Experimental Study of Cavitating Hydrofoils in Cascade

Abstract

Liquid filled hydraulic systems often operate in such a way that cavitation may take place in one or more of the components of the system. Most often the cavitation will take place in a pump or a turbine as the liquid velocity there is usually greatest in these devices. However, cavitation can also occur in bends or elbows or constrictions in the system, such as a venturi tube. When cavitation does take place, the region occupied by the cavitation process displaces liquid that was formerly there, creating in a sense a "reservoir", the volume of which depends upon the extent of the cavitation. In every case the amount of cavitation in any type of hydraulic device will increase as the system pressure is lowered. The liquid that has been displaced causes changes in the motion of the fluid throughout the system causing or requiring time-varying pressure gradients to occur. In most practical hydraulic systems in which cavitation can occur, these transient pressure changes die away and the liquid flow system operates about some steady mean value. Indeed, for some applications cavitation is deliberately introduced into the system in such a way as to cause the flowing system to operate at a steady, stable condition.