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-   -   Copying velocity field from one bc to another (http://www.cfd-online.com/Forums/cfx/22776-copying-velocity-field-one-bc-another.html)

jorllam June 27, 2006 10:39

Copying velocity field from one bc to another
 
Hi everybody,

I'm running a transient simulation in which, at the end of every time step, the velocity field from one boundary condition (an outlet bc with static pressure defined) must be the velocity profile for another boundary condition (an inlet bc with velocity profile defined) at the beginning of next time step. Both boundary condition surfaces have the same geometry and the same surface meshing (as if they were periodic), one is displaced from the other in the X axis direction.

I've tried to make it by creating user subroutines and junction box routines but it's being very hard to me knowing the data location used by the solver. Can anybody help me?

Thanks in advance!!

Robin June 27, 2006 19:33

Re: Copying velocity field from one bc to another
 
Make it a periodic. If they are just displaced in the X direction, it should work.

jorllam June 28, 2006 01:59

Re: Copying velocity field from one bc to another
 
Yes, the problem is these two bc's only share the velocity field, they have different pressure distributions. This is why I didn't set a periodic bc for these two bc's. I need to copy only the velocity profile at every time step.

Any other way of getting it?

Thank you anyway!

Robin June 29, 2006 10:54

Re: Copying velocity field from one bc to another
 
I see. Sounds like what you want is to model something that is linearly periodic, such as a tube bank or fully developed pipe flow. In version 11.0 you will be able to do this directly by specifying the mass flow rate or pressure rise across the periodic. In the current release (v10.0) the easiest way to do this is to specify a momentum source over your entire domain. The momentum source is essentially equal to your pressure drop. When you view the results, the pressure would essentially be the real pressure minus the pressure gradient.

Regards, Robin

jorllam June 30, 2006 02:08

Re: Copying velocity field from one bc to another
 
Yes, what I'm trying to model is something similar to a developed pipe flow. I think the best way to model it will be, as you said, placing a momentum source that makes the fluid recover the pressure drop. I hope this doesn't perturb very much the fluid velocity profile.

Thank you very much for your help Robin!

See you!


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