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RESEARCH PAPERS: Forced Convection

Turbulent Transport Measurements in a Heated Boundary Layer: Combined Effects of Free-Stream Turbulence and Removal of Concave Curvature

[+] Author and Article Information
M. D. Kestoras

Cyprus International Institute of Management, 21 Akademias Avenue, PO Box 378, Aglandjia, CY-2151 Nicosia, Cyprus

T. W. Simon

Department of Mechanical Engineering, University of Minnesota, 111 Church Street, S. E., Minneapolis, MN 55455

J. Heat Transfer 119(3), 413-419 (Aug 01, 1997) (7 pages) doi:10.1115/1.2824113 History: Received November 08, 1995; Revised April 03, 1997; Online December 05, 2007

Abstract

Turbulence measurements for both momentum and heat transport are taken in a boundary layer over a flat recovery wall downstream of a concave wall (R = 0.97 m). The boundary layer appears turbulent from the beginning of the upstream, concave wall and grows over the flat test wall downstream of the curved wall with negligible streamwise acceleration. The strength of curvature at the bend exit, δ99.5 /R , is 0.04. The free-stream turbulence intensity (FSTI) is ~8 percent at the beginning of the curve and is nearly uniform at ~4.5 percent throughout the recovery wall. Comparisons are made with data taken in an earlier study, in the same test facility, but with a low FSTI (~0.6 percent). Results show that on the recovery wall, elevated FSTI enhances turbulent transport quantities such as −uν and νt in most of the outer part of the boundary layer, but near-wall values of νt remain unaffected. This is in contrast to near-wall νt values within the curve which decrease when FSTI is increased. At the bend exit, decreases of −uν and νt due to removal of curvature become more profound when FSTI is elevated, compared to low-FSTI behavior. Measurements in the core of the flow indicate that the high levels of cross transport of momentum over the upstream concave wall cease when curvature is removed. Other results show that turbulent Prandtl numbers over the recovery wall are reduced to ~0.9 when FSTI is elevated, consistent with the rise in Stanton numbers over the recovery wall.

Copyright © 1997 by The American Society of Mechanical Engineers
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