Measurement and Calculation of Fluid Dynamic Characteristics of Rough-Wall Turbulent Boundary-Layer Flows

[+] Author and Article Information
M. H. Hosni

Department of Mechanical Engineering, Kansas State University, Manhattan, KS 66506-5106

H. W. Coleman

Mechanical Engineering Department, University of Alabama in Huntsville, Huntsville, AL 35899

R. P. Taylor

Thermal & Fluid Dynamics Laboratory, Mechanical and Nuclear Engineering Department, Mississippi State University, Mississippi State, MS 39762

J. Fluids Eng 115(3), 383-388 (Sep 01, 1993) (6 pages) doi:10.1115/1.2910150 History: Received October 21, 1991; Revised February 08, 1993; Online May 23, 2008


Experimental measurements of profiles of mean velocity and distributions of boundary-layer thickness and skin friction coefficient from aerodynamically smooth, transitionally rough, and fully rough turbulent boundary-layer flows are presented for four surfaces—three rough and one smooth. The rough surfaces are composed of 1.27 mm diameter hemispheres spaced in staggered arrays 2, 4, and 10 base diameters apart, respectively, on otherwise smooth walls. The current incompressible turbulent boundary-layer rough-wall air flow data are compared with previously published results on another, similar rough surface. It is shown that fully rough mean velocity profiles collapse together when scaled as a function of momentum thickness, as was reported previously. However, this similarity cannot be used to distinguish roughness flow regimes, since a similar degree of collapse is observed in the transitionally rough data. Observation of the new data shows that scaling on the momentum thickness alone is not sufficient to produce similar velocity profiles for flows over surfaces of different roughness character. The skin friction coefficient data versus the ratio of the momentum thickness to roughness height collapse within the data uncertainty, irrespective of roughness flow regime, with the data for each rough surface collapsing to a different curve. Calculations made using the previously published discrete element prediction method are compared with data from the rough surfaces with well-defined roughness elements, and it is shown that the calculations are in good agreement with the data.

Copyright © 1993 by The American Society of Mechanical Engineers
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