Abstract
An experimental study was conducted in order to clarify the response of the fully developed pipe flow to d- and k-type wall roughness of various streamwise lengths. The measurements were set to emphasize on the response processes, which are deformation and relaxation of the mean velocity profile related to the strength and type of roughness. Under the same effective pressure drop, comparison of the mean velocity profiles and three common characteristics of boundary layer thicknesses (displacement, momentum, and energy) revealed that the initial stage of the response to the flow depends on the type of roughness. The total recovery length until the fully developed state depends only on the effective pressure drop caused by the rough wall.
