Fairfield University Flight Documents

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About the Experiment

Our proposal is to investigate the physics of large-scale liquid drop impacts upon a smooth dry surface. Drop impact is an enormously important area of research today. Applications for drop impact range from Ink-Jet printing, wing-icing, and meteorology. As a drop of liquid impacts a smooth dry surface, a crown shaped splash emerges as the drop collapses. A rather surprising phenomenon, however, was discovered in 2005: when the atmospheric pressure around the impact is decreased, the splash ceases to occur. There seems to exist a relationship between the droplet characteristics and the atmospheric conditions. This relationship governs the threshold pressure, the atmospheric pressure at which a splash no longer results. One of the key parameters in splashing is the size of the drop. Previous ground based experiments have been limited in testable drop sizes due to the effects of gravity, which acts to detach the drop from the injector when the weight of the drop surpasses the adhesive force of the liquid, thereby limiting attainable sizes.

While strides are being made in understanding this phenomenon on Earth, particularly with smaller droplets, it has not been possible to test the scalability with larger drops. We propose to use the microgravity environment onboard the DC-9 to scale the drop sizes up much larger than is possible in ground based work to verify and extend our understanding into the regime of large drop sizes. Using a variation on an experimental setup proven in a previous microgravity experiment, we will form drops up to 5 times as large as those previously tested, and impact them on a smooth dry surface at nearly constant velocity. This process will be repeated while capturing the impacts on a high-speed camera, varying the atmospheric pressure up to ±10% in 2% increments from the theoretically calculated threshold pressure. Follow-up image processing will later let us confirm or reject the expectations. With many applications, ranging from printing, and surface coating to wing icing on airplanes, verification and further refinement of this model would be a welcomed contribution to the science community.

About the Equipment

Above is a to-scale concept model of our experimental apparatus, with the protective cover open, and the sled in the ending position. The following components are highlighted:

1. Base 2. Outreach Box 3. Computer 4. Vacuum Controller 5. Vacuum Pump 6. Power Supply

7. Linear Actuator 8. Electric Motor 9. High-Speed Camera 10. Vacuum Chamber 11. Digital Injector 12. Safety Box

View more pictures of the experiment

See the results

We will publish our findings, as well as the photos captured by our high speed camera. Check out our results section.

References Cited in Proposal

[1] CRC Handbook of Chemistry and Physics, 86th Edition.
[2] "Edgerton, Harold E.: falling drop of milk." Online Photograph. Encyclop¾dia Britannica Online. 6 Nov. 2006
[3] Fowles, Grant, and George Cassiday. Analytical Mechanics. Seventh ed. Belmont, CA: n.p., 2005.
[4] L—pez, J. M., et al. "The Orbital Liquid Experiment (OLE)." Unpublished essay. European Space Agency. Feb. 2002. 27 Oct. 2006 .
[5] Purvis, R., F. T. Smith. ÒDroplet impact on water layers: post-impact analysis and computations.Ó Philosophical Transactions of the Royal Society A 363 (2005).
[6] Quero, M., et al. "Analysis of Super-cooled Water Droplet Impact on a Thin Water Layer and Ice Growth." 44th AIAA Aerospace Sciences Meeting and Exhibit. Reno, NV. 2006.
[7] Rioboo, R., M. Marengo, C. Tropea. ÒTime Evolution of Liquid Drop Impact onto Solid, Dry Surfaces.Ó Experiments in Fluids 33 (2002).
[8] Schroeder, Daniel. An Introduction to Thermal Physics. N.p.: Addison Wesley Longman, 2000.
[9] Stow, C. D., M. G. Hadfield. ÒAn Experimental Investigation of Fluid Flow Resulting from the Impact of a Water Drop with an Unyielding Dry Surface.Ó Proceedings of the Royal Society of London 373 (1981).
[10] Suryo, Ronald and Osman A. Basaran. "Dripping of a Liquid from a Tube in the Absence of Gravity." Physical Review Letters (2006)
[11] Thoroddsen, S. T., J. Sakakibara. ÒEvolution of the fingering pattern of an impacting drop.Ó Physics of Fluids 10 (1998).
[12] Worthington, A. M. ÒOn the Forms Assumed by Drops of Liquids Falling Vertically on a Horizontal Plate.Ó Proceedings of the Royal Society of London 25 (1876-1877).
[13] Xu, Lei, Loreto Barcos, Sidney R. Nagel. ÒSplashing of liquids: interplay of surrounding gas and surface roughness.Ó Unpublished essay. August 7, 2006. 27 Oct. 2006 .
[14] Xu, Lei, Wendy W. Zhang, and Sidney R. Nagel. "Drop Splashing on a Dry Smooth Surface." Physical Review Letters 94 (2005).
[15] Yarin, A. L., D. A. Weiss. ÒImpact of Drops on Solid Surfaces: Self-Similar Capillary Waves, and Splashing as a New Type of Kinematic Discontinuity.Ó Journal of Fluid Mechanics 283 (1995).
[16] Yarin, A. L., D. A. Weiss. ÒSingle Drop Impact onto liquid films: neck distortion, jetting, tiny bubble entrainment, and crown formation.Ó Journal of Fluid Mechanics