Oscillations of Ventilated Cavities Expermental Aspects

Abstract : By injecting air in the low pressure regions of water flows, it is possible to obtain cavities similar to the attached cavities due to "true" cavitation. That ventilation is a current practice in the field of spillways for large concrete dams, especially in tropical zones. It is aimed to diminish the risks of erosion, as the speeds of the water flows ordinarily are very large: the stresses between concrete and water are diminished by the injected air, due to its compressibility which increases the characteristic time of contact and diminishes the forces for the same total impulse. Then the main problem is to calculate the ideal dimensions of the ducts by which atmospheric air is sucked up under the water flow (Chanson, 1999). Here our main concern is rather on the side of ventilated hydrofoils or, possibly, torpedoes.