🚀 go-pugleaf

In article <1992Dec17.221424.6404@nmt.edu> houle@nmt.edu (Paul Houle) writes:

> Is there any reason why [cavitation] couldn't be done in, say, liquid D2?
> Would the ultrasound necessarily vaporize the D2 before the cavitation
> process is set up?

I didn't give my answer to this one earlier, but it's a good question.

The UC paper gives the basic approach I'd take to answering it, which is
that to the degree that you can keep the vapor pressure down and surface
tension up, you should be able to get proportionately good UC effects.  The
absolute temperature (low in this case) shouldn't matter all that much
except as it affects these other two issues.

So your best bet would probably be to keep the D2 as cold as you can without
freezing it.  (Actually, that would apply to nearly any liquid at whatever
temperature range, at least according to what I've laid out in the UC paper.)

A general problem with such cold-gas liquids is that the Van der Waals forces
that hold them together are not very intense, so that the void surface will
tend to vaporize pretty quickly.  Without specific numerical models and some
baseline experimental data, it'd be hard to say the degree to which such
issues would affect the final result.

I'd say it would be an interesting experiment if you could set it up.

I would agree that the ultrasound heating could make it hard to keep at it
for very long, but then you might not need too many cycles just to check it
out for luminescence and/or UC effects.  You might also flow the liquid D2
throught the chamber (preferably at a modest rate) to provide cooling.

Also, you could probably get away with less intense ultrasound that might
reduce the heating problem.  That's because the Van der Waals intra-fluid
bonds of D2 should be easier to to rupture and stretch than the hydrogen
bonds of water.

				Cheers,
				Terry