p.s. the following code works fairly well --
crossIsoAdvec_modGrid=(Psi.arithmeticFaceValue * convCoeff).divergence
botFricCurl_modGrid=(DiffCoeff.arithmeticFaceValue *
Psi.faceGrad).divergence
I just want to make sure it is somewhat sensible...
On Thu, Feb 18, 2016 at 9:28 AM, James Pringle <[email protected]> wrote:
> Dear Jon --
>
> I am having a bit of a problem with your technique. All of my
> coefficients vary in space, e.g. they are define as follows:
>
> mesh = Grid2D(Lx=Lx,Ly=Ly, nx=nx, ny=ny)
>
> convCoeff=FaceVariable(mesh=mesh,rank=1)
> convCoeff.value[0,:]=....
> convCoeff.value[1,:]= ....
>
> DiffCoeff=CellVariable(mesh=mesh, rank=0)
> DiffCoeff.value = ...
>
> eq =
> (DiffusionTerm(var=Psi,coeff=DiffCoeff)+ExponentialConvectionTerm(var=Psi,coeff=convCoeff))
> eq.solve(var=Psi)
>
> So when I try to implement your suggestions of (DiffCoeff *
> Psi.faceGrad).divergence or (Psi * convCoeff).divergence I get errors
> because DiffCoeff is a Cell variable, and Psi.faceGrad is a face variable.
> Likewise for Psi*convCoeff
>
> So what is the most numerically constant way to solve this issue -- map
> DiffCoeff to face, or Psi.faceGrad to cell? Likewise should I map convCoeff
> to cell or Psi to face? I want to do it in the way that is most consistent
> with the underlying numerics.
>
> Thanks
> Jamie
>
> On Wed, Feb 17, 2016 at 9:43 AM, James Pringle <[email protected]> wrote:
>
>> Thank you, Jon, that is helpful. I would love to have the ability to find
>> the individual terms of the equation as calculated in the matrix that is
>> solved by fiPy. This would make closing budgets, etc, easier. But your
>> solution is a good start.
>>
>> Thanks again
>> Jamie Pringle
>> University of New Hampshire
>>
>> On Tue, Feb 16, 2016 at 4:53 PM, Guyer, Jonathan E. Dr. <
>> [email protected]> wrote:
>>
>>> James -
>>>
>>> I don't think there's a straightforward way to get at this.
>>>
>>> You can certainly write the explicit forms, e.g.,
>>>
>>> (DiffCoeff * Psi.faceGrad).divergence
>>>
>>> or
>>>
>>> (Psi * convCoeff).divergence
>>>
>>> but this isn't exactly the same as the matrix FiPy builds, as discussed
>>> at https://github.com/usnistgov/fipy/issues/461.
>>>
>>> I can see the value for diagnosing and simply understanding mechanisms,
>>> so I'll think about ways we might provide access to this.
>>>
>>> - Jon
>>>
>>> On Feb 12, 2016, at 10:18 AM, James Pringle <[email protected]> wrote:
>>>
>>> > I feel this should be an elementary question, but I can't seem to
>>> figure out how to answer it. I am solving a simple linear elleptic-ish
>>> equation with
>>> >
>>> > eq =
>>> (DiffusionTerm(var=Psi,coeff=DiffCoeff)+ExponentialConvectionTerm(var=Psi,coeff=convCoeff))
>>> > eq.solve(var=Psi)
>>> >
>>> > This works fine; the solution matches what I would expect. I have two
>>> questions:
>>> >
>>> > First, how can I obtain the value of the individual terms of the
>>> equation, evaluated with the solution in Psi?
>>> >
>>> > Second, is there any way to define my own new Psi (which is not an
>>> exact solution to the equation), and easily evaluate the DiffusionTerm and
>>> ExponentialConvectionTerm for that Psi?
>>> >
>>> > I am trying to illustrate how various parts of the solution evolve
>>> over the solution space, and how various approximations to the full
>>> solution differ from the full solution.
>>> >
>>> > Thanks to all who glance at this
>>> > James Pringle
>>> > University of New Hampshire
>>> >
>>> > _______________________________________________
>>> > fipy mailing list
>>> > [email protected]
>>> > http://www.ctcms.nist.gov/fipy
>>> > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
>>>
>>>
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>>
>>
>
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