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Modeling delta function as source

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Old   August 30, 2012, 18:02
Default Modeling delta function as source
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Vishal Nandigana
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Hi Foamers,

I would like to know if it is possible to include a delta function as
a source term in OpenFOAM. For instance, I would like to implement,

div(a*gradient(phi)) = -a_0*(c+(d*delta(x-x_c)))

where x_c is the position corresponding to the nodal point where delta
function is singular and the position changes at every time step.

Please let me know if we can implement this in OpenFOAM.


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Old   February 27, 2015, 06:55
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Hi Vishal,

I was wondering if you found an answer to this?

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Old   February 27, 2015, 13:42
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I assume, that you mean the dirac distribution by delta(x-x0).
You can approximate delta by a field that has the value 1/V in the grid cell containing x0 and 0 elsewhere, resulting in:

For a more accurate solution you may need to implement a jump boundary condition and split your mesh on each "side" of x0.
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Old   February 28, 2015, 09:37
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You can create a volScalarField filled with 0s. Then loop over the cells and check which one of them satisfy the delta condition, so that you can change their values to 1
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