multiple externalCoupled boundaries for multiple variables

Gerry Kan · May 14, 2019, 05:14

Howdy Folks:

I am wondering if it is possible to apply the externalCoupled boundary condition on different boundaries for different variables.

As a hypothetical example, I have a simple round pipe (three boundaries), for which I have velocity, pressure and temperature fields (as functions of position and time) for the boundaries from an external code. Effectively, I would like to have the following boundary assignments:

inlet: externalCoupled velocity (zeroGradient pressure and temperature)
outlet: externalCoupled pressure (zeroGradient velocity and temperature)
pipe wall: externalCoupled temperature (noSlip velocity and zeroGradient pressure)

So I have two questions ...

1) do I need to keep a separate comms directory (i.e. patchPoints / patchFaces) for each of the variable, or can I use a common comms directory where all patchPoints / patchFaces for all boundaries are included? (I believe it is a yes, but I would like to have a second opinion / confirmation).

2) Is it possible to prescribe velocity and pressure as externalCoupled at both the inlet and outlet? The solver will eventually be compressible so it should be possible, but my experience / gut feeling tells me otherwise.

Thanks in advance, Gerry.

jianglong · August 10, 2020, 05:42

Hi Gerry, I am facing the same problem as you. I need to couple two boundary patches for different variables. Have you solved this problem?

Gerry Kan · August 13, 2020, 13:48

Dear Jiang:

Kind of. I was busy with other things at the moment so I haven't got time to work on it. But again, I am building a new boundary condition based on that, which complicates matter a lot (and it forced me to go through the source code, and admittedly it was a very steep learning curve).

If you are just looking to couple OpenFOAM with another solver via file I/O as-is, the tutorial that came with OpenFOAM should be able to show you how to set it up. Of course you will need to write the file I/O interface.

Hope that helps, Gerry.

May 14, 2019, 05:14	multiple externalCoupled boundaries for multiple variables	#1
Gerry Kan Senior Member Gerry Kan Join Date: May 2016 Posts: 376 Rep Power: 11	Howdy Folks: I am wondering if it is possible to apply the externalCoupled boundary condition on different boundaries for different variables. As a hypothetical example, I have a simple round pipe (three boundaries), for which I have velocity, pressure and temperature fields (as functions of position and time) for the boundaries from an external code. Effectively, I would like to have the following boundary assignments: inlet: externalCoupled velocity (zeroGradient pressure and temperature) outlet: externalCoupled pressure (zeroGradient velocity and temperature) pipe wall: externalCoupled temperature (noSlip velocity and zeroGradient pressure) So I have two questions ... 1) do I need to keep a separate comms directory (i.e. patchPoints / patchFaces) for each of the variable, or can I use a common comms directory where all patchPoints / patchFaces for all boundaries are included? (I believe it is a yes, but I would like to have a second opinion / confirmation). 2) Is it possible to prescribe velocity and pressure as externalCoupled at both the inlet and outlet? The solver will eventually be compressible so it should be possible, but my experience / gut feeling tells me otherwise. Thanks in advance, Gerry.

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August 10, 2020, 05:42		#2
jianglong New Member Long Jiang Join Date: Mar 2019 Posts: 5 Rep Power: 7	Hi Gerry, I am facing the same problem as you. I need to couple two boundary patches for different variables. Have you solved this problem?

August 13, 2020, 13:48		#3
Gerry Kan Senior Member Gerry Kan Join Date: May 2016 Posts: 376 Rep Power: 11	Dear Jiang: Kind of. I was busy with other things at the moment so I haven't got time to work on it. But again, I am building a new boundary condition based on that, which complicates matter a lot (and it forced me to go through the source code, and admittedly it was a very steep learning curve). If you are just looking to couple OpenFOAM with another solver via file I/O as-is, the tutorial that came with OpenFOAM should be able to show you how to set it up. Of course you will need to write the file I/O interface. Hope that helps, Gerry.