Airflow dynamics induced by insect-inspired anisotropic flapping wings

In this work, we address the problem of inhomegeneous deformable flapping wings as observed, for instance, in insects where the veins fix the elasticity of the wings and their anisotropy. The wing is modeled as a very thin membrane supported by two stiffening main axes: the first at the leading edge, hence modulating the bending of the wing, and a second transversal one that modulates the torsion of the wing. The deformation of the flapping wings is observed using high-speed video recording. Both flexural and torsional stiffnesses are varied independently by varying the angle alpha between the main stiffening axes. We show that the optimization of the coupling between bending and torsion modes in terms of aerodynamic force generation seems to be consistent with the quadrature modes coupling found in the literature. Additionally, we use PIV measurements of the flow around and behind wings to understand the underlying mechanisms responsible for the benefits of quadrature modes coupling. The role of the leading edge vortices and their formation dynamics are also highlighted.