COMSOL Multiphysics™

multiphysics
applying flform to some subsystems. The output form can be forced by using the
property outform.
First, each application structure is converted to a FEM structure with all the
above-mentioned fields. Then the fields in fem1.*** are computed from the
corresponding fields in the subsystems according to the table below. The numbers
after the coefficient names refer to the subsystems in the order they are specified in
fem.appl.
TABLE 1-20:
QUANTITY
COMPOSITE SYSTEM
f, γ, g, r,
init
weak, dweak,
constr
gporder,
cporder
f 1
f 2
…
c, d a
, e a
, α, β, aqh , ,
c 1
0 0
0 c 2
0
0 0 …
var, varu, vart
var 1
var 2
...
The fields fem.***.expr are kept unchanged as far as possible; the only difference
being the permutation of ind-groups to suit a new ind vector if one is generated.
For ind groups where a particular expr variable is undefined, the entry [] is used.
Note that the coefficients in the second row of the table are weakly coupled in the
sense that the corresponding coefficients in the composite system are block
diagonal. This puts some limitations on the coupling between the subsystems. By
using general form, however, there are no limitations on the composite system
except for the da coefficient. The resulting stronger couplings are obtained by using
a call to femdiff with the full system resulting from the composition of the
subsystems. The properties Diff, Rules and Simplify control or supplement the
call to femdiff. Further couplings between applications can be introduced by the
method global_compute which is called for each application before femdiff.
308 | CHAPTER 1: COMMAND REFERENCE