Force measurements and cross-flow estimation on a flapping bird-like airfoil

Introduction 5 Figure 1: [1] - Aerovironment "Microbat". Introduction The birds’s ight has all along induced fascination. In the past because they were the only living creatures to be able to y, now because one is interested in which way their wing-propulsion is optimized. Nowadays, we have the knowledge and the materials to try to generate a bird-like ight (Fig. 1). A lot of solutions are possible using the wing-propulsion. For example it is possible to cite the military one where small UAV (Unmanned Aerial Vehicle) can be used on reconnaissance or spy missions. To this aim, it is important the manoeuvrability and the small dimensions of the UAV. Also civil uses are possible, like for the cartography. Looking at a distant future, knowing the birds’s ight secret could be useful to design airplanes and helicopters optimizing their ight through controlled vibrations of their wings or blades. Small dimensions UAV are called MAV (Micro Air Vehicles). Most of the small ying vehicles being developed can be divided into three categories: flxed wing (Fig. 2), rotary wing (Fig. 3) and apping wing (Fig. 1). The third conflguration, which imbibes nature, is the most di–cult to design and to build. There are many kind of studies about a lot of aspects, as in [2] where the bird ight is modeled to understand the ight bird dynamics and to describe the apping motion of the wing as close as possible to the natural cases. For this case the most di–cult thing is to represent the arm dihedral angles, the arm sweep angle, the arm twist angle, the forearm twist angles, wing spread extens, tail bend angles, tail twist angle, tail spread angle and duration of the wingbeat during the wingbeat (see flg. 4). In Aerodynamics of intermittent bounds in ying birds [3] the authors investigate the