CFD assessment of RANS model for simulation of fast mixing nozzle and coaxial flow using OpenFOAM

The Reynolds Averaged Navier Stokes Equation (RANS) model was applied to describe the turbulent flow in a millimeter channels by cross-flow impingement and also coaxial flow in a jet mixer. The effects of turbulent models in the CFD turbulent flow is studied to help the engineers and researchers in deciding the selection of turbulent model need to be use in order to save the simulation time and also to reduce the errors produced in their simulations. Good agreement of the CFD prediction with the experimental data in certain locations was obtained with the factor of species transport and velocity profile, where dependence of turbulent models and grid sizes were discussed in details. The results show that, the need of grid study is crucial to obtain reliable results with optimum consumption of computer power. SST and Launder Gibson RSTM models give superior results compare to the other models which both have their own area of applicability. Launder Gibson RSTM model has the capability to predict the flow with the presence of recirculation and vortices, while SST model favors more for the flow with less recirculation and high velocity. RANS model is incapable to reproduce the vortices structure in the pipe and nozzle but it capable in predicting the area of mixing and the velocity profile correctly in certain locations.