The streamwise turbulence intensity - a comparison between smooth and rough wall turbulent boundary layers

Authors: Segalini, A. S., Örlü, R., Castro, I.P., Alfredsson, P.H.
Document Type: Conference
Pubstate: Published
Journal: Progress in Turbulence V, Springer Proceedings in Physics, Proceedings of the iTi Conference in Turbulence 2012
Volume: 149   97-101
Year: 2014


Clear differences in turbulence intensity profiles in smooth, transitional and fully rough zero-pressure gradient boundary layers are demonstrated, using the diagnostic plot. A wide range of published data is considered and all zero-pressure gradient boundary layers yield outer flow u'/U values which are roughly linearly related to U/U_inf?, just as for smooth walls, but with a significantly higher slope. The difference in slope is due largely to the influence of the roughness parameter (Delta U+? in the usual notation) and all the data can be fitted empirically by using a modified form of the scaling, dependent only on Delta U/U_inf. It is observed that the turbulence intensity, at a location in the outer layer where U/U_inf? is fixed, rises monotonically with increasing DeltaU/U_inf regardless of the roughness morphology.