
From:  Tom Haeck 
Subject:  [Getfemusers] Displacements are meshsize dependent in a simple 2D linear elastic problem? 
Date:  Mon, 15 Dec 2014 15:32:58 +0000 
Hi all,
I am experimenting with a very simple 2D linear elastic problem. The domain is (more or less) rectangular with a circular hole in the middle. A constant pressure is acting radially outward on the faces of the hole in the middle (see attached image).
In order to calculate the force that is acting on each face of the hole in the middle, I multiply the constant pressure by the length of the face. Next, I calculate the resulting displacements. It struck me that the magnitude of the resulting displacement
is largely dependent on the size of the elements of the mesh. I would expect that larger forces acting on a few larger mesh elements would give more or less the same displacements as smaller forces acting on a lot of small mesh elements?
Moreover, when I use the magnitude of the vectors mesh.normal_of_face_of_convex(i.cv(),i.f())
as magnitude of the force vectors acting on the faces of the hole, the resulting displacements are independent of the mesh size. The magnitudes of the vectors mesh.normal_of_face_of_convex() are larger for smaller elements and smaller for bigger
elements. However, according to the documentation, mesh.normal_of_face_of_convex() returns vectors with magnitudes that are proportional to the area of the face?
To summarize:
Thx,
Tom

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