A vorticity confinement model applied to URANS and LES simulations of a wing-tip vortex in the near-field

In this study, the near-field (up to three chord lengths) development of a wing-tip vortex is numerically investigated at two angles of attack (five and ten degrees). The application of a vorticity confinement model to an Unsteady Reynolds averaged Navier-Stokes (URANS) model and Large Eddy Simulation (LES) is examined with the focus of preventing the rapid dissipation of vorticity in a wing-tip vortex. Vortex core size and trajectory were predicted well by the LES model, whereas the URANS model predicted a large vortex core, which remained constant with downstream distance. The LES model correctly predicted the jet-like axial velocity for an angle of attack of ten degrees and the LES and experimental axial velocity excess had the same value of 111% of free-stream velocity at two chord lengths downstream. The LES model predicted the turbulence in the vortex reasonably well as the maximum turbulent root mean square (rms) velocities were within 15% and 35% of experimental values at two and three chord lengths downstream for angles of attack of ten and five degrees respectively. The URANS model predicted the mean flow for an angle of attack of five degrees reasonably well but greatly under-predicted the mean flow for an angle of attack of ten degrees and the turbulence levels at all downstream locations.