Experimental Study on Cavitation-Induced Air Release in Orifice Flows

Cavitation leads to rapid degassing of fluids. Up to date, there is a lack of model approaches of cavitation-induced degassing. The aim of the present study is to gain a more thorough knowledge of the process. Therefore, the relation between cavitation intensity and air release is investigated experimentally for an orifice flow as function of cavitation number. For this, shadowgraphy imaging is used to visualize regions of steam and air volume downstream of the orifice. Analysis of the images shows a strongly nonlinear scaling behavior for both cavitation intensity and air release as a function of cavitation number. Three distinct regimes could be identified for cavitation-induced gas release. While an exponential scaling was found at high cavitation intensities, degassing rates appear to be nearly constant in the intermediate cavitation number range. Empirical scaling laws are given here that may serve as first model approach for the prediction of cavitation induced air release behind flow constrictions.