[jimteb]

Hi,

I would like to use a boundary condition at an inlet that allows a pressure-time profile to be specified, which is also non-reflective.

Currently I am using timeVaryingUniformFixedValue to create the pressure-time profile at the inlet, but I think I am getting reflections at the inlet. I have tried timeVaryingUniformInletOutlet which doesn't seem to help.

Can anyone advise if a boundary condition exists which does this?

thanks

[dancfd]

Hello James,

I am struggling with the same issue, though I am using a time-dependent U at the inlet. My domain consists of a C-grid with the outlet defined as the vertical section at the back, and the rest of the boundary as the inlet - similar to the tutorial nacaAirfoil. Since the angle of inflow is changing as a function of time, some of the time the inlet will be acting like an outlet.

I think a new boundary condition might be required - a blend of uniformFixedValue and supersonicFreestream/waveTransmissive, perhaps?

I will try to create a new BC that does this and post my results if I am successful. My C++ skills are not strong, but I will give it a shot.

Regards,

Dan

[dancfd]

Well trying to set up a new BC is not as straightforward as I thought. Starting from the basics, I followed the instructions at the link below just to try renaming an already-existing BC:

- I copied the waveTransmissive folder into $FOAM_USER_LIBBIN
- renamed all instances of "waveTransmissive" to "waveTransmissiveTimeVarying" in the files and filenames
- used the attached files in the Make directory
- successfully built libwaveTransmissiveTimeVarying.so

Then, in the nacaAirfoil case:
- added "libs ("libwaveTransmissiveTimeVarying.so");" to controlDict
- changed the pressure boundary type to "waveTransmissiveTimeVarying"

When I run it sonicFoam on it, though, I get the following error:

--> FOAM FATAL IO ERROR: 
Unknown patchField type waveTransmissiveTimeVarying for patch type patch

Valid patchField types are :

etc. Complete error in the attached log file.

Any ideas what could cause this? I hope to create a new BC; right now I cannot even copy and use an existing one! Note that I added the ".txt" extension to all attachments just so they could be uploaded.

Link for instructions: http://openfoamwiki.net/index.php/Ho...dary_condition

Thanks in advance for any assistance.

Daniel

[dancfd]

I made a mistake in the make/files file. Works now, will now look at combining waveTransmissive and uniformFixedValue.

Dan

New make/files:

$(FOAM_USER_LIBBIN)/waveTransmissiveTimeVarying/waveTransmissiveTimeVaryingFvPatchFields.C

LIB = $(FOAM_USER_LIBBIN)/libwaveTransmissiveTimeVarying

[alessandroB]

Hi,
I know I'm a little late to ask you an answer, but now I'm just working on a similar problem.
I need to have an outlet where I apply a time dependet boundary condition on pressure by a tabel, but also that allows propogation of waves, i.e. a waveTransmissive Boundary conditions where I give a table of values instead of just one fixedValue.
I couldn't get very well your procedure, if you could explain to me just another time it would be very important to me (I started few weeks ago with OpenFoam ).
Best regards.

[dancfd]

Hello Alessandro, I'm afraid I was not successful in the end, but reflection did not turn out to be much of a problem in my case so I let it go. Good luck,

Daniel