Turbulence Treatment in Steady and Unsteady Turbomachinery Flows

Abstract

The adequate representation of turbulence is crucial for the predictive accuracy of the computational method used in the turbomachinery design process. While unsteady simulations are of ever-increasing importance, steady Reynolds-Averaged Navier-Stokes computations will remain the workhorse of industrial CFD for some time. Turbulence treatments for both cases are presented. Since standard linear eddy-viscosity models exhibit some well-known deficiencies, a twofold strategy is pursued in the DLR-code TRACE: While the inclusion of turbomachineryspecific extensions to two-equation eddy-viscosity models forms the backbone of the turbulence modelling effort, Explicit Algebraic Reynolds Stress Models are currently validated for turbomachinery flows. With the continued increase in available computer power, unsteady computations are no longer beyond the realm of industrial CFD. In particular for flow features such as largescale separation and wakes, hybrid methods become increasingly popular. Here, Detached-Eddy Simulation is used, where a RANS treatment is retained for attached boundary layers while the separated areas of the flow are treated in an LES-type fashion. The results demonstrate the improved predictive accuracy as well as the feasibility of the presented approaches.