SOLVERS Parameters: ITERATION (Heat)

Description

Sets the iteration parameters that control the execution and convergence of the nonlinear Steady Heat and Transient Heat solvers.

ITERATION

Convergence tolerance

This parameter is used to check the convergence of a solution. It calculated similarly to the Displacement norm for structural solutions, except that instead of displacement, temperature is used.

Temperature is considered converged at the end of an iteration when the norm of the iterative temperature changes divided by the norm of the total temperature is less than the specified value. That is, when

where

= current total temperature vector,

= current iterative change in temperature,

= norm of a vector, and

is the Convergence tolerance.

Relaxation factor

The relaxation factor controls the time integration scheme. The default value, 0.6667, corresponds to a Galerkin scheme based on the finite element discretisation of time.

Iteration limit

This parameter specifies the maximum number of iterations allowed to obtain a converged solution. If convergence cannot be obtained within this many iterations, the current solution or time step is accepted and the solver continues.

GLOBAL STIFFNESS MATRIX UPDATE

By default, the thermal stiffness matrix is automatically updated at every time step in nonlinear transient heat problems.

Additional options are available for updating the thermal stiffness matrix in nonlinear transient heat problems:

At start of each row in the time step table

This is suitable for problems with no material nonlinearity.

After every saved step

This is suitable for problems with medium nonlinearity.

At every time step

This is suitable for problems with high nonlinearity.