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Technical Briefs

Mechanical Inhibition of Foam Formation via a Rotating Nozzle

[+] Author and Article Information
Alexander G. Bick

School of Engineering and Applied Sciences,  Harvard University, Cambridge, MA 02138

William D. Ristenpart1

Department of Chemical Engineering and Materials Science, Department of Food Science and Technology,  University of California, Davis, Davis, CA 35616wdristenpart@ucdavis.eduSchool of Engineering and Applied Sciences,  Harvard University, Cambridge, MA 02138wdristenpart@ucdavis.edu

Ernst A. van Nierop

Department of Chemical Engineering and Materials Science, Department of Food Science and Technology,  University of California, Davis, Davis, CA 35616School of Engineering and Applied Sciences,  Harvard University, Cambridge, MA 02138

Howard A. Stone2

Department of Chemical Engineering and Materials Science, Department of Food Science and Technology,  University of California, Davis, Davis, CA 35616School of Engineering and Applied Sciences,  Harvard University, Cambridge, MA 02138

1

Corresponding author.

2

Present address: Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544.

J. Fluids Eng 133(4), 044503 (May 12, 2011) (3 pages) doi:10.1115/1.4003987 History: Received August 11, 2010; Revised December 01, 2010; Published May 12, 2011; Online May 12, 2011

We recently discovered that bubble formation can be substantially prevented when an aqueous solution is sprayed into a bath of the same solution provided that any two consecutive drops impacting the same surface location do so with a time interval greater than the capillary relaxation time. Building on this observation, here we report a mechanical means of preventing foam formation during liquid addition: the nozzle delivering the liquid is rotated sufficiently rapidly so that no two successive drops impact the interface at the same location. Foam formation is reduced by as much as 95% without any chemical anti-foaming agents.

FIGURES IN THIS ARTICLE
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Copyright © 2011 by American Society of Mechanical Engineers
Topics: Nozzles , Drops , Bubbles
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Figures

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Figure 3

The normalized volume of foam produced by 2% SDS solutions as a function of time for different angular velocities and flow rates. (a) Flow rate = 7.8 ml/min. (b) Flow rate = 10 ml/min.

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Figure 2

Top and side views of the amount of foam formed by pumping a 2% solution of Dawn dish soap at 4.7 ml/min for 15 min into a 250 ml beaker for two different angular velocities. In each case, the images were captured immediately after dispensing was complete. (a) Stationary nozzle. (b) Nozzle rotating at 7.6 rad/s. Note that almost no foam is generated with the rotating nozzle.

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Figure 1

The experimental apparatus. (a) Side-view schematic (not to scale). The tip of the nozzle hnoz  = 7.5 cm above the beaker bottom and dnoz  = 2.4 cm from the gear center. The beaker diameter is D = 6.7 cm. (b) Top-view schematic. The gear and nozzle rotate with angular velocity ω. (c) Photo of the apparatus. The white objects are the gears; the gear on right is connected to a rotating shaft.

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