Large-Eddy Simulation of Wake Vortex Evolution from Roll-Up to Vortex Decay

Large-eddy simulation (LES) of wake vortex evolution from vortex generation until decay is performed by combining Reynolds-averaged Navier-Stokes (RANS) simulation and LES. An aircraft model and a surrounding flow field obtained from high-fidelity RANS simulation are swept through a ground fixed computational domain to initialize the wake. After the initialization, time integration of the wake is performed until vortex decay (2-3 minutes). The present paper describes the approach and some results from the simulations where the aircraft is represented by the DLR-F6 wing-body model. The results show that moderate mesh resolution in the wake initialization phase results in lower vortex circulation of wake vortex after roll-up, although the overall distribution of vorticity is not sensitive to the mesh resolution. Boundary condition in the flight direction is one of the key points to continue the time integration of wake vortex after its initialization. Periodic boundary conditions used in this study induce disturbances propagating from boundaries into the computational domain, which leads to faster decay of wake vortex.