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Old   May 15, 2008, 11:49
Default Urgent need
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ro
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Hi all,

I need to solve the fully developed flow in channel (thermally and hydrodynamically fully developed flow ) How can I do that .Since as I know the fluent solve the developing momentum and energy equations.

Thank you for your interset

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Old   May 17, 2008, 07:12
Default Re: Urgent need
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Andrew Clarke
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For hydrodynamic fluid flow, it is achieved by making the channel length at least 10 times the height of the domain or diameter of the channel.

1. Create a line (surface --> line/rake (in window for line rake surface: enter x0, x1 (=10h or 10x diamter), y0, y1 (=h or diamter) values) 2. Then create an xy velocity plot (plot --> xy plot (make sure the direction of the plot (x=1, y=0 OR y=1, x=0) is correct. 3. You will know that the flow is fully developed hydrodynamically if the velocity plot is parabolic shaped

www.nuc.berkeley.edu/.../soyumi/channel.html see figure 7 in this link... this is what your plot should look something like for hydrodynamic fully developed flow..

I am not one hundred percent sure about the thermal part.... sorry
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Old   May 17, 2008, 09:56
Default Re: Urgent need
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ro
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Dear Andrew Thank you very much

1-The figure is not fount in the mentioned link 2-I worked on 3D channels in heat exchanger with L=100*hydraulic diameter but the flow is start as developing and then reach the fully develop region .I need to solve the flow witout entrance region i.e I need the flow to be fully developed along the channels because the existing of the entrance region will affect the thermal results How can I solve this situation .

Thank you again
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Old   May 19, 2008, 05:18
Default Re: Urgent need
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Andrew Clarke
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You could create 2 seperate fluid zones.

1 - where developing flow is 2 - where developed flow is

Then you could apply your thermal conditions on the second fluid zone.... I could not be sure if this would work...

How exactly is your thermal results affected in the developed region?
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Old   May 19, 2008, 11:15
Default Re: Urgent need
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ro
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I need to calculate the fully developed value of overall heat transer coefficient for heat exchanger to compare it with its vale when the flow is developing flow to explore the effect of entrance region on the overall heat transfer coefficient and Nu .For two channel (two fluids ) and seperating wall.

I will repeat my question .How can I solve the fully developed flow in channel by fluent

Thank you very much for your interset
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Old   May 19, 2008, 13:30
Default Re: Urgent need
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Andrew Clarke
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In order to have to solve a fully developed region, you will need to obtain solved results from the end of the developing region...

1. Have you tried separating fluid zones where the transition occurs (i am currently looking into finding out how to do this myself)?

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Old   May 20, 2008, 12:48
Default Re: Urgent need
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ro
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I tried to solve a developing flow case and saved the velocity profile in the outlet of channel and then used this profile as a velocity inlet B.C at the channel inlet but when I ploted the central axial velocity along channel the velocity at inlet is equal to the velocity at the outlet but the velocity is increased beyond the inlet untile reach the fully developed value i.e the flow is developing but the velocity at inlet plan equal to the velocity at the exit plan
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Old   May 21, 2008, 09:29
Default Re: Urgent need
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Andrew Clarke
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Not sure what else I can advise you on...
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