UCLA Spinlab has another great video demonstrating the effects of rotation on a fluid. In a non-rotating fluid, flow over an obstacle is typically three-dimensional, with flow moving over as well as around the object. But in a steadily rotating fluid, as shown in the latter half of the video, the flow only moves around the obstacle, not over it. This non-intuitive behavior is part of the Taylor-Proudman theorem, which shows that flow around an obstacle in a rapidly rotating fluid will be two-dimensional and confined to planes perpendicular to the axis of rotation. (For the mathematically-inclined, Wikipedia does have a short derivation.) This 2D flow creates what are called Taylor columns over the obstacle. The Taylor column is like an imaginary extension of the original obstacle, turning the puck into a tall cylinder, and it’s real enough to flow, which diverts around it as though the column were there. (Video credit: UCLA Spinlab)
Tag: G. I. Taylor
Reader Question: National Committee for Fluid Mechanics Films
lazenby asks: Have you seen these guys? http://web.mit.edu/hml/ncfmf.html
Yes, absolutely! Those videos, which date from the 1960s, are so useful that they’re still shown to undergraduates today. (Or at least they showed several of them to us when I was junior!) They can seem a bit slow by current standards, but the films are full of great demonstrations of basic fluid mechanics. If the links on that page don’t work (or, if like me, you can’t stream RealPlayer), a lot of the videos can also be found on YouTube by searching for individual titles. The Low Reynolds Number Flow video is one of my favorites because it’s hosted by G. I. Taylor, one of the the most prolific and influential fluid mechanicians of the 20th century.