Aerodynamic performance and flow mechanism of 3D flapping wing using discrete vortex method

Abstract

In this work, we have performed numerical simulations of the flapping motion of a rectangular wing in a three-dimensional flow field using the discrete vortex method (DVM). The DVM method is computationally more convenient because it does not require the generation of a grid for the flow field at each time step as in other conventional simulation methods. In addition to the rigid wing case, the aerodynamic characteristics of a deformable wing are also investigated. The deformable wing is studied in various configurations, such as bending, twisting, and bending-twisting coupling (BTC), to provide a comprehensive analysis of its performance. In this study, we have introduced a novel aerodynamic technique in wing twisting. Unlike traditional wing rotation about a fixed root axis, our approach involves rotating the wing about a dynamically adjusted point located at the root of the leading edge. This novel approach was found to be effective in increase in the requisite aerodynamic force. The BTC wing represents reflects a sophisticated aerodynamic approach that optimally coordinates both twisting and bending deformations of the wing, resulting in a substantial improvement in its overall aerodynamic efficiency. The investigation of all four modes involves a detailed analysis of the flow mechanisms and vortex dynamics, which play a crucial role in influencing the aerodynamic forces, namely lift and thrust. The study aims to understand how these flow patterns change under different operating conditions and how these changes impact the generation of lift and thrust. The lift, thrust, and propulsive efficiency of all four modes are compared to provide a detailed understanding of their aerodynamic characteristics. The bent wing showed minimal improvements in lift and thrust compared to the rigid wing. In contrast, the twisted wing showed greater improvements in both lift and thrust. The BTC wing proves to be the most efficient method to improve aerodynamic performance during flapping. The parametric dependence of kinematic parameters such as asymmetric ratio (downstroke speed to upstroke speed), aspect ratio and reduced frequency on the aerodynamic performance was also investigated.