Discussion Forum

Hi all,

I posted in this forum several times. my last post was:


"I am trying to integrate particle flux around a surface of the sphere. So I am using surface integration from derived values. As you know the default coordinates in COMSOL is Cartesian. However, I need to do this integration on spherical coordinates (r, theta, phi). So I added the sys2( spherical coordinates) from definition. I previously run my program with Cartesian coordinates so everything are in x,y, z direction. Now that I added the new coordinates(spherical). How can I implement it in my results? I need to integrate particle flux on r direction over the entire range of theta and phi. But I can't find the concentration gradient in r direction. The only direction available are x,y, z. Please help me to use this new coordinates that I defined in my results. I really appreciate all the help that you guys give to me."

There are 2 questions:
1- Is there any way to change my PDE equation in spherical coordinates? The gradient part should be transform to spherical coordinate. Now it is: [d/dx, d/dy, d/dz], I need to change it to: [d/dr, (1/(r*sin(theta)))* d/d(theta), (1/r)*d/d(phi)].
When I define my equation and its gradient part in spherical coordinates then I will be able to do the integration of d(concentration)/dr over the surface.
2- How can I use reacf to determine the particle flux. I can not understand what reacf actually do? What is its dimension? And what does it compute. I need to know how to use it instead of integration of d(concentration)/dr in the entire surface of the collector.

I really need to find some answer. I can't make any progress at all. I really appreciate any answer.

Thanks,

Negin