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Research Papers

Manipulation of Water Jet Trajectory by a Nonuniform Electric Field in Water Jet Material Processing

[+] Author and Article Information
Satyabrata Mohanty

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208
e-mail: satyabratamohanty2016@u.northwestern.edu

Kornel Ehmann

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208
e-mail: k-ehmann@northwestern.edu

Jian Cao

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208
e-mail: jcao@northwestern.edu

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received January 20, 2015; final manuscript received March 1, 2016; published online March 23, 2016. Assoc. Editor: Nicholas Fang.

J. Micro Nano-Manuf 4(2), 021003 (Mar 23, 2016) (11 pages) Paper No: JMNM-15-1009; doi: 10.1115/1.4032904 History: Received January 20, 2015; Revised March 01, 2016

In spite of its applications in macromanufacturing processes, water jet processing has not been extensively applied to the field of micromanufacturing owing to its poor tolerance and lack of effective control of the jet impingement position. This paper investigates the phenomenon of liquid dielectrophoresis (LDEP) using a localized nonuniform static electric field to deflect and control the jet's trajectory at the microscale for a water jet in air. A new analytical modeling approach has been attempted by representing the stable length of a water jet as a deformable solid dielectric beam to solve for the deflection of the jet under the action of the electric field. This method bypasses the complicated flow analysis of the water jet in air and focuses specially on the effect of the electric field on the trajectory of a laminar water jet within the working length. The numerical analysis of the phenomena for this electrode configuration was carried out using comsol. Preliminary proof-of-concept experiments were conducted on a 350 μm diameter sized water jet flowing at 0.6 m/s using a pin plate electrode configuration where a deflection of around 10 deg was observed at 2000 V. The results from the simulation are in good agreement with the results obtained in the preliminary experiments. This novel approach of modeling the water jet as a deformable dielectric beam might be useful in numerous applications involving precise control of the water jet's trajectory particularly in microwater jet material processing.

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References

Figures

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Fig. 1

Demonstration of free-falling water stream deflected near a charged rod

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Fig. 2

A 15 deg of deflection is observed for a 250 μm water jet near the electrode probe with a positive voltage. Applied voltage: 250 V and flow rate: 50 cm3/min. The photograph is double exposed to show the undeflected and deflected jet [19].

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Fig. 3

(a) Pellat's original experiment with parallel electrodes, shown along the capillary rise along a wick [24] and (b) Jones's simple dielectric siphon consisting of two facing electrodes connecting upper and lower reservoirs [25]

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Fig. 4

Stability curves for different nozzle diameters d ranging from 50 to 200 μm, according to the simple model proposed by Sleicher and Sterling [20]

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Fig. 5

Schematic of the setup for preliminary experiments to observe the effect of nonuniform electric fields on water jet trajectory

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Fig. 6

Experimental setup to observe the bending effect of the electric field over the water jet

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Fig. 7

Image of the water jet and the pin electrode as captured by the CCD camera

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Fig. 8

Images of deflected water jet at voltages of 1300 V, 1500 V, 1800 V, and 2000 V

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Fig. 9

Model geometry for numerical simulation of the pin plate electrode

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Fig. 10

Modeling a steady water jet analogous to a solid beam

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Fig. 11

Boundary conditions for the electrostatics problem

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Fig. 12

Contour plot of the electric potential distribution for a control voltage of 2000 V

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Fig. 13

Surface plot of the electric field in the x-direction for the control voltage of 2000 V

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Fig. 14

Surface plot of the electric field in the z-direction for the control voltage of 2000 V

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Fig. 15

Surface plot of the electric field in the y-direction for the control voltage of 2000 V

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Fig. 16

Surface plot of the DEP force density in the x-direction for the control voltage of 2000 V

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Fig. 17

Parametric plot of DEP force density in the x-direction over the voltage range

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Fig. 18

Average DEP force density near the electrode tip over different voltages

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Fig. 19

Parametric plot of material displacement of the water jet measured over the center line of the jet over the range of voltages

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Fig. 20

Measurement of deflection of water jet section from experimental result at 2000 V using klonk image measurement software

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Fig. 21

Measurement of deflection of water jet section from numerical result at 2000 V for comparison with experimental results

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Fig. 22

Comparison of displacement of the jet between experiments and numerical simulations at different voltages

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Fig. 23

Percentage deviation of simulation results from experiments over different voltages

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