实验室造波条件对内孤立波发展影响的直接数值模拟

内孤立波具有振幅尺度大、能量集中的特点,其引起流场和密度场的迅速变化可能对海洋工程结构物以及水下潜体造成严重威胁。因此研究不同造波条件下生成的内孤立波运动的流场特征具有重要的学术意义和实际应用价值。采用直接数值模拟方法和给定的初始密度场密度跃迁函数,对重力塌陷激发内孤立波的运动过程进行研究,探讨了不同造波条件下,激发产生的内孤立波波型、涡度、振幅和水平速度等流场特征。结果表明:(1)直接模拟数值方法能够模拟内孤立波传播过程中的密度界面波型反转现象;(2)从定性和定量的角度,证实了不稳定内孤立波传播过程中存在能量的向后传递;(3)对于相同的台阶深度(水闸两侧初始密度界面的高度差),初始涡流保持相同,但是随着上下层水深比的减小,其强度下降显著;(4)台阶深度对初始涡流的垂直结构的影响要大于上下层水深比,且台阶深度对内孤立波的振幅、水平速度的影响显著。

DIRECT NUMERICAL SIMULATION OF THE EFFECT OF LABORATORY WAVE-MAKING CONDITIONS ON THE DEVELOPMENT INTERNAL SOLITARY WAVES

Internal solitary waves are characteristic of large scale and concentrated energy, and could cause rapid changes in the flow field and density field, which poses a threat to marine engineering structures and underwater submersibles. Therefore, studying the flow field characteristics of internal solitary wave motion generated under different conditions has important academic significance and practical application value. Therefore, the direct numerical simulation method was conducted with a given density transition function of initial density field to study the motion process of gravity-collapsed internal solitary waves. In addition, the flow field characteristics of internal solitary waves generated in different wave-making conditions, such as waveform, vorticity, amplitude, and horizontal velocity, were discussed. Results show that the direct simulation numerical method used in this paper can simulate the density interface waveform inversion during internal solitary wave propagation. Meanwhile, from the qualitative and quantitative perspectives, backward energy transmission during the propagation of unstable internal solitary waves was confirmed. The initial vortex remained identical at the same step depth but the decrease in strength as the depth of upper layer increases was significant. The step depth influenced the vertical structure of initial vortex more than the depth ratio of the upper vs lower layer did on wave generation. Moreover, the step depth had a significant effect on the amplitude and horizontal velocity in wave generation.