[cosine]

Hello,

I need to model mass transport in arteries. I have two domain e.g. one is a fluid domain (blood) and one is porous domain (arterial wall) as shown in the figures.

I create an interface between the fluid and porous domain. In the fluid, i create an additional variable (concentration) which is transferred in the domain. I want to transfer the variable from the fluid domain to the porous domain through the interface.
Do i need to add a subdomain and sources? I what cases a subdomain is necessary?
I have enable the beta features.
Should i enable the additional variable in porous domain also? Otherwise the concentration is not calculated.

Thank you very much for your time