Granular Liquid (Hints requested)

[easyCoder]

I am going to attempt a largish scale granular liquid experiment, involving very light granular material (e.g. ping pong balls, or styrofoam peanuts)

 

For a 6ft diameter pool filled 1ft deep of material, I am in the process of estimating how much vibrating power I'll need.

 

QUESTION: Must I sit the pool to a vibrating bed ? Or can I use speakers and rely on the sound waves propagating through the material and air gaps ? I assume this will be a function of power.

 

In experiments I have done so far, the resonance of the container is a dominating factor in getting the material to liquify, something I wasn't expecting. This is not to say that resonance of the material is irrelevant, I removed the container and found that material resonance is an important factor as well.

 

I also found that perfect resonance does not produce the most interesting effects. Best effect is a little off.

 

Resonance Questions

 

I am concerned that resonance will be the bugbear in this setup. Will the airgaps have resonance ? Will resonance change depending on volume of material ? Should I go for container resonance or material resonance if I have to pick one ? How much variance in resonant frequency can be realistically expected from a nonidentical material filler (like styrofoam peanuts) and how will this affect how much power I will need ? etc.

 

I would appreciate anyone with experience in this to offer some tips.

[insane_alien]

this may just be due to me being a chemical engineer but i think you would be better going for the fluidized bed approach to this, have a steady stream of air injected at the bottom of the bed and in a certain velocity range it will fluidize giving the same effect as agitation by vibrations.

[CaptainPanic]

I'm afraid that insane_alien is onto something: most people with experience in fluidization will have experience with air/gas flows going up through a bed of particles... because that's what is used in industrial application in chemical engineering.

 

The question that you are looking to answer is: how to scale up the previous version?

You already made a vibrating bed of liquidized (fluidized) particles. So, does power increase linearly with bed thickness? Does it change linear with the surface area (diameter ^2)?

 

I'd guess that the 2nd question is answered "yes". Bigger area means equally bigger power.

The thickness... I tend to say that it's linear with the thickness as well... or (assuming constant density) weight.

 

Therefore the power you need is a function of the volume: go form 1 m3 to 2 m3 of volume, you'll need twice the power.

[insane_alien]

I'm afraid that insane_alien is onto something

 

everybody should be afraid when i'm onto something

[easyCoder]

Hmmm.....

 

OK, I intend for people to immerse themselves in the pool, as a totally interactive exhibit (and for completely non-industrial purposes)

 

I have considered pumping air, but I wanted to go for effect, and thought that pumping 22Hz (with maybe some 100Hz overtones) through 4x400W speakers might be good effect.

 

It has the side benefit of providing a lovely relaxing vibrating massage machine effect.

 

Air would be more like a jacuzzi, itself a great thing to have, but... it's been done with water....

 

Air is NOT out of the question but I'd like to get it to work with speakers.

 

Is there hope for me ?

[Mr Skeptic]

everybody should be afraid when i'm onto something

 

I'm more afraid when people suggest using really loud sound to massage.

[CaptainPanic]

Is there hope for me ?

 

Read my post about scaling up your design. You had a working small scale design, didn't you?