COMSOL Multiphysics™

flform
where there is an implicit summation over the k and i indices in each product. n is
the space dimension. Affected fields are therefore ga, f, weak, da, ea, and dweak
from equ and g, weak, r, and constr from bnd, with weak, dweak, and constr the
only fields remaining. Other fields within equ and bnd, such as shape, init, var,
etc., remain unchanged.
In addition, when converting to weak form, flform tries to take fem.border into
account. That is to say that if fem.border is not 1 or on, there may be interior
boundaries on which boundary conditions should not be applied. This process is
carried out because meshextend and the solvers pay no attention to fem.border
when considering weak, dweak and constr, unlike ga, c, f, q, r, h, etc.
The function flform accepts the following property/value pairs:
TABLE 1-45: VALID PROPERTY/VALUE PAIRS
PROPERTY
NAME
PROPERTY VALUE DEFAULT DESCRIPTION
defaults off | on off Return default fields
outform coefficient |
general | weak
out fem | equ | bnd |
edg | pnt
coefficient
fem
Output form
Output variables
shrink off | on off Shrinks coefficients to
most compact form.
simplify off | on on Simplify expressions
Cautionary
Example
Conversion from general form to coefficient form, or from weak form to general or
coefficient form is not supported.
The following code shows how the convergence can be improved for a stationary
solution of the model “Resistive Heating”. The system is converted to general form,
the symbolic derivatives are computed using femdiff, and the system is solved with
femstatic.
% !!! First run the example under the multiphysics entry
fem = flform(fem,'outform','general');
fem = femdiff(fem);
fem.xmesh = meshextend(fem);
fem.sol = femstatic(fem,'report','on');
postsurf(fem,'T');
Alternatively, change the outform to weak and remove the femdiff call.
See Also
multiphysics, meshextend
182 | CHAPTER 1: COMMAND REFERENCE