Detecting and identifying underwater targets is still a pressing challenge. When underwater targets navigate near the water surface, the ocean surface significantly influences its vibration and acoustic characteristics. On one hand, ocean surface waves and the target’s draft condition alter its vibration behavior and surface acoustic loading. Only the submerged portion—the wetted hull—experiences hydrodynamic loading and radiates acoustic waves. On the other hand, ocean surface reflections generate virtual sources for underwater sound emissions, resulting in a sound field that is the superposition of contributions from both real and virtual sources. However, the irregular, undulating nature of the ocean surface presents substantial difficulties in accurately modeling the vibration-acoustic characteristics of nearby moving or stationary bodies. This report presents recent advances in the study of vibration-acoustic characteristics of targets near fluid interfaces. It particularly focuses on modeling approaches for the vibration and acoustic radiation of partially submerged cylindrical shells and open cylindrical shells, analytical techniques for understanding acoustic radiation mechanisms, and synchronized measurement methods for vibration and noise under dynamic ocean surface conditions. The study reveals that the air-water interface formed on the hull surface acts as a novel mechanism for generating line spectra below the ring frequency, originating from elastic wave propagation in the shell structure. It further elucidates the physical mechanism behind the formation of spectral peaks in target noise, which exhibit bright-dark interference fringes as draft depth varies, and provides corresponding predictive formulas. Moreover, the conventional planar interface model is extended to account for undulating ocean surfaces, leading to the development of theoretical frameworks for target acoustic-vibration characteristics under both regular and random wave conditions. These models enable a systematic investigation of the influence of wave parameters on vibration and acoustic radiation. The findings provide a robust theoretical foundation for analyzing the underwater noise characteristics of submerged vehicles in moored states and surface ships operating near the ocean surface.

Dr. Zhao Kaiqi serves as an associate professor and doctoral advisor at the School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University. His research focuses on how sound waves scatter and radiate from underwater objects, and how to control these acoustic fields. He has led more than 10 research projects, including grants from the National Natural Science Foundation of China, and has published over 20 papers in top-tier academic journals worldwide. He also holds 11 invention patents and 4 software copyrights, and has authored a specialized book. Among his honors are the First Prize in Teaching Achievement from Shanghai Jiao Tong University, the Second Prize for Excellent Graduate Textbooks, and the title of Outstanding Class Advisor. Served as a member of the Second committee of the Computational Acoustics Branch of the Chinese Acoustics society, a member of the Youth Work Committee of the Chinese Society of Naval Architects and Engineers, and a member of the editorial board of the journal “Digital Ocean & Underwater Warfare”.