Evaluation of Turbulence Models Performance in Predicting Incipient Cavitation in an Enlarged Step-Nozzle

H Naseri,M Gavaises,P Koukouvinis

doi:10.1088/1742-6596/656/1/012095

Abstract

Predictive capability of RANS and LES models to calculate incipient cavitation of water in a step nozzle is assessed. The RANS models namely, Realizable k-ε, SST k-ω and Reynolds Stress Model did not predict any cavitation, due to the limitation of RANS models to predict the low pressure vortex cores. LES WALE model was able to predict the cavitation by capturing the shear layer instability and vortex shedding. The performance of a barotropic cavitation model and Rayleigh-Plesset-based cavitation models was compared using WALE model. Although the phase change formulation is different in these models, the predicted cavitation and flow field were not significantly different.

Highlights

Formation of vapour due to cavitation affects the fluid flow and a two-way interaction exists between the bubbles and the turbulent oscillations
Mean streamwise velocities calculated by Realizable k-ɛ, Stress Transport (SST) k-ω and Reynolds Stress Model (RSM) model and the Large Eddy Simulation (LES) Wall Adaptive Local Eddy Viscosity (WALE) model at z = 1.5 mm are presented in figure 2
The RSM results overpredicts the velocity at the recirculation region and on average RSM results have ~20% more discrepancy with experiment velocities compared to two-equation models

Summary

Introduction

Formation of vapour due to cavitation affects the fluid flow and a two-way interaction exists between the bubbles and the turbulent oscillations. After the grid independency test, performance of three RANS models, namely the Realizable k-ɛ, SST k-ω and Reynolds Stress Model (RSM) is assessed and compared to Wall Adaptive Local Eddy Viscosity (WALE) LES simulation for incipient cavitation. Mean streamwise velocities calculated by Realizable k-ɛ, SST k-ω and RSM model and the LES WALE model at z = 1.5 mm are presented in figure 2. The most significant disparity between this two models is at the region between the recirculating flow and the bulk flow moving above it, where the SST k-ω over-predicts the velocity by ~24% and Realizable k-ɛ by ~20%.

Results

Conclusion