Power Requirements of Vertical Flight in the Dronefly

Power requirements in vertical flight in the dronefly (Eristarlis tenax; also known as hoverfly) are studied using the method of computational fluid dynamics. The flow solution provides the aerodynamic forces and torques; the inertial torques due to the acceleration of the wing-mass are computed analytically. From the aerodynamic and inertial torques, the mechanical power is obtained. It has been shown that at hovering flight, the specific power with 100% elastic energy storage is 43.51 W·kg−1 and that without elastic energy storage is 60.12 W·kg−1. During vertical flight, the specific power increases with the ascending ratio K (ratio of the ascending velocity to the tip velocity); it is proportional to K to the power of about 1.37. When flying upward at an ascending ratio of about 0.3, the power required is the same as that when the insect carries a load of about 50% of its weight.