Turbulent Flow Near a Rough Wall

[+] Author and Article Information
Yang-Moon Koh

Department of Mechanical Engineering, University of Ulsan, Ulsan 680-749, South Korea

J. Fluids Eng 114(4), 537-542 (Dec 01, 1992) (6 pages) doi:10.1115/1.2910065 History: Received June 13, 1991; Online May 23, 2008


By introducing the equivalent roughness which is defined as the distance from the wall to where the velocity gets a certain value (u/uτ ≈ 8.5) and which can be represented by a simple function of the roughness, a simple formula to represent the mean-velocity distribution across the inner layer of a turbulent boundary layer is suggested. The suggested equation is general enough to be applicable to turbulent boundary layers over surfaces of any roughnesses covering from very smooth to completely rough surfaces. The suggested velocity profile is then used to get expressions for pipe-friction factors and skin friction coefficients. These equations are consistent with existing experimental observations and embrace well-known equations (e.g., Prandtl’s friction law for smooth pipes and Colebrook’s formula etc.) as special cases.

Copyright © 1992 by The American Society of Mechanical Engineers
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