2024-02-27T06:01:40.000-0500

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For the pumping out case (removing liquid in the domain), the solution from the segregated and coupled in default options are quite different. Which coupled solver options are available to follow the segregated solution?

The following plot depicts the result of the outlet pressure of the pumping-out case.

The red line is a solution of the default coupled solver and the dashed yellow line is that of the default segregated solver. As shown, the results are far different.

If you want to use the coupled solver and think that red line is the true solution, which options are available for the coupled solvers to follow the segregated solution?

It would be helpful to use CCA (Continuity Convergence Accelerator) and reduced CFL for this case.

CCA is here:

The default URF of this is 0.1.

CFL option is here (in coupled implicit solver):

Maybe the default number is 50, but it would be better to reduce it.

By adopting CFL = 1 and URF = 0.01, the solution is changed as follows. See next plot.

Yellow solid line is the new solution with modified options. The final pressure is only 3 & 5 Pa, which is very similar to each other.

However, please note that these options may decrease the computation speed.

The red line is a solution of the default coupled solver and the dashed yellow line is that of the default segregated solver. As shown, the results are far different.

If you want to use the coupled solver and think that red line is the true solution, which options are available for the coupled solvers to follow the segregated solution?

It would be helpful to use CCA (Continuity Convergence Accelerator) and reduced CFL for this case.

CCA is here:

The default URF of this is 0.1.

CFL option is here (in coupled implicit solver):

Maybe the default number is 50, but it would be better to reduce it.

By adopting CFL = 1 and URF = 0.01, the solution is changed as follows. See next plot.

Yellow solid line is the new solution with modified options. The final pressure is only 3 & 5 Pa, which is very similar to each other.

However, please note that these options may decrease the computation speed.