Naked Science Forum
General Science => General Science => Topic started by: Abi on 28/04/2019 03:40:10
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Hello,
I understand sound can be attenuated by a cloud of liquid droplets, to some extent. Please is it possible to create fog by using acoustic levitation?
Thank you.
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Hello,
Please is it possible to create fog by using acoustic levitation?
Thank you.
Sound waves, particularly ultrasonic can disrupt the surface of water creating small water droplets which are thrown up and create a fog. Not levitation as such because the droplets are not repelled by the surface.
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It's fairly common to illustrate acoustic levitation with water drops, but typically that's just one drop or a handful.
A fog would require billions of drops and there's no easy way to get a sound pressure gradient that would hold them all up at the same time.
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Further to the point form @Colin2B I've seen water features at a local garden centre that comprise what I presume to be an acoustic mist generator. It produces a cold "fog" that hovers above the water for a while before dispersing. I suspect that high frequency sound waves are used to surmount the surface tension to produce smaller water droplets and these are temporarily suspended on local air currents.
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Further to the point form @Colin2B I've seen water features at a local garden centre that comprise what I presume to be an acoustic mist generator. ....
Yes, it is. Water is often passed over a vibrating plate which break up the water into fine droplets, often the same system is used in household humidifiers.
As you say, these droplets are small and light enough to drift on local air currents.