State space matrices including dirichlet BC

Asked by Praveen C on 2013-10-24

Hello
I want to compute linearized state space matrices of a non-linear system, like incompressible Navier-Stokes discretized with say Taylor-Hood elements. I know how to generate the matrices to obtain a linearized system like

M*du/dt = A*u + B*p
0 = B^T *u

but I want to completely eliminate the dirichlet degrees of freedom for the velocity. If I write velocity as

u = uf + ud

where

uf = free dofs
ud = dirichlet dofs

then I want a system like this

Mf*d(uf)/dt = Af*uf + Ad*ud + B*p

where I simply neglect the term d(ud)/dt. So here Mf, Af are smaller matrices from which dirichlet dofs have been completely removed.

Is there a simple way to construct these matrices ?

Thanks
praveen

Question information

Language:
English Edit question
Status:
Answered
For:
DOLFIN Edit question
Assignee:
No assignee Edit question
Last query:
2013-10-24
Last reply:
2013-10-25
Johannes Ring (johannr) said : #1

FEniCS no longer uses Launchpad for Questions & Answers. Please consult the documentation on the FEniCS web page for where and how to (re)post your question: http://fenicsproject.org/support/

Can you help with this problem?

Provide an answer of your own, or ask Praveen C for more information if necessary.

To post a message you must log in.