Effects of averaging of the driving force

[jan]

Averaging of the driving force is important to reduce the effect of the artificial solute trapping which is a problem for all phase-field methods when the spacial resolution is too low. You can swich on or off this averaging in the "Flags" section at the top of the input file.
Additionally you have to specify the "averaging length" for each active phase interaction (section "Phase Interaction Data"). This averaging length input allows you to adjust the extent of averaging. The input value is the length for the averaging across the interface in number of cells. A value of 0 will switch off averaging for the corresponding phase interaction.
The effect of a high averaging length is a strong reduction of artificial solute trapping, but at the expense of a reduced effective mobility (i.e. the front moves slower because the average solutal undecooling is increased), and at the expense of an increased grid anisotropy (which means that for example dendrites may tend to follow the grid direction instead of the anisotropy direction). In most cases it seems to be best to use values in the order of the interface thickness.
For fine-tuning the interface kinetics in quantitative work both the interface mobility and the averaging length has to be optimized (see here: http://board.micress.de/viewtopic.php?f=17&t=17 ).

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original message from Bernd

[Antoine]

Hello Bernd,

I may have misinterpreted this post (or this may be a misprint) but the comment: "i.e. the
front moves slower because the average solutal undecooling is increased" sounds strange
to me, is it the other way round (the front moves slower because the average solutal
undecooling is decreased ) or are their any subtleties...

Regards

[Bernd]

Hi Antoine,

Of course, you are right, it was a misprint, the average solutal undercooling is decreased!

Sorry for that...

Bernd