Experimental and numerical characterization of vortex mechanisms of lift generation on a wing in flapping motion
A low Reynolds number, flapping wings appears as an alternative to conventional concepts of fixed wings and rotary wings aircrafts. In the context of a practical application (micro air vehicles, MAVs), assessing the suitability of such mode of lift generation requires a detailed understanding of the key aerodynamic mechanisms involved and their impact on resulting forces. These are characterized by a strong unsteadiness and complex behaviors.This work focuses on the study of flapping flight at low Reynolds (around 1 000), in a hover configuration. The model consists of a rectangular wing with a symmetrical profile in a flapping motion. This mode is characterized by the generation of vortex structures more or less persistent that strongly influence the forces applied to the wing.The objective is to analyze the evolution of unsteady mechanisms and resulting forces. The study focuses in particular on a thorough analysis of e reference case, then compared to other results in a parametric study on the influence of aspect-ratio on the one hand, and on the kinematic of movement on the other.The means of investigation adopted for this study are both numerical and experimental. The analysis is based in part on a numerical approach using a DNS meshing technique “chimera”, and on experimental approach with 3C-3D TR-PIV measures. Direct measurement of unsteady low forces being difficult to consider, an important part of the work was to adapt a method for evaluating loads by applying momentum equation using PIV velocity fields. The bottleneck of this approach which is the evaluation of the pressure from the velocity fields is subject to special attention.