COMSOL Multiphysics™

elcplproj
All map types available for elcplextr can be used also in projection coupling
variables. The common combination of a unit source map and a linear
destination map is not very useful, though. Instead, there is a map type projection
which specifies srcdim+1 vertices in the source geometry and srcdim vertices in the
destination. The basis defined by vectors from the first source vertex to each of the
remaining vertices is mapped onto a right-handed orthogonal system with unit axes.
The basis described by the destination vertices is then mapped onto the first
srcdim-1 dimensions of the same orthogonal basis. This means that the direction
of integration is effectively from the first source vertex to the last.
In addition to the fields present in the elcplextr element, the elcplproj requires
an integration order for the line integrals evaluated for each destination point. The
iorder field specifies the order of polynomials that should be exactly integrated.
Cautionary
Projection coupling is only implemented for simplex meshes. When finding
integration limits, the elcplproj element works directly on the basic polyhedral
mesh. Therefore, results can be inaccurate if the mesh does not properly resolve the
geometry.
Parameter or time dependency in the source transformation is not properly detected
by the solvers, which means that the source transformation will not be updated
between parameter or time steps in that case. Solution dependencies in the
transformation are properly detected, but do not give any Jacobian contributions
from the transformation.
The automatic detection of nonlinear and time or parameter dependent problems
does not work properly in that all problems containing projection coupling variables
are considered to be nonlinear and time dependent.
Examples
Project the diagonal cross section distance on the left and bottom edges of a square.
clear fem
fem.geom = square2;
fem.mesh = meshinit(fem);
fem.elem = {};
el.elem = 'elcplproj';
el.g = {'1'};
el.var = {'d','d'};
clear map1;
map1.type = 'projection';
map1.sg = '1';
map1.sv = {'1','2','3'};
64 | CHAPTER 1: COMMAND REFERENCE