Large-eddy simulation of wing tip vortex in the near field

Large-eddy simulation with filtered-structure-function subgrid model and implicit large-eddy simulation (ILES without explicit subgrid model) using high-order accuracy and high resolution compact scheme have been performed on the tip vortex shedding from a rectangular half-wing with a NACA 0012 airfoil section and a rounded wing tip. The formation of the tip vortex and its initial development in the boundary layer and the near field wake are investigated and analysed in detail. The physics, why the tip vortex, which is originally turbulent in the boundary layer, is re-laminarised and becomes stable and laminar rapidly after shedding in the near field, is revealed by this simulation. The computation also shows the widely used second-order subgrid model is not consistent to six-order compact scheme and would degenerate the six-order LES results to second-order. Therefore, high-order schemes, grid refinement and six-order subgrid models are critical to LES approaches.