Numerical Simulation of Cavitating Water Jet by a Compressible Mixture Flow Method

Abstract

Concerned on the numerical simulation of high-speed water jet accompanied with intensive cavitation, a practical compressible mixture flow method is developed by coupling a simplified estimation of bubble cavitation and a flexible compressible flow computation procedure. Two-phase fluid media of cavitating flow are treated as a mixture of liquid and bubbles, and the mean flow of the mixture is computed by applying Reynolds Averaged Navier-Stokes equations for compressible fluids considering the effect of bubble expansion a/o contraction. The intensity of cavitation is evaluated by gas volume fraction which is governed by the compressibility of bubble-liquid mixture at the current status of mean flow field. High-speed submerged water jets issuing from a convergent-divergent nozzle are treated under different cavitation conditions. The results demonstrate that pressure decreases in the convergent section and cavitation occurs initially in the low-pressure region behind the throat near the wall. The gas volume fraction of cavitation bubbles reaches to 0.5 locally when the cavitation number is decreased to 0.1, and cavitation bubbles generated in the shear layer near the throat flow downstream along the jet periphery. Under the effect of cavitation bubbles the mass discharge coefficient of water jet decreases obviously compared to the case of no-cavitating one although the maximum velocity at the throat increases.

Keywords

• submerged water jet
• cavitation
• turbulent flow
• two-phase flow
• computational fluid dynamics