Hello,

I am working to solve Stokes problem on a domain that is discretized using two 
different types of mesh. A part of the mesh uses fem formulation and the rest 
uses nodal integral method (NIM) formulation (the details of which I will 
skip). However, the key takeaway is that NIM formulation of stokes uses 
pressure Poisson formulation instead of the continuity equation while FEM 
formulation uses the continuity equation. They are coupled at the interface. 
Right now, I am building a single matrix for the entire domain and solving it 
using fieldsplit option in a nested fashion. The matrix structure and the 
unknown vector are shown below.

My questions are:


  *   Are there any basic guidelines to solve these kind of problems.
  *   As I have mentioned I am currently using nested fieldsplit. The first 
split is using indices and the other split is done using detect saddle point 
option. is there a way to avoid using that option and doing it by combining set 
of indices or fields.

The matrix structure is
[Au_fem   Bp_fem   0   0]
[Cu_fem.       0          0   0]
[0            0        Du_nim    Ep_nim]
[0            0           0         Fp_nim]

the unknown vector is given by

[ufem pfem unim pnim]

Let me know if any additional information is needed.

Thanks,
Solomon.

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