yade-users team mailing list archive

[Václav Šmilauer <eudoxos@xxxxxxxx>]

>>>     
>>>       
>> Bruno, how does this value compare to critical timestep calculated from
>> elastic wave propagation speed along the particle calculated for
>> cotinuum, i.e. , which is 2*particle diameter / sqrt(Young's modulus /
>> density)?
>>     
> Wait a minute, what is "Young modulus" for you?
> If it is the real modulus of the spheres, it has no existence in Yade.
> If it is the modulus of the packing, it is changing all the time, just 
> because contacts are created/lost all the time (from 0 contacts at the 
> begining to around 5 per sphere after some iterations).
>   
ElasticBodyParameters::young, from which stiffnesses of elastic links
are normally calculated.
> There is a simple way to evaluate if a timestep is good or not :
> run the simulation and watch the evolution of unbalanced force (now 8th 
> column in WallStresses files generated by TriaxialStateRecorder) while 
> you increment dt manualy. When unbalanced force start to tend to a 
> constant non-zero value, or even increases more and more, dt is too large.
> You will see if your dt could be much larger without any trouble.
>   
That was not meant for triaxial test, I know I can use unbalanced force
there. (I will probably move that code somewhere else to make it
possible to use it in different simulations.)

The advantage is that it makes a (very rough) estimate without ever
running or even creating the simulation.

V.

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