A machine which generates bubbles with variable flow rate, sizes, colours (possibly fog filled), for observing air flow in various situations, and generally making an awesome bubble show.

Current air flow visualization machines mainly seem to use a stream of fog. I have noticed some bubble based machines for observing liquid flow. Spaced bubbles would be good because they'd allow you to track individual points as well as direction of flow.

How it might be made (just some ideas): a bubble wand supplied by a gas hose and a bubble-solution hose, and some control cables. The gas hose is attached to a compressor which can send variably mixed coloured gas down the hose at various flow rates (so you can computer control the colour and flow rate of the gas coming out of the compressor in real time). The fluid hose pumps fluid to the wand, perhaps with a mechanism for changing the viscosity of the fluid (this might be part of the mechanism for regulating bubble size). The bubble wand would have a series of computer controlled valves, which could control their diameter rapidly (perhaps this would help with bubble spacing and size). There would probably have to be some venting mechanism somewhere to prevent bad pressure variations in the gas hose.

A really nice refinement would be to have these computer controlled valves mounted in the hose itself, so that a bubble wand could be a relatively cheap item, which you just route the hose around, then you could have all sorts of shapes of bubble wand, from a straight line, to big circles or squares, or whatever.

I got the idea when I was on a rocky exposed bit of coast, and I had some children's blowing bubbles. The bubbles were really wild in the chaotic coastal air, and watching them really gave an idea of what the air was doing. A machine which had more and better bubbles would obviously make things even more obvious.
-- conskeptical, Aug 30 2007

soapscreen Soap_20Screen
one of my own favs [xenzag, Aug 30 2007]

Visualizing Airflow with Helium Bubbles http://www.sbse.org...AlShaaliKoenig1.pdf
Baked at UCLA/USC [csea, Aug 30 2007]

Particle Image Velocimetry http://acoustics.op...t_navaei_thesis.pdf
PIV, LDV, LDA, LSV are variants of the same technique. [csea, Aug 30 2007]

Commercial Source for Bubble Generators http://www.sageaction.com/
Where to buy one. [csea, Aug 30 2007]

the problem with bubbles is that they burst. In a closed environment, you could have neutrally bouyant helium polystyrene balls (made in the presence of helium rather than air), possibly even flourescent.

Apart from the practical applications, it would be cool to be in a room of these (probably with a mask and goggles). You could even wear a slightly charged wire mesh suit with switchable polarity to attract and repel the balls at will (if he was with you).
-- marklar, Aug 30 2007


bursting bubbles would only be a problem if too large a proportion of them were bursting.

Additionally, as a way of keeping packets of fog coherent until burst-time, the bubbles could be quite interesting too...
-- conskeptical, Aug 30 2007


yeah, I'd like to see videos of party balloons filled with various fogs/smokes being burst. How would different types of fog/smoke react to the tearing balloon material? Sounds interesting.
-- conskeptical, Aug 30 2007


[marklar] Careful choice of bubble mix can make bubbles last quite a long time, as long as the air movement isn't too violent - I don't think this would be very useful in a supersonic wind tunnel.
-- Cosh i Pi, Aug 30 2007


It probably deserves a better name [conskeptical] - nice idea +
-- xenzag, Aug 30 2007


I've added a couple of [links] that show the state of the art in looking at introduced particles to visualize fluid flow. I reviewed this field a few years back, hoping to be able to image acoustic waves in a room.

It turns out that the displacement of particles in air in a soundfield is inversely related to frequency, so that only at quite low frequencies could this be practical. (There is also the problem of the large "near dc" component, the airflow caused by convection, air conditioning, etc.)

It's amusing to note that one person's "noise" (i.e. these relatively large airflows superimposed on the tiny vibrations caused by sound) can be another person's "signal" (the macroscopic airflow.)
-- csea, Aug 30 2007



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