Eigenvalue
Solve a PDE eigenvalue problem.
Syntax
model.sol(sname).create(fname,"Eigenvalue")
model.sol(sname).feature(fname).set(pname,value)
 
model.sol(sname).feature(fname).create(fname2,LinearType)
 
model.sol(sname).feature(fname).create(fname2,"Advanced")
 
Here LinearType is any of the allowed linear solver feature types.
Description
Operation feature.
For both linear and nonlinear problems, the eigenvalue problem is that of the linearization about a solution U0. If the eigenvalue appears nonlinearly, COMSOL Multiphysics reduces the problem to a quadratic approximation around a value λ0 specified by the property eigref. The discretized form of the problem reads
where K, D, E, N, and NF are evaluated for U = U0 and λ = λ0. Λ is the Lagrange multiplier vector, and λ is the eigenvalue. The eigenvalue name can be given by the property eigname. The linearization point U0 can be given with the property U. The shift, described below, is compensated according to the linearization point for the eigenvalue. Therefore, changing the linearization point has no effect at all for linear or quadratic eigenvalue problems. The eigenvalue search method can be manual or a region in the complex plane (controlled by the property eigmethod).
The feature eigenvalue accepts the following property/value pairs:
Name of the controlling study step or "user" if the feature is controlled manually.
manual | region | all
Eigenvalue search method; the all method finds all eigenvalues for a full matrix and can only be used for small eigenvalue problems.
true | false
average | maximum | mass
on | off
init | solution
zero | solution object
current | solution store
on | off
on | off
Eigenvalue shift (when shiftregselect = manual).
auto | manual
auto | all | positive integer
on | off
auto | false
Specify where to look for the desired eigenvalues with the property shift. Enter a real or complex scalar; the default value is 0, meaning that the solver tries to find eigenvalues close to 0.
For more information about the eigenvalue solver, see Eigenvalue Solver in the COMSOL Multiphysics Reference Manual.