Re: [deal.II] Getting RHS values at nodes with DBC

2019-09-12 Thread Giorgos Kourakos
As always there is a "deal.ii" way of doing the calculations. The FEValues::get_function_gradients() is actually what I needed. I got a little bit confused with the FEValues::get_normal_vectors(). This seems to return the normal direction of the face and doesn't give any further info about the

Re: [deal.II] Getting RHS values at nodes with DBC

2019-09-03 Thread Daniel Arndt
Giorgos, You can find a discussion for how constraints are handled in deal.II in https://www.dealii.org/developer/doxygen/deal.II/group__constraints.html. Thank you for your feedback. > I'll try to explain what I try to calculate with the help of a standard > FEM textbook: > > [...] > > In the

Re: [deal.II] Getting RHS values at nodes with DBC

2019-09-03 Thread Giorgos Kourakos
Thank you for your feedback. I'll try to explain what I try to calculate with the help of a standard FEM textbook: [image: CaptureFEMbook.PNG] In the book the global system is partitioned so that the first row contains the known U1 dofs and the second row the unknown the dofs U2. They solve

Re: [deal.II] Getting RHS values at nodes with DBC

2019-09-02 Thread Wolfgang Bangerth
> In my case I solve a simple laplace problem, that represent groundwater flow > with non zero dirichlet boundary conditions > My goal is to estimate how much water comes in and out from the dirichlet BC > nodes. You're asking the wrong question. What you are looking for is a *flux*, which

Re: [deal.II] Getting RHS values at nodes with DBC

2019-08-31 Thread Giorgos Kourakos
This is a year old post but I'm dealing with the same issue so I decided to continue here instead creating a new one. In my case I solve a simple laplace problem, that represent groundwater flow with non zero dirichlet boundary conditions My goal is to estimate how much water comes in and out

Re: [deal.II] Getting RHS values at nodes with DBC

2018-08-03 Thread Wolfgang Bangerth
On 08/01/2018 03:34 PM, RAJAT ARORA wrote: If I understand correctly, I dont think that will work. The reason is because of the Dirichlet boundary conditions, the value of the rhs at those nodes is unknown until you solve for the system. I think it's unclear to me what exactly you want in

Re: [deal.II] Getting RHS values at nodes with DBC

2018-08-01 Thread Jean-Paul Pelteret
> However, now how do I get the value of the rhs at the nodes where DBC were > specified? So, are you wanting the values to which the DoFs on the Dirichlet boundary are going to be prescribed? This is the same as the values stored in the constraint matrix (assuming that it holds only

Re: [deal.II] Getting RHS values at nodes with DBC

2018-08-01 Thread RAJAT ARORA
Hi Jean, Thanks for your reply. If I understand correctly, I dont think that will work. The reason is because of the Dirichlet boundary conditions, the value of the rhs at those nodes is unknown until you solve for the system. On Wednesday, August 1, 2018 at 10:08:12 AM UTC-4, Jean-Paul