[petsc-users] convection terms in heat equation

[Sanjay Kharche]

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?

cheers
Sanjay