Hi everyone, I need to solve a convection-diffusion problem and I wonder what is the best software for numerically solving such a problem. I prefer to solve it with a software since my problem of interest is a 3D problem and it will be hard for me to solve it analytically. Is there any recommendations? I have used Comsol but I don't think the result is that accurate. In details, the problem is as follows: I have some dilute particles such as water vapor that needs to be removed. There is a small source where the concentration of this particle is fixed. I also have a strong nitrogen flow to help remove this particle. Briefly, I need to know how efficiently this particle can be removed, by diffusion (due to the concentration difference) and by convection (nitrogen flow).