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

I seem to remember something of the form of Cmu^0.25 * sqrt (k) exists at a wall...

friction velocity = sqrt( shear stress on wall/density )

You need to know the shear stress on the wall to calculate friction velocity.

Is this a homework problem? Check out "A First Course in Turbulence" (Tennekes & Lumley) Chapter 5.2

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.