Skin friction coefficient

Anna Tian · January 24, 2013, 18:56

Hi,

I'm looking for the skin friction coefficient formula that CFX uses. But I didn't find it on user manual.

Could you please tell me which skin friction coefficient formula does CFX use?

Thank you very much!

singer1812 · January 25, 2013, 11:51

tau_wall/(1/2*rho*Uinf^2)?

Not sure what you mean. Do you mean how do they get tau_wall?

Anna Tian · January 25, 2013, 19:08

Quote:

Originally Posted by singer1812

tau_wall/(1/2*rho*Uinf^2)?

Not sure what you mean. Do you mean how do they get tau_wall?

Yes. I guess it compute tau_wall by this

http://www.cfd-online.com/Wiki/Wall_shear_stress

But does it just set the fluid velocity at the wall as 0 then compute the (du/dy)_{y=0}? But how does it know du/dy at the wall(y=0) without knowing the wall shear stress in advance?

singer1812 · January 28, 2013, 10:25

That can be a complicated discussion. I suggest looking at chapter 2 of the CFX Theory Guide.

January 24, 2013, 18:56	Skin friction coefficient	#1
Anna Tian Senior Member Meimei Wang Join Date: Jul 2012 Posts: 494 Rep Power: 16	Hi, I'm looking for the skin friction coefficient formula that CFX uses. But I didn't find it on user manual. Could you please tell me which skin friction coefficient formula does CFX use? Thank you very much! __________________ Best regards, Meimei

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January 25, 2013, 11:51		#2
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	tau_wall/(1/2rhoUinf^2)? Not sure what you mean. Do you mean how do they get tau_wall?

January 28, 2013, 10:25		#4
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	That can be a complicated discussion. I suggest looking at chapter 2 of the CFX Theory Guide.