Large eddy simulation of turbulent separated flow over a three-dimensional hill

The turbulent flow separation from a three-dimensional curved body is a complex problem which plays an important role in practical applications. In recent laboratory studies Simpson and co-workers [1, 2, 3] investigated extensively the separated flow over and around a 3D hill at high Reynolds number using LDV measurement techniques, oil flow visualisation and hot-wire anemometry. The examinations reveal the complex flow physics associated with the geometry of the hill. Complex separation occurs on the leeside and the evolving vortical structures merge into two large counter-rotating streamwise vortices downstream. There is also some evidence of low frequency spanwise meandering of the vortices in the wake. The laboratory configuration mentioned above was simulated using LES. It consists of flow over and around an axisymmetric hill of height H = 78 mm and base-to-height ratio of 4; the approach-flow turbulent boundary-layer has a thickness of δ = 0.5H. The Reynolds number of the flow based on the free-stream velocity Uref = 27.5 m/s and the hill height H is Re = 1.3 · 10 .