Momentum theory

The momentum theory is a mathematical theory describing a simple model of a helicopter rotor .

The rotor is modeled as an infinitesimal thin disc, inducing a constant and vertical velocity. The basic state of an helicopter is hovering. This disc creates a flow around the rotor. Under certain mathematical premises of the fluid, there can be extracted a mathematical conection between power, radius of the rotor, torque and induced velocity. Friction is not included.