dolfin team mailing list archive

["Johan Hoffman" <jhoffman@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

Great!

/Johan

>>
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