A Two-Time-Scale Turbulence Model and Its Application in Free Shear Flows

A novel three-equation turbulence model has been proposed as a potential solution to overcome some of the issues related to the k-epsilon models of turbulence. A number of turbulence models found in the literature designed for compressed turbulence within internal combustion engine cylinders tend to exhibit limitations when applied to turbulent shear flows, such as those occurring through intake or exhaust valves of the engine. In the event that the flow is out of equilibrium where Pk deviates from epsilon, the turbulence models require a separate turbulence time-scale determiner along with the dissipation, epsilon. In the current research, this is accomplished by resolving an additional equation that accounts for turbulence time scale, tau. After presenting the rationale behind the model, its application to three types of free shear flows were given. It has been shown that the three-equation k-epsilon-tau model outperforms the standard k-epsilon model as well as a number of two-equation models in these flows. Initially, the k-epsilon-tau model handles the issue of the plane jet/round jet anomaly in an effective manner. Secondly, it outperforms the two-equation models in predicting the flow behavior in the case of plane wake, one that is distinguished by its weak shear form.