Unsteady Simulations of a Fan/Outlet-Guide-Vane System: Aerodynamics and Turbulence

The Paper presents the aerodynamic and turbulent aspects of a project devoted to creating and validating a high-fidelity computational-fluid-dynamics-based system for the prediction of the performance and noise associated with the fan/outlet-guide-vane configuration typical of modern turbofan aeroengines. Such a tool will be of significant value for evaluating low-cost analytical methods needed for tradeoff studies and fine tuning of low-order computational models for engine performance and noise prediction. For turbulence representation, the system offers two approaches: the unsteady Reynolds-averaged Navier–Stokes equations, and a zonal approach that treats the part of the flowfield upstream of the fan by unsteady Reynolds-averaged Navier–Stokes and the remaining part (the interstage, outlet guide vane, and exhaust regions) by improved delayed detached-eddy simulation combined with a volume synthetic turbulence generator for triggering the scale-resolving capability of the improved delayed detached-eddy simulation. Details of the proposed methodology are outlined, including problem statements for simplified (“duct-only”) and full (including the entire nacelle and external flow) configurations. The results are presented, demonstrating the capabilities of the methodology and its validation by means of comparison of the mean and unsteady flow characteristics with experimental data for the NASA source diagnostic test. The numerical database will be used for the investigation of noise-generation/propagation phenomena.