Control of inner iteration

totosor · June 30, 2021, 10:39

Hello everyone,

I am working on a coupling scheme between neutronic and thermohydraulic using starccm+ v2019.2.

The fact is each physic is solved by an implicit scheme but the coupling between them is explicit so I have to use a very small time step.

A solution consist in doing external iterations that means for a same time step, repeat an iteration but I didn't find anything in starccm+ to do so.

Another solution could be possibly the control of inner iteration, like .getSimulationIterator().step(n) but I don't know if the object exists for a Macro.

If anyone has already seen something like that and can answer me I would be very grateful.

Thomas.

fluid23 · June 30, 2021, 14:06

It is not clear to me what question you are asking here. Can you clarify?

totosor · July 1, 2021, 03:58

Hi,

So I'll try to clarify.

I am looking for something to repeat the same time step with the unsteady solver. (like saving all the fields calculated at time t=t_0+dt and go back to time t_0).

One idea I have would be to stop the computation between inner iterations but I don't know if it is possible.

Thx.

FliegenderZirkus · July 1, 2021, 08:28

Hi, I'm not sure if this helps, but you can run a specified number of iterations, e.g. 3, by writing

sim = getActiveSimulation();
sim.getSimulationIterator().iterate(3, true);

Running three time steps instead could look like this:

sim.getSimulationIterator().run(3, true);

There's also the step() method you mentioned and to be honest I'm not quite sure how that behaves - for a transient simulation and if if you specify number of steps I'd guess it's the same as run()?

June 30, 2021, 10:39	Control of inner iteration	#1
totosor New Member Thomas Join Date: Jun 2021 Posts: 2 Rep Power: 0	Hello everyone, I am working on a coupling scheme between neutronic and thermohydraulic using starccm+ v2019.2. The fact is each physic is solved by an implicit scheme but the coupling between them is explicit so I have to use a very small time step. A solution consist in doing external iterations that means for a same time step, repeat an iteration but I didn't find anything in starccm+ to do so. Another solution could be possibly the control of inner iteration, like .getSimulationIterator().step(n) but I don't know if the object exists for a Macro. If anyone has already seen something like that and can answer me I would be very grateful. Thomas.

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June 30, 2021, 14:06		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	It is not clear to me what question you are asking here. Can you clarify?

July 1, 2021, 03:58		#3
totosor New Member Thomas Join Date: Jun 2021 Posts: 2 Rep Power: 0	Hi, So I'll try to clarify. I am looking for something to repeat the same time step with the unsteady solver. (like saving all the fields calculated at time t=t_0+dt and go back to time t_0). One idea I have would be to stop the computation between inner iterations but I don't know if it is possible. Thx.

July 1, 2021, 08:28		#4
FliegenderZirkus Member Join Date: Nov 2019 Posts: 98 Rep Power: 7	Hi, I'm not sure if this helps, but you can run a specified number of iterations, e.g. 3, by writing sim = getActiveSimulation(); sim.getSimulationIterator().iterate(3, true); Running three time steps instead could look like this: sim.getSimulationIterator().run(3, true); There's also the step() method you mentioned and to be honest I'm not quite sure how that behaves - for a transient simulation and if if you specify number of steps I'd guess it's the same as run()?