I am applying a new boundary condition to a large cfd program. The conditions that I want to be applied are satisfied at that specific boundary, but the program does not converge anymore! Can anybody please give me some advice on where I should start looking for the source of this instability and divergence? This could be a general cfd question, so I am looking for general advice. Thanks. Sue

I think your question is too general. The general problem might be that your boundary conditions are not suitable for your flow problem, but you would need to give some details for us to judge on that. Another possibility is that your boundary condition is simply not working (implementation problem). Again, we can't judge on that without knowing any details. So there's your general advice.