An investigation of lift augmentation in forced pitching and flapping rotors

Lift increment in a pitching and flapping rotor due to stall delay and vortex shedding is investigated. The unsteady aerodynamics and dynamic stall effects on a pitching airfoil section is modeled using Peters-He and Leishman-Beddoes models. Correlation with experimental results, available in literature, is also presented. Effect of frequency and amplitude of pitching and flapping inputs on the performance, specifically, coefficient of thrust is investigated. In addition, the effect of mean angle on lift augmentation is also studied. The correlation brings out clearly the strengths of Peters-He and Leishman-Beddoes model in capturing the aerodynamic environment of rotating blade with a prescribed motion. The unsteady motions imparted onto the blade through pitch and flap prescribed motion shows promise as lift augmentation strategies.