Experimental study of water entrainment of density currents in converging sections

The most important factor in shortening the useful life of dams is settling of fine sediment. A lot of dam’s reservoirs were filled by sediment due to this process and became useless. One of the most important phenomena that affect on sedimentation process is density current, so recognize the effective process in this phenomenon is very important for researchers and their management in dam’s reservoirs. Changing in successive cross sections inclusive convergences and expansions are the effective parameters on hydraulic of density current. The role of these factors in the density current phenomenon should be specified and the effective works done for management of reservoir sedimentation. So, in this research, we tried to investigate water entrainment of density currents in converging sections. The Experiments were carried out in a flume with changeable bed slope with three convergence angles (8, 16 and 25 degree), three discharges (0.58, 0.98 and 1.28 lit/s), three concentrations (10, 16 and 25 gr/lit) and three bed slopes (0.009, 0.0125 and 0.016). The Results showed that increasing of converging angle will increase water entrainment. Finally an equation is presented for water entrainment in convergent angles.