Free Wake Model Of Hovering Rotors Having Straight Or Curved Blades

A free-wake model of hovering rotors or rotors in axial flight is derived. Straight or curved blades can be analysed. The blades are modelled as lifting surfaces having one cell in the chordwise direction. The wake is divided into near and far regions. The near-wake is formed of straight vortex elements while semi-infinite helical vortex lines form the far wake. Results for two rotors having straight blades are presented. Convergence and stability of the numerical model are investigated. Comparison with experimental results shows good agreement in most of the cases.