Hi John,

when you do that, you constrain the velocity over the whole boundary, and this has to be compatible with the incompressibility of the fluid. I am aware of the fact that what you did is compatible in the continuous case, but here, IMO due to a rather coarse mesh, it does not work. I have tried removing 'u.1' : -1.0, and it works. but vice versa it does not - the given velocity probably still too much. Anyway, my CFD ingorance is rather deep, so take what I have written with a grain of salt. (Any CFD experts around?).

r.

On 07/26/2012 07:21 PM, John C. Hart wrote:

If I alter the example file stabilized_navier_stokes.py to include an outflow boundary condition (in addition to its inflow) by adding the line:

'Outlet_velocity' : ('Outlet', {'u.1' : -1.0, 'u.[0,2]' : 0.0}),

to the ebcs, then the oseen solver doesn't converge, and I get:

"warning: (almost) singular matrix! (estimated cond. number: 1.5e+19)"

Is there an issue using both inflow and outflow boundary conditions with the oseen solver?

Thanks, -John