OK. I understand the importance of the order when two or more regions contain the same nodes.

I have not understood the difference between using

'select' : 'vertices of surface -v (r.Inlet +v r.Outlet)', and 'select' : 'vertices of surface -f (r.Inlet +v r.Outlet)'. In the documentation on the sfepy website, I have seen the example:

'Gamma1' : ("""(cells of group 1 *v cells of group 2)
                   +v r.Right""", 'facet', 'Omega'),

Here, why is there a +v between (cells of group 1 *v cells of group 2) and r.Right instead of +f?

On Wednesday, September 21, 2016 at 9:57:22 AM UTC+2, Robert Cimrman wrote:
On 09/20/2016 02:48 PM, Nikhil Vaidya wrote:
> I will try giving the command line arguments to simple.py. I have not been
> able to get postproc.py running on my machine. I am using paraview. What
> should I do to view the data in paraview?

Just open it and display the variables with regions names.

> I will also try with your suggested region definitions.
> In the problem definition file, does the order all definitions matter? If
> yes, what should be the correct order? This is something that is not clear
> to me...

No, it does not matter.

But in the boundary condition case, when regions overlap, you might want to
influence the order (i.e. which condition is actually applied in the overlap
nodes) - for this purpose, the ebcs are applied in the lexicographic order of
their names.


> On Tuesday, September 20, 2016 at 2:09:21 PM UTC+2, Robert Cimrman wrote:
>> 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