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time step in flow3D

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Old   March 27, 2014, 10:22
Question time step in flow3D
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mina salehi
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Hi All.
I have many questions about Flow 3D.
I've just started working with the software.

1) selection of time step in Flow 3D is basedon? I don't know, how select time step?

2)what is selected finish condition based on ? finish time or fill fraction?

3) How to determine the number of mesh cells?

Thanks alot for your guiding.
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Old   March 28, 2014, 06:39
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Maxime
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Hello,

1) What do you mean by "basedon" ? Flow 3D calculates the best time step during simulation. But you can define min and max time step in "numerics" option (optional).

2) Depend on what you search. What do you want to simulate with Flow 3D ? If you simulate cavity filling (for exemple casting process), "Fill fraction" is good.
To watch water comportment into a tube, you have to select "Finish time".

3) With the "FAVOR" method ("Mesh & Geometry" tab). You apply a cell size (or cells number), then you can watch your geometry modelisation with these mesh conditions. Reduce cell size if the geometry isn't correctly modelised.

Good luck
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Old   March 30, 2014, 04:02
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mina salehi
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Dear macsim
Thanks a lot.
I do not know how I would choose the time step?

I want to simulate flow over a weir. Which one should I choose? Fill fraction or Finish time?

Thanks.
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Old   March 30, 2014, 07:23
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Maxime
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Hello mina,

I think you can do a first simulation with an initial time step at 0.01 (numerics option). And depending results, try to minimize this initial time step.

For flow over a weir you have to choose finish time. For its value, try to calculate it depending of your simulation conditions (where the fluid is starting, during how many time you want to see flow over the weir...).

Have a nice Sunday.
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Old   April 4, 2014, 13:40
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mina salehi
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Thanks a million
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