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Ubar and Ubulk

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Old   July 4, 2007, 07:20
Default Hi to all Can u please tell
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hadi tartoussi
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Hi to all

Can u please tell me what is the difference betwwen Ubulk and Ubar (for a LES turbulent channel flow) and how to calculate it for a given Re-tau.

Thanks in advance

Hadi
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Old   July 4, 2007, 13:06
Default for the case of isothermal pla
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Maka Mohu
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for the case of isothermal plane channel flow:

In literature, Ubulk usually is a volume averaged velocity which is a single number while, Ubar is usually an averaged (more accurately, an integral of) velocity (in time (after reaching fully developed flow and in homogeneous directions (x, z))), so it is a function of wall normal coordinate (Y); one can obtain Ubulk from Ubar by:

Ubulk=integral of (Ubar dy); where y is wall normal direction and Ubar is function of y;

have a look at postChannel utility;

If you are running your simulation by specifying Re_tau, then you are computing dimensionless variables. Try to derive the equations to be sure what are you doing. Have a nice day!

Best regards,
Maka.
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Old   July 5, 2007, 09:52
Default Thanks alot for ur explanation
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hadi tartoussi
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Thanks alot for ur explanation.

But i am confused about Ubar in transportproperties (channelOodles solver) is it the centerline velocity? or bulk velocity?

Actually i ran postchannel for channel395 tutorial and i have the same problem as urs posted on Monday, December 11 2006: (PostChannel: collapsed field result inconsistancy)
can u please tell me how did u solve this problem?

Thanks in advance
regards
Hadi
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Old   July 6, 2007, 08:44
Default Hi Hadi, Ubar is the bulk v
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Maka Mohu
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Hi Hadi,

Ubar is the bulk velocity. I posted the solution of the postChannel problem in the message that you referred to. Please recheck the message to read the solution.

Best regards,
Maka
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