multiple externalCoupled boundaries for multiple variables

Gerry Kan · May 14, 2019, 04:14

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, 04:42

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, 12:48

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, 04:14	multiple externalCoupled boundaries for multiple variables	#1
Gerry Kan Senior Member Gerry Kan Join Date: May 2016 Posts: 347 Rep Power: 10	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.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Implicit vs. explicit treatment of variables at zero gradient outflow boundaries	eltenedor	Main CFD Forum	0	February 21, 2015 15:37
[General] Programmable Filter: when multiple inputs, how to verify which input is which?	macfly	ParaView	0	July 12, 2014 11:14
Using Variables from multiple Physics Continua in Field Function	cwl	STAR-CCM+	3	November 4, 2013 16:23
Boundaries and conservative variables	pankos	Main CFD Forum	0	April 2, 2011 03:50
PHI file structure	Eugene	Phoenics	9	November 2, 2001 22:00

August 10, 2020, 04:42		#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, 12:48		#3
Gerry Kan Senior Member Gerry Kan Join Date: May 2016 Posts: 347 Rep Power: 10	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.