Effect of leading-edge slot on energy capture performance of semi-active flapping airfoil

To rise the efficiency of energy capture for semi-active flapping airfoils power generator at low flow speed, a flow control approach via leading edge slots is carefully examined using numerical method. The energy capture performances of airfoil that affected by slot types formulated with different incline angles are analyzed. The results show that the energy capture power and efficiency of the semi-active flapping airfoils can be improved by cutting appropriate slots on the leading edge of airfoil. Among the carried-out calculations, when the incline angle is from 15° to 17°, better energy capture performances are obtained compared with original airfoil without slots, and 17° incline slots configuration is the best with 9.23% higher mean power coefficient. By further examination of the flow structure, it can be found that the 17° incline slot can make leading edge vortex reattached to the surface of flapping airfoil and evolve tardily along the airfoil surface, to keep flapping airfoil with high lift in the process of reciprocating flapping, which makes the flapping airfoil possessing better energy capture performances.