# 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

 $$\large{ C_f= \frac{\tau}{ \frac{1}{2} \; \rho \; v^2 } }$$ $$\large{ C_f = \frac{\tau}{q} }$$

### Where:

$$\large{ C_f }$$  = skin friction coefficient

$$\large{ \rho }$$  = density of fluid

$$\large{ q }$$  = dynamic pressure

$$\large{ \tau }$$ (Greek symbol tau) = shear stress of fluid

$$\large{ v }$$  = velocity of fluid