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Research Papers: Fundamental Issues and Canonical Flows

Dye Visualization of In-Line Twin Synthetic Jets in Crossflows—A Parametric Study

[+] Author and Article Information
Xin Wen

School of Mechanical Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: wenxin84@sjtu.edu.cn

Hui Tang

Department of Mechanical Engineering,
The Hong Kong Polytechnic University,
Kowloon, Hong Kong
e-mail: h.tang@polyu.edu.hk

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 20, 2016; final manuscript received March 28, 2017; published online June 20, 2017. Assoc. Editor: Peter Vorobieff.

J. Fluids Eng 139(9), 091203 (Jun 20, 2017) (8 pages) Paper No: FE-16-1111; doi: 10.1115/1.4036410 History: Received February 20, 2016; Revised March 28, 2017

This paper presents a parametric study on the interaction of twin circular synthetic jets (SJs) that are in line with a crossflow over a flat plate. The resulting vortex structures under different actuation, and flow conditions are investigated using two-plane dye visualization in a water tunnel. The influence of four independent nondimensional parameters, i.e., the Reynolds number (ReL), Strouhal number (St), velocity ratio (VR), and phase difference (Δϕ), on the behavior of the twin SJs is studied. It is found that the increase of Reynolds number causes the SJ-induced vortex structures more turbulent, making the twin SJ interaction less organized. The increase of velocity ratio pushes the occurrence of interaction further away from the wall and makes the resulting vortex structures more sustainable. The St has no obvious influence on the interaction. And three types of vortex structures are observed under different phase differences: one combined vortex, two completely separated vortices, and partially interacting vortex structures. Based on this parametric study, a simple model is proposed to predict the resulting vortex pattern for the twin SJ interaction.

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Figures

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Fig. 1

Schematic of (a) the test plate and (b) the twin SJ actuators (all numbers are in mm)

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Fig. 2

Schematic of the two-plane dye visualization system

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Fig. 4

Evolution of vortex structures in a crossflow for case 4. Upper two rows: two-plane views of a single SJ. Bottom two rows: two-plane views of twin SJs with zero phase difference. The horizontal line represents the edge of the boundary layer.

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Fig. 5

Two-plane dye visualization showing the influence of ReL on single- and twin-SJ-induced vortex structures. The twin SJs are introduced with zero phase difference. The horizontal line represents the edge of the boundary layer.

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Fig. 6

Two-plane dye visualization showing the influence of VR on single- and twin-SJ-induced vortex structures. The twin SJs are introduced with zero phase difference. The horizontal line represents the edge of the boundary layer.

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Fig. 7

Two-plane dye visualization showing the influence of St on single- and twin-SJ-induced vortex structures. The twin SJs are introduced with zero phase difference. The horizontal line represents the edge of the boundary layer.

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Fig. 8

Two-plane dye images of the twin SJs at various phase differences for case 4. The horizontal line represents the edge of the boundary layer.

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Fig. 9

Summary of side view dye visualization at different phase difference for all cases, showing the spacing and resulting interaction between the vortices produced by the twin SJ actuators. The horizontal line represents the edge of the boundary layer.

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