13. Investigation of the Unsteady Aerodynamics of Insect Flight: The Use of Immersed Boundary Method

The study of insect flight is fascinating not only due to its underlying unsteady aerodynamic principles but also for its practical applications in the development of micro-aerial vehicles. The flapping motion of insect wings involves large translational and rotational components. Consequently, the conventional body-fitted moving-mesh computational methods face mesh tangling issues that require expensive re-meshing strategies. In addition, accomplishing such simulations involve considerable human intervention. Immersed boundary methods are ideally suited to simulate insect flight as the flow around the wings are simulated in a fixed Cartesian grid; due to which, neither mesh moving strategies nor re-meshing is required. However, the enforcement of boundary conditions on flapping wings is challenging and is achieved by an appropriate force field. In this chapter, we use the continuous forcing immersed boundary method to study the unsteady aerodynamics of an idealized flapping motion of a hovering insect. Flapping flight in the inclined stroke planes are studied to understand the associated flow dynamics. Furthermore, the effect of phase difference on the aerodynamics of insects with tandem wings (e.g., dragonfly) and the presence of ground are also considered. Results are analyzed in terms of the cycle variation of forces, vortex dynamics, and coherent structures.