Detached-eddy simulation of the F-15E at high alpha

Detached-eddy simulation (DES) is used to predict the massively separated flow around an F-15E at 65-deg angle of attack. The calculations are performed at flight conditions corresponding to a chord-based Reynolds number of 13.6 x 10(6) and Mach number of 0.3. Flowfield solutions are obtained using unstructured grids with the commercial solver Cobalt: the average mesh spacing from solid surfaces to the first cell center from the wall under one viscous unit. The influence of the mesh size is assessed using a series of three grids ranging from 2.85 x 10(6) cells to 10 x 10(6) cells. In addition, the influence of the time step is investigated using three simulations with varied time steps. DES predictions are assessed via comparison to Boeing's stability and control database as well as to solutions of the Reynolds-averaged Navier-Stokes (RANS) equations. These are steady, with the Spalart-Allmaras model. Both RANS and DES predictions of integrated forces exhibit a relatively weak dependence on the grid density for the range examined. In the DES the wake region is characterized by complex and chaotic three-dimensional structures with direct resolution of a reasonable range of length and timescales. In general, both RANS and DES predictions of averaged quantities exhibit favorable agreement with the database. DES predictions of the lift, drag, and pitching moment, which were averaged over as many as 150 inertial timescales, agree with the data more favorably than the RANS results, but both methods are within 10% of the database. The cost of DES was approximately seven times higher than the steady RANS calculations on the same grid.