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Calculation of Cf in Openfoam

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Old   January 21, 2014, 23:46
Default Calculation of Cf in Openfoam
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rajesh
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Dear all,

I am doing simulation of flow past Selig airfoil.. I am wondering how to calculate co-efficient of friction?? if anybody knows. Pls respond.
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Old   January 22, 2014, 13:05
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Eric Robertson
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Use the "wallShearStress" utility and find the resultant of the three components that are output for you. This gives you \tau _w. Divide that by freestream dynamic pressure and you get Cf.
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Old   January 23, 2014, 06:35
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Dear Eric

Thanks for your reply. I calculated resultant of the three components as
V = sqrt(u_sq+v_sq+w_sq). Is this the way to calculate resultant of 3 components? By this i get only positive values. If there is separation in the flow, i should get negative Cf.
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Old   January 23, 2014, 08:56
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Eric Robertson
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That is correct.

Since your flow has separation, there will be a local minimum value of Cf accompanied by an increase. I'm other words, your graph will approach zero Cf but will begin to diverge away from it. You must locate this value and manually place a negative sign next to the values in your region after separation.
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Old   January 27, 2014, 05:09
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Dear Eric,

Thanks a lot
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