Before solving the coupled fluid flow and heat transfer problem, you may want to patch an initial temperature or solve the steady conduction problem as an initial condition. The coupled problem can then be solved as either steady or transient. Because of the nonlinear nature of these problems, however, in most cases a transient solution approach is preferred.
You can specify the under-relaxation factor applied to the liquid fraction equation in the Solution Controls Task Page.
Solution →
Controls
Specify the desired value in the Liquid Fraction Update field under Under-Relaxation Factors. This
sets the value of in the following equation
for updating the liquid fraction from one iteration (
) to the next (
):
(27–1) |
where is the predicted change
in liquid fraction.
In many cases, there is no need to change the default value
of . If, however, there
are convergence difficulties, reducing the value may improve the solution
convergence. Convergence difficulties can be expected in steady-state
calculations, continuous casting simulations, simulations involving
multicomponent solidification, and simulations where a large value
of the mushy zone constant is used.