海岸带水生植物群落间动量输运和质量输运的水动力学特征研究

The hydrodynamics of wave interaction with coastal vegetation is of great scientific and engineering interest for its effects on transport of nutrients, pollutants, and on wave attenuation. Most studies simplified aquatic vegetation as circular cylinder arrays due to complicated flow field between single vegetation. However, to date, the physical mechanisms responsible for solute transport and shoreline protection have not been established. Few systematic investigations of hydrodynamic coefficients on cylinder arrays are addressed and local turbulence characteristics is not clear, hence present study will investigate the mechanism of wave energy dissipation and the characteristics of turbulent vortex in emergent and submerged cylinder arrays based on model experiments and homogenization method. A direct force measurement method is applied to investigate the effect of submergence depth, cylinder density, wave conditions on hydrodynamic coefficients. The relation of dimensionless parameters such as KC number, Reynolds number with drag coefficient and inertial coefficient is analyzed. PIV system is used to measure the local flow field around cylinder to obtain phase-averaged velocity filed. The characteristics of turbulence are investigated by analyzing turbulent Reynolds stress, velocity gradient and turbulent viscosity. Furthermore, the influence of various flow conditions and geometric parameters on turbulence diffusion and solute transport are studied. Based on model experiments and homogenization method, the theoretical model for momentum and mass transport between cylinder region and open water above is presented, which can help understand the influence of aquatic vegetation on coastal environment.

以水生植物对水域生态环境的维护以及护岸减灾为背景，针对目前缺乏波浪环境中柱群水动力系数以及局部流场特性机理不清的问题，本项目从模型实验和多尺度理论分析两个途径研究出水和没水柱群中的波能耗散和物质输运机理以及湍流涡场特征。采用直接测量群柱中单个圆柱受力的方法获得浸没深度、柱群密度、波浪条件对水动力的影响，考察KC数、雷诺数以及波长水深比等无量纲参数与水动力系数的相关关系；通过PIV流场测量分析相位平均流场的湍流流动特征，获得柱群中湍流雷诺应力、速度梯度以及湍流涡粘性系数的分布规律，研究不同流动状态和柱群几何参数对湍流粘性扩散、物质输运参数的影响规律。根据物理模型实验和多尺度分析方法建立波浪环境中柱群内外动量交换引起的波能耗散和物质输运的理论模型，为研究水生植物群落对近岸水动力环境的影响提供理论指导。

以水生植物对水域生态环境的维护以及护岸减灾为背景，针对目前缺乏波浪环境中柱群水动力系数以及局部流场特性机理不清的问题，本研究从模型实验研究和多尺度理论分析两个途径研究了出水和没水柱群中的水动力特性及流场特性。采用了直接测量群柱中单个圆柱受力的方法获得浸没深度、柱群密度、波浪条件对水动力的影响；考察了KC数、雷诺数以及波长水深比等无量纲参数与柱群水动力系数的相关关系，基于多孔介质思想建立了简化模型得到了阻力系数与雷诺数和孔隙率的相关关系，并通过大量实验数据拟合得到了阻力系数经验公式，公式中包含了没深的影响；自主搭建了PIV流场测量系统和三维非接触多点波面测量系统研究了柱群内部的流场特性，得到了柱群内部垂向流动结构、剪切流动特性及相平均流场特性。基于大量物理模型实验和多尺度理论分析方法，建立了波浪环境中柱群内外动量交换引起的波能耗散和物质输运的理论模型，为研究水生植物群落对近岸水动力环境的影响提供理论指导。