I am running a basic test case
I am running a basic test case using icoFoam. I defined a 2D channel with two walls, an inlet, and an outlet. The walls have a no-slip boundary condition U=uniform(0 0 0). The inlet has a boundary condition of U=uniform(1 0 0) which causes flow into the channel with a uniform velocity profile. The outlet BC is of type zeroGradient for U. All pressure boundaries are of type zeroGradient. This setup produces the following error:
Reading/calculating face flux field phi
Starting time loop
Time = 0.001
Mean and max Courant Numbers = 0 0.1
BICCG: Solving for Ux, Initial residual = 1, Final residual = 9.49086e-09, No Iterations 1
--> FOAM FATAL ERROR : Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
From function adjustPhi(surfaceScalarField& phi, const volVectorField& U,const volScalarField& p
in file adjustPhi/adjustPhi.C at line 108.
If I set one wall b.c. OR the internalField to U=uniform(0.00001 0 0) then the expected parabolic velocity profile develops. Reducing the time step does not help.
Can someone please explain why this is happening, and how to set it up correctly?
Have a look at your boundary c
Have a look at your boundary conditions on the velocity. In FOAM, we typically use fixed value U and zero gradient pressure at the inlet and fixed pressure and zero gradient U at the outlet. There is an option of using zero gradient on both p and U at the outlet, but then the code needs to adjust the outlet velocities in order to achieve global continuity. The message says it cannot do that for some reason.
Oops. I thought I had set the
Oops. I thought I had set the output pressure to zero instead of zeroGradient, but after checking I realize that it was in fact zeroGradient. No wonder it wasn't working. Thanks for the tip. I'll post my results as a tutorial sometime.
Your comments helped a lot.
great help. Also valid for SimpleFoam!!!
thanks a lot!!!
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