The multi-spherical shells composite structure is a common structurural form of manned submersibles. A vibro-acoustic coupling model of multi-spherical shells system considering acoustic field coupling between shells was established by using the translationnal addition theorem for spherical wave function. The acoustic field coupling characteristics and their influencing factors of a series of spatially-distributed spherical shells were studied. The results show that the acoustic field interaction can change the coupling between the modes of the spherical shells. The contribution of a single mode to the vibration of the spherical shell is no longer limited to a single peak, and thus affects the spectral characteristics of the acoustic radiation. Both shells of the double spherical shells system generate acoustic radiation. There is a strong field coupling effect between two spherical shells under axial excitation. When the excitation force deviates from the axial direction, the field coupling effect gradually weakens. The double spherical shells system composed of spherical shells with different scales expands the frequency range of effective coupling, and the modal characteristics of both shells appear in the acoustic field. When the spherical shells are arranged in series, the acoustic field coupling has a transmission effect. While the spherical shells are distributed at different angles, the spatial distribution of acoustic field becomes more complex.

The interaction between level ice and offshore pile structures is a complex process, which often involves the breaking, failure and accumulation of sea ice. The issure of level ice failure is essentially a problem related to brittle failure of ice materials. However, the failure mechanism of traditional finite element method has great limitations in this problem, which cannot reasonably reflect the deformation and motion state of broken ice. Therefore, it is necessary to explore the existing numerical simulation technology and establish a reasonable modeling method to solve the key points related to level ice damage problems. In this paper, a user-defined constitutive model was introduced to simulate mechanical properties of sea ice material, and the cohesive elements were used to refect the generation and propagation of ice cracks. Through the simulation of the interaction between pile structures and level ice, the failure mode of ice material and the interaction load between pile structures and level ice were analyzed, and the reliability of the proposed method was verified by comparing with the relevant model tests. The results show that the method used in this paper can effectively simulate the compression and bending failure of level ice under the action of pile structures, and the ice load can be accurately predicted. The relevant conclusions are of great significance for ice load prediction and the structure design of offshore pile structures.