表面波-湍流边界层相互作用数值研究

Interaction between the surface wave and turbulent flow is often seen in the wind, wave and current coupling phenomena occuring in the marine atmospheric boundary layer. In this project, we aim at studying the coupling system of the surface wave under gravity and its above atmospheric turbulent boundary layer by using numerical simulation. (1) Numerical modeling of the surface wave-turbulent boundary layer (SW-TBL) coupling system: The TBL on the SW is computed by direct numerical simulation (DNS) and large eddy simulation (LES) based on the body-fitted grid and the pseudo-spectral method, while the surface wave motion is solved by using the high-order spectral (HOS) method. Both the growing wind wave and the developed swell states are considered in simulation. (2) Statistics and dynamics of the SW-TBL coupling system: On one hand, the statistics and dynamics of the SW under the forcing of the TBL are studied; on the other hand, effect of the SW on the statistical characteristics of the TBL and the energy transfer between the SW and the TBL are analyzed. Meanwhile, in the outer layer of the TBL at high Reynolds numbers, the very-large-scale motion (VLSM) is identified, and its effect on the inner layer and the SW by superposition and modulation is examined. Interaction among the motions with different scales is investigated by using the spectral analysis. (3) Examination of the parametrization models for the SW-TBL coupling system: Dependences of the mean velocity profile similarity and the surface roughness on the Reynolds number, wave age and wave slope are disclosed, and the parametric models of the wave growth rate, the drag coefficient and the vertical momentum transfer are examined by comparing with the directly computed results.

表面波与湍流相互作用常见于海洋大气边界层中风、波及洋流间的耦合现象。本项目利用数值模拟，对重力作用下的表面波与其上方的大气湍流边界层的相互作用问题开展研究。(1)表面波-湍流边界层耦合数值模拟方法：波动表面湍流边界层采用基于动态曲线坐标与伪谱方法的直接数值模拟与大涡模拟，同时采用高阶谱方法计算表面波运动，考虑风浪和涌浪两种状态；(2)表面波-湍流边界层耦合统计特性及动力学过程：分析湍流作用下的表面波统计特性及演化规律，同时关注表面波对湍流边界层统计特性的影响及二者间的能量传输规律，考察高雷诺数条件下湍流边界层外区超大尺度结构及其对内区和表面波的调制与叠加效应，利用谱分析描述不同尺度间湍流的相互作用；(3)表面波-湍流边界层耦合参数化模型检验：考察不同雷诺数、波龄和波陡等参数下平均速度剖面相似性和表面粗糙度变化规律，利用波增长率、阻力系数与垂向动量输运的直接计算结果对其参数化模型进行检验。

本项目利用数值模拟对表面波-湍流边界层耦合特性和动力学机制开展了研究，对于自然界风致水波问题的理解及建模有重要的科学意义，取得的主要成果包括：(1) 发展了一套高效的表面波-湍流边界层耦合数值模拟方法；(2) 系统揭示了表面波-湍流边界层耦合统计特性及动力学过程；(3) 建立了新的波形表面湍流边界层统计特性的参数化模型。相关研究对行波表面湍流边界层的统计特性和能量传输规律有了进一步的理性分析，对高雷诺数条件下湍流内外区及表面波之间相互作用有了深入的认识，深化了风-波耦合动力学机制的理解，并为其参数化模型的改进提供了指导。研究成果已发表SCI收录论文40篇，包括Journal of Fluid Mechanics论文5篇，Physical Review Fluids文章2篇，Physics of Fluids文章16篇（3篇被选为Featured Article，8篇被选为Editor’s Pick），International Journal for Numerical Methods in Fluids文章1篇（封面论文），以及Ocean Engineering文章1篇。