R. B. Wade

P RESENT day interest in the high-speed performance of hydrofoil boats, ship propellers, pumps, and turbines has resulted in an intensive study of cavitation in liquid flows. During this process the flow field changes significantly from that of a homogenous single-phase flow. Forces, pressure distributions, and other performance characteristics are then correspondingly altered and these changes must be reflected in the design parameters of machines in which cavitation is to take place. The effects of cavitation on the performance of pumps and turbines are found empirically by testing complete units to determine the change in the output quantities such as head and efficiency as the inlet pressure (or an appropriate cavitation index) is changed. Such tests, though useful and even essential for application, offer little physical insight into the cavitation process itself. Experimental studies have been carried out on isolated cavitating hydrofoils of a type useful for propellers and for hydrofoil boat applications. These studies reveal more of the mechanics of the cavitation process than do overall performance tests although they do not pertain directly to complete turbomachines. As is well known, a cascade or lattice of hydrofoils simulates one important aspect of the flow through axial turbomachines. The present highly developed state of the axial flow compressor owes much to the thorough experimental and theoretical studies of