Changes in Turbidity Current Flow Velocity Due to the Obstacle Height and an Abrupt Decrease in a Reservoir Bed Slope

Turbidity currents are the main process for the transport and deposit of sediments in reservoir, especially in the deepest part near the dam, where vital structures such as power intakes and bottom outlets are located. The existence of an obstacle in such current can cause a decrease in the velocity and thickness of the second turbidity current which, occurs after the obstacle. In this study that was carried out as a two-dimensional experimental study, the effect of a solid obstacle, its height on the vertical distribution profiles of the velocity, when there is an abrupt decreasing in the bottom slope, was investigated. Separate non-dimensional equations for the vertical distribution of velocity in different cases were developed. The coefficient of the non-dimensional equations were compared with each other. Results indicated that the existence of an obstacle can reduce the velocity of the turbidity current, which passes the obstacle, about 20%-50%, and also can reduce the discharge of the current by increasing the relative height of the obstacle from 0.0091 to 0.273 by about 20% -60%, respectively. This effect on turbidity current’s velocity and discharge would be increased by the increasing the height of the obstacle. The results also indicate that the highest change in the current discharge occurred in the jet region of the velocity profile.