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Research Papers: Forced Convection

Energy Separation in the Wake of a Cylinder

[+] Author and Article Information
R. J. Goldstein

Heat Transfer Laboratory, Department of Mechanical Engineering, University of Minnesota, 111 Church St. SE, Minneapolis, MN 55455rjg@me.umn.edu

K. S. Kulkarni

Heat Transfer Laboratory, Department of Mechanical Engineering, University of Minnesota, 111 Church St. SE, Minneapolis, MN 55455kaustubh@me.umn.edu

J. Heat Transfer 130(6), 061703 (Apr 23, 2008) (9 pages) doi:10.1115/1.2891222 History: Received January 17, 2007; Revised August 02, 2007; Published April 23, 2008

Energy separation is a spontaneous redistribution of total energy (enthalpy) in a fluid without external work or heat flow, resulting in some portion of fluid having higher total energy (enthalpy) and another portion having lower energy (enthalpy) than the surrounding fluid. The present study investigates the mechanism of energy separation in the vortex field behind an adiabatic circular cylinder. Time-averaged velocity and temperature measurements are carried out in the wake of a cylinder in a cross flow of air. The measurements are performed at downstream locations of three, five, seven, and ten diameters, for a Reynolds number, based on upstream velocity and cylinder diameter, of 9.2×104 and freestream Mach number of 0.22. The measured velocity and recovery temperature data are expressed in nondimensional form as an energy separation factor. The distribution of energy separation factor indicates that the main cause of energy separation is the periodic vortex flow in the wake. The vortex strength and the separation effect decrease as the flow moves downstream. However, energy separation is observed even ten diameters downstream.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Velocity field and total temperature distribution near a vortex (13)

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Figure 2

Variation of total temperature along a path line in a vortex street (14)

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Figure 3

Schematic diagram of test apparatus

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Figure 4

Schematic diagram of recovery temperature probe (all dimensions in mm)

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Figure 5

Recovery factor calibration of recovery temperature probe

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Figure 6

Effect of turbulent fluctuations on measurement of local dynamic temperature (x∕D=3, Re=9.2×104)

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Figure 7

Time-average velocity profile at x∕D=−20,3,5,7,10 for Re=9.2×104

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Figure 8

Turbulent intensity profile at x∕D=−20,3,5,7,10 for Re=9.2×104

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Figure 9

Time-average energy separation factor profile at x∕D=−20,3,5,7,10 for Re=9.2×104

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Figure 10

Time-average normalized enthalpy flux profile at x∕D=−20,3,5,7,10 for Re=9.2×104

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Figure 11

Time-average enthalpy flux profile at x∕D=−20,3,5,7,10 for Re=9.2×104

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