| Author | Message | ||
     Mike Rosing (drmike) New member Username: drmike Post Number: 1 Registered: 07-2005 |
I am new to flexpde and have just started something a bit complicated. I think boundary conditions are the problem, but I'm not sure. I have a 2D, ycylinder problem, with 5 variables and 5 equations. The problem contains 3 regions, all with the same radius and stacked on top of each other. The physics is electrostatics with two fixed potentials on one radial line, and I'm trying to find the velocity and number density of ions in a solution. I have the potential defined on the outline of the problem region, and the ion density defined on some radial lines. The "natural" boundary condition is used to create symmetry along the r=0 axis for the velocity components. I get the error: The Linear System Solver has encountered a Singular Diagonal Block at Node Row 1. An equation has collapsed to 0=0. It then lists a bunch of subroutines. What am I doing wrong? | ||
| Mike Rosing (drmike) New member Username: drmike Post Number: 2 Registered: 07-2005 |
I asked the people at FlexPDE for help, and found that the main problem was not setting initial conditions correctly. By using the INITIAL VALUES section, all my equations work. I've also found the TRANSFER function. So I can create solutions with simple conditions, and build on them to create better initial conditions for follow on problems. Looks like I'm on the way to good modeling! |