Higher Order Turbulence Modelling for Industrial Applications

Abstract

Today, industrial flow simulations are almost exclusively based on two-equation turbulence models, mostly the k-є model. This model has shown a good performance even in complex flows, considering the simplicity of the equations and the severe modeling assumptions involved. A potential remedy is the application of second moment closure (SMC) models. As these models solve a transport equation for each stress component, anisotropies can be handled in a more general way. The production terms in these equations can be treated exactly, a fact that introduces more physics into the simulation without modeling and is very important for simulating streamline curvature effects. Two-second moment closures are compared to the standard-k-є turbulence model and for that a curvature correction method is discussed. All calculations are performed with a new wall function method that enables consistent grid refinement. The calculation on multiple grid levels ensured grid independence. The investigated flows include effects like adverse pressure gradient, separation, and streamline curvature. The applied SMC models include a higher amount of physics that leads to superior results for simple flows like a rotating pipe test case. Some of these effects are also captured with a modified k-є model. For more complex flows that are influenced by a combination of various physical effects, the expected advantage of the SMC models is not always obvious and sometimes, the results even deteriorate compared to the k-є model.