Computational Fluid-Structure Interaction of a Flapping Wing in Free Flight Using Overlapping Grids

The study of the interaction between a flexible flapping wing and the ambient fluid is an important step in the design of Micro-Aerial-Vehicles and Unmanned-Underwater-Vehicles. The growth in computational power and resources has led researchers to carry out extensive numerical computations to predict forces on rigid flapping wings. However, computations on passively deforming flapping wings are sparse in literature. In this research, a computational framework for predicting the deformation of a flapping wing due to aerodynamic forces is presented. The incompressible flow solver based on overlapping grids used in previous flapping wing aerodynamic studies by the authors is enhanced with a structural dynamics model and the coupled set of fluid dynamics and structural dynamics equations are solved using an implicit partitioned algorithm. The effects of spatial and temporal accuracy of the discretized structural dynamics equation on computed solutions are analyzed. It is shown that a proper combination of time step, numerical relaxation and damping yields stable numerical solutions. By treating each deformed airfoil shape as a rigid body at a given time instant, the position of the airfoil is computed based on the aerodynamic forces for different flexibilities. It is shown that an airfoil with moderate flexibility travels the fastest. Extensions to flexible wings are also presented.