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Research Papers: Fundamental Issues and Canonical Flows

# Unsteady Structure and Development of a Row of Impingement Jets, Including Kelvin–Helmholtz Vortex Development

[+] Author and Article Information
Li Yang, Hongde Jiang

Department of Thermal Engineering,
Tsinghua University,
Beijing 100084, China

Phillip Ligrani

Propulsion Research Center,
Department of Mechanical
and Aerospace Engineering,
University of Alabama in Huntsville,
Huntsville, AL 35811

Jing Ren

Department of Thermal Engineering,
Tsinghua University,
Beijing 100084, China
e-mail: renj@tsinghua.edu.cn

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 10, 2014; final manuscript received December 8, 2014; published online February 2, 2015. Assoc. Editor: Oleg Schilling.

J. Fluids Eng 137(5), 051201 (May 01, 2015) (12 pages) Paper No: FE-14-1369; doi: 10.1115/1.4029386 History: Received July 10, 2014; Revised December 08, 2014; Online February 02, 2015

## Abstract

Considered is a cylinder channel with a single row of ten aligned impinging jets, with exit flow in the axial direction at one end of the channel. For the present predictions, an unsteady Reynolds-Averaged Navier–Stokes (RANS) solver is employed for predictions of flow characteristics within and nearby the ten impingement jets, where the jet Reynolds number is 15,000. Spectrum analysis of different flow quantities is also utilized to provide data on associated frequency content. Visualizations of three-dimensional, unsteady flow structural characteristics are also included, including instantaneous distributions of Y-component vorticity, three-dimensional streamlines, shear layer parameter $ψ$, and local static pressure. Kelvin–Helmholtz vortex development is then related to local, instantaneous variations of these quantities. Of particular importance are the cumulative influences of cross flows, which result in locally increased shear stress magnitudes, enhanced Kelvin–Helmholtz vortex generation instabilities, and increased magnitudes and frequencies of local flow unsteadiness, as subsequent jets are encountered with streamwise development.

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## Figures

Fig. 1

Impingement jet channel configuration and coordinate system

Fig. 2

Local numerical mesh distribution of the impingement jet channel employed for numerical predictions [23]

Fig. 3

Time sequence of distributions of normalized instantaneous Y-component vorticity along cross section plane 1 of the impingement jet channel for Re of 15,000

Fig. 4

Distributions of normalized instantaneous Y-component vorticity along cross section planes 1–4 of the impingement jet channel for Re of 15,000

Fig. 5

Instantaneous three-dimensional distributions of jet core regions, and regions of augmented swirl near the exits of jets 7–9 for Re of 15,000

Fig. 6

Time sequence of instantaneous distributions of static pressure and augmented magnitude of shear layer parameter ψ along cross section plane 1 of the impingement jet channel for jets 3 and 4, and jets 7 and 8, with Re of 15,000

Fig. 7

Time sequence of instantaneous distributions of static pressure and augmented magnitude of Y-component of vorticity along cross section plane 1 of the impingement jet channel for jets 3 and 4, and jets 7 and 8, with Re of 15,000

Fig. 8

Time sequence of instantaneous distributions of three-dimensional streamlines and augmented magnitude of Y-component of vorticity along cross section plane 1 of the impingement jet channel for jets 3 and 4, and jets 7 and 8, with Re of 15,000

Fig. 9

Instantaneous distributions of three-dimensional streamlines, static pressure, and augmented magnitude of shear layer parameter ψ along cross section plane 1 of the impingement jet channel for jets 3 and 7, with Re of 15,000

Fig. 10

Time sequence of instantaneous distributions of secondary flow vectors along the streamwise cross-sectional plane of the impingement jet channel for jet 7, with Re of 15,000

Fig. 11

Time sequence of instantaneous distributions of axial velocity along a cross-sectional plane of the impingement jet channel for jet 7, with Re of 15,000

Fig. 12

Time-variation and frequency spectra of instantaneous turbulence kinetic energy for central locations along the impingement jet channel for impingement jets 1, 5, and 9 with Re of 15,000

Fig. 13

Frequency spectra of instantaneous velocity fluctuations in the X, Y, and Z directions, instantaneous temperature fluctuations, and instantaneous turbulence kinetic energy for central locations along the impingement jet channel for impingement jets 1, 5, and 9 with Re of 15,000

Fig. 14

Frequency spectra of instantaneous turbulence kinetic energy for different Y-locations along the impingement jet channel for impingement jets 1, 5, and 9 with Re of 15,000

Fig. 15

Time-averaged flow streamlines along cross section plane 1 of the impingement jet channel for Re of 15,000. Also presented are distributions of root-mean-square temperature within different streamwise cross-sectional planes of the impingement jet channel for jets 1–10, with Re of 15,000.

Fig. 16

Root-mean-square magnitudes of fluctuating static pressure, static temperature, turbulence kinetic energy, spanwise velocity component, and normal velocity component for different streamwise cross-sectional planes of the impingement jet channel for jets 1–10, with Re of 15,000

Fig. 17

Time-averaged distributions of turbulence kinetic energy, shear stress, static pressure (all determined along cross section plane 1 of the impingement jet channel), and surface heat flux (determined along the surface of the impingement jet channel) for impingement jets 1, 2, 5, 6, 9, and 10, with Re of 15,000

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