[Pablo2120]

Dear Foamers;


In OpenFOAM, what is the criterion used by OpenFOAM (v7 in my case) to reduce the timestep?.



I'm running a case with a fixed timestep of 0.0005. When I let OpenFOAM adjust it, it reduces the timestep to 0.0001, and I don't know why, because with the timestep of 0.0005 I'm obtaining the same results with the same quantity of iterations.


Regards,


Pablo.

[HPE]

Hi,

- Could you please share your `controlDict`?
- OF can adjust the simulation time-step based on many criteria, one of the most common is Courant number via `maxCo` entry within `controlDict`.
- If you would like to ensure the simulation time-step is constant, you can impose it by placing the `adjustableTimeStep false;` entry into `controlDict`.

Hope this helps a bit.

[Pablo2120]

Sure, here is my controlDict.

application     interFoam;

startFrom       startTime;

startTime       5.25;

stopAt          endTime;

endTime         15;

deltaT          0.0005;

writeControl    adjustableRunTime;

writeInterval   0.05;

purgeWrite      0;

writeFormat     binary;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  no;//yes;

maxCo           1.0;

maxAlphaCo      1;

maxDeltaT       1;
//functions
//{
//    #includeFunc Q
//    #include "surfaces"
//    #include "forces"
//}

// ************************************************************************* //

I was using maxCo=0.98 before. Then I changed it to 1.0 AND (at the same time) I changed adjustTimeStep to "no". So I didn't noticed the effect of courant number change (now the simulation is running).

[HPE]

so, solved?