플래핑 날개 장치와 고정된 날개 장치에서의 Cd 차이

Abstract

In this research, we recreated a three dimensional flapping motion of Canada Geese utilizing a two-jointed arm model and then we studied the features of a flapping mechanism. These were compared with those of a fixed wing in the respect of aerodynamics and kinematics using CFD. The three dimensional flapping motion was completed by using three angles (Ψ1, Ψ2, Φ2) caused with Rod1 and Rod2 of the two-jointed arm model. Utilizing this three dimensional flapping motion, we figured out that it took 0.25 s to draw a cosine curve which means one cycle of the flapping motion was completed. At this moment, the elevation (c) was 2.55 c and the wing frequency was f = 4. Moreover, the AoA (Angle of Attack) of S1223 aerofoil was represented as α = 0°. The downstroke and upstroke of the flapping motion are one thing another. During the downstroke, the wing was stretched while it is folded during the upstroke. The wing-tip of geese draws a vertical 8 shape in one cycle by the sweep angle defined as Φ2. This is important difference between previous studies and this study in the respect of morphology. When the Lift coefficient (CL) and Drag coefficient (CD) were set similarly to those of a fixed wing, the flapping wing showed a area which had minus drag coefficient (-CD). This is the prominent feature of the flapping motion that did not appeared in the fixed wing. In conclusion, using a three dimensional flapping motion, it is possible to develop a MAVs that is more efficient with the effect of reduced drag coefficient than when using a fixed wing.