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-   -   Boundary conditions (uniform flow) (http://www.cfd-online.com/Forums/flow-3d/112011-boundary-conditions-uniform-flow.html)

mahdi1 January 20, 2013 07:49

Boundary conditions (uniform flow)
 
Hello everybody

I have a problem in flow 3d.
I want to simulate a flow in a channel without slope to find velocity distribution in cross section. (flow is uniform)
could you please tell me that what I should choose for Boundary conditions and Initial condition.

Thanks.

zandi January 20, 2013 17:58

hi
see the example "flow over a weir" in manual

mahdi1 January 20, 2013 18:38

Reply to Ms Zandi
 
Hello Ms Zandi

Thanks for your reply. But I think that there is a misunderstanding about my question.
when you simulate flow over a weir, flow situation is not constant.
But I want to simulate a channel with only Uniform flow (after developed flow). As far as I just have flow depth and geometry of channel and according to them I want to find velocity distribution in cross section. when there is a slope in channel, It is done easily by Periodic boundary condition. But in a channel without slope I don't know how I can do it.

Do you have any suggestion?

Regards,
Mahdi

zandi January 21, 2013 03:26

Quote:

Originally Posted by mahdi1 (Post 402986)
flow over a weir, flow situation is not constant.
But I want to simulate a channel with only Uniform flow (after developed flow). As far as I just have flow depth and geometry of channel and according to them I want to find velocity distribution in cross section. when there is a slope in channel, It is done easily by Periodic boundary condition. But in a channel without slope I don't know how I can do it.

greetings,
as far as I know CFD programs treat all problem as unsteady state (therefor they need initial condition) and after a while if the reach to a staedy condition they give a notification or somthing. you can choose an "additional finish condition" in such problems inorder to stop solving when it is acting like steady, in Flow-3d you can find it in "model stup/general".

I dont have advanced knowledge on your problem but offer you do it as other problems and let yourself to know what cfd could have done.
for BC you may choose specified pressure due to depth in advanced you may choose periodic condition by giving velocity time tabe or etc. i'm not so friendly whit periodic .
but what you mean by uniform!!

mahdi1 January 21, 2013 06:09

Quote:

Originally Posted by zandi (Post 403026)
greetings,
as far as I know CFD programs treat all problem as unsteady state (therefor they need initial condition) and after a while if the reach to a staedy condition they give a notification or somthing. you can choose an "additional finish condition" in such problems inorder to stop solving when it is acting like steady, in Flow-3d you can find it in "model stup/general".

I dont have advanced knowledge on your problem but offer you do it as other problems and let yourself to know what cfd could have done.
for BC you may choose specified pressure due to depth in advanced you may choose periodic condition by giving velocity time tabe or etc. i'm not so friendly whit periodic .
but what you mean by uniform!!


To get information about Periodic boundary condition, I suggest you that read Technical note 60. You can download it through below link.

http://www.flow3d.com/resources/flow...-papers-2.html

Good Luck

zandi January 21, 2013 15:35

tnx
:) you too


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