A fast fully coupled FEM/BEM method for structural-acoustic interaction problems with a uniformly moving source

When a structure moves uniformly at high-speed, the structural-acoustic coupling significant alters the acoustic field distribution compared to conditions without coupling. We propose a hybrid numerical method combining the finite element method (FEM) for structural vibration and the convective boundary element method (BEM) for sound propagation in uniform flow to predict the acoustic field of a uniformly moving body. We introduce the acoustic-analogy Lorentz (a-a Lorentz) transformation to accelerate the convective BEM. To establish the structural-acoustic coupling condition, we derive a mapping method for different physical fields and spacetimes based on the time and space transformations of the a-a Lorentz transformations. A fully coupled solution scheme based on the fast multipole method (FMM) has been developed. By integrating the FEM matrix into the boundary element equation, we eliminate structural degrees of freedom and address the ill-conditioned issue of the direct coupling matrix. Additionally, the FMM efficiently handles large-scale problems. We construct a semi-analytical model to verify the proposed method's correctness and efficiency. The impact of varying Mach numbers and structural elasticity modulus on the coupling effect is analyzed indicating that coupling analysis is essential under high-speed conditions. A full-fuselage model is computed to validate the method's efficiency for large-scale problems.