Author(s): Yaan Hu; Shiping Ruan; Xiujun Yan
Linked Author(s): Yaan Hu
Keywords: High velocity flow; Cavitation erosion; Chute aerator; Air concentration distribution; Vacuum tank
Abstract: With the developments of the dam construction technologies and the builds of the dams higher than 300 meters, the problems of cavitation and its damage with high water head, large discharge and narrow gorge have become much more serious. As far as air entrainment for cavitation control was concerned, thus, more attentions have been paid on the research of aerated flows through chute aerators. Lateral and bottom aerators are often used for the purpose of air entrainment to alleviate cavitation on sidewall and chute bottom. Because of the complexity of high velocity and two-phase flow, physical model test in vacuum tank is generally acknowledged to be more reliable than numerical simulation, i. e. the model is designed based on the gravity similarity, and the test is carried out at reduced pressure to meet the requirement that the cavitation number of model and prototype remain constant. As is well known, it is a good way for evaluating the cavitation of prototype without aerators generally, but it turns out that there are some difference in those projects have an aerator because little air remains in water and vacuum tank, so the model air concentration of wall layers downstream from an aerator is far less than prototype, this would lead to incorrect prediction (such as there is cavitation in model but no cavitation in prototype). This paper studies the similarity of air concentration of wall layers downstream from an aerator in different vacuum，discusses the critical vacuum degree while the air concentration in a model equal to the prototype, and develops a test method to maintain it similar in vacuum tank when theoretical vacuum is greater than critical value.
Year: 2013