Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why does gravity cause secondary flow in pipes?

  1. Feb 14, 2010 #1
    In a straight pipe flow, secondary flow patterns (i.e. perpendicular to the axis of the pipe) arise due to gravity in the form of two counterrotating vortices (or so I heard).

    But why is the dynamics at all changed in the presence of a gravitational field? Why isn't the pressure just modified in such a way that gravity is effectively cancelled? Gravity is a conservative force after all, so can be written as the gradient of a scalar field. Why isn't this scalar field just added to the pressure, resulting in a modified pressure, leaving the dynamics unchanged?

    Is this a stability issue, with the sketched scenario possible, but unstable?
     
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted