wallShearStress

idrama · July 7, 2011, 02:58

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, 05:37

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, 09:37

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, 02:58	wallShearStress	#1
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 17	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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Problems with YPlusRAS and wallShearStress	Peter85	OpenFOAM Post-Processing	21	May 4, 2016 05:15
Post-Processing with Fluent-> wallShearStress	LenDey	OpenFOAM Post-Processing	1	January 2, 2011 06:14
wallShearStress with compressible flow	Ruehri	OpenFOAM Post-Processing	0	June 11, 2010 04:14
wallShearStress & creatTurbulenceFields in OF 1.6	ar_mofidi	OpenFOAM	3	April 15, 2010 03:39
wallShearStress for compressible flow	cbarry	OpenFOAM	2	October 12, 2009 10:28

July 11, 2011, 05:37		#2
David* Member David GISEN Join Date: Jul 2009 Location: Germany Posts: 68 Rep Power: 16	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, 09:37		#3
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 17	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.