In reply to Grimer's message of
Thu, 04 May 2006 19:05:19 +0100:
Hi Frank,
<snip>
(Grimer wrote)
> I would think that you do. I see the current as putting
> the equivalent of a mechanical stress on the water and
> "cracking" it open. These cavitation cracks could be at
> negative pressures of up to 60,000 psi.
Where do you get 60,000 psi from?
Regards,
Robin van Spaandonk
I thought you would never ask. <g>
But since you have, let me regale you with an
excerpt from our Southampton Conference paper,
an opus so brilliant that one of the delegates
approached us at the conference dinner and said.
"That paper of yours. It was a hoax, wasn't it?"
We nearly wet ourselves, laughing. 8-)
=================================================
GRIMER, F.J. and R.E.HEWITT. The form of the
stress-strain curve of concrete interpreted
with a di-phase concept of material behaviour.
Structure, Solid Mechanics and Engineering Design.
Proceedings of the Southampton 1969 Civil
Engineering Conference. (M.Te'eni, Ed.),
Wiley Interscience, pp 681 - 691, 1972.
EXCERPT
----------------------------------------
6.3. The Relation between Pressure and Volume
of Water at Constant Temperature
----------------------------------------
In a 'solid-fluid' hierarchical system both the
nth order 'solid' and 'fluid' components can be
considered as materials comprised of 'solid' and
'fluid' components of the (n + 1)th order.
For example, in a clay-water system the clay
particle structure and the water are the quasi-
'solid' and quasi-'fluid' of the first order.
Dropping a hierarchy and considering next the water,
the water molecules and the van der Waals space
are the solid and fluid components of the second
order. If this concept is valid then the van der
Waals space can be treated as a fluid in a high
state of tension and the water molecules as a
skeletal structure in a balancing state of
compression. An external stress on the water
will be added to the internal stress to give
a total stress and this value of total stress
will act upon the skeletal molecular structure.
Since the model postulates that the behaviour
of each hierarchy is essentially similar.
It follows that all physical relations measured
from true origins must have the same mathematical
form whether they are the product of a single
hierarchy or a combination of hierarchies,
i.e. they must all be power laws. Therefore let
us assume that the relation between total stress,
P, and total volume, V, for water is of the form
P = - k.V^n
where P = p + i, and
p = external stress and
i = internal stress applied by van der Waals fluid
whence,
(p + i) = -k.V^n
log(p + i) = -(n log V + log k)
dp/(p + i) = -n(dV/V)
Therefore by plotting V(dp/dV) against p it
is possible to determine both n, the power
of the relation, and the negative intercept
i, the internal stress. This was done for
water using Bridgman's data taken from the
International Critical Tables
(Bridgman. 1928) which gives the relation
between pressure and volume for water up to
pressures of 12.000 atmospheres. It was found
that n = 6 and that the internal pressure was
of the order of thousands of atmospheres.
The relation for 60C between the total pressure
(taking the internal pressure as 3750 atmospheres)
and the experimental points is so good (Figure 8}
that it is necessary to show the deviations
between the calculated and the actual values by
a subsidiary graph in which the deviations are
magnified by a factor of 10. Also. the fact that
the power is an integral value suggests that the
underlying mechanisms are relatively simple and
the analysis of the relation into simpler parts
should not be too difficult.
=================================================
You will find the full Monty in the File Section at,
http://groups.yahoo.com/group/Beta-atmosphere_group/
Cheers,
Frank
