"It's like catching the fish that swallowed the queen's ring", Herzog by Saul Bellow For research opportunities, check here . In the News: NPR Tumblr, June 17, 2013, also on my blog, and a video can be found on FY Fluid Dynamics! and here. Altering the Shape of Water Drops. Water drops are spherical due to surface tension , that is, because of cohesive forces. Water molecules want to be adjacent to one other and far away from molecules that are different from them, like air or oil molecules. This has the effect of minimizing water's surface area; hence, water drops are spherical. This is shown in the upper image, in the figure below, of spherical water drops flowing inside a jet of oil. To reduce cohesive forces or surface tension, actually the interfacial tension between water and oil, surfactants, such as soap, are added to water. Since surfactant molecules have two ends, one that is attracted to water and one that isn’t, surfactant molecules disrupt the cohesive forces at the interface. Consequently, if the surfactant molecules are strong enough and the disruption of the cohesive forces is widespread, the spherical shape of water drops no longer prevails. This is shown in the bottom image. (Photo credit: L. L. A. Adams)  |
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