Friction velocity (shear velocity)


Friction velocity, is a form by which a shear stress may be re-written in units of velocity. It is useful as a method in fluid mechanics to compare true velocities, such as the velocity of a flow in a stream, to a velocity that relates shear between layers of flow. Shear velocity is used to describe shear-related motion in moving fluids. A general rule is that the shear velocity is about 1/10 of the mean flow velocity.

Related formulas


u_τFriction velocity (m/s)
τ shear stress in an arbitrary layer of fluid (N/m2)
ρDensity of the fluid (kg/m3)