Hi all, I'm studying step-20 tutorial example. But, I can't understand it, because it seems to have different things compared to step-3 in terms of boundary condition.
In the introduction of step-3, it is said that ∫Ω∇φ⋅∇u−∫∂Ωφn⋅∇u=∫Ωφf. The test function φ has to satisfy the same kind of boundary conditions (in mathematical terms: it needs to come from the tangent space of the set in which we seek the solution), so on the boundary φ=0 and consequently the weak form we are looking for reads Since φ=0, there is no kind of boundary term(that is second term in the left hand side of above Eq) in weak form that is (∇φ,∇u)=(φ,f), To do this, "VectorTools::interpolate_boundary_values" and "MatrixTools::apply_boundary_values" are used in step-3. However, in step-20, the boundary condition is not zero anymore. Instead of using "VectorTools::interpolate_boundary_values" and "MatrixTools::apply_boundary_values", the boundary term for pressure is added in the weak form. So, in assemble_system, there is part for boundary of preesure. As in step-20, I thought adding boundary term in weak form(in assemble_system) can replace using the above two things. However, in step-3, Boundary is zero unlike step-20. So there is nothing to add in assemble_system. So, I thought it would be OK If I erase the above two things for ZeroBoundaryCondition. But the result is not... The error is "SolverControl::NoConvergence (it, res)". I don't know what is the difference between erasing the two things in step-3 and inputting zero values in PressureBoundaryValues<dim>::value in step-20. And, what I have to do to apply zero boundary condition when FESystem<dim> is used as in step-20. Thank you. Kyusik. -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
