Author(s): Ceyda Polatel; Marian Muste; Virendra C. Patel; Thorsten Stoesser; Wolfgang Rodi
Keywords: Large-Scale Roughness; Double-Averaged Velocity Profile; LSPIV; LES
Abstract: The present paper investigates double (time and space) averaged velocity profiles in open- channel flow over large-scale roughness elements for providing a simplified description of the flow structure and its velocity profiles. Mean velocity profiles and turbulence characteristics are obtained numerically and experimentally for surfaces roughened by two-dimensional dunes and transverse square ribs. The roughness geometry and height (k) are of the k-type. The Reynolds number, based on the flow depth (h) and the bulk velocity (Ub), is between 23, 200 and 32, 600, and the submergence (h/k) ranges between 4 and 8. 5. Large Eddy Simulation (LES) and Laser Doppler Velocimetry (LDV) experiments are jointly employed to study double averaged velocity and turbulence characteristics with sufficient spatial resolution and accuracy to reveal important structural properties of the flow, including the two-layer structure of the averaged flow, the virtual origin of the rough surface, and the extent of the inner region.