Experimental Investigation of Turbidity Flow in 90 Degree Bend with Mobile Bed

Abstract

Turbidity currents in the ocean and lakes are driven by suspended sediment. The vertical profiles of velocity and excess density are shaped by interaction between the current and bed as well as between the current and the ambient water. This paper presents 48 series of experiments in which saline gravity currents flow through a laboratory sinuous flume. flume contains three successive bends with three different relative curvature radiuses: R/B=2, 4 and 6, 8.5m length, 20cm width and 70cm height. Experiments performed by four discharges (0.7, 1, 1.5, 2 lit/s) and four concentrations (10, 15, 20, 25 gr/lit). ADV was used to record the local velocity. According to the results of experiments on the mobile bed, increasing the concentration of the incoming flow, the flow velocity of the fluid is also increased and, the maximum velocity occurs near the bed instead of the top of the current. The important point in the flow rate profiles is that the rate of increase in velocity depends on changes in the form of the bed due to the increase in concentration. By increasing concentrations of turbidity flow, the shear stress of the bed is also increased. Therefore, the rate of increase in velocity will occur by removing the bed forms and reducing the roughness and shear stress of the bed. Thus, increasing the concentration increases the power of the current, so at the beginning, the roughness and shear stress of the bed increased and then by removal of bed forms shear stress decreased.