Efficiency enhancement of a self-propelled pitching profile using non-sinusoidal trajectories

A symmetrical profile is subjected to non-sinusoidal pitching motion. The airfoil has a chord length c=0.006 m and a semi-circular leading edge with a diameter of d=0.001 m. The extrados and intrados are two straight lines that intersect at a tapered trailing edge, and the pitching pivot point is positioned at the leading edge. The pitching frequency is in the range of 1<f<190 Hz, while the tangential amplitude of the flapping trailing edge varies from 18% to 114% of the foil cord. To improve the airfoil propulsive performance, two-dimensional numerical simulations are implemented on FLUENT. The Reynolds number based upon the maximum profile thickness t varies in the range of 35<Re<210, comparable to insect’s Reynolds numbers. The foil movement is executed using a dynamic mesh technique and a user defined function (UDF). The adopted mesh has 70,445 nodes with 5,1960 quadrilateral cells. The results are in good agreement with prior experiments, and, compared to sinusoidal oscillations, show that non-sinusoidal flapping trajectories lead to advancing velocity increase of 550%. Additionally, if improved propulsive efficiency is sought, non-sinusoidal flapping lead to better thrust.