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Research Papers: Flows in Complex Systems

Examination of a Variable-Diameter Synthetic Jet

[+] Author and Article Information
Spencer O. Albright

Department of Mechanical Engineering,
Washington State University Vancouver,
14204 NE Salmon Creek Ave.,
Vancouver, WA 98686
e-mail: spencer.albright@email.wsu.edu

Stephen A. Solovitz

Associate Professor
Mechanical Engineering,
Washington State University Vancouver,
14204 NE Salmon Creek Ave.,
Vancouver, WA 98686
e-mail: stevesol@vancouver.wsu.edu

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received June 29, 2015; final manuscript received June 8, 2016; published online August 11, 2016. Assoc. Editor: Mark F. Tachie.

J. Fluids Eng 138(12), 121103 (Aug 11, 2016) (9 pages) Paper No: FE-15-1440; doi: 10.1115/1.4033912 History: Received June 29, 2015; Revised June 08, 2016

Synthetic jet actuators are used to produce net axial momentum flow without net mass flux. Through strategic application, such devices can be used for flow control, propulsive thrust, and cooling. A novel application uses a variable-diameter orifice to constrict the exiting flow, and the motion can be synchronized with the pulse of the jet. This device is examined using phase-locked particle image velocimetry (PIV), permitting investigation of the flow fields and momentum flow. When compared to fixed-diameter synthetic jets, the variable-diameter actuator produces a larger vortex ring that lingers nearer the aperture. In addition, the experiments show increased momentum when the aperture is contracted in phase with the pulsing jet, with peak levels more than twice that of a constant-diameter jet.

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References

Figures

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Fig. 1

Schematic of experimental apparatus

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Fig. 2

(a) Schematic of the piston and aperture, shown to scale. (b) Image of the aperture frame, showing the iris in its mounting frame, the end of the driving pneumatic cylinder, and the control rod.

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Fig. 3

Transient response of the velocity field downstream of the exit aperture for a fixed exit diameter of 0.11D, when the aperture is fully closed. The eight phases displayed are spaced approximately 43 deg apart. The displayed vector density is reduced by 50% in each direction to aid in visualization.

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Fig. 8

Axial velocity profiles for the time-averaged jets along the centerline

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Fig. 7

Transverse velocity profiles for the time-averaged contracting jet at various axial positions

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Fig. 6

Transverse velocity profiles for the time-averaged jets at the same downstream location, x/D = 0.5

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Fig. 5

Transient response of the velocity field downstream of the exit aperture for a contracting exit diameter. The eight phases displayed are spaced approximately 43 deg apart. The current aperture position is shown in each phase. The displayed vector density is reduced by 50% in each direction to aid in visualization.

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Fig. 4

Transient response of the velocity field downstream of the exit aperture for a fixed exit diameter of 1D, when the aperture is fully open. The eight phases displayed are spaced approximately 43 deg apart. The displayed vector density is reduced by 50% in each direction to aid in visualization.

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Fig. 9

Transient response of the axial momentum flow rate downstream of the exit aperture for a fixed exit diameter of 0.11D, when the aperture is fully closed. The eight phases displayed are spaced approximately 43 deg apart.

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Fig. 10

Transient response of the axial momentum flow rate downstream of the exit aperture for a fixed exit diameter of 1D, when the aperture is fully open. The eight phases displayed are spaced approximately 43 deg apart.

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Fig. 11

Transient response of the axial momentum flow rate downstream of the exit aperture for a contracting exit diameter. The eight phases displayed are spaced approximately 43 deg apart.

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