[gerardosrez]

Hi cfd colleagues,

What are the pressure boundary conditions I have to set for the following boundaries?:

1) Flow entering through a boundary.
2) Flow exiting through a boundary (corrected mass flow).
3) Wall with no slip condition.

For (3) I use isolated boundary for pressure equation (no diffusion through boundary), but I'm not sure what do I have to use for (1) and (2) because I'm confuse if I have to set 0 value for pressure nodes at the exit (let's say a pipe or duct exit) or is it a no diffusion boundary condition on pressure equation.

This is a collocated variable CVFEM scheme on triangular grids...

Best regards...

[juliom]

Dear Gerardo.
In your first question, you may use dinamic pressure.
In your second question, I would use 0, because I assume your are using "outflow" as a result, you will have the other pressure, from an explicit way.
At any wall the pressure you selecte is the same as you define as a pressure reference!
Greetings !!!! from INELMECA!!

[FMDenaro]

Originally Posted by gerardosrez

Hi cfd colleagues,

What are the pressure boundary conditions I have to set for the following boundaries?:

1) Flow entering through a boundary.
2) Flow exiting through a boundary (corrected mass flow).
3) Wall with no slip condition.

For (3) I use isolated boundary for pressure equation (no diffusion through boundary), but I'm not sure what do I have to use for (1) and (2) because I'm confuse if I have to set 0 value for pressure nodes at the exit (let's say a pipe or duct exit) or is it a no diffusion boundary condition on pressure equation.

This is a collocated variable CVFEM scheme on triangular grids...

Best regards...

depends on your case ... are you solving compressible of incompressible flow? The mathematical problem is different ...

[gerardosrez]

Originally Posted by FMDenaro

depends on your case ... are you solving compressible of incompressible flow? The mathematical problem is different ...

Hi FMDENARO, right now I´m solving incompressible flow but I´m interested in compressible flow too because this solver will be improved for solving the shallow water equations so I need both advises ..


Thanks in advance FMDENARO...

[FMDenaro]

this paper can give useful suggestions

Poinsot T. et Lele S. (1992). Boundary conditions for direct simulations of compressible reacting flows. Journal of Computational Physics. 101, 1, 104-129.

otherwise, for incompressible flows, when the pressure equation is derived from the continuity constraint (divergence-free velocity field), the boundary conditions for the pressure are derived from the Hodge decomposition