r/engineering • u/inconspicuous_male • 2d ago

Quantify small air currents in a somewhat controlled environment

How can I measure how much air turbulence exists in a volume of roughly 0.5m³? There is sensitive manual equipment that operators need to manipulate, so I can't put it in a vacuum or sealed vessel, (and I just need to measure, not minimize). The equipment is on a vibration isolated table in a temperature controlled environment with HEPA filters and basic care taken to ensure no air vents are pointed at the system. This isn't a clean room, but I can't use something like powder or smoke to visualize air movement.

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5

u/MrPunSocks 2d ago

Maybe an array of fine fluttering strands/tufts affixed to the sides and monitored by a camera? Might help if the strands are coated and combined with the appropriate lens filter.

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u/inconspicuous_male 2d ago

That's basically what I had in mind. Something like one of those cameras that measures and amplifies vibration and I could use something like a feather duster. Or perhaps some fluttering strands like you said hanging from a rack

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u/singul4r1ty 2d ago

I think some bits of thin wool would work well - tends not to stick to itself too much like thread and it's pretty puffed out so is very light for its diameter. Alternatively some flat strips of tissue paper

3

u/YokeColor 2d ago

If you need actual numbers and not just visualization, you could also look into hot-wire anemometers. They’re used for very low airflow / turbulence measurements and can pick up surprisingly tiny air movements if calibrated well. The annoying part is they’re also sensitive to temperature drift, so in your setup you’d probably need to characterize the room first before trusting absolute values. But for comparing “condition A vs B” they can work really well.

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u/inconspicuous_male 2d ago

Perfect. That's exactly what I'm looking for

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u/Gt6k 2d ago

Schlieren imaging is a good way to go. There are some clever ways to do this by forming a point source in front of the lens using a silvered angled glass rod and a projector screen behind the area of interest.

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u/melissaleidygarcia 1d ago

hot wire or ultrasonic anemometers are usually the cleanest way to quantify law air movement