قارن الطرق

	خط المروحة الرافعة	نظرية عنصر الشفرة والزخم
المجال	هندسة الطيران والفضاء	هندسة الطيران والفضاء
العائلة	Process / pipeline	Process / pipeline
سنة النشأة	1929	1889
صاحب الطريقة	Sydney Goldstein	William Froude, Heinrich Glauert
النوع	Design theory	Analysis method
المصدر التأسيسي	Goldstein, S. (1929). On the vortex theory of screw propellers. Proceedings of the Royal Society of London. Series A, 123(792), 440–465.	Froude, W. (1889). On the elementary relation between pitch, slip, and propulsive efficiency. Transactions of the Institution of Naval Architects, 30, 94–103.
الأسماء البديلة	lifting line theory, propeller design method, Goldstein method	BEM theory, rotor performance prediction, actuator disk method
ذات صلة	3	3
الملخص	Propeller lifting line theory is a mathematical framework for analyzing and designing ship propellers by modeling each blade as a lifting line with circulation distribution. Developed by Sydney Goldstein in 1929 and refined by Kerwin and others, the method accounts for blade loading, wake effects, and propeller interactions. Lifting line theory provides efficient predictions of propeller thrust, torque, and efficiency and remains standard in preliminary propeller design and optimization.	Blade element momentum theory (BEM) is a fundamental method for analyzing rotor performance by combining blade element aerodynamics with momentum conservation. Developed initially by Froude and refined by Glauert and Leishman, BEM decomposes a rotor into radial blade elements, computes local aerodynamic forces, and sums contributions to predict total thrust, torque, power, and efficiency. BEM is standard for helicopter, wind turbine, and propeller design.