The potential for cavitation damage in a spillway can be given by the Cavitation Index. If the cavitation index is less than the critical value, then cavitation damage can occur. Since 1953 (Peterka, 1953) it has been understood that cavitation damage is suppressed with sufficient air concentration, even when the cavitation index is less than the critical value. Therefore, calculating air concentration in spillway flows is essential for predicting cavitation damage. On a spillway, the turbulent boundary layer thickness grows with downstream distance. When the turbulent boundary layer reaches the free surface, air entrainment begins. This paper presents contemporary methods for calculating boundary layer development and entrained air concentration and compares different methods with field measurements. The paper discusses the data that empirical methods are based on. Results of the work are presented in the context of new experimental results to determine the required air concentration to prevent cavitation damage (Gessler et.al, 2024).
