NUMERICAL INVESTIGATION ON THE STRUCTURE OF HIGH-SPEED CAVITATING WATER JET ISSUING FROM AN ORIFICE NOZZLE

A practical mixture flow approach to the numerical simulation of turbulent cavitating flows is developed by coupling a simplified estimation of bubble cavitation to a compressible mixture flow computation. The mean flow of two-phase mixture is calculated by neglecting the slip between bubbles and surround liquid. Navier-Stokes equations for compressible fluids are used to describe the unsteady mean flow field and the RNG k-epsilon model is adopted for modeling of the flow turbulence. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase varying with the mean flow. The flow structure of submerged water jets issuing from an orifice nozzle is investigated numerically. Both non-cavitating and cavitating jets are calculated under different cavitation numbers in order to clarify the cavitation property of submerged water jet. The results demonstrate that the intensity of cavitation denoted by the maximum value of gas volume fraction and the area of strong cavitation indicted by high value of gas volume fraction increase with the decrease of cavitation number. Under the effect of cavitation bubbles the discharge coefficient of orifice nozzle decreases with the cavitation number.