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RESEARCH PAPERS: Jets, Wakes, and Impingment Cooling

Self-Preserving Mixing Properties of Steady Round Nonbuoyant Turbulent Jets in Uniform Crossflows

[+] Author and Article Information
F. J. Diez

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8058diez@jove.rutgers.edu

L. P. Bernal, G. M. Faeth

Department of Aerospace Engineering,  The University of Michigan Ann Arbor, Michigan 48109-2140

J. Heat Transfer 127(8), 877-887 (Mar 01, 2005) (11 pages) doi:10.1115/1.1991868 History: Received May 15, 2004; Revised March 01, 2005

The self-preserving mixing properties of steady round nonbuoyant turbulent jets in uniform crossflows were investigated experimentally. The experiments involved steady round nonbuoyant fresh water jet sources injected into uniform and steady fresh water crossflows within the windowed test section of a water channel facility. Mean and fluctuating concentrations of source fluid were measured over cross sections of the flow using planar-laser-induced-fluorescence (PLIF). The self-preserving penetration properties of the flow were correlated successfully similar to Diez [ASME J. Heat Transfer, 125, pp. 1046–1057 (2003)] whereas the self-preserving structure properties of the flow were correlated successfully based on scaling analysis due to Fischer [Academic Press, New York, pp. 315–389 (1979)]; both approaches involve assumptions of no-slip convection in the cross stream direction (parallel to the crossflow) and a self-preserving nonbuoyant line puff having a conserved momentum force per unit length that moves in the streamwise direction (parallel to the initial source flow). The self-preserving flow structure consisted of two counter-rotating vortices, with their axes nearly aligned with the crossflow (horizontal) direction, that move away from the source in the streamwise direction due to the action of source momentum. Present measurements extended up to 260 and 440 source diameters from the source in the streamwise and cross stream directions, respectively, and yielded the following results: jet motion in the cross stream direction satisfied the no-slip convection approximation; geometrical features, such as the penetration of flow boundaries and the trajectories of the axes of the counter-rotating vortices, reached self-preserving behavior at streamwise distances greater than 40–50 source diameters from the source; and parameters associated with the structure of the flow, e.g., contours and profiles of mean and fluctuating concentrations of source fluid, reached self-preserving behavior at streamwise (vertical) distances from the source greater than 80 source diameters from the source. The counter-rotating vortex structure of the self-preserving flow was responsible for substantial increases in the rate of mixing of the source fluid with the ambient fluid compared to corresponding axisymmetric flows in still environments, e.g., transverse dimensions in the presence of the self-preserving counter-rotating vortex structure were 2–3 times larger than transverse dimensions in self-preserving axisymmetric flows at comparable conditions.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Water channel facility (a), and experimental setup (b)

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Figure 2

Sketches of a steady round nonbuoyant turbulent jet in a uniform crossflow showing the definition of penetration properties measured in this investigation

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Figure 3

Flow regime map for of the developing flow and self-preserving regions for steady turbulent plumes in crossflows

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Figure 4

Instantaneous PLIF image of the cross section of a steady round nonbuoyant turbulent jet in a uniform crossflow (d=3.2mm, Reo=5300, uo∕v∞=26, (xc-xos)∕d=101 and y∕d=315 and Δt=50ms between frames)

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Figure 5

Trajectory of the axes of the vortex system and transverse spacing between the vortex axes, in terms of the self-preserving variables for round nonbuoyant turbulent jets in uniform crossflows

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Figure 6

Streamwise and transverse penetration distances in terms of the self-preserving variables for the penetration properties of round nonbuoyant turbulent jets in uniform crossflows

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Figure 7

Plots of the development of mean and rms concentration of source fluid in terms of self-preserving variables for transverse paths through the vortex axes for steady round nonbuoyant turbulent jets in uniform crossflows

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Figure 8

Plots of mean concentrations of source fluid in terms of the self-preserving variables for various vertical and horizontal paths for steady round nonbuoyant turbulent jets in uniform crossflows within the self-preserving region

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Figure 9

Plots of rms concentration of source fluid in terms of self-preserving variables for various vertical and horizontal paths for steady round nonbuoyant turbulent jets in uniform crossflows within the self-preserving region

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Figure 10

Contour plot of mean concentration of source fluid in terms of self-preserving variables over the flow cross-section for steady round nonbuoyant turbulent jets in uniform crossflows within the self-preserving region

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Figure 11

Contour plots of rms concentration fluctuations of source fluid in terms of self-preserving variables over the flow cross section for steady round nonbuoyant turbulent jets in uniform crossflows within the self-preserving region

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