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-   -   exponentially decaying boundary condition (http://www.cfd-online.com/Forums/openfoam/123753-exponentially-decaying-boundary-condition.html)

mcgintygs September 20, 2013 03:51

exponentially decaying boundary condition
 
I'm considering a simple diffusion problem using laplacianFoam and trying to add a simple boundary condition that decays exponentially with time, something like exp(-A*t), where A is some constant and t is time. My problem is concerned with the concentration, C, of some drug and so I have modified the standard laplacianFoam code to `C' rather than `T'.


Firstly, can anyone advise me how to set this up so that foam computes the boundary condition value at each new timestep?

Secondly, as a quick-fix attempt, I looked at

http://www.openfoam.org/version2.1.0...conditions.php

and tried to do this by tabulating some values.

My "C" file in the "0" folder looks like:


FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object C;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 -3 0 0 1 0 0];

internalField uniform 0;

boundaryField
{
impermeable
{
type zeroGradient;
}
source
{
type uniformFixedValue;
uniformValue table
(
(0 1)
(360 0.3)
);
}
defaultFaces
{
type empty;
}
}

Presumably the tabulation means that at time t=0 the value is 1 and at time 360 the value is 0.3? although this isn't clear at all from the link above. What value is taken at other times?

Anyway, the code seems to run, but I cannot view it in paraFoam - the error is

"ERROR: In /builddir/build/BUILD/ParaView-3.8.1/VTK/IO/vtkOpenFOAMReader.cxx, line 6349
vtkOpenFOAMReaderPrivate (0x3af1990):
Wrong list type for uniform field
"

I'm not sure if this a a problem with my code or simply the paraview.

Any help much appreciated

ahmmedshakil September 20, 2013 04:49

Hi,
Have tried with groovyBC: http://openfoamwiki.net/index.php/Contrib_groovyBC

hrvig October 22, 2013 00:31

Did you manage to solve this problem?
I am having the same problem

mcgintygs October 28, 2013 05:06

Yes, groovyBC did the job


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