approximate size of simulation scale

[CKJK]

Hello all,

If I want to simulate something on micrometer scale, should I set approximate size to 10^-6, to keep all units SI unit? Or, set approximate size on 10^-3, to use millimeter, ton, kPa unit system? Does this affect the simulation data check process? Because I tried once, there was an error stated that the step is too small, I wonder if that was due to the small scale of size.

Thanks a lot in advance!

 

[FEA way]

Approximate part size can’t be smaller than 0.001. This limit is used to prevent the model from exceeding the geometry engine’s limit which is 10^-6. You should consider changing units if your part is very small.

 

[IceBreakerSours]

I am not sure if the unit system had anything to do with the error message you observed.

To the larger point, you do not want to be working in a unit system whose round-off error will cause serious cumulative effect on the results. If you are taking hundreds of thousands or millions of time steps, then round off is something to be aware of on the explicit side. I have rarely had to worry about this because, more often than not, my input uncertainties dominate any uncertainty in the numerical method employed. That is only to suggest that you have to keep the big picture in your mind.

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