Abstract
LESs are carried out in turbulent channel flows to investigate on the effects of realistic wall roughness on turbulence structures. To this aim irregular 2D and 3D roughness geometries were reproduced superimposing sinusoidal functions. The two configurations, having the same mean roughness height, give rise to different values of the roughness function in the log region. Thus, not only the mean statistical quantities of the roughness affect turbulence but also the element shape plays a fundamental role. The spatial inhomogeneities of the height of the roughness peaks and cavity regions locally destroy the coherent pattern of the flow and strongly modify the elongated turbulence structures typical characteristic of flat surfaces.
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