Direct Numerical Simulations of turbulent channel flow roughened with 2D triangular bars: On the Effective Distribution parametrization

Turbulent flows over rough surfaces are a common phenomenon in engineering applications, yet predicting how the roughness affects the turbulent flow remains a challenge. In the present paper, we expand the results of Bruno et al. (2024) on the new geometrical parameter, the Effective Distribution (ED). Specifically, the effect of roughness on turbulent intensities has been investigated. The ED demonstrates improved correlations with both drag and roughness function across a wide range of surface configurations, including irregular rough surfaces generated by random sinusoidal functions. A detailed analysis of the ED equation reveals that the contributions of higher pinnacles and the spacing between roughness elements, play a dominant role in capturing the impact of roughness on drag and turbulent intensities. To investigate this issue, a detailed analysis of turbulent intensities modification induced by the roughness is performed, thus showing the highest pinnacle’s role. These results emphasize the importance of considering these terms in the parametrization of rough surfaces. • A new geometrical parameter of the roughness, the Effective Distribution, is defined. • Direct numerical simulation of turbulent flow in a channel 2D roughness. • The ED improved drag correlation by accounting for peaks above mean Roughness. • The ED improved drag correlation by accounting for wake regions from the highest elements. • The ED improved drag correlation by accounting for distances between elements.