dolfin team mailing list archive

["Dag Lindbo" <dag@xxxxxxxxxx>]

>> On Tue, Feb 12, 2008 at 10:23:09AM +0100, Dag Lindbo wrote:
>>> Hello all!
>>>
>>> In the stokes demo (taylor-hood), I notice spurious pressure spikes
>>> near
>>> the corners. What is causing these?
>>>
>>> I changed to a paraboloc inflow profile (consistent with the no-slip
>>> BCs),
>>> but the problem remains. Further, I ran the same problem on a
>>> unitsquare
>>> mesh (see plot attached). The pressure spikes are large. Is the demo
>>> problem ill posed?
>>>
>>> Thanks!
>>> Dag Lindbo, KTH
>>
>> I would also suspect the boundary conditions for the velocity
>> to be the problem, but if you still see the spikes with a parabolic
>> inflow profile (which is zero at the no-slip boundaries) then I have
>> no idea.
>>
>> --
>> Anders
>
> Is this in all corners? Could you send a plot?
>
> /Johan

Problem solved. Thanks for the help! The error is that the facets adjacent
to the corners no get properly marked for noslip BC.

Fix to get the correct subdomain markers, in demo/mesh/subdomain/main.cpp:

class Noslip : public SubDomain
  {
    bool inside(const real* x, bool on_boundary) const
    {
      return (x[1] > 1.0 - DOLFIN_EPS || x[1] < DOLFIN_EPS) && on_boundary;
    }
  };

/Dag & Shilpa

>
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