Experimental Analysis on the Water Entrainment of Turbidity Current over a Mobile Bed

Study of Turbidity Current, as one of the most important phenomena affecting the sedimentation in the reservoirs of dams, is essential. Since most of the research studies have been conducted under experimental conditions on rigid beds, the effect of erodible bed and the formation of the bed form on the turbidity current specifications is not yet clear. Therefore, in this Research, the study of the turbidity current in two conditions of rigid and mobile bed was conducted in order to determine water entrainment specification and the effective hydraulic parameters. The results showed that water entrainment changes depended on the variation of bed roughness and the type of bed form. Also, water entrainment of turbidity current was initially reduced by about 25% with the change in the bed shear stress, relative to the rigid bed, due to formation of small bed forms; then, it increased by about 30%, forming the larger bed forms; finally it decreased with increasing the flow strength and removing the bed forms. In addition, comparison of the results of the present study with previous research showed that the formation of bed forms increased water entrainment in a constant Richardson number up to 50%.