Skin Friction Coefficient

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Skin friction coefficient, abbreviated as \(C_f\), a dimensionless number, is the ratio of shear stress and dynamic pressure of a free stream.


Skin Friction Coefficient formulas

\(\large{ C_f= \frac{\tau}{ \frac{1}{2} \; \rho \; v^2 }  }\) 

\(\large{ C_f =  \frac{\tau}{q}  }\)

Symbol English Metric
\(\large{ C_f }\)  = skin friction coefficient \(\large{ dimensionless }\)  
\(\large{ \rho }\)  = density of fluid \(\large{\frac{lbm}{ft^3}}\) \(\large{\frac{kg}{m^3}}\)
\(\large{ q }\)  = dynamic pressure \(\large{ lbf }\) \(\large{ N }\)
\(\large{ \tau }\) (Greek symbol tau) = shear stress of fluid \(\large{\frac{lbf}{in^2}}\)  \(\large{Pa}\)
\(\large{ v }\)  = velocity of fluid \(\large{\frac{ft}{sec}}\) \(\large{\frac{m}{s}}\)


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Tags: Coefficient Equations