Thank you for your reply sir
My problem involves the diffusion of polystyrene nanoparticles in water. These nanoparticles have surface charges, and there is an external electric field is used to accelerate the species diffusion.
In the model, I have enabled the species transport model, and selected inlet diffusion.
And I'm trying to use the UDF to add the additional flux resulting due to the effect of the external electric field (electromigration of species).
Here, electric flux is calculated to be added as an additional source in the transport equation.
And under source terms, I have added the UDF for C8H8 (polystyrene which is the diffusing species).
Hope I answered your question.