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Ideal gases and Vector calculus

  1. May 16, 2005 #1
    In my physics book, the 4 properties of an ideal gase are

    1. nonviscous
    2. steady flow (laminar)
    3. incompressible
    4. irrotational

    My question is the properties of being irrotional the same as the vector functions that have a Curl=O iff irrotational

    My physics book states the irrotional functions have no angular momentum, but my caclulus book does not give a physical defention of an irrotional function, only a mathmatical defention.

    So am I right to aqquate the two defentions to gether
  2. jcsd
  3. May 16, 2005 #2

    This sounds more like the definition of an ideal fluid, than an ideal gas.

    But your guess seems right to me. Incompressiblity implies that the flow has no divergence, so irrotational probably means no curl.

    But if this is important you should wait until somebody who knows something about fluids has a chance to answer. I don't know much about them; I'm just guessing. ;-)
  4. May 16, 2005 #3
    Oppss, hehe I meant Ideal fluid
  5. May 16, 2005 #4


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    1.An ideal gas IS AN IDEAL FLUID.

    2.Incompressible,means the density constant,by the law of mass conservation,the divergence of the convective velocity field is zero.

    3.Irrotational means that the curl of the convective velocity field is zero.

    4.Nonviscous means no friction between neighboring fluid layers.The viscosity tensor is identically zero.The kinetic tension tensor is diagonal and has one independent component,the negative of hydrostatic pressure.

  6. May 16, 2005 #5
    I thought most gase where compressable, pv=nrt...v can be compressed
  7. May 16, 2005 #6


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    So what...?

  8. May 16, 2005 #7

    Claude Bile

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    Well, there is an apparent discrepancy here, how can an ideal gas be an ideal fluid when an ideal gas can be compressed, yet an ideal fluid, by definition is incompressible.

    To the OP, some spelling suggestions;

    gas, not gase
    irrotational, not irrotional
    calculus, not caclulus
    definition, not defention
    mathematical, not mathmatical
    equate, not aqquate
    together, not to gether

    Please take the time to check your spelling, it can get frustrating for those who are trying to answer your question.

  9. May 17, 2005 #8


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    It's just a semantic thing. Gases are considered to be fluids (along with liquids). What you're describing at the top is an ideal incompressible fluid. You're right that ideal gases are not incompressible.
    Last edited: May 17, 2005
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