Fluid Chains

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In this video, Steve Mould tackles a question many of us have likely wondered: just why does falling water make this chain-like shape? When pouring from a slit-like orifice, water jets take on this undulating pattern. While I have no issue with Steve’s explanation of surface tension oscillations driving the shape, I’ll quibble a little bit with the idea that this hasn’t been studied. Personally, I’d connect it to the fishbone instability, which classically occurs when two jets collide. At low flow rates, though, the colliding jets form a pattern very much like this one. And if you look just past the initial conditions at the container opening, all of these flows have thicker jet-like rims colliding. I think the flows in these videos are just a slightly messier version of the low-flow-rate fishbone. What do you think? (Video and image credit: S. Mould)

  1. Jeremy Hughes

    This phenomenon is strictly related to the nozzle and little to do with surface tension. As you said, “we have to make sure we get the nozzle right.”

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