  We present a novel three-dimensional (3D) variational aeroelastic framework
for flapping wing with a flexible multibody system subjected to an external
incompressible turbulent flow. The proposed aeroelastic framework consists of a
three-dimensional fluid solver with delayed detached eddy simulation (DDES) and
a nonlinear monolithic elastic structural solver for the flexible multibody
system with constraints. Radial basis function (RBF) is applied in this
framework to transfer the aerodynamic forces and structural displacements
across the discrete non-matching interface meshes while satisfying a global
energy conservation. The fluid equations are discretized using a stabilized
Petrov-Galerkin method in space and the generalized-$\alpha$ approach is
employed to integrate the solution in time. The flexible multibody system is
solved by using geometrically exact co-rotational finite element method and an
energy decaying scheme is used to achieve numerical stability of the multibody
solver with constraints. A nonlinear iterative force correction (NIFC) scheme
is applied in a staggered partitioned iterative manner to maintain the
numerical stability of aeroelastic coupling with strong added mass effect. An
isotropic aluminum wing with flapping motion is simulated via the proposed
aeroelastic framework and the accuracy of the coupled solution is validated
with the available experimental data. We next study the robustness and
reliability of the 3D flexible multibody aeroelastic framework for an
anisotropic flapping wing flight involving battens and membranes with composite
material and compare against the experimental results. Finally, we demonstrate
the aeroelastic framework for a bat-like wing and examine the effects of
flexibility on the flapping wing dynamics.
