wallShearStress

idrama · July 7, 2011, 03:58

Hello Foamers,

I have a simple question about computing wall shear stresses: what is the difference between:

(1) tau_w=mu*grad(U) | y=0

and

(1) tau_W=mu [ grad(U)-grad(U)^T ] . n

where mu is the viscosity, U the velocity and n the surface normal.

Cheers

David* · July 11, 2011, 06:37

Hi Claus,
the second one makes no sense to me, why would you substract a transposed tensor from it's original? Where did you find this formula?
Regards,
David

idrama · July 11, 2011, 10:37

It can be found in several books about mechanics; there it is treated as the generalization of newtons law. The term even appears in the incompressible navier stokes equation.

July 7, 2011, 03:58	wallShearStress	#1
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 18	Hello Foamers, I have a simple question about computing wall shear stresses: what is the difference between: (1) tau_w=mu*grad(U) \| y=0 and (1) tau_W=mu [ grad(U)-grad(U)^T ] . n where mu is the viscosity, U the velocity and n the surface normal. Cheers

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July 11, 2011, 06:37		#2
David* Member David GISEN Join Date: Jul 2009 Location: Germany Posts: 70 Rep Power: 17	Hi Claus, the second one makes no sense to me, why would you substract a transposed tensor from it's original? Where did you find this formula? Regards, David

July 11, 2011, 10:37		#3
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 18	It can be found in several books about mechanics; there it is treated as the generalization of newtons law. The term even appears in the incompressible navier stokes equation.