Cavitation Onset in an Impulsively Accelerated Liquid Column

Abstract

This paper introduces a novel piston-driven apparatus to study the onset of cavitation in an impulsively accelerated liquid column as it compresses a closed gas volume. The experiment is monitored using high-speed videography and piezoelectric pressure transducers. Cavitation onset is observed in the liquid column as it undergoes an abrupt deceleration and is associated with a sudden drop in pressure in the liquid that leads to negative pressure (tension). A novel numerical modeling approach is introduced where the liquid column is treated as a spring-mass system. This approach can reproduce compressibility effects in the liquid column and is used to investigate the wave dynamics responsible for the onset of tension and cavitation in the liquid column. The model is formulated as a coupled set of non-linear differential equations that reproduce the dynamics of an experiment while capturing the pressure wave activity in the liquid column. A parametric study is conducted experimentally and numerically to investigate the behavior behind the onset of cavitation. The mechanism for the onset of cavitation is identified as a series of wave reflections at the boundaries of the liquid column, and this mechanism is found to be well reproduced by the model. While a traditional cavitation number criterion is shown to be unable to predict cavitation onset in our experiment, our numerical model is found to correctly predict the onset of cavitation for a wide range of experimental parameters.