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Research Papers: Fundamental Issues and Canonical Flows

Characteristics of Turbulent Three-Dimensional Offset Jets

[+] Author and Article Information
M. Agelin-Chaab

 E. H. Price Ltd. Winnipeg, Manitoba R2K 3Z9 Canada

M. F. Tachie

 University of Manitoba Winnipeg, Manitoba R3T 5V6 Canada

J. Fluids Eng 133(5), 051203 (Jun 07, 2011) (9 pages) doi:10.1115/1.4004071 History: Received April 17, 2010; Revised April 09, 2011; Published June 07, 2011; Online June 07, 2011

Three-dimensional turbulent offset jets were investigated using a particle image velocimetry technique. Three jet exit Reynolds numbers, Rej  = 5000, 10,000, and 20,000, and four offset heights, h/d = 0.5, 1.0, 2.0, and 4.0, were studied. The mean flow and turbulence statistics were studied over larger downstream distances than in previous studies. The decay and spread rates were found to be nearly independent of Reynolds number and offset height at certain exit diameters (x = 73d) downstream and h/d ≤ 2. The decay rates of 1.18 ± 0.03 and spread rates of 0.055 ± 0.001 and 0.250 ± 0.005 in the wall-normal and lateral directions were obtained, respectively. The reattachment lengths are also independent of Rej but increase with offset height. The locations of the maximum mean velocities increased linearly with streamwise distance in the self-similar region. It was observed that profiles of the mean velocities, turbulence intensities, and Reynolds shears stresses are nearly independent of Rej and h/d far downstream. The triple products in the symmetry plane indicated turbulence transport from the outer region of the jet towards the wall region.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

A sketch of a (a) sectional view of an offset jet through the symmetry plane and (b) three-dimensional wall jet. The symbols Uj , Um , ym , y0.5 , and z0.5 denote jet exit maximum mean velocity, the local maximum mean velocities, the wall-normal location of Um , the wall-normal location of 0.5Um , and lateral location of 0.5Um , respectively. Also U, V, and W are the local mean velocities in the streamwise, wall-normal, and lateral directions, respectively, while u, v, and w are the corresponding turbulence intensities.

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Figure 9

Profiles of (a) streamwise mean velocities U, (b) streamwise turbulence intensities u, (c) lateral turbulence intensities w, and (d) Reynolds shear stresses −uw in the lateral plane. y*  = y/y0.5 .

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Figure 10

Profiles of (a) streamwise mean velocities U, (b) streamwise turbulence intensities, u, (c) wall-normal turbulence intensities v, and (d) Reynolds shear stresses uv in planes offset planes at z/d = 0, 1, 2, and 4. z*  = z/z0.5 .

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Figure 11

Profiles of the turbulence structural parameters (a) v2 /u2 and (b) uv/2k in the symmetry plane. y*  = y/y0.5 .

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Figure 12

Profiles of the triple velocity products in the symmetry plane. (a) u3 , (b) u2 v, (c) uv2 , and (d) v3 . y*  = y/y0.5 .

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Figure 2

(a) A schematic of the test section showing arrangement of PIV system for measurements in the x-y plane and (b) a picture of the experimental setup for measurements in the x-y plane

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Figure 3

Profiles of streamwise (a) mean velocities and (b) turbulence intensitites close to the jet exit x/d = 0.6 for three Reynolds numbers

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Figure 4

Mean streamlines and iso-ontours of the ((a) to (c)) mean velocities (U*  = U/Uj ) and ((d) to (f)) turbulence kinetic energy [k*  = (u2  + v2 )/Uj 2 ] in the near field for h/d = 1 in (a) and (d), h/d = 2 in (b) and (e), and h/d = 4 in (c) and (f)

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Figure 5

Variation of (a) local maximum mean velocity Um , (b) location of Um , ym , (c) wall-normal jet half width y0.5, and (d) lateral jet half width z0.5 . Note the insert in (d). Symbols in (b) to (d) are as in (a) unless stated otherwise.

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Figure 6

Profiles of (a) streamwise mean velocities U, (b) streamwise turbulence intensities u, (c) wall-normal turbulence intensities v, and (d) Reynolds shear stresses uv

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Figure 7

Profiles of mean: streamwise velocities U ((a) and (b)); and wall-normal velocities V ((c)and (d)). y*  = y/y0.5 and y**  = (y/ym )/(y0.5 /ym )

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Figure 8

Profiles of (a) streamwise turbulence intensities u, (b) wall-normal turbulence intensities v, and (c) Reynolds shear stresses uv in the symmetry plane. y*  = y/y0.5 and y**  = (y−ym )/(y0.5 −ym )

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