Experimental study and numerical sizing model for cavitation zone characterisation in cavitating venturis

Abstract

Cavitating venturi is popular as an elegant passive flow control device used in varied engineering applications. Cavitating venturi can be sized appropriately for operating with an anchored flow rate for various industrial applications. In the current work, we present the experimental results of the cavitation zone lengths in five planar venturis with different throat widths and divergent angles obtained for a pressure ratio range of 0.4 to 0.95 and an inlet Reynolds number range of 8.0 × 10 4 to 2.25 × 10 5 . The cavitation zone lengths are obtained for quasi-steady conditions through high-speed imaging. The extracted lengths for the venturis indicate a transition in the cavitation zone behaviour and have a dependence on the divergence angle and cavitation intensity. The extracted data forms the primary dataset for validating the numerical model which we present in the subsequent part of the work. The model is a one-dimensional homogeneous two-phase model with a two-step Euler integration of the Rayleigh-Plesset equation as closure to handle the bubble dynamics. The model shows a prediction of the experimentally obtained cavitation lengths within ±10 % (for small divergent angles) and ±25 % (for large divergent angles) specifically at high cavitation intensities when the cavitation zone fills the divergent portion. Finally, we demonstrate the applicability of the model as a typical engineering sizing tool to predict the operating pressure ratios. The model could predict the experimentally obtained critical pressure ratios and the minimum pressure ratios within ±12 % and ±20.7 % respectively for the planar venturis. Specifically, if the interest is in containing the cavitation zone within the divergent portion, this model could definitely be an aid in sizing a cavitating venturi for varied engineering applications. © 2023, Indian Academy of Sciences.