COMSOL Multiphysics™

femtime
Reassembly” on page 439 in User’s Guide. The corresponding value is a string or a
cell array of strings.
The property Tlist must be a strictly monotone vector of real numbers.
Commonly, the vector consists of a start time and a stop time. If more than two
numbers are given, the intermediate times can be used as output times, or to control
the size of the time-steps (see below). If just a single number is given, it represents
the stop time, and the start time is 0.
The property Tout determines the times that occur in the output. If Tout=tsteps,
then the output contains the time steps actually taken by the solver. If Tout=tlist,
then the output contains interpolated solutions for the times in the Tlist property.
The default is Tout=tsteps, except when the property Tsteps=free and Tlist
has length greater that 2, in which case Tout=tlist.
The property Tsteps controls the selection of time steps. If Tsteps=free, then the
solver selects the time steps according to its own logic, disregarding the
intermediate times in the Tlist vector. If Tsteps=strict, then time steps taken by
the solver contain the times in Tlist. If Tsteps=intermediate, then there are at
least one time step in each interval of the Tlist vector.
For more information about the time-dependent solver; see “The Time-Dependent
Solver” on page 385 in COMSOL Multiphysics User’s Guide.
Example
Solve the heat equation
------
∂u
– ∆u
= 0
∂t
on a square geometry -1 ≤ x, y ≤ 1. Choose u(0) = 1 on the disk x 2 +y 2 < 0.4 2 , and
u(0) = 0 otherwise. Use Dirichlet boundary conditions u = 0. Compute the solution
at times linspace(0,0.1,20).
clear fem
fem.geom = square2(2,'pos',[-1 -1])+circ2(0.4);
fem.mesh = meshinit(fem);
fem.shape = 2;
fem.equ.c = 1; fem.equ.da = 1;
fem.bnd.h = 1;
fem.equ.init = {0 1};
fem.xmesh = meshextend(fem);
fem.sol = femtime(fem,'report','on','tlist',linspace(0,0.1,20));
postanim(fem,'u')
170 | CHAPTER 1: COMMAND REFERENCE