Shear thickening fluid in vortex based cavitation device – will it cavitate?

Abstract

Most hydrodynamic cavitation studies have focused on Newtonian or shear-thinning fluids, whose viscosity decreases with increasing shear rate. In contrast, shear-thickening fluids (STFs) exhibit the opposite rheological behaviour: the high shear rates generated in cavitating regions increase the local viscosity, damping velocity gradients, weakening pressure reduction, and potentially delaying or suppressing cavitation. This short communication numerically investigates the cavitation behaviour of STFs in a vortex-based hydrodynamic cavitation device. A transient CFD model employing the URANS SST k–ω turbulence model, the Singhal cavitation model, a homogeneous mixture multiphase formulation, and a power-law shear-thickening rheological model was used. Simulations were performed for different viscosity-growth exponents and throat velocities. The results show that the vortex device can still establish a distinct low-pressure vortex core, localized viscosity redistribution, enhanced turbulent kinetic energy, and vapour generation under suitable operating conditions. At a throat velocity of 3 m/s, increasing the viscosity-growth exponent weakens the swirl-induced pressure depression, suppresses cavitation, and reduces the pressure drop from approximately 302 kPa to 59 kPa. Increasing the throat velocity to 6 m/s restores the pressure depression and significantly expands the cavitation region. The spatial overlap of vapour volume fraction, vorticity, and turbulent kinetic energy indicates the potential for cavitation-assisted micro-mixing without moving impeller blades. Within the assumptions of the present model, these findings indicate that vapour formation is predicted in shear-thickening fluids over an identifiable operating window, rather than establishing feasibility for dense suspensions generally. They provide a foundation for further experimental validation and for improved understanding of the hydrodynamic cavitation in shear-thickening fluids.