DNS and LES of Flow Over Smooth and Rough Wavy Walls*

Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of turbulent flows over smooth and rough wavy walls has been conducted. The Smooth Wavy Wall is described by a sinusoidal wave in the streamwise direction with amplitude to wavelength ratio of 0.05. Small-amplitude sinusoidal roughness elements are superimposed on to the Smooth Wavy Wall to obtain the Rough Wavy Wall. The smaller undulations on the Rough Wavy Wall represent undulations that LES resolutions do not resolve, and for cases where the roughness elements could still, have an influence on the resolved flow field. Our flow simulations are characterised by Reynolds number of 2390 based on bulk velocity and channel half-height. The budget terms of the Reynolds Stress Transport Equations reveal strong coupling between wall-topography and turbulence dynamics in the near wall region. Flow separation at the crest of the Smooth Wavy Wall and the formation of a persistent recirculation zone near the trough are observed along with a shear layer spanning multiple wavelengths.