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[Sacha Duverger <question701782@xxxxxxxxxxxxxxxxxxxxx>]

Question #701782 on Yade changed:
https://answers.launchpad.net/yade/+question/701782

Sacha Duverger posted a new comment:
Thank you for your answer, yes cell.velGrad is always symmetric in my
simulations.

The automatic determination of the flip matrix was very convenient for me since I don't really understand yet how it is computed. From what I understand of [6]:
 - all diagonal coefficients a_ii are always zero
 - non diagonal coefficient a_ij  are a rounded ratio between the scalar product of the i^th and j^th  base cell vectors and the squared norm of the i^th  base cell vector

So I guess a_ij is the cosine of a rotation angle, but not quite the
angle between the i^th and j^th  base cell vectors because they don't
necessarily have the same norm. Also there is this round operation: I
don't understand why it is performed, and why in two steps (floor +
int).

Is there a simpler expression of the flip matrix when cell.hSize has
always been deformed with a symmetric cell.velGrad ?

Thanks,

Sacha

[6]: https://gitlab.com/yade-
dev/trunk/-/blob/277c4f0c4a94dd1df423e8d499e56a457d356ea0/preprocessing/dem/Shop_01.cpp#L66-72

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