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#1
Old 04-10-2008, 10:47 AM
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Floating water Droplets? What's the Explanation?

I was sitting in the car, watching the raindrops fall..and noticed that drops of water were flying over the wet surface of the hood. My question-are these droplets being repelled by an electrostatic field? I suppose the drops could pick up a negative charge, and if the water surface is also negatively charged, then the droplets would be repelled-explaining the motion I observed.
Anybody know about this phenomena?
#2
Old 04-10-2008, 11:22 AM
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Quote:
Originally Posted by ralph124c
I was sitting in the car, watching the raindrops fall..and noticed that drops of water were flying over the wet surface of the hood. My question-are these droplets being repelled by an electrostatic field? I suppose the drops could pick up a negative charge, and if the water surface is also negatively charged, then the droplets would be repelled-explaining the motion I observed.
Anybody know about this phenomena?
Youd need a big fricking electromagnetic field to levitate that many water droplets, Id guess that what youre seeing are drops bouncing off the hood.
Did you see individual droplets actually levitating for some time or just a layer of droplets some distance from the surface?
#3
Old 04-10-2008, 11:26 AM
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What you were seeing are probably air bubbles that sometimes form when a raindrop hits water. However, your lack of a good description of the phenomenon makes it difficult to say.
#4
Old 04-10-2008, 11:39 AM
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Do you mean how the water follows the airstream when the car is in motion? Or are you talking about something happening when you are stopped?
#5
Old 04-10-2008, 11:40 AM
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Quote:
Originally Posted by Q.E.D.
What you were seeing are probably air bubbles that sometimes form when a raindrop hits water. However, your lack of a good description of the phenomenon makes it difficult to say.
Not air bubbles.
I've seen this many times. If you direct a stream of water into a pool of water, at just the right volume / velocity, the stream will break up when it hits the surface, and little balls of water will go skittering across the surface. Some of them can last for quite a while (seconds), before they "pop" and get absorbed into the body of water.

Last edited by beowulff; 04-10-2008 at 11:40 AM.
#6
Old 04-10-2008, 11:44 AM
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Water surface tension. Until that breaks the droplet remains on its own.
#7
Old 04-10-2008, 11:49 AM
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Oh, are you just referring to beading? If so, see surface tension
#8
Old 04-10-2008, 08:48 PM
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Quote:
Originally Posted by beowulff
I've seen this many times. If you direct a stream of water into a pool of water, at just the right volume / velocity, the stream will break up when it hits the surface, and little balls of water will go skittering across the surface. Some of them can last for quite a while (seconds), before they "pop" and get absorbed into the body of water.
There was a really cool photo of something like this in Science News last July 28th. Unfortunately, it's a subscriber-only link. It shows a stream of oil falling into a rotating pan of the same stuff. The stream "bounces" twice, forming a couple of arches like a sea serpent before finally slipping in past the surface tension.

The paper describing it is supposed to be in Physical Review E.

When I read the OP, though, I thought he meant the droplets were floating in air above his hood. I don't think I've seen that, unless the car was moving and they were caught in laminar flow above the turbulent air?

Last edited by mwbrooks; 04-10-2008 at 08:50 PM.
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