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