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Research Papers: Fundamental Issues and Canonical Flows

The Maximum Skin Friction and Flow Field of a Planar Impinging Gas Jet

[+] Author and Article Information
Adam Ritcey

Department of Mechanical Engineering,
McMaster University,
Hamilton, ON L8S 4L8, Canada
e-mail: ritceya@mcmaster.ca

Joseph R. McDermid

Department of Mechanical Engineering,
McMaster University,
Hamilton, ON L8S 4L8, Canada
e-mail: mcdermi@mcmaster.ca

Samir Ziada

Department of Mechanical Engineering,
McMaster University,
Hamilton, ON L8S 4L8, Canada
e-mail: ziadas@mcmaster.ca

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 6, 2017; final manuscript received April 27, 2017; published online July 18, 2017. Assoc. Editor: John Abraham.

J. Fluids Eng 139(10), 101204 (Jul 18, 2017) (13 pages) Paper No: FE-17-1081; doi: 10.1115/1.4036717 History: Received February 06, 2017; Revised April 27, 2017

The maximum skin friction and flow field are experimentally measured on a planar impinging gas jet using oil film interferometry (OFI) and particle image velocimetry (PIV), respectively. A jet nozzle width of W = 15 mm, impingement ratios H/W = 4, 6, 8, 10, and a range of jet Reynolds numbers Rejet = 11,000–40,000 are tested to provide a parametric map of the maximum skin friction. The maximum skin friction predictions of Phares et al. (2000, “The Wall Shear Stress Produced by the Normal Impingement of a Jet on a Flat Surface,” J. Fluid Mech., 418, pp. 351–375) for plane jets agree within 5% of the current OFI results for H/W = 6, but deviates upward of 28% for other impingement ratios. The maximum skin friction is found to be less sensitive to changes in the impingement ratio when the jet standoff distance is roughly within the potential core length of the jet. PIV measurements show turbulence transition locations moving toward the nozzle exit with increasing Reynolds number, saturation in the downstream evolution of the maximum axial turbulence intensity before reaching a maximum peak upon impingement, followed by sudden damping at the plate surface. As the flow is redirected, there is an orthogonal redistribution of the fluctuating velocity components, and local peaks in both the axial and transverse turbulence intensity distributions at the plate locations of the maximum skin friction.

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References

Figures

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Fig. 1

Light and camera setup at image station indicating the coordinate system. Flow direction (x) on plate is normal to page.

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Fig. 2

The interferogram obtained on the impingement plate surface (left). The oil is applied at an angle to the flow ψ≈45deg to obtain the entire skin friction distribution with one image, similar to the technique of Dogruoz et al. [34]. Note the line of symmetry along the jet stagnation line (left). The corresponding pixel intensity distribution along the vertical dashed line in the interferogram, which is used to determine fringe spacing (right).

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Fig. 3

Schematic of the experimental impinging air jet setup at the wind-tunnel exit

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Fig. 4

Kinematic viscosity versus temperature calibration curve for 50 cS silicon oil performed with a capillary viscometer in a temperature controlled bath

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Fig. 5

PIV setup for capturing flow field

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Fig. 6

Particle image velocimetry of the velocity magnitude for Rejet = 11,000 H/W=8 (left) and Rejet = 40,000 H/W=8 (right)

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Fig. 7

Centerline velocity decay for Rejet = 11,000, 20,000, 30,000, 40,000 and H/W=8. The dashed line represents Eq. (9) developed by Beltaos and Rajaratnam [5].

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Fig. 8

Particle image velocimetry of the axial turbulence intensities (left) and transverse turbulence intensities (right) for Rejet = 11,000 and H/W=8

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Fig. 9

Particle image velocimetry of the axial turbulence intensities (left) and transverse turbulence intensities (right) for Rejet = 40,000 and H/W=8

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Fig. 10

The maximum axial turbulence intensity in the jet column region (−1.5 < x/W < 1.5) as a function of downstream distance for Rejet = 11,000, 20,000, 30,000, 40,000, and H/W=8

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Fig. 11

The maximum transverse turbulence intensity in the jet column region (−1.5 < x/W < 1.5) as a function of downstream distance for Rejet = 11,000, 20,000, 30,000, 40,000 and H/W=8

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Fig. 12

Instantaneous smoke visualizations of the planar impinging gas jet for Rejet = 11,000 (left) and Rejet = 20,000 (right) for H/W=8. Flow is moving from the left (jet exit) to the right (impingement plate) in each image.

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Fig. 13

The maximum axial turbulence intensity in the impingement plate region (7 < z/W < 8) as a function of impingement plate distance for Rejet = 11,000, 20,000, 30,000, 40,000 and H/W=8

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Fig. 14

The maximum transverse turbulence intensity in the impingement plate region (7 < z/W < 8) as a function of impingement plate distance for Rejet = 11,000, 20,000, 30,000, 40,000 and H/W=8

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Fig. 15

Particle image velocimetry of the velocity profiles (left) and axial turbulence intensity levels (right) at the jet exit z/W = 0.8 (z/H = 0.1) for Rejet=11,000, 20,000, 30,000, 40,000 and H/W = 8

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Fig. 16

Effect of Rejet on skin friction distribution for H/W = 4. The centered markers are binned averages of the plotted data.

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Fig. 17

Skin friction distributions at Rejet = 11,000 for different jet impingement ratios, H/W = 4, H/W = 6, H/W = 8, H/W = 10. The centered markers are binned averages of the skin friction data.

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Fig. 18

The maximum skin friction as a function of jet Reynolds number Rejet for different impingement ratios H/W. The data points are the maximum skin friction values obtained from the current OFI experiments. The solid lines on the plot represent the maximum skin friction predictions of Phares et al. [25] using Eq. (4) for two-dimensional impinging jets.

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