Physicist Lord Kelvin may be right about thermodynamics, fluid dynamics, electronics, and his successes in engineering, stellar evolution and life cycles, analysis of asymptotic functions, and kinetic energy. But his theory of the movement of small objects rotating in water, seems wrong.
In 1871, a scientist whose real name was William Thompson suggested the existence of a particular shape, an ‘isotropic helicoid’ which he said would rotate naturally when dropped into a liquid.
He describes what this thing is like. For 150 years, his idea was described as an elegant illustration of the power of symmetric analysis. The idea was so convincing that, apparently, no one really tested it.
Quoted from IFL Science, Wednesday (4/8/2021) many Victorian mathematicians may be shocked after a group of modern physicists finally tested Kelvin’s guess and it appears he was wrong.
"Although symmetric analysis showed that the particles should begin to rotate as they precipitate, we did not detect a rotation-translation coupling in our experiments. This raises the question of whether Lord Kelvin's original argument was flawed," concluded the team whose research was published in Liquid Physical Studies
Following instructions based on Lord Kelvin’s theory, the 3D team printed five small isotropic helicoids, namely spheres with a number of ‘fins’ placed on its surface, at angles of 90 and 45 degrees to the center circle.
The key to its shape is the properties that look the same from any angle. It is the ‘isotropic’ part of the ‘isotropic helicoid’. The team varied the size and shape of the fins for each of the five experiments, but all produced the same results: none were proven.
According to Kelvin’s initial hypothesis, what should happen when a helicoid is dropped into a liquid is, it will start to rotate, because the strange shape interacts with the dynamics of the liquid surrounding it. The deeper it sinks, the faster it falls.
But what actually happens when a helicoid is dropped into a liquid, especially silicone oil, is that it falls to the bottom without spinning at all. In fact, the researchers suspect that the anticlimactic properties of their experiments may be the reason why we don’t see others trying them.
"In Kelvin's manuscript, he explicitly describes how to make an isotropic helicoid, including the materials that will be used, showing that he made it," said study leader Greg Voth.
"I personally suspect that Kelvin and others have since produced isotropic helicoids and have seen that the measured translational-rotational couplings are determined by fabrication quality constraints, and therefore, they do not publish measurements."
According to the researchers, the problem is that the ‘translation rotational coupling’, which refers to the interaction between fluid and form, is too small to be seen. Using Mathematical modeling, they found that most of the torque (rotational force) produced by the fins failed to be carried over the helicoid. That means, overall, only a small amount of torque is developed, and it seems that Kelvin’s hypothesis has failed.
But with some modifications, according to the team, Lord Kelvin’s reputation can still be saved. They are now working to optimize the design of the helicoid so that its rotation can be measured. “We made a small clutch, but it’s still there,” Voth said.
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