Numerical Prediction of the Formation of a Recirculation Zone and Turbulent Mixing in Swirling Flows

Abstract

Numerical investigations were made of the flow characteristics and mixing in turbulent swirling flows based on the k-ε two equation turbulence model. The predicted results were compared with the experiments. The following was conclued. (1) The formation of the recirculation zone at the nozzle exit was predicted by the computations. Modification of the turbulence model, considering the effects of the stream line curvature due to the swirl, is needed to predict the experiments. The retardation of the turbulent transport of momentum in the central part due to the swirl of solid body rotation enhances the formation of the recirculation zone. (2) The formation of the recirculation zone promotes the mixing of the fuel and air even if the turbulence effective diffusivity becomes small due to swirl effects. (3) The density-gradient effects incorporated with the swirling flow must be taken into consideration to predict the mixing of fuel and air.