Direct Numerical Simulation of Separated Turbulent Flow over a Wavy Boundary

The impact of a wavy surface on turbulent flow is investigated by direct numerical simulation. By means of finite differences in terrain following coordinates, the method treats the flow in a plane channel with wavy lower and flat top surfaces. Both surfaces are smooth. The lower surface wave amplitude is 0.05 and the wavelength is 1 in units of the mean channel height. The Reynolds number in terms of mean velocity and mean channel height is 6760. Parameter studies are performed with different resolution, Reynolds number and geometrical shape of the surface wave. If the vertical resolution is fine enough to resolve the viscous surface layer, a recirculation zone develops as expected for this surface geometry and Reynolds number. The comparison with existing experimental data shows good agreement when the precise details of the surface wave geometry, which deviates slightly from a sinusoidal profile, is taken into account.