COMSOL Multiphysics™

femlin
Purpose
femlin
Solve linear or linearized stationary PDE problem.
Syntax
Description
fem.sol = femlin(fem,...)
fem = femlin(fem,'Out', {'fem'},...)
[Ke,Le,Null,ud] = femlin(fem,...)
[Kl,Ll,Nnp] = femlin(fem,...)
[Ks,Ls] = femlin(fem,...)
fem.sol = femlin('In',{'K' K 'L' L 'M' M 'N' N},...)
fem.sol = femlin(fem) solves a linear or linearized stationary PDE problem
described by the (possibly extended) FEM structure fem. See femstruct for details
on the FEM structure.
fem.sol = femlin(fem, 'pname','P', 'plist',list,...) solves a linear or
linearized stationary PDE problem for several values of the parameter P. The values
of the parameter P are given in the vector list.
fem = femlin(fem,'out',{'fem'}) modifies the FEM structure to include the
solution structure, fem.sol.
[Ke,Le,Null,ud] = femlin(fem) partially solves the PDE problem by
eliminating the constraints. The solution of PDE problem can be obtained by the
scripting command u = u0+Null*(Ke\Le)+ud, where u0 is the linearization point.
[Kl,Ll,Nnp] = femlin(fem) partially solves the PDE problem by using the
Lagrange method. The solution can then be obtained by u = Kl\Ll, and then u =
u0+u(1:Nnp).
[Ks,Ls] = femlin(fem) partially solves the PDE problem by approximating the
constraints with stiff springs. The solution to the PDE problem is u = u0+Ks\Ls.
fem.sol = femlin('in',{'K' K 'N' N 'L' L 'M' M}) solves a pre-assembled
PDE problem.
u = femlin('in’,{'K' K 'L' L},’out’,’u’) is equivalent to solving the linear
system using u = K\L, with the important difference that you have access to all
linear system solvers (except Geometric multigrid) using the Linsolver property.
Consider the FEM discretization of a stationary PDE problem:
0 = L–
N T Λ ,
M
where L, N, and M depend on the solution vector U. femlin solves the linearized
form of this problem:
124 | CHAPTER 1: COMMAND REFERENCE