[pooyanni]

Hi everyone,

I am trying to run a compressible flow simulation using the rhoCentralFoam solver. However, due to convergence issues, I want to improve my initial conditions in the domain from the solution of another solver on the same geometry and mesh. Is it possible to use mapFields for this purpose between two different solvers? For example using icoFoam solution as the initial condition for rhoCentralFoam (although density is not resolved in the icoFoam).

As a more general question, what are the ways to provide a more realistic boundary condition to improve the solution speed and convergence in more expensive simulations.

Thanks

[GerhardHolzinger]

Yes, you can.

And now for more details

You can create an incompressible twin-case to compute a velocity field with which to initialize the compressible case.

With the incompressible case, you can initialize this case using the potentialFoam solver.


Note, that you should not map the pressure field, since the pressure has different dimensional units in the incompressible and compressible case.

Also, the phi field has a different dimension in incompressible and compressible cases.


Since mapFields maps all matching fields between two cases, you need to restrict the mapping to U, and possibly the turbulent fields.

[pooyanni]

Originally Posted by GerhardHolzinger

Yes, you can.

And now for more details

You can create an incompressible twin-case to compute a velocity field with which to initialize the compressible case.

With the incompressible case, you can initialize this case using the potentialFoam solver.


Note, that you should not map the pressure field, since the pressure has different dimensional units in the incompressible and compressible case.

Also, the phi field has a different dimension in incompressible and compressible cases.


Since mapFields maps all matching fields between two cases, you need to restrict the mapping to U, and possibly the turbulent fields.

Hi Gerhard,

Thanks for your response. That's good news! Do you know of any tutorial that explains this in more details. I am wondering how can I specify only the velocity field during mapFields operation? I looked at "mapFields -help" but could not find any options related to that.

Regards

[GerhardHolzinger]

In the case that a tool does let you specify certain fields, simply make sure that the intended fields are the only ones that are present.


Since, you can't tell mapFields to only map the U field, follow such a procedure:

• Run the source case, i.e. the case from which you want to map the solution
  
• Define all fields of the destination case, the case you want to map onto, in the 0.org folder
• Create an empty 0 folder, and copy only U from 0.org to 0
• Map the solution from the source case to the destination case, since U is the only field in the 0 folder, only U is mapped
• Copy the remaining fields from 0.org to 0

[pooyanni]

Originally Posted by GerhardHolzinger

In the case that a tool does let you specify certain fields, simply make sure that the intended fields are the only ones that are present.


Since, you can't tell mapFields to only map the U field, follow such a procedure:

• Run the source case, i.e. the case from which you want to map the solution
• Define all fields of the destination case, the case you want to map onto, in the 0.org folder
• Create an empty 0 folder, and copy only U from 0.org to 0
• Map the solution from the source case to the destination case, since U is the only field in the 0 folder, only U is mapped
• Copy the remaining fields from 0.org to 0

That makes sense. Thanks a lot for the guidance!

Best