水面下的波浪——海洋内波

  目的  旨在探究内孤立波作用下航行体水动力特性的变化规律及机理。  方法  基于强分层假设下的内孤立波mKdV理论，采用有限体积法离散不可压缩纳维−斯托克斯方程，结合速度入口造波和重叠网格方法，建立分层流中的波−体耦合数值计算模型。模拟不同内波环境下内孤立波与固定、悬浮航行体耦合作用过程，通过数值求解得到航行体的水动力载荷变化规律。  结果  结果表明：水下航行体所受作用力和力矩幅值随波幅的增加而增大；固定航行体接近于两层流体分界面时受到的影响更大，而悬浮航行体接近于内孤立波波谷纵深时，受到的影响更显著；初始俯仰角的增大会导致航行体水平力幅值剧烈增大；具有初始航速的航行体受到内孤立波主波和尾波共同作用后会发生“掉深”现象。  结论  研究结果对于水下航行体的安全操纵具有一定参考价值。

Billow under the sea surface-internal waves in the ocean

  Objective  This paper aims to explore the hydrodynamic characteristics of underwater vehicles under the action of internal solitary waves.  Methods  Based on the internal solitary wave mKdV theory under the strong stratification assumption, the incompressible Navier-Stokes （N-S） equation is discretized by the finite volume method. Combining the velocity entrance wave-making and overset grid methods, a numerical model of an underwater vehicle coupled with internal solitary waves in stratified flow is established. Through this model, the coupling process of internal solitary waves and fixed and suspended vehicles in different internal wave environments is simulated, and the variation law of the hydrodynamic load is obtained by numerical solution.   Results  The amplitude of the force and moment of the underwater vehicle increases with the increase in wave amplitude. When the position of the fixed vehicle is close to the interface of two layers of fluid, it is more severely affected. When the suspended vehicle is close to the wave trough, the impact is more significant. The increase in the initial pitch angle will lead to a sharp increase in the horizontal force amplitude of the vehicle. In addition, the