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-   -   Robin B.C=Mixed B.C ? (http://www.cfd-online.com/Forums/openfoam-solving/69464-robin-b-c-mixed-b-c.html)

ksookhak October 23, 2009 13:41

Robin B.C=Mixed B.C ?
 
Hi

Fro the Robin B.C:

dC/dy = a * C

where a is constant, C is scalar concentration and y is direction normal to the wall, How can I use the Mixed B.C? What will be the following terms?

refValue, refGradient, valueFraction and value?

Thanks in advance!

spl1504 January 5, 2011 09:37

Robin BC
 
Hi all,

some already posted the same question as I have here, but I could not find any answer that helped me.

I need to implement a Robin boundary condition of the form

c=a*dc/dx

with "a" being a constant, "x" the axis and "c" my volScalarField which is calculated by just one PDE (c(t,x,y,z)).
Can anyone give me a hint? I am not too familiar with programming in C++, so I have difficulties to understand the code of the OpenFOAM boundary conditions....:confused:

Maybe the answer is obvious for some of you, but unfortunately not for me, so I would really appreciate a help ...

Thanx

McCarra January 10, 2011 05:55

All types of boundary conditions for a volScalarField are:

advective
buoyantPressure
calculated
cellMotion
cyclic
directMapped
directionMixed
empty
fan
fixedFluxPressure
fixedGradient
fixedInternalValue
fixedPressureCompressibleDensity
fixedValue
freestream
freestreamPressure
inletOutlet
inletOutletTotalTemperature
mixed
oscillatingFixedValue
outletInlet
outletMappedUniformInlet
partialSlip
processor
rotatingTotalPressure
sliced
slip
surfaceSlipDisplacement
symmetryPlane
syringePressure
timeVaryingMappedFixedValue
timeVaryingMappedTotalPressure
timeVaryingTotalPressure
timeVaryingUniformFixedValue
timeVaryingUniformInletOutlet
totalPressure
totalTemperature
turbulentInlet
turbulentIntensityKineticEnergyInlet
uniformDensityHydrostaticPressure
uniformFixedValue
waveTransmissive
wedge
zeroGradient

In the thread "movingCone with time-dependent displacement" are also all the types por pointScalarField and volVectorField.

Maybe one of these types could help you!

benk January 11, 2011 10:50

I think the solution to your problem is in this post:
http://www.cfd-online.com/Forums/ope...condition.html

which I basically stole from this post:
http://www.cfd-online.com/Forums/ope...acianfoam.html

spl1504 January 12, 2011 05:11

So, unfortunately there seems to be no way to get around groovyBC when I am looking for a very general BC?!

I had a closer look at the other BCs but did not succeed in actually understand them, they seem very specific to me.

I downloaded groovyBC and followed the instructions on http://openfoamwiki.net/index.php/Contrib_groovyBC
but when I run the demo cases and use paraview for the visualisation, I always get a problem by seeing the velocity U, paraview shuts down directly. I tried the two versions of the libs hint, given on the website, but this did not change the problem. Does anyone have an idea what could be wrong?

(I use OpenFOAM-1.6.x).

Thank you very much..

benk January 12, 2011 11:33

I'm not sure about your paraview problems, maybe try posting/searching this thread: http://www.cfd-online.com/Forums/ope...burb-mesh.html

It seems as if groovyBC is just an interface for the mixed boundary condition which shows up in the list posted by McCarra above. So if you're good at C++ and don't want to use groovyBC, then you can try compiling your own boundary condition based on mixed.


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