Not sure, but IMHO it has something to do with your region definitions. The
inlet and outlet regions contain the wall nodes, so there is no no-slip
condition in those nodes.

Check:

./simple.py pipe_flow_test_copy.py --save-regions-as-groups --solve-not
./postproc.py -b pipe_7f_long_regions.vtk --layout=row

You might want to change the wall region to:

     'select' : 'vertices of surface -f (r.Outlet +v r.Inlet)',

and apply the walls condition as the last one by naming it ebc_4, so that is is
lexicographically after the inlet and outlet ones.

r.

On 09/19/2016 02:33 PM, Nikhil Vaidya wrote:
> Hello!
>
> I am solving for steady laminar flow through a pipe. The issue I am facing
> is the following:
>
> I have given a velocity boundary condition at the pipe inlet. For the
> outlet, I examined the following two cases:
>
> 1) Pressure boundary condition at outlet.
>
> 2) No boundary condition prescribed at outlet.
>
> For both cases, I get a strange jump in the velocity at the pipe outlet. In
> the attached files you can see the velocity and pressure plotted along the
> axis(from inlet to outlet) of the pipe. Why do I see a jump in the velocity
> for both cases? How do I specify outlet conditions in sfepy?
>
> Another observation that I have made is that for case 1, there is a jump in
> the pressure value at the outlet. In case 2, this pressure-jumps goes away.
>
> Best regards,
> Nikhil
>