Experimental Study on Control of Sedimentary Density Current by Rough Bed and Obstacle

Density or gravity currents have been always one of the main causes for sedimentation along many of the dam reservoirs. So controlling this phenomenon is very important for increasing useful life of such reservoirs. In this research study the effect of a combination of rough bed and obstacle on the control of sedimentary density current has been investigated. Experiments were conducted in a tilting flume with 780 cm length, 35 cm width, and 70 cm depth in hydraulic laboratory of Ahwaz University, Iran. One obstacle with the height equal to depth of the body of density current flow was used. Small cubic pieces with the dimensions of 15×15 mm2 were used to produce the rough bed. Three heights of cubic pieces (0.5, 1.0 and 1.5 cm), three lengths of bed roughness (0.5, 1.0 and 1.5 m), and three roughness positions (downstream, upstream and both sides of obstacle) were considered as the main variables in this research study, in total 28 experiments were carried out. Discharge and concentration (density) of density current flow were kept constant and the bed slope was set to zero during all experiments. It was found that a combination of obstacle and roughness was able to block the density current up to 90%, whereas obstacle alone with the considered height could only decrease the transport of density current about 50%. Rough bed at upstream of the obstacle was found to be more effective than downstream of it.