عنوان مقاله [English]
One of the dangers that threatens spillways when excessive flooding pass is cavitation. Flow aeration using aeration systems has been used as one of the most effective methods to prevent the occurrence of this phenomenon. In this research, Flow-3D software was used to simulate flow through the spillway aerator of chute in CFD-method. To validate the results of a numerical model, Hager and Pfister (2010) laboratory data are used and the results indicate that they are in good agreement with the laboratory data. Then, the effect of geometric parameters such as height and angle of ramp, offset height and chute slope on the changes in air concentration, flow characteristics such as velocity and pressure to determine the cavitation index in order to determine distance between two aerators was explained. The average air concentration is as layer changes in the depth of flow and the reduction of air concentration is as exponential function. The value of the cavitation index is greater than the critical value during 11 meters after aerator in the chute spillway and there is no risk of cavitation occurrence. Considering the calculated concentrations, it can generally be concluded that by decreasing the air concentration in the chute bed to the values of 0.0001, 0.001, 0.01 and 0.1, chutes with slopes of 10, 12, 30 and 50 degrees do not require more aeration, respectively.