Hi everybody, I have a relaxation scheme for a Poisson equation. I have implemented both Dirichlet and Neumann Boundary Conditions. But I notice that the Neumann condition required more iteration to converge. Is it a right behaviour?

It is possible depending on your solution technique that more iterations are required with a Neumann bc.

When you have a Dirichlet bc, only one solution for Poisson equation is possible, since the solution must relax to that at the boundary. With a Neumann bc however, infinite solutions are possible, since only the zero derivative condition needs to be satisfied i.e at the boundary d(variable)/dn = 0