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Momentum balance derivation in equations

  1. Nov 21, 2012 #1
    I'm a little confused, in my fluid mechanics course we've covered many equations and they are all derived using an x-direction fluid flow. If I was to use these in a system in which fluid flowed in the y-direction would I have to re-derive them? Or would it be more of a case of using a horizontal system in a vertical direction?
  2. jcsd
  3. Nov 21, 2012 #2


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    Welcome to PF!

    Hi Fishinev! Welcome to PF! :smile:
    Do you mean that the entire flow is horizontal, so that gravity doesn't have to be taken into account?

    In that case, if you want to apply the equations to a vertical system, you'll need extra (ρgh) terms to deal with gravity.
  4. Nov 21, 2012 #3
    If this is a gas dynamics question you can usually ignore body forces such as gravity at chemical engineering scales.

    If this is a liquids questions then a body force such as gravity may well come into play.

    Remember in chemical engineering other body forces are often also in play.
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