# Specifying initial conditions with cyclic boundary conditions

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 November 13, 2018, 16:59 Specifying initial conditions with cyclic boundary conditions #1 Member   Join Date: Apr 2016 Posts: 30 Rep Power: 10 Hi all, I am trying to use a modified transient twoPhaseEulerFoam with cyclic boundary conditions. Now I have to specify the initial volume fractions,velocities,pressures etc at the INLET. How do I do that because I have specified cyclic in the boundary conditions? How do I specify initial non uniform internal field values without using the list option since the mesh is complex? Thanks and regards, Shantanu Vachhani

 November 14, 2018, 11:07 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,695 Rep Power: 66 cyclic is the entry for type that you need to specify (for every field). There's still an entry for value that you need to specify (for every field). That's where your initial condition goes.

 November 14, 2018, 15:19 #3 Member   Join Date: Apr 2016 Posts: 30 Rep Power: 10 Even after entering a value at the boundary while zero in the uniform field, the simulation doesn't take that into consideration because the alpha(volume fraction) values are zero at every time step. Furthermore , the courant number is very less because I have specified non zero velocity at the inlet while the internal filed is (0 0 0). Could you think of a reason why is this happening? Thanks and Regards, Shantanu Vachhani Code: Courant Number mean: 2.29238e-15 max: 3.88904e-15 Max Ur Courant Number = 2.49311e-16 Time = 1.5e-05 PIMPLE: iteration 1 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999662, Final residual = 0.999662, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.999985, Final residual = 1.14001e-05, No Iterations 1000 PIMPLE: iteration 2 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999683, Final residual = 0.999683, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.999994, Final residual = 1.07173e-05, No Iterations 1000 PIMPLE: iteration 3 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999698, Final residual = 0.999698, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.999992, Final residual = 9.86466e-06, No Iterations 1000 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. GAMG: Solving for psi, Initial residual = 0, Final residual = 0, No Iterations 0 ExecutionTime = 101.63 s Courant Number mean: 1.542e-15 max: 2.61096e-15 Max Ur Courant Number = 1.60923e-16 Time = 2e-05 PIMPLE: iteration 1 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999708, Final residual = 0.999708, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.99999, Final residual = 8.67989e-06, No Iterations 1000 PIMPLE: iteration 2 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999722, Final residual = 0.999722, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.999996, Final residual = 8.37368e-06, No Iterations 1000 PIMPLE: iteration 3 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999731, Final residual = 0.999731, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.999995, Final residual = 7.84835e-06, No Iterations 1000 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. GAMG: Solving for psi, Initial residual = 0, Final residual = 0, No Iterations 0 ExecutionTime = 134.49 s Courant Number mean: 1.13366e-15 max: 1.91734e-15 Max Ur Courant Number = 1.08311e-16 Time = 2.5e-05 PIMPLE: iteration 1 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999737, Final residual = 0.999737, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.999994, Final residual = 7.00422e-06, No Iterations 1000 PIMPLE: iteration 2 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999745, Final residual = 0.999745, No Iterations 0 min T.air 300.01 min T.water 300.002 smoothSolver: Solving for p_rgh, Initial residual = 0.999998, Final residual = 6.72276e-06, No Iterations 1000 PIMPLE: iteration 3 MULES: Solving for alpha.air MULES: Solving for alpha.air alpha.air volume fraction = 0 Min(alpha.air) = 0 Max(alpha.air) = 0 Constructing momentum equations Selecting patchDistMethod meshWave Selecting patchDistMethod meshWave --> FOAM Warning : From function const volVectorField& Foam::wallDist::n() const in file fvMesh/wallDist/wallDist/wallDist.C at line 200 n requested but 'nRequired' not specified in the wallDist dictionary Recalculating y and n fields. smoothSolver: Solving for e.air, Initial residual = 1, Final residual = 1, No Iterations 0 smoothSolver: Solving for e.water, Initial residual = 0.999752, Final residual = 0.999752, No Iterations 0 min T.air 300.01 min T.water 300.002

 November 19, 2018, 12:55 #4 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,695 Rep Power: 66 I'm still confused what you are trying to do. With cyclic BC, there is no more an inlet. Your initial condition is specified in value of the internalField and if you ordinary BC's the value of the boundaryField. But you have cyclic and no longer is it necessary to specify value in the boundaryField and only the internalField. Now the question is what you like to specify as the initial condition for the internalField. And yes you must think in terms of internalField. Probably the solution will involve the setFields utility. AliE likes this.

 November 26, 2018, 00:00 #5 Member   Join Date: Apr 2016 Posts: 30 Rep Power: 10 LuckyTran, Thank you for the response. However I have one question about using cyclic boundary condition. When I am using cyclic boundary condition , my internal field specified for volume fraction is 0.5. Now using cyclic boundary condition this value remains same throughout the domain as the simulation progresses. This means there is no mass transfer which is physically incorrect. When I use normal inlet and outlet boundary condition, observable mass transfer is observed. Could you think of the reason why cyclic boundary condition is giving wrong results? Thanks and Regards, Shantanu Vachhani