[zwbmimi]

It’s about drug diffusion. I use UDS here. The whole simulation geometry is divided into two parts, the left one(T) and the right one(N). Of course, the two parts have a conjunction line. The flow materials in the two parts are different, but the drug can diffuse in the two parts.
I want to define (i) the value of drug concentration are the same at each side of the conjunction line, (ii) and the gradient of the drug concentration are also the same at each side of the conjunction line (The equations are sent as attachment). My question is how to define the boundary condition. Now, I define it as INTERIOR, but I am not sure it is correct.