[petsc-users] convection terms in heat equation

[Matthew Knepley]

On Fri, May 15, 2015 at 4:43 PM, Sanjay Kharche <
Sanjay.Kharche at manchester.ac.uk> wrote:

>
> Dear All
>
> When I put in my convection terms, my solution is not well behaved.
> Following is an elaboration. I am wondering if I missed something in Petsc.
>
> I am solving the 3D heat equation with convection terms using second order
> finite differences and the boundary conditions are 1st order. It is solved
> on an uneven geometry defined inside a box, where a voltage variable
> diffuses. I am using a ts solver. The 3D DMDA vector uses a star stencil (I
> have also tried the box stencil). I assign the RHS at FD nodes where there
> is geometry. I get a stable solution if I do not have convection terms.
> However, when I use the convection terms, an error seems to build up.
> Eventually, the non-geometry part of the box also starts having a non-zero
> voltage. I checked my FD scheme for errors in terms. I also tested it out
> on a non-petsc explicit solver. The scheme is correctly written in the RHS
> function. The explicit solver is stable for the integration parameters I am
> using. Can you suggest what could be missing in terms of Petsc or otherwise?
>

Use the Method of Manufactured Solutions to check your residual function.

  Matt


> cheers
> Sanjay
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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