The Effect of Experimental Facility Dynamics on a Cavitation Instability

Abstract

This paper presents the results of an investigation assessing the role experimental facility dynamics might play in determining the nature of a recently observed instability on a cavitating propeller (Duttweiler and Brennen 1999). To address this question, a theoretical model of the facility dynamics is developed. Experiments were conducted to measure the response of the water tunnel facility to volumetric excitations of varying amplitude and frequency, and the measurements are compared with the response predicted by the model. The dynamics of the propeller cavitation are characterized by estimating two parameters (cavitation compliance and mass flow gain factor) previously employed in developing a system transfer function for cavitating pumps (Brennen 1994). Finally, the characteristics of a model for the complete system, incorporating both the cavitating propeller and the experimental facility dynamics, are discussed.