Please ignore -- I just realized I am being a dolt. For those of you who
stumble across this thread and would like avoid making the same mistake, I
believe that
psi.faceGrad.constrain(1.0*mesh.faceNormals,faceMask)
constrains the faceGrad to some value, here 1.0*mesh.faceNormals, where
faceMask is true. If I want to set it the gradient to some value which is
normal in my coordinate system, I just have to provide a (2,numberOfFaces)
array with the appropriate values of the derivatives of psi in it. There is
nothing magical about the mesh.faceNormals other than that it gives you
useful information about the orientation of the face in your variable
space.
Sorry to waste everyones time.
Jamie
On Fri, Jul 1, 2016 at 10:35 AM, Pringle, James <[email protected]>
wrote:
> Dear fipy folks --
>
> I am solving a problem of ocean circulation on a thin spherical shell; the
> domain is too large to ignore the spherical nature of the earth. The
> problem is of the form
>
> eq = (DiffusionTerm(var=Psi,coeff=DiffCoeff)+
> ExponentialConvectionTerm(var=Psi,coeff=convCoeff))
>
> And I have incorporated all the of the appropriate metric terms for a
> spherical shell into the coefficients above. My problem comes as I strive
> to make the solution more realistic by applying Neumann BC's to some parts
> of the problem. The usual formulation for setting \Del\dot\Psi \dot normal
> = 1
>
> psi.faceGrad.constrain(1.0*mesh.faceNormals,faceMask)
>
> will not work because on a spherical shell the gradient is equal to
>
> \Del f = (1/r) dF/d(lat)*(unit vector latitude) +
> (1/(r*cos(lat)))*dF/d(long)*(unit vector longitude)
>
> Is there any easy way to constrain the faceGrad to something like
>
> constant = A*dPsi/dx+B*dPsi/dy
>
> where x and y are the spatial coordinates, and A and B are arbitrary
> factors? That way I could easily include the metrics...
>
> Thanks,
> Jamie 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 ]
