Influence of viscosity and device scale on pressure drop and cavitation inception: Vortex based cavitation devices
Abhijeet H. Thaker, Ketan Madane, Vivek V. Ranade
Abstract
Hydrodynamic cavitation (HC), and particularly vortex based cavitation devices are being increasingly used for processing high viscosity systems ranging from emulsions, slurries and sludges. It is therefore, essential to quantitatively understand the influence of viscosity and device scale on cavitation inception and pressure drop. No such information is currently available. In this work, for the first time, we present data and useful correlations covering a wide range of operating parameters and device scales to estimate pressure drop and cavitation inception. We have experimentally and computationally investigated key flow characteristics of vortex based cavitation devices. The cavitating flow in such devices was simulated over a wide range of viscosities and over a range of device scales. Experiments were carried out using aqueous solutions of glycerol up to a viscosity of 800 cP. Cavitation inception was identified using acoustic signals. The simulated values of pressure drop and cavitation inception were compared with the experimental data. New correlations for estimating pressure drop (Euler number) and cavitation inception were developed. The correlations were able to describe three distinct regimes observed in the experimental data of pressure drop. The pressure drop and throat velocity required for the inception of cavitation were found to increase with an increase in viscosity. The presented results and developed correlations will be very useful for designing vortex based cavitation devices for a variety of applications.