Large-eddy Simulation of a Three-dimensional Diffuser

Sanjeeb Bose, Stanford University

Boundary layer separation in diffuser flows is a significant source of performance loss in many applications, including gas turbine engines and Formula One race cars. The present objective is to evaluate the predictive capability of large-eddy simulation (LES) for these separating flows at coarser resolutions. Explicitly filtered LES of an Re=50,000 three-dimensional, stalled diffuser are performed. The exact geometry of the experiment performed by Kolade and Eaton (2010) is replicated, and a separate LES of a turbulent duct flow is coupled to the diffuser LES to provide the time-dependent inflow conditions. Accuracy of the LES in predicting the mean velocity profiles and turbulent fluctuations, specifically with regard to the dynamics of the three-dimensional separation bubble, will be assessed by comparing it with the measurements of Kolade and Eaton. The influence of the subgrid scale model also will be analyzed in both regions where the boundary layer remains fully attached and in regions of temporally intermittent separation.

Abstract Author(s): S.T. Bose, P. Moin, and F. Ham