Experimental Studies on Thickness and Vertical Velocity Distribution of Turbidity Current

Study of turbidity current hydrodynamics plays an important role in increasing the economical life of dams though reduction in sediment accumulation. In the present experimental study, the effect of entrance densimetric Froude number of turbidity current in sub and super critical conditions (Fr =0.6-3.5) have been tested through effect of channel slope and change related to opening height of entrance gate on vertical distribution of flow velocity and current's thickness under two dimensional flow conditions. The experiments were run in a 12 m-long by 0.2 m-wide by 0.5 m-high channel. Kaolin with the specific gravity of 2.65 and the mean particle diameter, D50, equal to 4.5 μm, was used as the cohesive suspended material. The results show that due to increasing in Froude number of entrance flow, the thickness of the turbidity current was increased while the layer-averaged velocity was decreased in the longitudinal direction. When the inlet densimetric Froude number reaches 0.7, the turbidity current tends to reach to a stable condition. Also the results show that the equivalent height of average velocity is about 0.8 times of the depth-averaged thickness of the current.