AIR DEMAND DOWNSTREAM OF BOTTOM OUTLET LEAF GATES

Aeration downstream of outlet gates has been found as an effective way to eliminate cavitation risk. Although many works have been done and various relationships have been introduced to predict the quantity of entrained air, but still there are uncertainties in using these expressions for various conditions. Therefore, the designers of such structures are usually recommended to perform experimental investigations on scaled physical models to determine the quantity of air requirement downstream of outlet gates. This process is not only expensive, but also time consuming. In this paper, experimental information of air demand downstream of outlet gates is used to check the validity of different expressions which have been introduced to predict the quantity of air entrainment in such structures. Experiments were performed at Water Research Institute of Iran on several physical models of bottom outlets of new dams in Iran. The results showed considerable differences between the experimental results and those of expressions reported in previous studies.