Hi, sorry for the late reply.
On Fri, Feb 4, 2011 at 5:07 AM, Wolfgang Bangerth <[email protected]>wrote: > > > clearly. What I am interested in is the discretization of Stokes equation > > (here in weak form) > > a(y,v)+b(p,v)=(u,v) plus incompressibility and boundary conditions. > > Just to be clear: y and v are vector valued, and p is a scalar? How about > your > control function u? It must be a vector too, right? > > u, y, and v are vector valued and p is scalar. > I now want to assemble N. The ingredients I have are the Stokes FE system > from which I have assembled K, B, M_y,M_p and am now > looking for a way to get the rectangular N. I have the standard Stokes FESystem probably a bastardized version of step 22. Essentially, I have a discretization of y and p and was hoping as I want to use Q1 for the components of u to stick with the original FESystem or am I making my life too complicated here? What variables are in your FESystem, and consequently in your DoFHandler? If > your DoFHandler discretizes y,p,u, then you could build all the matrices > that > correspond to your problem in one BlockSparseMatrix, where the (0,2) block > would then be exactly N. > > > > I guess if the numbering of the nodes is such that K=blkdiag(K_1,K_2) for > > two components I could assemble a matrix [M_y,N_1^{T};N_1 M_p] > > and then construct my N from the N_1 block. Would this be a sensible way > to > > approach this? > > Yes. > If I do a component renumbering of the variable without any cuthill it seems that my K is not of the form K=blkdiag(K_1,K_2) and then I am not sure how to construct N from an N1 block. What would be the appropriate ordering to get the K=blkdiag(K_1,K_2) form? Thanks for your time. Best, Martin > > W. > > ------------------------------------------------------------------------- > Wolfgang Bangerth email: [email protected] > www: http://www.math.tamu.edu/~bangerth/ > > -- *Martin Stoll* *Postdoctoral Research Fellow* Computational Methods in Systems and Control Theory Max Planck Institute for Dynamics of Complex Technical Systems Sandtorstr. 1 D-39106 Magdeburg Germany Email: [email protected] URL : http://www.mpi-magdeburg.mpg.de/people/stollm Tel :+49 391 6110 384
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