# InterFoam (PimpleFoam) not obeying DeltaT in ControlDict

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 February 28, 2018, 15:12 InterFoam (PimpleFoam) not obeying DeltaT in ControlDict #1 Member   Shafik Walakaka Join Date: Oct 2017 Posts: 38 Rep Power: 5 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 Last edited by walakaka; February 28, 2018 at 15:45. Reason: InterFoam, PimpleFoam, ControlDict, DeltaT, Courant

 March 1, 2018, 11:35 #2 New Member   Join Date: Apr 2014 Location: Germany Posts: 24 Rep Power: 8 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

March 1, 2018, 13:57
#3
Member

Shafik Walakaka
Join Date: Oct 2017
Posts: 38
Rep Power: 5
Quote:
 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,

• 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?

Kind regards
Shafik