Numerical modeling of fluid-structure interactions by using a hybrid method of IB-LBM and ANCF

The study on coupling dynamics of flexible multibody-fluid interactions is of paramount importance for the design of aircraft, flying biomimetic systems and underwater soft robots. This paper presents a novel computational methodology for simulating flexible multibody-fluid interactions. The methodology combines the lattice Boltzmann method to model fluid dynamics and the absolute nodal coordinate formulation to describe flexible multibody systems. Then, it uses the immersed boundary method to simulate moving and deforming boundaries within fluid flows. The innovation of the methodology lies in two aspects. First, the shear-improved Smagorisky model is introduced into the flexible multibody-fluid coupling to efficiently capture turbulent flows under large motions and significant rotations. Second, a structural predictor is used to effectively reduce the interaction time-lag problems so as to assure the consistency of dynamic responses and energy conservation at the interface. The proposed methodology is validated through three classical benchmarks first, and then the fluttering dynamics of a flexible biomimetic butterfly in air is simulated. All numerical simulations demonstrate that the new methodology can effectively address the complex coupling dynamics of flexible multibody-fluid systems.