COMSOL Multiphysics™

poisson
Purpose
poisson
Fast solution of Poisson’s equation on a rectangular grid.
Syntax
Description
fem.sol = poisson(fem,...)
fem.sol = poisson(fem) solves Poisson’s equation with Dirichlet boundary
conditions on a regular rectangular grid. A combination of sine transforms and
tri-diagonal solutions is used for increased performance.
The boundary conditions must specify Dirichlet conditions for all boundary points.
The mesh fem.mesh must be a regular triangular mesh on a rectangular geometry,
for example, generated by meshpoi. Details on the mesh representation can be
found in the entry on femmesh.
The algorithm handles the f and γ coefficients. The c coefficient is set to one. All
other coefficients are ignored. Only a one-dimensional system can be handled, that
is, only fem.dim = 1 is allowed.
The weak solution form must not be used when generating the extended mesh.
Therefore set fem.sol='coefficient' before calling meshextend.
Apart from round-off errors, the result should be the same as using femlin.
The function poisson accepts the following property/value pairs:
TABLE 1-22: VALID PROPERTY/VALUE PAIRS
PROPERTY
NAME
PROPERTY VALUE DEFAULT DESCRIPTION
Const cell array Definition of constants
Nullfun flnullorth | flnullorth Null space function
flspnull
Out fem | sol | u sol Output variables
Diagnostics
Cautionary
If fem.geom does not seem to describe a rectangle, an error is displayed.
The function only works in 2D. The function only supports linear Lagrange
elements.
Compatibility The properties Context and Tpoint are obsolete from FEMLAB 3.0.
The property Variables has been renamed to Const in FEMLAB 2.3.
See Also
meshpoi
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