COMSOL Multiphysics™

femwave
Use fem.rules to specify additional differentiation rules. The derivative of the
Inverse hyperbolic tangent function atanh can, for example, be specified as
{'atanh','1./(1-x.^2)'}. It can also be stored as a field in the fem structure.
Cautionary The properties bdl, out, rules, and sdl are obsolete in FEMLAB 3.0.
The h and r coefficients at level 4 of the syntax must be given either as a scalar
numeric value, or a string containing an expression.
You should set the ODE Suite parameter maxorder to 2 for the solver ode15s for
wave type problems. This is automatically done by the graphical user interface.
Compatibility
In FEMLAB 1.0, when using general form, you had to apply femdiff before
femwave. This was because the h coefficient in fem affects the result of the r
coefficient in the output fem1, and h had to be computed by symbolic
differentiation by femdiff. In FEMLAB 1.1, h is automatically computed by
femwave if not provided. Therefore femdiff can be applied after the femwave call
in FEMLAB 1.1.
See Also
femtime
176 | CHAPTER 1: COMMAND REFERENCE