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Dribbling teapot enigma solved

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October 27, 2009

Science has helped defeat the dreaded 'teapot effect' and dribbling teapots (left) could b...

Science has helped defeat the dreaded 'teapot effect' and dribbling teapots (left) could be a thing of the past

You may not be entertaining the Queen of England but when pouring someone a cup of tea from a proper teapot it’s annoying, nay embarrassing, when the tea drips down the spout and splashes into the saucer or onto the cucumber sandwiches (well, at least a plate of biscuits). French scientists know this feeling only too well and have employed technology to put an end to this horrendous social faux pas.

The “teapot effect” is the less than imaginative term given to items which exhibit the nasty problem of dribbling, particularly at low flow rates. At higher flow rates, flow separation occurs where the layer of fluid closest to the boundary becomes detached from it and the fluid flows smoothly over the lip. But as the flow rate decreases, the boundary layer re-attaches to the surface causing dribbling.

But a full and thorough scientific explanation of why this happens has so far eluded scientists. Previous studies have shown that a number of factors affect this process such as the radius of curvature of the teapot lip, the speed of the flow and the "wettability" of the teapot material.

Now Cyril Duez at the University of Lyon in France and his colleagues have identified the single factor at the heart of the problem and shown how to tackle it. They say the culprit is a "hydro-capillary" effect that keeps the liquid in contact with the material as it leaves the lip. The previously identified factors all determine the strength of this hydro-capillary effect.

To overcome it Duez says first you must make the lip of the spout as thin as possible. Then coat the lip with the latest generation of superhydrophobic materials that strongly repel water. And, presto - no more damp sandwiches!

Putting teapots aside, there are probably a few more applications for Duez’s discovery and other scientists will surely be interested in his results. For instance, in certain materials the hydro-capillary effect can be controlled electronically, meaning dribbling can be turned on or off. Can’t think of an application myself, but there must be plenty out there.

Via MIT Technology Review.

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10 Comments

face it : there are nations who just can't pur tea properly :)

(I think that the effect is connected to tea dried to the underside of the funnel too)

Károly Hőss
28th October, 2009 @ 02:45 am PDT

If you are that shallow to have something like a drip on a tea spout set you off, then you need to reassess your life and determine what is truly important to you...because really, in the grand scheme of things, a dripping tea spout is trivial.

ed

Ed
28th October, 2009 @ 10:03 am PDT

Or, you could just do what the Chinese figured out thousands of years ago.....

Drill a hole under the spout, no more dribbles.

Chris Maresca
28th October, 2009 @ 02:58 pm PDT

What a waste of time. Universities are strange places sometimes.

hughmama
28th October, 2009 @ 06:49 pm PDT

@Ed: I would disagree. Sometimes, in the REALLY grand scheme of things, solving some of these little "trivial" questions can lead to big breakthroughs in science and technology.

Like the engineer who noticed a soft candy bar in his pocket standing next to a radio antenna... who cares? He took the time to figure out this "little" curiousity, and it reaped huge rewards, and we now have microwave ovens for energy and time-efficient cooking for billions of people.

Or how about the doctor who saw how a laser was being used to shape silicone computer chips? He went away in wonder, and ended up patenting the excimer laser for refractive eye surgery. A little idea with huge rewards for himself and society.

The examples are endless... so I'd be careful about berating anyone's scientific endeavors and judging them from your own, dare I say shallow?, perspective.

Sincerely,

Dr. Rings, MD

matthew.rings
28th October, 2009 @ 11:54 pm PDT

good comment Dr Rings !

robinyatesuk2003
29th October, 2009 @ 02:38 am PDT

She is not the 'Queen of England' but is the Queen of the United Kingdom! England is only one quarter of the UK!

Terry Pardy
30th October, 2009 @ 12:58 am PDT

... which does makes her the Queen of England then.

Si Lowe
31st October, 2009 @ 11:40 am PDT

Dr. Rings, you're spoton. i wouldn't have put it better myself. it is still too early for anyone to "throw away" the discovery. The concept of the Fax machine was thus thrown away and many many years were lost until it picked up again all because someone felt the technology was shallow. When the japanese came into the scene it became a cornerstone of communications and has stood the test of time...Shallow? No! Fact is what we know now is equal to the tip of a needle and what we don't know is equal to a giant iceberg.

Moiseraela
2nd November, 2009 @ 12:47 am PST

Surely the answer is to have the lip of the spout hang over, in the way that you have a groove under a window sill. The liquid will not flow upwards.

Looking at the photo, I wonder how the water is dripping from the spout, as the pot is horizontal, and why is the liquid flow different in the two pictures?

windykites1
7th July, 2010 @ 04:01 pm PDT
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