[osimonsimon]

The problem is like this: a empty room with one inlet and one outlet. I am using simpleFoam solver and I've added a scalar transport equation in the solver to calculate the concentration at the outlet. The transport scalar is released at the inlet. And it is working well.

Now I have a question: Since this model might be extended to solve more than 30 species (transport scalar), it might be a burden to solve all these transport equations every iteration. Can I solve the flow field first and then "freeze" it while solving the transport equation? How could I do it?

The other question is: how could I get the surface average concentration at the outlet? I tried to follow the "scalarTransport" example "pPrime2" and I could get all the cell face value at the outlet and then average them (since the grid is uniform). But I know it is quite a detour and there should be a much easy way to do it. Please give me some hint. A example will be even better for a C++ beginner like me.

Thank you very much!