# Boundary conditions (uniform flow)

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 January 20, 2013, 07:49 Boundary conditions (uniform flow) #1 Member   mahdi Join Date: Jan 2013 Posts: 43 Rep Power: 5 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.

 January 20, 2013, 17:58 #2 Senior Member     Fatema Zandi Goharrizi Join Date: Mar 2009 Posts: 156 Rep Power: 9 hi see the example "flow over a weir" in manual

 January 20, 2013, 18:38 Reply to Ms Zandi #3 Member   mahdi Join Date: Jan 2013 Posts: 43 Rep Power: 5 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

January 21, 2013, 03:26
#4
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Fatema Zandi Goharrizi
Join Date: Mar 2009
Posts: 156
Rep Power: 9
Quote:
 Originally Posted by mahdi1 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!!

January 21, 2013, 06:09
#5
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mahdi
Join Date: Jan 2013
Posts: 43
Rep Power: 5
Quote:
 Originally Posted by zandi 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!!

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

Good Luck

 January 21, 2013, 15:35 #6 Senior Member     Fatema Zandi Goharrizi Join Date: Mar 2009 Posts: 156 Rep Power: 9 tnx you too

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