NUMERICAL PREDICTION OF TURBULENT MIXING IN A VARIABLE-DENSITY SWIRLING PIPE-FLOW

Numerical predictions are compared with experiments on turbulent mixing in variable density swirling flows, where He or CO2 is coaxially injected in turbulent swirling air flows in a pipe. The calculation employs two kinds of stress/flux equation model, i.e. the density-weighted Favre-averaged form and the density-unweighted conventional-averaged form. The calculation based on the former model can predict the phenomenon that the mixing of He is strongly retarded due to swirl than that of CO2, whereas the latter model fails to predict this. Comprehensible interpretations of the interrelation between turbulent mixing, density non-homogeneity and swirl-induced pressure gradient are presented.