Experimental Study the Performance of Bottom Cavitator in Water Conveyance Tunnel and its Effect on Separation Length

Cavitation is one of the most common and destructive causes of spillways and water conveyance tunnels. One of the most effective ways to prevent the cavitation is to aerate the current, provide the pressure and prevent excessive suction. The longer is the separation length downstream of the air entrance to flow, the more efficiency of cavitator. Conventional types of aerators (cavitators) in hydraulic structures including ramps, steps, grooves, and their combinations. In this research, the performance of 19 cavitators with different geometries in a pressurized flow inside a box tunnel, for 5 discharges with/without aeration were investigated. All experiments were performed for 3 times to validate the experimental results and reduce the experimental errors. Statistical analysis of the experimental results showed that the type of cavitator had considerable effects on the separation length. In spite of the positive effects of ramp height and discharge on separation length, the angle of ramp, step height, and groove depth had non-significant effects on separation length. Finally, two combined aerators were proposed, which in practice had better results in comparison with conventional aerators in hydraulic structures.