# Calculate CF

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 January 24, 2012, 11:00 Calculate CF using Tecplot #1 New Member   Andreas Piskopakis Join Date: Jan 2011 Posts: 4 Rep Power: 7 Hi all I am tring to calculate the cf in tecplot. cf = 2*tau_wall/(density*free stream velosity**2) Until now I have not found one way to calculate the τw(tau wall) in tecplot. So I am thinking If it is possible to calculate Cf from the equations that i found in this site. http://www.cfd-online.com/Wiki/Skin_...on_coefficient Thank you for your time Last edited by Odusseas; January 27, 2012 at 05:31.

 January 24, 2012, 13:21 #2 Senior Member   duri Join Date: May 2010 Posts: 160 Rep Power: 8 I think for turbulent case you can estimate u+ from y+ based on the model you are using. Once u+ is available estimate u* which is sqrt(shear stress/density). In case of laminar flow you need to export gradient at wall to tecplot that directly gives shear stress. The formula given in that link is for flat plate in case of other geometry you can refer to Fluid Dynamic Drag by Hoerner. Odusseas likes this.

 January 26, 2012, 06:52 #3 New Member   Andreas Piskopakis Join Date: Jan 2011 Posts: 4 Rep Power: 7 Hi Duri Thank you for your answer My final goals are to compute Cf,u+,y+ For Cf I have Cf = 2Tw/(rho*U_ref^2) where Tw = wall shear stress Tw = mu*(dUp/dy) where Up = velocity parallel to the wall So I need to compute Tw For u+ I have u+ = Up/u* and u* = sqrt(Tw/rho) So, I need also here the Tw For y+ I have y+ = u*y/v And I have the same problem here. So For Cf,y+,u+ I need the Tw I read the tecplot manuals but I didn't found samething relative to the Tw. Do you know any other way to compute Tw from tecplot?? Can tecplot calculate this?? Thank you for your time Kind Regards

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