About the Sectionwise Data Format for Data Export
When exporting data on the sectionwise data format, the program evaluates the entered expressions at a number of points in each mesh element. For example, evaluating in Lagrange points of order 1 means that the expressions are evaluated at the vertices of each mesh element. When a vertex is shared by more than one mesh element (as is typically the case) this means that the expressions are evaluated several times at that coordinate, but using the shape functions in the different mesh elements. The values of these evaluations at the same point might not be equal, depending on the expression being evaluated. In particular, derivatives are typically discontinuous across mesh element boundaries and usually have different values.
Once all the evaluations have been made, the data is checked for duplicate values (that is, evaluations with the same coordinates and the same values of the expressions). Such duplicates are removed before the data is exported to file. With smoothing turned on, a smoothed variant of the derivative is evaluated, which is continuous across mesh element boundaries, so in such cases there are many duplicates. When evaluating at Gauss points, the evaluation points are always in the interior of mesh elements, so there are never any duplicates.
To avoid the removal of duplicates, you can export several expressions to the same file, and then the values of all expressions must agree to be considered duplicates. Another way to ensure that no duplicates are removed is to add the variable
meshelement
to the list of expressions.
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Data
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See
Table 21-13
for links.
