yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

>  I am sorry to ask a novice question again.. Assuming that this 
> equation (I dw'/dt + [w' cross Iw']= T') is going to be used, all 
> viarables are in the local frame and the inertia matrix will be 
> aligned to the principal axis.  Since inertia can be represented by a 
> vector, does the Inertia 3x3matrix need to be generated? 
No.
But I have a doubt now : what is the definition of w' or w'' in the 
local frame? Don't we have by definition w=w'=w''=0 in a frame attached 
to the body? Probably just my imagination...

>  
> In this case, only variables that have to be transformed from local to 
> global coordinates (vice-versa) are the angular velocity (w), angular 
> acceleration (dw'/dt) and torque(T)?
>  
"In this case", I think you are right.

> Btw, is this problem with Newton's Damped Law only?  Or YADE does not 
> yet implement the 'accurate' method to calculate the dynamics 
> non-spherical particles?
>  
Not implemented accurately. Sufficient for you or not depends what you 
want to simulate.
> P.S.  I am interested in this because of the ellipsoid. I'll look at 
> superquadratics too (after days of deciding).  The thing is i'm stuck 
> at quarternions & rigid body dynamics. <sigh>
>  
Give superquadratics the inertia of spheres, they won't complain. ;)

Bruno



>  
> Yours sincerely,
>  
> CW Boon
>
>
>  
>
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