garage19
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 posted on 31/3/08 at 03:07 PM |
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Anybody good with fluid/gas dynamics?
What i need to know is are the properties of air flow effected by how many atmospheres of pressure it is under?
Or does air flow behave the same at atmopheric pressure as it does at twice atmospheric pressure?
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02GF74
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| posted on 31/3/08 at 03:38 PM |
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that is quite a tough questions.
air flow is due to difference in air pressure, the bigger the difference, faster it flows.
now depending on what it is flowing through - e.g. pipe diameter, shape, surface etc. flow can be turbulent or laminar flow so yes, the flow
changes.
dunno about the your specific question.
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Mr Whippy
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| posted on 31/3/08 at 03:41 PM |
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Depends on what your characteristics you’re interested in, viscosity would increase as would friction as would the momentum of the gas stream. I don’t
think turbulence changes much as aircraft wings are often tested in water and aircraft stall at 15 deg regardless of air density (just at lower wing
loadings for thin air)
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Macbeast
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| posted on 31/3/08 at 03:47 PM |
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I'm guessing, but since air is elastic, when it's under pressure it occupies a smaller volume therefore the molecules are closer together.
This would make its "viscosity" higher so it would require more effort to move it through a constriction.
You would also have to consider the heating effect, assuming the heat of compression is not removed as in, eg an intercooler.
But I gave up at enthalpy and entropy and did social studies instead 
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garage19
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| posted on 31/3/08 at 03:54 PM |
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I'm looking at even flow between cylinders in an inlet manifold.
For example if you had a manifold that gave nearly equal air flow to each port at less tahn one atmosphere would that equal flow change if you put
that airflow under a bar of pressure such as in a turbocharged application?
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Mr Whippy
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| posted on 31/3/08 at 04:07 PM |
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oh I see where your going with this, would the flow take a different path through the manifold, slightly but only in area's that are open, not
in a tube. I doubt you'd ever notice, I use to deal with the flow of mud through offshore drill bits and the calculations (computer handled
these  ) had to take into account the muds density
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Rob Palin
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| posted on 31/3/08 at 04:32 PM |
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In answer to the original question, yes, flow physics for air is identical between 1 and 2 atmospheres - it doesn't go all funky until much more
extreme highs/lows than that.
Will it give the same pressures? All other things being equal, yes, but they most probably won't all be equal if you've changed the
intake length & pressure-inlet conditions. I have no idea how much of a difference that would make, however. There are incredibly sophisticated
ways & means of working it out, but you're probably better just giving it a go and seeing what happens. Sorry. 
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britishtrident
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| posted on 31/3/08 at 06:41 PM |
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Speed of sound in the manifold will change also but shouldn't affect the flow balance much if at all.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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