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Non-reflective inlet boundary conditions

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Old   March 18, 2014, 15:32
Default Non-reflective inlet boundary conditions
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James
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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
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Old   April 6, 2014, 09:15
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Daniel
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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
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Old   April 6, 2014, 17:32
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Daniel
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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:
Code:
--> 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
Attached Files
File Type: txt log.sonicFoam.txt (3.7 KB, 0 views)
File Type: txt options.txt (218 Bytes, 1 views)
File Type: txt files.txt (172 Bytes, 3 views)
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Old   April 7, 2014, 23:47
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Daniel
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I made a mistake in the make/files file. Works now, will now look at combining waveTransmissive and uniformFixedValue.

Dan

New make/files:

Code:
$(FOAM_USER_LIBBIN)/waveTransmissiveTimeVarying/waveTransmissiveTimeVaryingFvPatchFields.C

LIB = $(FOAM_USER_LIBBIN)/libwaveTransmissiveTimeVarying
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