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Old   February 13, 2003, 06:51
Default very basic question regarding fluid mechanics
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praveen
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Hi guys,

How can I find friction velocity if I know the bulk velocity. fluid is water. i am using a square duct configaration. i know only the bulk Reynolds number and fluid properties.

please help me.

praveen
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Old   February 13, 2003, 11:15
Default Re: very basic question regarding fluid mechanics
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Holidays
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I seem to remember something of the form of Cmu^0.25 * sqrt (k) exists at a wall...
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Old   February 13, 2003, 11:26
Default Re: very basic question regarding fluid mechanics
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Praveen
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friction velocity = sqrt( shear stress on wall/density )

You need to know the shear stress on the wall to calculate friction velocity.
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Old   February 13, 2003, 11:53
Default Re: very basic question regarding fluid mechanics
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ken
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Is this a homework problem? Check out "A First Course in Turbulence" (Tennekes & Lumley) Chapter 5.2
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Old   February 14, 2003, 04:19
Default Re: very basic question regarding fluid mechanics
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Holidays
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Praveen,

Thank you, but I believe I knew that. However the formula I gave you is used in CFD at the walls I believe. You could check T&L as Ken adviced.
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