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[Chiara Modenese <question191800@xxxxxxxxxxxxxxxxxxxxx>]

Question #191800 on Yade changed:
https://answers.launchpad.net/yade/+question/191800

Chiara Modenese proposed the following answer:

On 27 Mar 2012, at 12:05, Chareyre wrote:

> Question #191800 on Yade changed:
> https://answers.launchpad.net/yade/+question/191800
> 
> Chareyre proposed the following answer:
>> a high rigid modulus (usually quartz GPa), induce a high P wave speed,
> and a smaller size makes dt = r/ vp even much more smaller than the
> usual sample in the tutorial
> 
> This statement is correct.
> The thing that puzzles me in your question is you don't mention the number of particles, which is for sure the first parameter to consider.
> 
>> So I do not know how to deal with this ques.
> 
> Use a smaller number of particles?
I agree that this could be one possible solution.
> 
> The number of particles aside, changing mass and/or strain rate does not help in general (unless strain rate is excessively small initially, of course), because higher mass needs slower strain if you don't want to get inertial effects in your results (similarly, faster strain needs smaller mass).
> The only way to speed things up is to decrease stiffness.
I have to disagree with this last statement. Decreasing the inter-particle stiffness (the Young's modulus, in case of Hertzian contacts) won't solve your problem because your results are likely going to be affected by the reduced stiffness. In other words, you would be simulating a different material. This is the case for shear type tests which I suppose are what you are after? In other scenarios, I reckon that the stiffness is less important (like in flow kinematics).

Chiara

> 
> "Then how can I simulate 10e10 particles with stiffness 10e12", you may
> ask. You can't, or you have to be very patient.
> 
> Also note that GlobalStiffnessTimeStepper will help you to find the
> largest possible timestep, while PWave only gives a rough estimate.
> 
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