Is there a way to enforce my timestep?

Shawn_A · November 9, 2011, 13:30

I'm using pimpleDyMFoam to simulate a vertical axis wind turbine with a stationary outer domain and a rotating inner domain using the ggi. I would like to be able to strictly enforce my timestep. I have tried to raise my maxCo to 100 (yes, I know the implications) but the deltaT used in the solution will never go higher than 0.000556 (my desired deltaT is 0.00278 which corresponds to 1 deg rotation at 60 RPM). The maxCo in the solution is ~7.33 so it never approaches 100.

Is there another parameter I should look at to get my deltaT to where I want? Convergence doesn's seem to be an issue at this Co/deltaT (7.3/5.6e-4) yet.

Thanks,
Shawn

kwardle · November 9, 2011, 13:40

Is there a reason you cannot simply change system/controlDict such that:

deltaT 0.00278;
adjustTimeStep no;

This should give you a constant time step.
-Kent

Shawn_A · November 10, 2011, 11:53

Wow...I guess I've been looking at this too long. That command is literally 2 lines above maxCo.

Thanks Kent!

November 9, 2011, 13:30	Is there a way to enforce my timestep?	#1
Shawn_A Member Shawn Join Date: Oct 2011 Posts: 56 Rep Power: 14	I'm using pimpleDyMFoam to simulate a vertical axis wind turbine with a stationary outer domain and a rotating inner domain using the ggi. I would like to be able to strictly enforce my timestep. I have tried to raise my maxCo to 100 (yes, I know the implications) but the deltaT used in the solution will never go higher than 0.000556 (my desired deltaT is 0.00278 which corresponds to 1 deg rotation at 60 RPM). The maxCo in the solution is ~7.33 so it never approaches 100. Is there another parameter I should look at to get my deltaT to where I want? Convergence doesn's seem to be an issue at this Co/deltaT (7.3/5.6e-4) yet. Thanks, Shawn

November 9, 2011, 13:40		#2
kwardle Senior Member Kent Wardle Join Date: Mar 2009 Location: Illinois, USA Posts: 219 Rep Power: 21	Is there a reason you cannot simply change system/controlDict such that: deltaT 0.00278; adjustTimeStep no; This should give you a constant time step. -Kent atg likes this.

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November 10, 2011, 11:53		#3
Shawn_A Member Shawn Join Date: Oct 2011 Posts: 56 Rep Power: 14	Wow...I guess I've been looking at this too long. That command is literally 2 lines above maxCo. Thanks Kent!