yade-users team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

On 27 April 2010 12:53, Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx> wrote:

>
>  Would not just be simply an initial velocity you assign, which might
>> change once your body hits another one, isn't it?
>>
> In that case, you just assign an initial velocity (body.vel=.., no engine,
> no blocked DOF). This is not what I call a "prescribed-something" body, just
> the usual dynamic body with some initial conditions.
>
>  We could ideally also define a coefficient of restitution, that would be
>> equal to one if no dissipation occurs during the impact. Why do you think
>> this is not understandable?
>>
> In my understanding, "restitution coefficient" results from
> Newton+contactLaw, not from artificialy controling the displacement or
> velocity.
>
>
>>    Also, kinetic energy of velocity/displacement controlled bodies
>>    should not count in the total kinetic energy, only
>>    prescribed-force bodies should.
>>
>> I cannot see why not..
>>
> I was not reffering to bodies with an initial velocity, but bodies which
> are not subjected to Newton's law. They had no kinetic energy to the system
> since they are not dynamic (motion not modified by mass).
>
>
>
>>    Chiara, did you try the blockedDOF trick?
>>
>> I try. I let you know.
>>
> Well, perhaps it was irrelevant. I still don't know what you are looking
> for...
> For initial velocities at least, blockedDOFs are useless.
>

You are right in all what you say, Bruno. In fact forcing displacements is
not really the same as applying a force.
I was only testing a contact law forcing displacements, but now I realize
that the best way to check that is actually applying a force (constant or
variable in time) or an initial velocity (in the way you suggest).
ciao, Chiara

>
> Ciao.
>
>
> Bruno
>
>
>
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