[walakaka]

Hi everyone,

I have set DeltaT in my ControlDict to 0.5 however the simulation is not using my updated DeltaT. What could be the possible case here?

Could someone also please enlighten me what the MaxAlphaCo represents? (Is it important?)

My logfile is given below (You can see that deltaT is not 0.5):

************************************

Courant Number mean: 0.302718 max: 1.41204
Interface Courant Number mean: 0.0231892 max: 0.990276
deltaT = 0.008971
Time = 24.4193

PIMPLE: iteration 1
smoothSolver: Solving for alpha.water, Initial residual = 0.000360174, Final residual = 1.52004e-09, No Iterations 3
Phase-1 volume fraction = 0.520186 Min(alpha.water) = -5.20278e-05 Max(alpha.water) = 1.01577
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.520186 Min(alpha.water) = -0.000213347 Max(alpha.water) = 1.01577
DICPCG: Solving for p_rgh, Initial residual = 0.00755176, Final residual = 0.000356144, No Iterations 4
time step continuity errors : sum local = 3.02096e-05, global = -4.21979e-09, cumulative = 0.000897624
DICPCG: Solving for p_rgh, Initial residual = 0.000451891, Final residual = 1.72557e-05, No Iterations 18
time step continuity errors : sum local = 1.46355e-06, global = -1.61657e-09, cumulative = 0.000897622
PIMPLE: iteration 2
smoothSolver: Solving for alpha.water, Initial residual = 0.000276768, Final residual = 1.24055e-09, No Iterations 3
Phase-1 volume fraction = 0.520186 Min(alpha.water) = -5.20278e-05 Max(alpha.water) = 1.01577
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.520186 Min(alpha.water) = -0.000201375 Max(alpha.water) = 1.01577
DICPCG: Solving for p_rgh, Initial residual = 0.000855169, Final residual = 4.08855e-05, No Iterations 6
time step continuity errors : sum local = 3.46725e-06, global = -1.14264e-09, cumulative = 0.000897621
DICPCG: Solving for p_rgh, Initial residual = 5.79757e-05, Final residual = 2.82631e-06, No Iterations 73
time step continuity errors : sum local = 2.39672e-07, global = -1.09359e-09, cumulative = 0.00089762

***************************************

My controlDict file is given below (Where DeltaT is set to 0.5):

***************************************

FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application interFoam;

startFrom latestTime;

startTime 0;

stopAt endTime;

endTime 60;

deltaT 0.5;

writeControl adjustableRunTime;

writeInterval 0.5;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression uncompressed;

timeFormat general;

timePrecision 6;

runTimeModifiable yes;

adjustTimeStep yes;

maxCo 3;
maxAlphaCo 1;

maxDeltaT 1;

*****************************************

Regards
Shafik

[MSF]

Hello,

you set adjustTimeStep to yes, so your maximum time step will be calculated based on your Co-number. If you want to run the simulation with a fixed time step just set adjustTimeStep to no.

Best,

Moritz

[walakaka]

Originally Posted by MSF

Hello,

you set adjustTimeStep to yes, so your maximum time step will be calculated based on your Co-number. If you want to run the simulation with a fixed time step just set adjustTimeStep to no.

Best,

Moritz

Hi Moritz,

Thank you for your reply! Could you also clarify the following for me please:

• Difference between maxCo and maxAlphaCo
• If adjustTimeStep yes; how is the timestep regulated? (based on maxCo, maxAlphaCo, maxDeltaT?)
• If adjustTimeStep yes; Will the software be trying to achieve the maximum possible timestep to reduce simulation time?

I appreciate your help!

Kind regards
Shafik