COMSOL Multiphysics™

elsconstr
Purpose
elsconstr
Define pointwise constraints controlled by shape functions.
Syntax
el.elem = 'elsconstr'
el.g{ig} = geomnum
el.geomdim{ig}{edim}.ind{eldomgrp} = domainlist
el.geomdim{ig}{edim}.shelem = meshcases | shapelist
meshcases.default = shapelist;
meshcases.case{elmcase} = shapelist;
meshcases.mind{elmcase} = caselist;
shapelist{eldomgrp}{ishape}{3*i-2} = bmtypename
shapelist{eldomgrp}{ishape}{3*i-1} = shapename
shapelist{eldomgrp}{ishape}{3*i} = shapeparams
el.geomdim{ig}{edim}.constr{eldomgrp}{ic}{j} = constrexpr
el.geomdim{ig}{edim}.cshape{eldomgrp}{ic} = ishape
Description
The elsconstr element defines pointwise constraints where the type of constraint
is determined by a shape function object. The idea is that the constraint points are
selected to be appropriate for variables having the corresponding shape function.
For the syntax of the ind field, see elempty. For the syntax of the shelem field, see
elshape. A difference to the syntax in elshape is that the cell array shapelist has
three levels instead of two.
The expressions that are used to formulate the constraint are given in the constr
field, and the index of the corresponding shape function object is given in the
cshape field. More precisely, in element geometry ig, dimension edim, and
element domain group eldomgrp, constraint number ic is defined by the shape
function object with index
ishape=el.geomdim{ig}{edim}.cshape{eldomgrp}{ic}. The expressions
needed to formulate this constraint is given by the cell array
el.geomdim{ig}{edim}.constr{eldomgrp}{ic}. The number of expressions ne
in this cell array depends on the shape function object.
The elsconstr constraint element is only implemented for the shape functions
shlag, shcurl, and shdiv. For shlag, the number of expressions ne=1, and this
expression is constrained to be zero in the node points of the shlag object. For
shcurl, the number of expressions ne=sdim, and these expressions are considered
as components of a vector. The tangential component of this vector is constrained
to be zero in the node points for the shcurl shape function. For shdiv, the number
of expressions ne=sdim, and these expressions are considered as components of a
104 | CHAPTER 1: COMMAND REFERENCE