# Boundary condition in Femlab

1. Sep 27, 2007

### mery

Does anybody know how to put BC at the center of a circle.

2. Sep 27, 2007

### Loren Booda

In terms of the complex plane? Just a guess, we may need more detail. By Femlab do you mean Fermilab?

3. Sep 27, 2007

### Loren Booda

Potential energy, in the case of a mass (or charge) in typical gravitational (or electromagnetic) field, is zero approaching infinite radius and approaches infinity negatively at zero radius; in such a field, kinetic energy that is zero approaching infinite radius approaches infinity at zero radius.

Did I get it right?

4. Sep 28, 2007

### PerennialII

I'll take a tad different approach . The easiest way is to introduce some sort of a geometric entity to the center of the circle, for example when doing the model in the first place. You can edit it later however if you've just drawn a circle ... from under "draw" go an edit the section and then 'reassemble' it again with the new geometric features (for example after having sliced the circle, added a point at its center etc.). There are other ways of doing it without modding the domain, but wouldn't go there first if just need the simplest solution available.

5. Sep 28, 2007

### clive

I think you should give more details about your specific problem but anyway, you have to look for internal BC in your software. If this is not possible, just replace the disk with a donut whose internal radius is very small. In this way you will be able to apply regular BCs near the center of the computational domain.

6. Nov 14, 2009

### edwin1214

Hi everyone. I'm interested to know more on the way to input BC by specifying the coefficients. Have been reading the manual but still blur. Example, specifying zero mass transfer at the end of a column in a 1D system. Lil help pls?