Discussion Forum

Hello all,

I am modeling a 3D diffusion problem which primarily consists of a circular boundary constrained to a concentration of zero, surrounded by a much larger sphere with boundaries constrained to a given constant concentration value. I am seeking to identify the flux through the circular boundary, by using the Boundary Integration function at the circular boundary, as well as by creating an arrow plot which creates a "mesh" of arrows in a square-shaped layer just above the boundary.

In order to verify that the model is behaving as it should, I created a similar model with the circular boundary being doubled in radius (and thus quadrupled in area), expecting to see the flux value be quadrupled as well. However, the flux value has only doubled, and by the arrow plot, the flux value of elements in the middle of the circular boundary is half of what it was in the smaller case. I cannot come up with any explanation for this, and was hoping that someone with a better understanding of what the program is doing here might be able to explain this behavior.

Thanks!