The advance ratio (J) is a dimensionless parameter used in the analysis of propellers and rotors, particularly in the field of aerodynamics and flight mechanics. It describes the ratio of the forward speed of the aircraft or vehicle to the rotational speed of the propeller or rotor. The advance ratio is an important parameter in understanding the efficiency and performance of these propulsion systems.
J = Advance ratio V = Forward speed of the aircraft or vehicle relative to the air (in m/s) n = Rotational speed of the propeller or rotor (in revolutions per second, RPS) d = Diameter of the propeller or rotor (in meters)