title: COMSOL 2 phase flow volume fraction of fluid always 1
body: <p>I am trying to simulate the invasion of one fluid into a pipe full of another fluid in COMSOL. The fluids are taken incompressible and the flow laminar. I run the time dependent phase flow, phase field simulation.
  However, in the results I get the volume fraction of fluid 1 at all times equal 1.
  I want to see the invasion of fluid 1 into fluid 2 step by step.</p>