CFD-CSD coupled aeroelastic analysis of a highly flexible flapping wing in hover
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Copyright 2019 by the Vertical Flight Society. Flapping wings are typically very flexible structures undergoing large deflections, leading to complex nonlinear interactions between aerodynamics and structure. This strong fluid-structure coupling and the complicated flow physics make the performance of such systems extremely difficult to predict through numerical simulations. The challenges arise from the highly unsteady, viscous and vortex-dominated nature of the flowfield leading to strong nonlinearities in aerodynamic loads as well as the accurate representation of the structural dynamics of the flapping-wing. This paper presents a computational framework, where a computational fluid dynamics (CFD) solver is coupled with a nonlinear structural solver to simulate highly flexible flapping wings with significantly improved fidelity. The CFD solver utilized is a compressible Reynolds-averaged Navier-Stokes solver to resolve the complex, highly vortical, three-dimensional flow. The CSD solver accounts for the geometric nonlinearities due to large rotations, in-plane strain, initial curvature and transverse shear deformations and encapsulates the exact deformed shape. A multivariate interpolation scheme, using radial basis functions, is presented, which results in a unified formulation for the fluidstructure interpolation and mesh motion problems. The objective of the study is to understand the unsteady aerodynamic mechanisms that affect the force production on a flexible wing undergoing a hummingbird-like flapping kinematics.
