DNS of Flow Over Smooth and Rough Wavy Walls at $\mathit{Re}_\lambda=4760$

Direct Numerical Simulations of turbulent flows over smooth and rough wavy walls has been conducted. The \textit{Smooth Wavy Wall} is described by a sinusoidal wave in the streamwise direction with amplitude to wavelength ratio $a/\lambda=0.05$. Small-amplitude sinusoidal roughness elements are superimposed on to the \textit{Smooth Wavy Wall} to obtain the \textit{Rough Wavy Wall}. The smaller undulations on the \textit{Rough Wavy Wall} represent undulations that a Large Eddy Simulation may not be able to resolve, but whose effects should be reflected on the resolved flow field. The flows 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 near the wall. Flow separation at the crest of the \textit{Smooth Wavy Wall} and the formation of a persistent recirculation zone near the trough are observed along with a shear layer spanning multiple wavelengths.