Hi,

I have to solve diffusion-advection PDE using finite difference method. The problem has two regions with different diffusion coefficients and velocities. At the interface between the two regions types of boundary condition :

1. No contact resistance
C1 = C2
- D1*dC1/dx + v1*C1 = - D2*dC2/dx + v2*C2

2. With surface resistance
- D1*dC1/dx + v1*C1 = - h (C2-C1)
- D1*dC1/dx + v1*C1 = - D2*dC2/dx + v2*C2

I am using fully-implicit in time and central-difference in space scheme and Tridiagonal Matrix Algorithm (Thomas's algorithm). However I found problem in doing FD approximaton at the interface. I would like to know if anybody may have some hints for this problem

Thank you in advance