COMPARISON OF 3 K-EPSILON TURBULENCE MODELS FOR PREDICTING VENTILATION AIR-JETS

Published data on unconfined plane-wall jets and plane-free jets were reviewed and used to assess the accuracy of numerical simulations. A p lane-free jet was numerically simulated using the standard k-epsilon m odel and four nonuniform grid patterns (70 x 32, 100 x 52, 120 x 60, a nd 120 x 74). The solution for a plane-free jet with adequate grid res olution was in good agreement with the published data. A plane-wall je t was numerically simulated using Jive different grids (70 x 32, 100 x 52, 120 x 60 120 x 74, and 120 x 92) and three k-epsilon turbulence m odels (the standard k-epsilon model, Lam and Bremhorst low Reynolds nu mber model, and Lam and Bremhorst low Reynolds number model with wall functions). The simulations predicted velocity decay and velocity prof ile well, but overpredicted the jet spread and entrainment ratio by 20 to 40%, indicating the need for a better turbulence model for wall je t predictions.