Flow in Turbulent Wall Layer Over Uniform Roughness

Abstract

A boundary-layer survey has been conducted on a rough plate consisting of uniform spherical particles arranged in a random and compact fashion. Strong turbulent mixing was observed in a region within a quarter of the particle size from the top of the particles. Such mixing is important to transfer or transport processes near a rough wall. The data of the normal axis of the present rough surface are found to be located at a distance of 1/50 of the particle diameter below the top of the particles. This reference data are different from that used by Nikuradse, indicating a possible modification of some numerical constants determined by Nikuradse.