Calculation of the air-capturing ability of a flow behind an aerator ledge

Abstract

Aerators are used for saturating the bottom layers of a flow with air, which is an effective measure for controlling cavitation erosion, and they also provide intense oxygen enrichment of the water. An aerator usually consists of a device providing separation of the flow from solid boundaries (ledge, ski-jump bucket, or their combination along with a groove) and a system ventilating the separation zone. The air can enter under the nappe through flow separation regions near the side walls and behind piers or through special air ducts, as for example, on the San Roque chute spillway. The main difficulty when calculating aerators is a determination of the air-capturing ability of the flow. It is necessary to know the discharge of the air entrained by the flow as a function of the vacuum in the space under the nappe, since these parameters are the initial ones for calculating the air ducts. The authors present here the calculation of the air-capturing ability of a flow behind an aerator ledge.