[lost.identity]

I'm trying solve a simple diffusion problem in spherical coordinates. One of the boundary conditions I use of Neumann type where I specify that the temperature gradient at the inlet is zero.

The way I'm trying to implement it in my code as as follows

T (at node 1) = T at (node 2).

But since the solution progresses from node 1 to node 2 and so on, does this mean that I have to use the temperature of node 2 at the previous timestep?

If on the other hand the Neumann boundary conditions were specified at the outlet

T (end) = T (end-1)

which works fine by using the temperature values of the previous node.

Thanks.