Measurement and calculation of fluid dynamic characteristics of rough-wall turbulent boundary-layer flows
- Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering
- Univ. of Alabama, Huntsville, AL (United States). Mechanical Engineering Dept.
- Mississippi State Univ., Mississippi State, MS (United States). Mechanical and Nuclear Engineering Dept.
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 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.
- OSTI ID:
- 5829884
- Journal Information:
- Journal of Fluids Engineering; (United States), Journal Name: Journal of Fluids Engineering; (United States) Vol. 115:3; ISSN JFEGA4; ISSN 0098-2202
- Country of Publication:
- United States
- Language:
- English
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