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Research Papers: Forced Convection

Effect of Upstream Shear on Flow and Heat (Mass) Transfer Over a Flat Plate—Part I: Velocity Measurements

[+] Author and Article Information
K. Ghosh

Department of Mechanical Engineering, Heat Transfer Laboratory, University of Minnesota, Minneapolis, MN 55455kalmech@me.umn.edu

R. J. Goldstein1

Department of Mechanical Engineering, Heat Transfer Laboratory, University of Minnesota, Minneapolis, MN 55455rjg@me.umn.edu

1

Corresponding author.

J. Heat Transfer 132(10), 101701 (Aug 03, 2010) (7 pages) doi:10.1115/1.4001608 History: Received April 10, 2009; Revised April 01, 2010; Published August 03, 2010; Online August 03, 2010

A parametric study investigates the effects of wall shear on a two-dimensional turbulent boundary layer. A belt translating along the direction of the flow imparts the shear. Velocity measurements are performed at 12 streamwise locations with four surface-to-freestream velocity ratios (0, 0.38, 0.52, and 0.65) and a momentum-based Reynolds number between 770 and 1776. The velocity data indicate that the location of the “virtual origin” of the turbulent boundary layer “moves” downstream toward the trailing edge of the belt with increasing surface velocity. The highest belt velocity ratio (0.65) results in the removal of the “inner” region of the boundary layer. Measurements of the streamwise turbulent kinetic energy show an inner scaling at locations upstream and downstream of the belt, and the formation of a new self-similar structure on the moving surface itself. Good agreement is observed for the variation in the shape factor (H) and the skin friction coefficient (cf) with the previous studies. The distribution of the energy spectrum downstream of the belt indicates peak values concentrated around 1 kHz for the stationary belt case in the near wall region (30<y+<50). However, with increasing belt velocity, this central peak plateaus over a wide frequency range (0.9–4 kHz).

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the experimental apparatus

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Figure 2

Velocity profiles, case 1 (stationary belt)

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Figure 3

Determination of the virtual origin

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Figure 4

Universal velocity profiles based on pseudo and true scalings (uw=6 m/s)

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Figure 5

Universal velocity profiles based on pseudo and true scalings (uw=10 m/s)

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Figure 6

Variation in the shape factor

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Figure 7

Variation in the skin friction coefficient

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Figure 8

Nondimensionalized streamwise TKE

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Figure 9

Variation in the power spectrum along x

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