Parametric Study on Ridges Inducing Secondary Motions in Turbulent Channel Flow

A DNS parametric study of streamwise‐aligned rectangular ridges is carried out in a fully developed turbulent channel flow with constant flow rate at $Reb=18000$. The simulations were carried out systematically varying the ridge height h, width w and structural wavelength $S$. The ridges generate a strong large‐scale secondary motion, which is measured in terms of the integral swirl strength. Of the presented cases, the configuration with the ridge height$h=0.1\delta$, $S/w=4$, $S=1\delta$ produces the strongest secondary flow of $4.5\mathrm{\%}$ $U_b$. The varying flow topology is discussed as a result of the varying ridge dimensions.