Non-Newtonian Fluids / When liquids behave like solids


Like many individuals, I’ve tried very laborious to neglect my days in junior highschool. That was an disagreeable time in my life for all the same old causes, and fortunately most of it’s now a dim blur. However just a few nice moments do stand out in my reminiscence. A type of was a report I did for my ninth-grade science class. For causes I now not recall, the subject I selected was Pascal’s Regulation, and I should have ready nicely for that 10-minute presentation, as a result of I might most likely arise and provides just about the identical speak at the moment, regardless that I by no means went on to check any extra about it.

Pascal’s Regulation describes the conduct of fluids in a closed system, and says, to oversimplify considerably, that the stress the fluids exert is all the time the identical all through the system. That is the precept that permits hydraulic presses to work—a small quantity of pressure utilized to a piston pushing down on fluid can exert way more pressure on a bigger related piston, making it kind of like a liquid lever. The identical impact has functions in every little thing from scuba diving to air flow techniques and dam development.

Pascal, Meet Fisher
Though that little snippet of data has stayed with me all this time, that marked the extent of what I knew about fluid mechanics till a pair years in the past, once I wrote an article right here about Space Pens. These pens, legendary for with the ability to write in zero gravity, in a vacuum, or in nearly every other scenario, use a particular thixotropic ink, a substance that’s usually in a gel state however which turns right into a liquid when it’s agitated—that’s, when the ball rolls in opposition to it. It’s liquid simply lengthy sufficient to stream onto the paper, after which it turns semisolid once more. (As spiffy as that’s, some House Pen ink seems to have shocking issues, which you’ll be able to examine in Space Pens with Purple Ink: A Sad Tale on I Am Joe’s Weblog.)

A number of months in the past, some very cool movies began making the rounds: individuals doing stunts with one thing known as “non-Newtonian fluids.” When you’re not an engineer, that won’t sound very intriguing, till you take a look at guys operating throughout the floor of a vat full of an answer of cornstarch and water, however sinking into it once they stand nonetheless. That’s an actual eye-opener. Or another guys taking a handful of the identical liquid goop and slapping it into strong balls, which then flip again into liquid as quickly because the agitation stops. These are simply a few the numerous wacky properties exhibited by non-Newtonian fluids—substances that change their viscosity in response to emphasize. (See 8 YouTube Videos Featuring Non-Newtonian Fluid Experiments at SenseList.) And positive sufficient, the ink from my House Pen is in the identical class.

Non-Newtonian fluids vary from the unique to the mundane. You’ve most likely made a cornstarch-and-water combination numerous instances in your personal kitchen, and if you happen to made sufficient of it, you too might stroll throughout its floor. Assuming the proportion of starch to water is correct, the answer will get all of a sudden thick and agency when pressure is utilized to it, as you might have seen when attempting to stir it when making ready a sauce. Stir extra slowly, and it flows extra simply.

Going with the Circulate
However not all non-Newtonian fluids behave this manner. A few of them get runnier when underneath stress, resembling House Pen ink and paints that adhere to a brush when at relaxation however glide on simply when the comb is utilized to a floor. Additionally within the thixotropic class in addition to in your kitchen: ketchup and honey.

There are nonetheless different varieties, too, which have totally different patterns of fixing viscosity. Such different substances as quicksand, Foolish Putty, blood, dough, and gelatin fall underneath the broad non-Newtonian heading. Against this, Newtonian fluids, or what most individuals consider as regular fluids, are these (like water) whose viscosity is set solely by temperature and stress. Positive, water will get a lot agency if the temperature is lowered sufficient, however no quantity of pressure could make liquid water behave like a strong.

The ethical of the story? When you’re caught in a non-Newtonian fluid—or junior highschool—the trick is to stay calm. The extra you battle, the tougher it will get. —Joe Kissell

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Extra Details about Non-Newtonian Fluids…

The Wikipedia has useful articles on Non-Newtonian Fluid, Newtonian Fluid, and Pascal’s Law.

The video that began the present Non-Newtonian Fluid craze is A pool filled with non-newtonian fluid on YouTube. However there are many them; see 8 YouTube Videos Featuring Non-Newtonian Fluid Experiments at SenseList.

Different assets on non-Newtonian fluids:

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