Flow Enhancement and Cavitation Suppression in Nozzle Flow by Viscoelastic Additives

Numerical simulations of turbulent cavitating nozzle flow of Phan-Thien-Tanner and Newtonian fluids are compared to study the effect of viscoelastic additives on cavitation dynamics. The results show that viscoelasticity can stabilize the flow-field and reduce turbulence and vorticity inside the nozzle. Subsequently small scale vortices are suppressed and larger eddies become dominant in the flowfield. Vapor formation in the core of Kelvin-Helmholtz vortices in the shear layer is delayed and overall vapor volume fraction inside the nozzle is reduced by viscoelasticity. Therefore, the density of the two-phase flow passing through the nozzle is higher and the pressure drop across the nozzle is reduced. Hence flow resistance due to turbulence and cavitation inside the nozzle is reduced and the mass flow rate is enhanced.