Turbulent air flow over rough surfaces - Mean flow parameters

The objective of the study was to examine experimentally the turbulent flow structure near a repeated-rib geometry rough-walled surface as a function of the ratio of roughness height to pipe radius (K/R), the ratio of spacing between the elements to roughness height (P/K), and the axial position with the rib cycle. The centerline axial flow velocity was found to vary sinusoidally in the axial direction within a rib cycle for P/K greater than 10 for K/R = 0.1437 and P/K greater than 13 for K/R = 0.100. The roughness effect on the mean velocity profiles was characterized using a logarithmic equation which utilized an error in origin and a roughness function that was a function of the error in origin. The equation was found to be valid for P/K values of 7 or less for K/R = 0.1437 and 13 for K/R = 0.1 geometries.