural rivers, especially in lowland alluvial plains. In this research, a meandering channel was designed in order to explore the effect of sediment supply on the flow characteristics. The water level, three-dimensional (3D) instantaneous velocity and riverbed elevation were measured using a digital wave altimeter, a 3D acoustic Doppler velocimeter and a 3D laser scanner, respectively, and the flow characteristics with and without sediment supply were compared. Under the same discharge, the transverse slope of the water surface in the case with sediment was larger than that without sediment and the change was steep; the change in the longitudinal slope of the water surface was small in the upper half bend and large in the lower half bend. By increasing the water discharge, the number of secondary flow vortices at the apex of the meandering channel increased. The trends of the mainstream lines with and without sediment supply were roughly opposite and the difference between them decreased with increasing discharge. The lateral and vertical turbulence intensities of the flow near the outer bank were larger in both cases (with and without sediment). In the case with sediment, the turbulent kinetic energy of the cross-section was larger near the bed and the water surface.