0
Research Papers: Fundamental Issues and Canonical Flows

An Experimental Study of a Turbulent Wall Jet on Smooth and Transitionally Rough Surfaces

[+] Author and Article Information
N. Rostamy

D. J. Bergstrom1

Department of Mechanical Engineering,  University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 Canadadon.bergstrom@usask.ca

D. Sumner

Department of Mechanical Engineering,  University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 Canadadavid.sumner@usask.ca

J. D. Bugg

Department of Mechanical Engineering,  University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 Canadajim.bugg@usask.ca

1

Corresponding author.

J. Fluids Eng 133(11), 111207 (Nov 11, 2011) (8 pages) doi:10.1115/1.4005218 History: Received November 01, 2010; Revised September 28, 2011; Published November 11, 2011; Online November 11, 2011

The effect of surface roughness on the mean velocity and skin friction characteristics of a plane turbulent wall jet was experimentally investigated using laser Doppler anemometry. The Reynolds number based on the slot height and exit velocity of the jet was approximately Re = 7500. A 36-grit sheet was used to create a transitionally rough flow (44 < ks +   < 70). Measurements were carried out at downstream distances from the jet exit ranging from 20 to 80 slot heights. Both conventional and momentum-viscosity scaling were used to analyze the streamwise evolution of the flow on smooth and rough walls. Three different methods were employed to estimate the friction velocity in the fully developed region of the wall jet, which was then used to calculate the skin friction coefficient. This paper provides new experimental data for the case of a plane wall jet on a transitionally rough surface and uses it to quantify the effects of roughness on the momentum field. The present results indicate that the skin friction coefficient for the rough-wall case compared to a smooth wall increases by as much as 140%. Overall, the study suggests that for the transitionally rough regime considered in the present study, roughness effects are significant but mostly confined to the inner region of the wall jet.

FIGURES IN THIS ARTICLE
<>
Copyright © 2011 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 11

Variation of skin friction coefficient with Reynolds number over a rough surface

Grahic Jump Location
Figure 10

Variation of skin friction coefficient with Reynolds number over a smooth surface

Grahic Jump Location
Figure 9

Variation of the wall shear stress with streamwise distance over the smooth surface using momentum-viscosity scaling

Grahic Jump Location
Figure 8

The experimental data and overlap solutions for a smooth wall jet in inner variables

Grahic Jump Location
Figure 7

The experimental data and overlap solutions for a smooth wall jet in outer variables

Grahic Jump Location
Figure 6

Mean velocity profiles in inner scales over smooth and rough surfaces

Grahic Jump Location
Figure 5

Comparison of the outer wake layer velocity defect law proposed by Afzal [7] with the present smooth-wall data

Grahic Jump Location
Figure 4

Mean velocity profiles in inner scales over smooth surface

Grahic Jump Location
Figure 3

Mean velocity profiles in outer scales over smooth and rough surfaces

Grahic Jump Location
Figure 2

Uniform mean velocity profile close to the jet exit

Grahic Jump Location
Figure 1

Schematic representation of a plane wall jet over smooth and rough surfaces

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In