2 1 GfsSimulation GfsBox GfsGEdge {} {
  Refine 5
  Solid (x*x + y*y - 0.125*0.125)
  RefineSolid 6
  Time { end = 5 }
  SourceViscosity 1.
  OutputSimulation { start = 1.0 } file.gfs
}
 GfsBox {
  left   = Boundary { BcDirichlet P 1 }
  top    = Boundary { BcDirichlet U 0 BcDirichlet V 0 }
  bottom = Boundary { BcDirichlet U 0 BcDirichlet V 0 }
}
GfsBox {
  right  = Boundary { BcDirichlet P 0 }
  top    = Boundary { BcDirichlet U 0 BcDirichlet V 0 }
  bottom = Boundary { BcDirichlet U 0 BcDirichlet V 0 }
}
1 2 right