Research

Liquid Antispiral

Spiral formations are common in nature, from galaxies to chemical reactions. But most examples in nature rotate such that their arms trail the direction of rotation. Viewed side-on, this makes the arms appear to spiral outward from the the center. The opposite – an antispiral, where the arms appear to be drawn in toward the center – also exists, but there are far fewer examples. Which is why it’s notable that physicists have described a new one, seen above.

You’re watching silicone oil draining through a plate with an array of holes in it. There’s a reservoir of oil on top supplying a constant flow rate. The patterns that form in this system vary widely – they can form between one and six arms – but the results are always antispirals. The driving mechanism seems to be the periodic nature of the discharge from individual holes, which is caused by a Rayleigh-Taylor instability. Hopefully systems like this can shed some light on why spirals are often preferred over antispirals. (Image and research credit: H. Yoshikawa et al.; via APS Physics)

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