Fluid Dynamics

For those that don't know, I'm something of a math/science geek. So when I saw these YouTube videos posted at Good Math, Bad Math, I knew that I had to post them here as well. Both are illustrations of the interesting and unusual properties of certain liquids.

The first is a demonstration and explanation of the "Kaye Effect" which is, as Mark Chu-Carroll notes:

...you take a substance like liquid shampoo, and allow a thin stream of it to pour down from a height onto a smooth surface, the stream will periodically "bounce", producing a stream leaping up from the point of contact

Apparently the phenomena wasn't particularly well-understood and the researchers who made the video are suggesting a possible cause. The video is really cool:

The second is a demonstration of a phenomena most likely known to just about any cook who has ever made gravy or had to thicken a sauce. When cornstarch is added to water in the proper proportion it forms what's known as a "non-Newtonian fluid" (so-called because the properties of the resulting suspension don't conform to Newton's conception of viscosity). What this means in simple terms is that the viscosity of the fluid will vary with the amount of stress or strain applied. When mixing cornstarch with water, one might notice, for example, that it's easy to pour the syrupy liquid, but that a spoon dropped into the measuring cup will bounce off of the surface, just as if it were solid. A couple of guys (it looks like they're from a Spanish talk show) took advantage of this unusual property to create a situation where they can almost literally walk on water. A very effective demonstration of the manner in which stress/strain alters the viscosity of the fluid: stepping down increases strain and thus increases the viscosity while remaining motionless decreases strain and decreases the viscosity. Again, very cool:

HT: Good Math, Bad Math