2022-07-18T15:04:39.000-0400

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We provide a procedure to stop a simulation as soon as a specified monitor value has converged.

Suppose you want a simulation to stop running as soon as a certain value has converged. How can we achieve this?

For illustration, we want the simulation to stop as soon as the pressure drop has converged. “Converged” means in this example that the pressure drop stays within a range of 10 Pa over 50 iterations (in a steady simulation) or 10 time steps (in the corresponding transient case).

Let’s first consider the steady case. Here the procedure is as follows:

a) Create a pressure drop report (Reports>New Report>Flow/Energy> Pressure Drop)

Create monitor and plot from this report

b) Create a new Stopping Criterion based on this report

(Stopping Criteria>New Monitor ‘Criterion and choose “Pressure Drop”)

In the properties of this new Stopping Criterion choose as Criterion Option: “Asymptotic”.

Then under “Asymptotic Limit” set in the properties [Max-Min] to 10 Pa and Number of Samples to 50:

When running the steady simulation the solver stops as soon as the pressure drop varies by a maximum of 10 Pa over 50 iterations.

Now let’s consider the transient case. Here we want the solver to stop as soon as the pressure drop varies by a maximum of 10 Pa over 10 time steps.

The procedure is almost identical to the steady case. Again, in the properties of “Asymptotic Limit” we set [Max-Min] to 10 Pa and choose 10 as Number of Samples.

Now we are almost finished. The only thing left to do is to tell the solver to step the outer iterations (= the time steps) and not the inner iterations within a single time step.

This is found in the properties of “Pressure Drop 1 Monitor Criterion”. Untick “Stop Inner Iterations”:

Now all is set up correctly. When executing the simulation, it correctly stops after the pressure drop varies by less than 10 Pa over 10 time steps.

For illustration, we want the simulation to stop as soon as the pressure drop has converged. “Converged” means in this example that the pressure drop stays within a range of 10 Pa over 50 iterations (in a steady simulation) or 10 time steps (in the corresponding transient case).

Let’s first consider the steady case. Here the procedure is as follows:

a) Create a pressure drop report (Reports>New Report>Flow/Energy> Pressure Drop)

Create monitor and plot from this report

b) Create a new Stopping Criterion based on this report

(Stopping Criteria>New Monitor ‘Criterion and choose “Pressure Drop”)

In the properties of this new Stopping Criterion choose as Criterion Option: “Asymptotic”.

Then under “Asymptotic Limit” set in the properties [Max-Min] to 10 Pa and Number of Samples to 50:

When running the steady simulation the solver stops as soon as the pressure drop varies by a maximum of 10 Pa over 50 iterations.

Now let’s consider the transient case. Here we want the solver to stop as soon as the pressure drop varies by a maximum of 10 Pa over 10 time steps.

The procedure is almost identical to the steady case. Again, in the properties of “Asymptotic Limit” we set [Max-Min] to 10 Pa and choose 10 as Number of Samples.

Now we are almost finished. The only thing left to do is to tell the solver to step the outer iterations (= the time steps) and not the inner iterations within a single time step.

This is found in the properties of “Pressure Drop 1 Monitor Criterion”. Untick “Stop Inner Iterations”:

Now all is set up correctly. When executing the simulation, it correctly stops after the pressure drop varies by less than 10 Pa over 10 time steps.