Forward

In the Forward tab the desired solver for the forward simulation can be selected and the appropriate numerical parameters can be specified. For the solver for the inverse simulation see Inverse.

Note

Usually the default values should not be changed. Figure 41. Numerical parameters dialog, Forward tab

Item

Description

Forward solver and Preconditioner

Determines which solver will be used in forward simulation, see Linear system equations solvers , default is STABBiCG.

The default preconditioner is ILU.

Parameters

Specifies the parameters for the selected solver:

• Maximal inner iterations

Number of maximal allowed iterations needed to solve one linear system of equations ( “inner iterations” ), integer number, default is 1000 (iterative solvers only).

• Maximal outer iterations

Number of maximal allowed re-computations of the coefficients of the system of equations for non-linear problems. This reconstruction of the matrix together with the solving is called an “outer iteration”, integer number, default is 500.

• Desired residuum

Desired accuracy of the computation; must be a small real number, default is 1e-12.

• Residuum improvement factor

At each “outer iteration” the solver is asked to perform inner iterations until the actual residuum has got smaller than the residuum of the previous outer iteration divided by this factor, default is 10 times.

• Forward relaxation factor

At each iteration, when a new value is computed, only this fraction from the variation is taken. Real number between 0 and 1, default is 0.5.

For time-dependent computations choose a value closer to 1.

For pseudo-stationary computations choose a value closer to 0.

Others

Miscellaneous numerical options:

• Track interface

Turns on the adjustment of the phase boundary in a two phase material when calculating temperature. The vertices next to the phase boundary are moved in order to match with the melting isothermal.(default: false)

• enthalpy method

If selected (default), latent heat is released in the mushy zone around the phase change temperature, as described in the materials dialog section. In certain cases in conjunction with phase tracking this turns out to be unstable. If you unselect the enthalpy method here, latent heat will be released only in the control volumes around vertices tagged as lying on the interface, which sometimes is more stable. Attention: While using the enthalpy metod the interface velocities sign is positive if growth is upwards, and viceversa, with this method, a positive value means solidification, a negative one melting!