Isotropic helicoid

{{short description|Helical shape with equal rotation and drag in all orientations}}

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In fluid dynamics, an isotropic helicoid is a shape that is helical, so it rotates as it moves through a fluid, and yet is isotropic, so that its rotation and drag are the same for all orientations of the particle. It was first proposed by Lord Kelvin in 1871, who described a specific geometry with twelve vanes placed around a sphere.{{cite journal |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |volume=42 |issue=281 |date=1871 |pages=362–377 |title=Hydrokinetic solutions and observations |author=William Thomson |url=https://www.tandfonline.com/doi/abs/10.1080/14786447108640585 |doi=10.1080/14786447108640585 |access-date=13 October 2021|url-access=subscription }} As of 2021, such a phenomenon has yet to be proven by researchers.{{cite web |last=Crane |first=Leah |title=Strange 3D-printed shapes test 150-year-old mathematical theory |website=Newscientist.com |publisher=New Scientist |date=16 July 2021 |url=https://www.newscientist.com/article/2284174-strange-3d-printed-shapes-test-150-year-old-mathematical-theory/ |access-date=10 August 2021}}