Viscous Effects in Inception and Development of Cavitation on Axi-Symmetric Bodies Part I - Cavitation Inception Part II - A Semi-Empirical Method to Predict Cavitation Separation on Smooth Bodies

Abstract

The schlieren method was developed as a flow visualization technique for use in water tunnels. The process of cavitation development on two axi-symmetric bodies was studied using this approach and found to be greatly influenced by the presence of a previously unreported viscous laminar separation. On these bodies, cavitation inception was observed to take place within this separated region which occurs far downstream of the minimum pressure point. On one of these bodies, the incipient cavitation index was found to be closely correlated with the negative value of the pressure coefficient at the point of laminar separation. Approximate computations of the position of transition on a body without laminar separation indicate that the incipient cavitation index is closely correlated with the negative value of the pressure coefficient at the predicted point of transition. Cavitation separation under fully developed conditions is found to be preceded by a viscous laminar boundary layer separation on bodies which possess the latter separation under fully wetted conditions. An empirical method is proposed to compute the position of cavitation separation on such bodies and the method applied to a sphere and a cylinder showed good agreement with experiments.