Large-eddy simulation of three-dimensional flow around a hill-shaped obstruction with a zonal near-wall approximation

The focus of the paper is on the performance of an approximate ‘zonal’ near-wall treatment applied within a LES strategy to the simulation of flow separating from a three-dimensional hill at high Reynolds numbers. In the zonal scheme, the state of the near-wall layer of the flow is described by parabolized Navier–Stokes equations solved on a sub-grid embedded within a global LES mesh. The solution of the boundary-layer equations returns the wall shear stress to the LES domain as a wall boundary condition. Simulations are presented for grids containing between 1.5 and 9.6-million-nodes, the one on the finest grid being a pure LES. The comparisons included demonstrate that the zonal scheme provides a satisfactory representation of most flow properties, even on the coarsest grid, whereas the pure LES on the coarsest grid completely fails to capture the separation process.