https://www.youtube.com/watch؟v=iiBpUIStTe0
Slow-motion video of boiling ice, a research project of the Laboratory of Nature-Inspired Fluids and Interfaces at Virginia Tech.
Sprinkle a few drops of water on a very hot pan, and it will soar into the air, sliding around the pan with a wild abandon. Physicists at Virginia Tech have discovered that this can also be accomplished by placing a thin, flat disk of ice on a heated aluminum surface, according to new paper Published in the journal Physical Review Fluids. The problem: There is a much higher critical temperature to be achieved before the ice disk can rise.
as we are I mentioned earlier, in 1756, a German scientist named Johann Gottlob Leidenfrost mentioned noticing it for the unusual phenomenon. He noted that water usually splashes onto a very hot pan and evaporates very quickly. But if the pan’s temperature is well above the boiling point of water, “shiny mercury-like droplets” will form and fly across the surface. called “Leidenfrost effect in honor of him.
In the next 250 years, physicists came up with a viable explanation for why this happened. If the surface is at least 400 degrees Fahrenheit (well above the boiling point of water), cushions of water vapor or steam form underneath, keeping it raised. The Leidenfrost effect also works with other liquids, including oils and alcohol, but the temperature at which it appears will be different.
phenomenon still mesmerizing Physicists. For example, in 2018, Discovered by French physicists That the drops not only run on a pillow of steam; As long as it’s not too big, it also pushes itself. This is due to an imbalance of fluid flow within the Leidenfrost droplets, act like Small internal drive. The large drops showed a balanced flow, but as the drops evaporated, becoming smaller (about half a millimeter in diameter) and more spherical, an imbalance of forces occurred. This caused the droplets to spin like a wheel, aided by a kind of “ratchet” effect of tilting downward in the same direction as the fluid flowing in the drop. French physicists called their discovery “the Leidenfrost wheel”.
In 2019, an international team of scientists I finally determined the source From the accompanying cracking sound reported by Leidenfrost. Scientists found it It depends on the size of the drop. Smaller drops will slide off the surface and evaporate, while larger drops will explode with this apparent fracture. The culprit is particle contaminants found in almost any liquid. Larger droplets will start with a higher concentration of contaminants, and this concentration increases as the droplets shrink. They end up in such a high concentration that the particles slowly form a kind of crust around the droplet. This projectile interferes with the steam cushion that holds the droplet high, and explodes when it hits the surface.
And last year, MIT scientists determined why droplets are propelled across a hot oil surface 100 times faster than exposed metal. Under the right conditions, a thin layer formed outside each drop, like a mantle. As the droplet became hotter, small bubbles of water vapor began to form between the drop and the oil, and then moved away. Subsequent bubbles typically formed near the same spots, forming a single vapor path that would propel the droplet in the preferred direction.
But can you achieve the Leidenfrost effect with ice? That’s what the Virginia Tech team set out to find out. “There’s a lot of paper around liquid lifting, we wanted to ask a question about lifting ice,” Co-author Jonathan Borico said:. “It started as a curiosity project. Our research was motivated by the question whether it is possible to obtain a three-phase Leidenfrost effect with solid, liquid and vapor. “
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