a Stagnation flow

Beyond Simple Coiling

Runny fluids, unlike the thick, viscous kind, are able to do much more than just coil. In these examples, the authors used oils with viscosities from 400 to 6,000 cSt—runnier than honey but thicker than water.

a Stagnation flow. For relatively low viscosity, short fall heights and high flow rates, the fluid falls straight down and spreads out equally in all directions over the plate. These conditions apply to common household fluids such as water and olive oil. That said, even these fluids can be made to coil under the right conditions. If you could pour olive oil from a height of 10 cm at a rate of 1 mL over 40 minutes, it would coil.

b Rotary folding. The rope folds back on itself periodically while the entire folding pattern itself rotates about a vertical axis, creating a twisting effect.

c Supercoiling. Supercoiling is the technical term for what happens to twisted telephone cords, which experience large secondary coiling on top of the tightly coiled structure they already have. In the case of fluids, the descending stream creates a hollow cylinder, which in turn coils as a whole. The secondary coiling is more sedate, occurring about a tenth as fast as the primary coiling.

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a Stagnation flow

Damien Ropero


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