# yade-users team mailing list archive

## Re: How many particles can be simulated one time, and how long it will take to get a good result?

```Kan,

You will have to define the problem a bit differently probably...

5-10 days of simulated time * 1million particles * (stiffness of rocks /
density of rock) =
I don't even want to imagine the computation time it will need!

Perhaps think about spliting the timescales of different physical
phenomena perhaps, and define the boundary conditions so that it will
avoid millions of particles. Also, coarse "meshing" for regions far from
the the wellbore may help to reduce the number of particles perhaps.

Bruno

kan a écrit :
> Hi, Vaclav,  Bruno ,
>
> I would like to use some code in YADE to do a simulation of rock
> failure , actually, it should be failure of a wellbore,--of course I
> need to write my code too.
> the simulation is requested to be field scale---it is terrible because
> the time may be more than 100years, so I would like to know the
> general information about the computing time.
> The material is the rock of sandstone, or clay, so the typical
> diameter of the 'body' should be in the range of 0.001mm to 1 mm, but
> I am not clear about the stiffiness, and the result should be after
> initial failure has passed 5-10 days(the real world time) because I
> want to track the failure procedure--I do no tknow how many iterations
> it needs.
>
> I know this question is very open, so I would like to know the general
> information about the time consuming.
> 1 Million is a lot, but it is still less than the requestment of the
> advisor who wants a field scale simulation, which means the sample may
> be many m^3, I am sure it will take many many years, so do you have
> result for with this way I can reduce the total particle number; or
> use a smaller sample but use some method to get a resonable result
> that can used to understand the field condition; Or, other advice with
> you experience? Appreciated.
>
> Thanks.
> Have a good day.
>
> Kan,
>
>
>
>
>
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>     Today's Topics:
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>       1. Re: How many particles can be simulated one time, and how
>          long it will take to get a good result? (Bruno Chareyre)
>
>
>     ----------------------------------------------------------------------
>
>     Message: 1
>     Date: Mon, 23 Jul 2007 11:33:08 +0200
>     From: Bruno Chareyre < bruno.chareyre@xxxxxxxxxxx
>     <mailto:bruno.chareyre@xxxxxxxxxxx>>
>     Subject: Re: [Yade-users] How many particles can be simulated one
>            time, and how long it will take to get a good result?
>     Message-ID: <46A475D4.8050001@xxxxxxxxxxx
>     <mailto:46A475D4.8050001@xxxxxxxxxxx>>
>     Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
>
>     Hello Kan
>
>     There is no precise answer to your question, unless you give us the
>     stiffness of particles, their density and sizes, and the number of
>     iterations you need. I can confirm the numbers given by Vaclav below,
>     but they can fluctuate a lot depending on the parameters of the model.
>     To give you an idea, the number of particles in my DEM simulations are
>     usually between 10,000 and 20,000; and the computations need often
>     more
>     than 1 hour. But again, they need more than an hour because I need
>     more
>     than 100,000 iterations. Would I need only 1000 iterations, then the
>     computation time would be 100 times less.
>     The only thing I'm sure is that 1 million particles is a lot.  I
>     don't
>     think somebody tried this before.
>
>     Bruno
>
>
>
>
>
>
>     >> 2. How long will it take to get a good result if I simulate about
>     >> 1Million particles with my computer? or how long it will take
>     to compute
>     >> 1sec at real-world time, or what is the general time step in
>     the DEM
>     >> part of YADE---the level of 1 ms, or 0.001 ms?
>     >>
>     >
>     > Those who have done large simulations (Bruno, Janek?) can
>     respond from
>     > experience. For the timestep, it will be in the order of elastic
>     wave
>     > propagating over the distance of particle diameter. E.g. for
>     concrete with
>     > particles of 1mm and 4000m/s, it would give some 2.5e-7s , i.e.
>     250ns (am I
>     > wrong here?).
>     >
>     > There is dynamic timestepper that will adjust dt based on
>     stiffnesses of
>     > interactions.
>     >
>     > Regards,
>     >
>     > Vaclav
>     > _______________________________________________
>     >
>     >
>
>
>
>     ------------------------------
>
>     _______________________________________________
>
>
>     End of Yade-users Digest, Vol 13, Issue 12
>     ******************************************
>
> ------------------------------------------------------------------------
>
> _______________________________________________
>

--

_______________
Chareyre Bruno
Maitre de conference

Institut National Polytechnique de Grenoble
Laboratoire 3S (Soils Solids Structures) - bureau I08
BP 53 - 38041, Grenoble cedex 9 - France
Tél : 33 4 76 82 52 76
Fax : 33 4 76 82 70 00
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