# [petsc-users] CFD code with immersed boundary

Arun Kamath arun.kamath.m at gmail.com
Wed Nov 7 14:18:46 CST 2012

```My previous post gave a completely wrong meaning I guess, with a
missing punctuation.

Matt, you got it right. I wanted to know how do I deal with the ghost
cells arising from the physical domain, when I am using an
unstructured grid. Since DA works with structured grids only, as far
as I understood.

Thanks.

Are you saying that you have an unstructured grid with ghost cells, and you
would like PETSc to produce
a Vec of the correct size and Mat with the correct preallocation for that
grid and discretization, just as DA
does for structured grids?

Thanks,

Matt

On Wed, Nov 7, 2012 at 9:31 AM, Arun Kamath <arun.kamath.m at
gmail.com <https://lists.mcs.anl.gov/mailman/listinfo/petsc-users>>
wrote:

>* Hi!*>* I am working with a CFD code  where I need to solve the Poisson Pressure*>* equation. We solve a two phase flow problem which results in a jump in the*>* coefficients and a non symmetric system.*>**>* The boundary conditions are fulfilled using immersed boundary method ghost*>* cells at the solid boundaries of the domain.*>* I read about the DAs to deal with the boundary conditions, but they are*>* applicable to only "IJK" matrices as per my understanding.*>* So when I am using the "Aij" (CSR) matrix, how would you suggest I deal*>* with the ghost cells of the physical domain while forming the matrix and*>* the vector?*>**

>* Thanks a lot.*>* --*>* Arun Kamath*>* PhD Stipendiat*>* NTNU, Trondheim*>**>

--
Arun Kamath
PhD Stipendiat
NTNU, Trondheim
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