On Thu, Nov 22, 2012 at 4:07 PM, Kerem Yunus Camsari <[email protected]>wrote:
> Hi all, > > I have a doubt regarding the solution I obtain from FiPy in a specific > problem I am attempting. > I am solving the 1-Dimensional Fokker-Planck Equation Using FiPy. > As this has a convection term, you might want to use a transient term as well just for the evolution. It might help debug the problem. > The diffusion coefficient I use is usually a function of position, and > sometimes go to zero in the middle of the grid. > In this case, I expect the electron density (G^n(x)) to go to zero, > because there can be no current when the diffusion coefficient reaches zero > inside the grid. > However the solution shoots up to infinity when D2(x) goes to zero, and > current isn't zero. I think this is wrong, but I am not sure what I am > doing wrong. > Below are the screenshots of the Diffusion Coefficient and Drift > Coefficient and Gradient of Diffusion Coefficient along with the solution I > am getting: > It might be that you need a harmonic or geometric mean at the faces for the diffusion coefficient. This will actually prevent flux in the places where the diffusion coefficient is zero > > I can post the FiPy script I am using to get this, but maybe the reason > why G^n(x) blows up is already apparent. > Not off hand. It would seem like it has something to do with the non-existent diffusion coefficient. Make sure you can get a solution with a constant diffusion coefficient and then change its dependence on x gradually. So that it doesn't go to zero, but just to something small. It might give you a clue. Cheers -- Daniel Wheeler
_______________________________________________ fipy mailing list [email protected] http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
