Large Eddy Simulation of a Realistic Aircraft Configuration

We discuss the application of Large Eddy Simulation (LES) to complex aircraft geometries and the prediction of quantities of interest in these settings. The test case is that of the NASA High Lift Common Research Model. Calculations are carried out using the charLES finite volume flow solver. Lift and drag forces as well as pitching moment data are validated against experimental data collected at the QinetiQ test facilities, with sectional static pressure measurements used to corroborate the accuracy of the integrated quantities. Grid convergence studies across the lift curve reveal systematic improvement of the solution with increasing grid density. The lift coefficient at maximum lift and the stall angle of attack are predicted to near the accuracy tolerances required by industry for use in design and certification by analysis, while drag also shows very good agreement with the experimental measurements on the finest grid. The key missing feature in the free air simulations is a large wing root separation bubble at stall. We find that inboard separation appears when wind tunnel effects are included in the simulations. The LES calculations, using the charLES code, leverage key technologies such as low dissipation and entropy preserving numerical schemes, physics-based subgrid and wall models, and rapid high-quality unstructured Voronoi grid generation to enable tractable simulation turnaround times. Calculations on the GPU accelerated charLES flow solver achieve statistical convergence within 7 hours on a grid numbering more than half a billion cells at a flight condition in the post-stall regime.