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About sethoflagos

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  • Birthday 10/10/1958

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    Lagos, Nigeria
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    Classical Music, Natural Science, Food Preservation, Games Theory, Laughing, Ladies, the Geological Record, Deep Time, Beer and species Rhododendron.
  • College Major/Degree
    Chemical Engineering - UMIST
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  • Biography
    As far as I remember, I got very drunk in all sorts of different places.
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    Government Advisor

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  1. On further consideration, by omitting the pressure terms from the Navier-Stokes, haven't you lost control of the conservation of energy? For a rotating system, I can visualise material falling into an equatorial disk from both sides, but there appears to be no mechanism in your system for it to cross the boundary. The momenta will just cancel (conserving momentum) but then so will the corresponding kinetic energy! Restoring the pressure term (which in context, is an expression of the system internal energy) will keep the 1st Law books straight and avoid some embarrassing infinite densities.
  2. In principle, your equations look okay given your stated constraints, but I would strongly recommend converting to polar coordinates to get as much help as possible from its symmetries. Given that your gravitational field terms are directly analogous to the pressure gradient terms in Navier-Stokes applications that I'm somewhat familiar with, you may find that at least for some simple starting conditions, the method of characteristics may help convert your PDEs into ODEs which would then be amenable to numerical integration. However, you're using Gauss' Law where I would normally b
  3. So in this viewpoint, there is no preferred (spatial) direction for any of the forces at play here. I was going to proceed to my follow-up question of what happens (to us) when there's no preferred direction for gravitational forces. But I'm now getting the feeling that you've already answered that. In that it's not about 'us' - it's about how mass acts on spacetime. And we're just little specks riding on that ebb and flow. Humbling thought. Thank you once again, Markus.
  4. Yes, that's the general picture I'm asking about.
  5. All is clear. Many thanks, Markus.
  6. I meant the necessity of the early universe itself being spatially infinite in this case as opposed to a (near) pointlike spatial singularity.
  7. My immediate thought was that cooking may convert some indigestible starch to a more digestible form. But then I started wondering how many calories you would expend in thawing out frozen chips in your stomach.
  8. Yusuf Automotive LPG is an undeveloped market in the US. In Europe it is developed a little more but nothing like as much as in the Middle East, Asia and Australia. Therefore there is little experience on this site regarding your question. Also, the proportion of propane to butane specified for each country varies with climate. In Britain and Ireland, automotive LPG is almost pure propane while some Mediterranean countries specify up to 80% butane. I don't know the standard for Iran (I had to ring a friend to check you had moved onto unleaded gasoline!) but I would expect your LPG to
  9. Engineering Databook SI Version (aka GPSA Databook), Gas Processors Suppliers Association, 11th Edition 1998 has probably helped resolve more day-to-day issues for me over recent years than any other. But most enjoyable .... probably Pump Handbook, Kurassik & al, 3rd Edition 2001. Comprehensive, very readable, more Aha! moments per chapter than you can shake a stick at. Honourable mention to 'Understanding Atmospheric Dispersion of Accidental Releases', Devaull et al.,AIChE 1995 just for the unfortunate title really.
  10. I've seen a number of references to space flowing across a black hole event horizon at the speed of light. If space can be lost in this way, what happens to the vacuum energy associated with that space? i.e. Does it increase the mass of the black hole?
  11. Many apologies for this OP as I'm sure it has been raised many times before. IFF the universe were truly infinite in spatial extent (and I appreciate the 'unknowability' aspect of this), would this imply perforce that whatever the energy density of the earliest moments of the universe, it too would have been spatially infinite? In such circumstances, would GR predict gravitational effects to be compressive, tensile or ... just undefined.?
  12. By applying an external magnetic field to the system, haven't you introduced new potential energy terms boosting the system total energy? As the magnetic particles descend this new energy gradient to a new equilibrium position how is this energy going to be dissipated other than in the form of heat? As a practical example, you might compare and contrast the removal of particulates from eg coal-fired power station flue gas by electrostatic precipitators. The pretty efficient separation of gas and solids suggests an entropy decrease, but on the other hand, electricity is consumed, and
  13. Wow! A third of a million views! Best come clean since we're under such scrutiny: After much deliberation, I've come to the conclusion that at least one of these statements is correct. A little more thought on my part at the time, and I should have realised this for which I apologise. If the premise of the OP were correct, the kinetic energy necessary for convective flow would be sourced by a reduction in internal energy of the flowing fluid (as is normal in fluid processes). No external shaft work necessary. From this it clearly follows that the OP case is a far-from-equilib
  14. Could one choose to define 'pressure exchange' as an 'exchange of gravitational potential energy'? Not clear on whether pressure is something that can be 'exchanged'. 'Propagated into another medium' for sure, but 'exchanged' usually tends to imply a conserved quantity, doesn't it?
  15. It's effectively a time reversed Coe and Clevenger test - the progressive fluidisation of a packed bed of buoyant particles rather than the more industrially significant progressive compaction of denser particulates from a suspension. I agree with joigus that it's not saying anything significant about pressure here. No measurements seem to be taken so I question whether it's actually saying anything about anything.
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