Experimental Study on the Effect of Quadrate Hydraulic Jet Distance relative to Sediment Surface on the Efficiency of Hydrosuction Systems

The entry of sediments in to the lake of dams over many years and the sedimentation within the reservoirs is on inevitable phenomenon and it is expected that with the reduction of reservoir volume of dams, planning for exploitation of dam and water allocation for various issues such as agriculture, industry and drinking became difficult (Ashrafi vaghefi et al., 2008). Reducing the volume of the reservoir will shorten the useful life of the dams and any neglect of this issue, especially in arid and semi-arid countries of the world, can be a serious threat (Emamgholi Zadeh 2008). One of the effective methods for sediments removal from reservoirs of dams is the hydro suction method, in this method, the difference between water level in reservoir and downstream is used as suction force for sediment transfer. In this method, using the minimum volume of water, the maximum amount of sediment are discharged and saved costs (Chin et al., 2010). Also, other advantages of this method can be environmental compatibility due to controllable amount of outlet sediments, low muddy and ability to concentrate dredging to one area and also the ability to transfer siphon dredging, the low cost of constructing and installing, ability to perform even in low water seasons, waste of less water and non-interrupted operation. It seems that combining hydrosuction and water jet methods in addition to having the mentioned advantages, increases the sediment removal efficiency, which is received less attention of researchers. Therefore, in this research, the effect of jet arrangement and hydraulic jet distance relative to sediment surface on improving sediment removal in jet- hydrosuction method has been studied.