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李宇航, 李广华, 侯冬冬, 尤云祥. 南海分层环境水下航行体内波尾迹水面响应特性研究. 力学学报, 待出版. DOI: 10.6052/0459-1879-23-555
引用本文: 李宇航, 李广华, 侯冬冬, 尤云祥. 南海分层环境水下航行体内波尾迹水面响应特性研究. 力学学报, 待出版. DOI: 10.6052/0459-1879-23-555
Li Yuhang, Li Guanghua, Hou Dongdong, You Yunxiang. Surface signature characteristics of the internal wave generated by a submerged body in the South China. Chinese Journal of Theoretical and Applied Mechanics, in press. DOI: 10.6052/0459-1879-23-555
Citation: Li Yuhang, Li Guanghua, Hou Dongdong, You Yunxiang. Surface signature characteristics of the internal wave generated by a submerged body in the South China. Chinese Journal of Theoretical and Applied Mechanics, in press. DOI: 10.6052/0459-1879-23-555

南海分层环境水下航行体内波尾迹水面响应特性研究

SURFACE SIGNATURE CHARACTERISTICS OF THE INTERNAL WAVE GENERATED BY A SUBMERGED BODY IN THE SOUTH CHINA

  • 摘要: 在实际海洋中由于太阳的照射以及盐度在空间分布的差异使得海水密度分布不均, 在深度上形成密度梯度变化的密度跃层. 当水下航行体在海洋中航行时, 会对背景流体产生扰动进而形成尾迹, 内波尾迹具有传播时间长、传播范围广的特点, 通过尾迹对水下航行体的踪迹进行探测成为可能. 针对实尺度水下航行体激发内波表面响应特性问题, 以中国南海东沙海域为研究对象, 首先介绍了实际海洋盐度、温度、密度以及浮频率垂向分布情况. 然后基于中国南海东沙附近实际海况, 采用含有自由表面的理论模型模拟了长100 m直径10 m的细长体体积源在不同潜深不同航速航行时激发的水面响应特性, 揭示了航行体不同状态对表面波高场, 表面速度场以及表面散度场的影响. 研究表明: 当浮频率减小、跃层距离表面增加或水下航行体距离跃层位置增加都会导致内波模态的幅值降低. 中国南海东沙附近的海洋跃层在夏季跃层较薄, 浮频率较大容易造成较大的内波, 而冬季跃层较厚且距离表面较远, 水下航行体产生内波较小.

     

    Abstract: The fluid density commonly stratifies in the ocean due to the vertical distribution of temperature and salinity. Coupled with a certain source of excitation, the surface wave and internal wave will be generated simultaneously. Compared with the surface wave, the internal wave has the characteristics of a long period and large amplitude. The emission of internal waves by submerged bodies in a stratified fluid is an important phenomenon in the ocean. It is possible to detect the submerged body through the internal waves. To study the surface signature in full scale generated by a submerged body, taking the Dongsha Sea area of the South China Sea as the research object, the vertical distribution of ocean salinity, temperature, density and Brunt–Vaisala (BV) in the Dongsha sea area is introduced in detail. Based on the actual sea conditions in Dongsha sea area, the surface wave excited by a slender volume source with 100m long and 10m diameter sailing at different depths and speeds is simulated by using the theoretical model with free surface boudary condition. The characteristics of the surface wave elevation field, velocity field and surface divergence field are studied. The results show that the amplitude of internal wave mode deceases if the BV frequency becomes smaller, the pycnocline is getting further away from the surface, or the submerged body is getting further away from the pycnocline. The pycnocline of the South China Sea is thinner and closer to the surface in summer, resulting in the bigger amplitude of internal wave mode. The pycnocline of the South China Sea is thicker and getting further away from the surface in winter, resulting in the smaller amplitude of internal wave mode.

     

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