yade-dev team mailing list archive

[Václav Šmilauer <eu@xxxxxxxx>]

> (1) "It is believed that the first method is generally more convenient,
> since it will let  :yref:`Cell.trsf` reflect only the transformation
> produced during the simulation, independently of the initial period
> geometry."
"it is believed": who? "We believe" perhaps would be better, no? Or just 
that "We chose the first method..."

For the sake of consistency (Cell, O.cell &c), I would say "cell 
geometry", not "period geometry". (The same sub 2.)
> (2) "In all cases, the period geometry should not be modified during a
> simulation, be it via Hsize, trsf, or refSize. The velocity gradient
> :yref:`Cell.velGrad` is the only variable that let the period
> deformation be correctly accounted for in constitutive laws and Newton
> integrator"
>
> Side comment on (1) : it will need to change the behaviour of setTrsf
> one day if we really want to uncouple trsf and Hsize. For instance, one
> could like to type trsf=identity after a deformation process (i.e. after
> some iterations) in order to set the current state as the reference for
> further deformation. It should have no effect on Hsize. Currently, it
> would mess the simulation big time.
>
> For (2), am I too restrictive?
I think it is better to say how it works than that it would "mess the 
simulation big time". There is naturally a question whether assigning 
trsf should change hSize or not, as you say.

1. One view is that if assigning trsf would just change the cummulated 
deformation (and refSize as well, of course, but not hSize), without 
changing geometry at all; going this way will make it more difficult to 
set the geometry based on a transformation matrix (not very difficult, 
though).

2. The opposite view is that trsf expresses transformation WRT the 
reference state, therefore changing trsf should change the geometry as 
well (current behavior).

In both cases moreover, refSize must be kept in sync with the reference 
hSize column norms. Nothing conclusive from my side whether 1. or 2. 
should be preferred. Perhaps others can give their opinions?

v.