A Modified k-ε Closure for Turbulent Self-preserving Jets

Abstract

This paper presents a modified k-e model for turbulent self-preserving jets. It is well known that the standard k-ε model yields reasonable solutions for both the plane and round jets, however, with different sets of coefficients. It is believed that such behavior might be due to the inadequacy of the modeling of the production/distruction terms in the ε-equation,where cε1 and cε2 are assumed to be constants. Based on the analysis of the k- and ε-equations at the state of equilibrium near the outer edge of the turbulent jet, a set of model constants and a variable form for the production coefficient in the dissapation equation, cε1, h ve b en logically derived. This modification significantly improved the agreement of the calculations with experimet for both the plane and the round jets equally well with no need to tune any of the model coefficients. The calculated mean and turbulent profiles, the jet spreading rate and the mean centerline velocity decay rate are compared with the most recent experimental data. The numerical solutions show that the modified turbulence model employed in the present study predicts both plane and round jets with the same set of constants and parameters equally well.