fem_basis_t6_display, a MATLAB code which reads data defining a quadratic triangular ("T6") mesh and displays the basis function associated with any node in the mesh.
The entire mesh is shown (which could be a problem for large meshes!). However, a finite element basis function is nonzero over only a relatively small number of elements. Over these elements, the basis function is quadratic, and the curved nature of this part of the surface is suggested by taking many plot points in this region.
The best part of the presentation is that MATLAB allows the user to turn the plot or zoom in and out, which makes it much easier to understand the information that is being presented.
The triangular mesh is defined by a node file containing the coordinates of nodes, and an element file containing sets of the six nodes that make up each element.
Note that the six nodes making up each element are to be listed in a particular order, in which the vertices come first, followed by the midside nodes. Moreover, the first midside node is the one between vertices 1 and 2, as suggested by the following diagram:
3
|\
| \
| \
6 5
| \
| \
| \
1---4---2
In general, a mesh of quadratic triangles allows the sides to be bent. However, for this application, it is assumed that the sides of each triangle are straight, that is, that each midside node lies on the line segment joining the corresponding vertices.
fem_basis_t6_display ( 'prefix', node_index )where
The computer code and data files described and made available on this web page are distributed under the MIT license
fem_basis_t6_display is available in a MATLAB version and an Octave version.
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