Spinning Tops

Flow around a spinning top.

What does the flow look like around a spinning top? Here, researchers used dye to visualize what happens in a Newtonian fluid (like air or water) as well as a viscoelastic fluid. The Newtonian fluid (upper images) divides into two circulating zones, one below the top and one above. They both take the shape of a toroidal, or donut-shaped, vortex, visible here in cross-section.

The long molecules of the viscoelastic fluid lend it elasticity to resist stretching. The result is a very different flow field. Beneath the top, there’s still a toroidal vortex, though it appears tighter. But around the upper part of the top, there’s a butterfly-like region of recirculation! (Image credit: B. Keshavarz and M. Geri)

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