Blow air


I'm currently planning for an installation that needs to blow air at a hanging fabric to create some ripple effects. The software side isn't the problem here, but I would appreciate if someone could give me some advice on the hardware used to generate the air blow.

The fabric will be free hanging on wires from the ceiling and the air device needs to be hidden somewhere, so my assumption is that the air needs to pass a distance of 1-2 meters and still be strong enough to move the fabric. The fabric itself will be roughly the size of a t-shirt with similar weight and there will be multiple fabrics lined up next to each other, so the spread of the air has to be considered.

The options that I'm currently considering are:

  • A hidden air compressor with plastic hoses/pipes pointed at the fabric and controlled trough solenoids
  • Centrifugal (squirrel cage) fans directly controlled trough an Arduino. Main concern is if they are powerful enough over the discance
  • Regular, PC style, fans, perhaps stacked. Main concern again is power over distance and spread.

What do you think? Thanks

It really is going to depend on the actual effect you are looking for. Compressed air will make it is 'poof' quickly, while a fan will just provide a mostly steady current which will oscillate the fabric and will take some time to start moving.

The power over distance will depend on your baffles. If you have them tapered, the air will be more focused and have more power to travle over distance. If your fabric is very light, it won't take much at all to move it and it will probably move a lot on its own anyway.

Another option is a series of air cannons. Basically a flexible diaphragm (like a balloon) that you pull back and release quickly to send a strong poof of air.

I'm looking more for single bursts, or poofs instead of a constant blow. It should wave a similar to a flag, but only for a short time. Can't you just keep the valves open for longer to create a longer burst of air? I'm thinking of the typical DIY air compressors that you would use in your garage, and they can provide a constant airflow for some time and the compressor kicks in when the pressure falls below a threshold.

The tapering sounds interesting too, and I would probably need to build a prototype to see if they will work.

I though about the air cannons, but mechanically triggering them with an arduino sounds a bit complicated.

I suggest you set up a test rig and just point a few fans at your hanging fabric and see which ones provide the sort of air flow you need. Start with whatever you have to hand (hair drier, ventilation fan etc) and then try moving to larger or smaller fans until you find one that does what you need.

Once you've selected the fans you can start thinking about how to power and control them.

haraldini: Can't you just keep the valves open for longer to create a longer burst of air?

Of course. In practice, I am not sure it will give you the effect you are looking for. Worth experimenting with, of course.

Also, if you are looking for a rippling effect, have you considered moving your air-stream instead of using several air sources?

This type of thing is one of those that are difficult to predict exactly how it will behave, so experimentation is best as PeterH pointed out.