Air-Entrainment in High Head Gated Conduits

For the successful operation of high head gated conduits, adequate supply of air is of paramount importance. However, no dependable solution is yet available to determine the required quantity of air for different flow types. Based on systematic experiments backed by theoretical considerations, suitable relationships and diagrams have been developed that predict results compatible with prototype measurements. Conduit roughness has no significant effect on air-entrainment. No linear relationship has been found to exist between the head and the maximum air-entraining capacity of the flow. Measurements of air velocity by means of high speed cinematography indicate that the velocity at the interface is much higher than the mean velocity of water flow and that the air velocity distribution is far removed from being logarithmic.