Numerical-analytical hybrid calculation method for acoustic radiation of underwater vehicles with internal vibration isolation system

The application of floating raft isolation technology can effectively reduce mechanical noise in ships and underwater vehicles. Mastering accurate design calculation methods is key to further improving the vibration reduction and noise reduction performance of floating raft systems. More efficient modeling and solving techniques, broader frequency range applicability, and more accurate simulation of isolation components are the current focal points in the research and practical application of design calculation methods for floating raft systems. This paper proposes a hybrid multi-layer substructure integration method, combining analytical and numerical techniques, to improve the computational efficiency of vibration and acoustic radiation analysis in underwater vehicles with vibration isolation systems. The underwater vehicle is divided into a main hull (stiffened cylindrical shell) and internal multi-layer substructures (base, isolators, floating raft, etc.). The main hull is solved analytically, while the base and floating raft are modeled using modal synthesis super-element method to obtain dynamic stiffness matrices. The isolator is modeled using the four-terminal parameter method. These substructures are then integrated to compute the overall structure's vibration and acoustic radiation. For scenarios where the internal vibration isolation system is modified, only the local substructure needs to be recalculated and coupled with the rest of the structure, improving efficiency while maintaining accuracy. This method addresses the frequency limitation bottlenecks of pure numerical methods, extending the frequency range to several kilohertz and enabling significant breakthroughs in broadband applicability. The dynamic stiffness matrices of floating raft isolators, which can be obtained from experimental tests, enhance the method's practical engineering value. The validity of the proposed method is verified through numerical examples and experimental comparisons, and some underlying patterns are discussed during the evaluation process.