EFFECTS OF HYPER-CONCENTRATED SEDIMENT ON LARGE SCALE COHERENT VORTEX IN AN OPEN CHANNEL WITH SQUARE RIBS

Abstract

 The hyper-concentrated sediment laden flows have caused flood control, river environment and irrigation problems such as aggradation and clogging. Several researchers documented the effects of large concentrations of sediments on the fluid properties such as the viscosity, the density, and the reduction of fall velocity of bed sediment particles, the increase of sediment discharge. However, such a sediment flow feature has not been investigated in detail on the effects of suspended clay concentration on large scale vortex structure. In this paper, we experimentally investigated velocity fluctuations in hyper-concentrated sediment laden-flow in an open channel with two-dimensional square ribs by using Particle Image Velocimetry(PIV). The results showed that rheological properties significantly dissipated the large scale coherent vortex identified on the second invariant of the velocity gradient tensor over the bed with square ribs by comparison with the clear water flow.