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Fluid Mechanics - terminology

  1. Jul 5, 2007 #1
    Hi, I'm just trying to get a feel for a subject that I plan to take but I'm unsure about the meaning of a certain term which frequently arises.

    The term 'flow' comes up a lot and I'm wondering what it could mean (or refers to) in the context of a pipe flow problem. I know my question is vague but as an example if I'm given a PDE (for the function u(z,t) say) for a pipe flow problem, what am I actually solving for? Would u(z,t) be the velocity of the fluid? Any help would be good thanks.
    Last edited: Jul 5, 2007
  2. jcsd
  3. Jul 6, 2007 #2


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    This is kind of tough to answer because a "flow" problem can mean different things to different people.

    In your case of the PDE, u is "usually" reference for velocity in one of the 3 orthogonal directions. In Navier-Stokes equations, the notations are [tex]u_{x}, u_{xx}, u_{y}, u_{yy}, u_{z}, u_{zz}[/tex] and [tex]u_{t}[/tex] for for the x direction equation. The corresponding notations for y and z directions are v and w. These are all velocity vector components. Eventually, one would have to integrate their velocity profile over a surface area to come up with a volumetric flow in the case of something like flow in a pipe.
  4. Jul 8, 2007 #3
    Thanks for the explanation.
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