Topic summary
Skin friction
Extracted from the Wikipedia article Skin friction drag.
Skin friction drag or viscous drag is a type of aerodynamic or hydrodynamic drag, which is resistant force exerted on an object moving in a fluid. Skin friction drag is caused by the viscosity of fluids and develops from laminar to turbulent drag as a fluid moves more rapidly across the surface of an object. Skin friction drag is generally expressed in terms of the Reynolds number, which is the ratio between inertial force and viscous force.