極低レイノルズ数における基本的翼型の空力特性と後流特性

抄録

The airfoil is one of the most elemental devices for flying or swimming robots to control flow and its reacting force, which determines their basic performances. We have been requiring more precise knowledge about the aerodynamic characteristics of the airfoil especially in low Reynolds-number ranges less than 106, because of the recent miniaturization of robots such as unmanned aerial vehicles known as UAVs or drones and micro air vehicles known as MAVs, in addition to the importance of insect/bird flight dynamics and so on. In the present study we investigate the relationship between various aerodynamic characteristics and attack angle α for FP (a flat plate) by water-tank experiment at Re = 100 – 800. Then, we reveal the effects of α upon various aerodynamic characteristics. In order to discuss these revealed α effects, we further compare the flow visualization around the airfoils by water-tank experiment in terms of the velocity vector and vorticity at α = 0 – 30 deg. The experimental results are based on PIV analysis. From the experimental results, we can classify the flow into three categories; namely, (1) steady and two-dimensional, (2) unsteady (periodic) and two-dimensional, (3) unsteady and three-dimensional (periodic with random noise). As Re and α increase, the flow shifts from (1) to (2) and then to (3). In the present experiment, long- wavelengths instability in the span direction was visualized in the process of development of the three-dimensional structure (longitudinal vortex).