Thin, flapping wings: Structural models and fluid-structure interactions

With a long-term goal of understanding the influence of wing flexibility on the aerodynamic performance of a flapping wing, the authors have considered a three-dimensional, insect wing inspired structure. A nonlinear finite element formulation is used to model this structure, which consists of veins and membranes that hold the veins together. Each vein contributes to the structural rigidity of the wing, and it is discretized with beam elements. The surface of the wing is modeled by using thin membrane elements. Numerical evaluation of the aerodynamic forces is carried out by using the unsteady vortex-lattice method (UVLM). In the computational framework, the fluid-structure systems are fully coupled by using a fixed-point iteration scheme. Investigations into the primary deformation modes of the coupled system are carried out to assess the contributions of spanwise, as well as chordwise deformations to the generated aerodynamic loads.