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-   -   Transient periodic boundary condition setting (https://www.cfd-online.com/Forums/fluent/213273-transient-periodic-boundary-condition-setting.html)

jiemodanni December 20, 2018 06:38

Transient periodic boundary condition setting
 
hi,
Now I am faced with this problem. I want to calculate the fully developed flow field in the circular pipe. In order to save resources, I use the flow periodic boundary condition.Because I cannot get the pulse of speed, my time step size has been set. I doubt that the periodic boundary can be used for transient calculation. I hope you can help me and tell me how to set it.Fluent is version 16.0.
thank you.

LuckyTran December 20, 2018 10:55

Periodic BC's can be used in transient calculation. Your doubts are completely unfounded.

jiemodanni December 21, 2018 05:36

Quote:

Originally Posted by LuckyTran (Post 719731)
Periodic BC's can be used in transient calculation. Your doubts are completely unfounded.

I first calculated the steady-state calculation example, and then took the steady-state result as the initial condition to calculate the unsteady flow field, but I did not observe the pulsating phase of the velocity, I gave a fixed mass flow rate.10,000 steps have been calculated, and the time step length is 0.0001. Can you tell me specifically how to set it? I don't know if there is something wrong with my setting.
thank you

LuckyTran December 21, 2018 16:26

Fully developed pipe flow doesn't develop pulsatile behavior... why are you looking for it?

jiemodanni December 21, 2018 21:25

1 Attachment(s)
Quote:

Originally Posted by LuckyTran (Post 719855)
Fully developed pipe flow doesn't develop pulsatile behavior... why are you looking for it?

I want to get this information about the instantaneous flow field. I've attached the picture below. I'm just going to use the transient calculation and the periodic boundary. I don't know why I can't get it。Attachment 67416

jiemodanni December 21, 2018 21:36

2 Attachment(s)
Quote:

Originally Posted by LuckyTran (Post 719855)
Fully developed pipe flow doesn't develop pulsatile behavior... why are you looking for it?

But all I get is this kind of flow field distribution, whether it's steady state or transient.
Attachment 67417

The following is the periodic boundary condition that I set.
Attachment 67418

Good man, can you tell me what I can do to get the transient velocity field? Thank you.

LuckyTran December 21, 2018 23:10

you need to be running transient LES


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