Investigation of Reynolds Stress Model for Complex Flow Using CONVERGE

The Reynolds stress turbulence model (RSM) has been developed to go beyond the Boussinesq hypothesis and to improve turbulence modeling of flows with significant mean streamline curvature and secondary flow. In this paper the RSM in commercial CFD software CONVERGE is tested for its performance and robustness when applying to complex flows. Several validation cases including flow over flat plate, vortex combustor, diesel engine spray and combustion were selected to test the RSM. The swirling flow in vortex combustor, non-reacting but vaporizing ECN Spray A (free jet) and Sandia small bore diesel engine case are used to demonstrate the benefits of the RSM over the widely used RNG k-epsilon model without model tuning. The vortex combustor case shows the RSM can provide good prediction for strong swirling flow. ECN spray A case was used to demonstrate that the RSM can accurately predict the liquid and vapor penetration lengths of a free jet under diesel engine conditions. Accurate spray-wall interaction is quite important for modern diesel engine combustion where piston bowls facilitate and rely on spray-wall interactions for better combustion efficiency and emission reduction. It is found that the RSM can improve the prediction of cylinder pressure compared to the RNG k-epsilon model using the small-bore diesel engine case. All test results show that the RSM is robust and its computational overhead compared to the RNG k-epsilon model ranges from 17% to 78% for test cases.