[Natasha]

I'm trying to do a simple implementation to study the advection-diffusion-reaction dynamics in a straight pipe.

I have points positioned along the length of the pipe (blue dots in the image above).

I came across a blog ([link](https://www.comsol.com/blogs/how-to-...the-weak-form/)) that explains how a point source is implemented. However, I am not really sure how to adapt it in this case.

The equation that captures the concentration dynamics is the following


The R in the last term of RHS corresponds to sink/source and the units is generally defined in mol/m^3 s. I want to define R = kc where the units of k is per sec. But I want to define R only at the points colored blue (i.e only as a point source/sink and not as a line source or sink).

I would like to ask for suggestions on how this implementation can be done.
By default COMSOL allows the implementation of a line source since the source/sink term R is associated with area.

[1]: https://i.stack.imgur.com/mDdtnm.png
[2]: https://i.stack.imgur.com/08Rkw.png

[Natasha]

Any suggestions?