Application of k-ε turbulence models with density corrections to variable density jets under subcritical/supercritical conditions

A density correction method is presented for improving the performance of k-ε turbulence models for variable-density jets under subcritical and supercritical conditions. The functional relationship between density and turbulence variables was obtained by considering the logarithmic layer and local equilibrium conditions and the basic form of the relationship was discussed with the large-eddy simulation results. The modified eddy viscosity and a source term of the ε-equation were introduced in four k-ε models, and the modified models were tested for helium, air, and carbon dioxide jets in the presence of co-flowing air. The velocity and density fields of the density-corrected models were in good agreement with the experiment. Cryogenic nitrogen jets under near-critical and supercritical pressures were selected for examining the applicability of the models to the variable density flow with heat transfer. The high velocity decay rates of the original models were found to be considerably reduced in the modified models. The effect of density correction was consistent among the four k-ε models with wall function and near-wall treatment.