[totalart]

Hi,

I'm a beginner of OPENFOAM. While I was running LTSinterfoam, I realized that there is 'time step continuity error : sum local = (positive value), global =(negatice value), cumulative=(negative value)' at every time step. Can anybody explain me what they are and how I should interpret them?

And another question is how we set the deltaT for LTSinterfoam. If I understand correctly, this solver uses local timestep for individual cell and enables higher timestep than normal interfoam which I used to set deltaT based on Courant No.
Thank you.

[crst15]

Hi,

I'm also new to OpenFOAM, but as far as I know we shouldn't have increasing magnitude of time step continuity error. If it increases by the time, it simply means there is something wrong because the result diverges (not converges as we want). Maybe the following link can explain you further.

http://www.cfd-online.com/Forums/ope...ontinuity.html

Cheers

[ashim]

Hi,

Good morning. I am trying to simulate open water propeller test using SRFSimpleFoam in OF2.3. I have generated the mesh for one blade and used cyclic boundary conditions at two sides. Actually I have followed the mixer2D tutorial for settings. First few iteration the time step continuity error is low, but after that it increases rapidly and ends with error message. I am trying to fixed it two weeks, but no progress. Here is few iteration

Time = 6e-06

smoothSolver: Solving for Urelx, Initial residual = 0.0190493, Final residual = 1.01643e-05, No Iterations 1
smoothSolver: Solving for Urely, Initial residual = 0.012259, Final residual = 4.56347e-07, No Iterations 1
smoothSolver: Solving for Urelz, Initial residual = 0.0170663, Final residual = 1.89593e-06, No Iterations 1
GAMG: Solving for p, Initial residual = 0.0411541, Final residual = 0.00191992, No Iterations 4
GAMG: Solving for p, Initial residual = 0.00134279, Final residual = 3.44485e-05, No Iterations 2
GAMG: Solving for p, Initial residual = 0.173049, Final residual = 0.0036369, No Iterations 2
GAMG: Solving for p, Initial residual = 0.0646702, Final residual = 0.0013047, No Iterations 2
GAMG: Solving for p, Initial residual = 0.00432385, Final residual = 8.53338e-05, No Iterations 2
time step continuity errors : sum local = 0.00232644, global = -1.78199e-05, cumulative = -2.88707e-05
smoothSolver: Solving for omega, Initial residual = 0.922408, Final residual = 0.0350594, No Iterations 1
smoothSolver: Solving for k, Initial residual = 0.0786531, Final residual = 1.48775e-05, No Iterations 1
ExecutionTime = 337.56 s ClockTime = 344 s

forces forces output:
sum of forces:
pressure : (8.45846e+13 -2.65505e+14 -5.83726e+13)
viscous : (-378.866 -5462.69 -368.562)
porous : (0 0 0)
sum of moments:
pressure : (6.53804e+14 -4.71993e+12 9.72357e+14)
viscous : (7562.62 -757.113 4064.07)
porous : (0 0 0)

Time = 7e-06

smoothSolver: Solving for Urelx, Initial residual = 0.0140894, Final residual = 3.96715e-05, No Iterations 1
smoothSolver: Solving for Urely, Initial residual = 0.017558, Final residual = 1.73655e-06, No Iterations 1
smoothSolver: Solving for Urelz, Initial residual = 0.0139923, Final residual = 1.83734e-06, No Iterations 1
GAMG: Solving for p, Initial residual = 0.0113594, Final residual = 0.000151688, No Iterations 2
GAMG: Solving for p, Initial residual = 0.0652213, Final residual = 8.94586e-05, No Iterations 2
GAMG: Solving for p, Initial residual = 0.0650613, Final residual = 0.00243042, No Iterations 1
GAMG: Solving for p, Initial residual = 0.00323469, Final residual = 4.73796e-05, No Iterations 2
GAMG: Solving for p, Initial residual = 0.00364623, Final residual = 1.65598e-05, No Iterations 2
time step continuity errors : sum local = 0.143907, global = 0.00524195, cumulative = 0.00521308
smoothSolver: Solving for omega, Initial residual = 0.999544, Final residual = 3.8592e-05, No Iterations 2
smoothSolver: Solving for k, Initial residual = 0.993538, Final residual = 6.10023e-06, No Iterations 1
ExecutionTime = 358.45 s ClockTime = 365 s

forces forces output:
sum of forces:
pressure : (-7.04173e+16 -1.56929e+17 1.23398e+16)
viscous : (-4717.25 205.91 5827.73)
porous : (0 0 0)
sum of moments:
pressure : (4.4669e+16 -3.78855e+16 -3.36375e+17)
viscous : (-35983.8 11404.4 -56450)
porous : (0 0 0)

Time = 8e-06

smoothSolver: Solving for Urelx, Initial residual = 0.0347293, Final residual = 0.000141556, No Iterations 1
smoothSolver: Solving for Urely, Initial residual = 0.0403256, Final residual = 8.2105e-05, No Iterations 1
smoothSolver: Solving for Urelz, Initial residual = 0.0600461, Final residual = 3.13792e-05, No Iterations 1
GAMG: Solving for p, Initial residual = 0.196797, Final residual = 0.00967483, No Iterations 12
GAMG: Solving for p, Initial residual = 0.827418, Final residual = 0.00201151, No Iterations 2
GAMG: Solving for p, Initial residual = 0.773869, Final residual = 0.00206367, No Iterations 2
GAMG: Solving for p, Initial residual = 0.314569, Final residual = 0.00111685, No Iterations 2
GAMG: Solving for p, Initial residual = 0.431347, Final residual = 0.00120815, No Iterations 2
time step continuity errors : sum local = 159.278, global = 0.309805, cumulative = 0.315018
smoothSolver: Solving for omega, Initial residual = 0.642481, Final residual = 0.0111688, No Iterations 2
smoothSolver: Solving for k, Initial residual = 0.977907, Final residual = 1.18426e-09, No Iterations 1
ExecutionTime = 389.33 s ClockTime = 396 s

forces forces output:
sum of forces:
pressure : (-1.17572e+19 -2.33548e+19 2.47823e+18)
viscous : (38074.8 424621 19459.2)
porous : (0 0 0)
sum of moments:
pressure : (2.80483e+18 -8.00298e+18 -5.93121e+19)
viscous : (-562076 79148.1 -272804)
porous : (0 0 0)

Time = 9e-06

smoothSolver: Solving for Urelx, Initial residual = 0.00515184, Final residual = 1.12754e-06, No Iterations 1
smoothSolver: Solving for Urely, Initial residual = 0.0053851, Final residual = 3.32492e-07, No Iterations 1
smoothSolver: Solving for Urelz, Initial residual = 0.00522129, Final residual = 1.18371e-06, No Iterations 1
GAMG: Solving for p, Initial residual = 0.75356, Final residual = 0.0369052, No Iterations 30
GAMG: Solving for p, Initial residual = 0.999982, Final residual = 0.0454414, No Iterations 1
GAMG: Solving for p, Initial residual = 0.801074, Final residual = 0.000428337, No Iterations 2
GAMG: Solving for p, Initial residual = 0.507745, Final residual = 0.00235907, No Iterations 1
GAMG: Solving for p, Initial residual = 0.825081, Final residual = 0.00399446, No Iterations 1
time step continuity errors : sum local = 5.81592e+08, global = 2992.39, cumulative = 2992.71
smoothSolver: Solving for omega, Initial residual = 0.0122672, Final residual = 1.49319e-07, No Iterations 3
smoothSolver: Solving for k, Initial residual = 0.999937, Final residual = 5.77743e-11, No Iterations 1
ExecutionTime = 435.06 s ClockTime = 442 s

forces forces output:
sum of forces:
pressure : (7.48374e+21 -1.01239e+21 -2.86926e+21)
viscous : (3.48195e+09 1.19635e+10 1.42081e+09)
porous : (0 0 0)
sum of moments:
pressure : (2.25222e+22 2.40735e+21 5.73868e+22)
viscous : (-8.81645e+09 1.41756e+09 6.47987e+09)
porous : (0 0 0)

I hope someone will help to solve this problem. Any kind of hint, suggestions is appreciated.

Ali