Spanwise variations in nominally two-dimensional rough-wall boundary layers

摘要: Laboratory experiments have been conducted in two separate boundary layer facilities to investigate steady spanwise variations mean velocity discovered during studies of developing flows over regular arrays large roughness elements. Regular variation was found with a wavelength, moderated by the growing layer, which an integer multiple repeating unit roughness. Amplitude greater than ±5% were and ±10% turbulence quantities. Due dominating nature this phenomena throughout care should be taken undertaking local measurements aimed at identifying flow caused heterogeneity.