[alpha2rock]

I am working on a reactive precipitation problem (for BaSO4 crystals). My aim is to obtain a spatial distribution of these particles as obtained inside the flow reactor. Please elaborate on any good approach to such a problem.
Here are a few of my concerns, in the approach I followed:
1. Since I will be using a no. of coupled transport and population balance equations, along with volumetric and surface reactions. Can I define complex reaction rates also used as source terms in the transport equations from within the Fluent GUI or do I need to define all equations manually using UDFs?

2. I am using 2 liquid reactants i.e. BaCl2 and Na2SO4. What is the best way to define the materials - as 3 species BaCl2(l), Na2SO4(l) and BaSO4(s) with corresponding transport equations or as 5 species Ba2+, Cl-, (SO4)2-, Na+, and BaSO4(s). If the latter, how to approach defining radicals in a liquid?

3. Even with transport equations defined with UDFs, should I use any of the multiphase or discrete phase models for the flow?

4. As the population balance equations are also coupled with the transport equations (due to nucleation and growth of particles). How can UDFs be structured to get the final particle size distribution over space?

Answer to any and all concerns are appreciated. Any insights or suggestion of an alternate approach will also help.

[vinerm]

There are two ways to define reactions, either using the reactions within Fluent or using source terms; essentially reactions lead to source terms in various flow equations. If you use source terms, then you have to use UDF. Otherwise, you don't need UDF until you want to define reaction rates using UDFs.

The species depend on reactions. You can include radicals, however, the reactions will be stiff, requiring much smaller time-scale than flow time-scales. If objective is to predict final discrete phase sizing, then this may not be required.