波流共同作用下粉沙运动过程非线性特征

Estuaries and coasts in China are always characterized by complex boundary conditions, lots of islands and bed materials of silt. Under co-action of combined waves and currents, silt is easily incipient and suspension. Moreover, sand ripples formed on the bed, vortex structures developed in the bottom currents, and further enhance sediment suspending, exhibiting a fluid-boundary-sediment interactive system. Different combinations of waves, currents and bed materials would result in entirely different interactive systems and hence different transport phenomenons with significant non-linear characteristics.By theoretical analysis, flume (tank) experiment, and filed observation, this project mainly investigates the non-linear characteristics of silt transport process under combined waves and currents, including sediment incipient, bed evolution, bottom dynamic response, non-uniform suspended load transport. In addition, formulas of the sediment initial motion, ripple geometry, vorticity，turbulent energy and turbulent diffusion coefficient on rippled bed, concentration and diameter distribution for non-uniform sediment. It would provide a theoretical basis for prediction of sudden sedimentation in the coastal and estuarine deep waterway.

我国河口海岸边界地形复杂、岛屿众多，且底床多为粉沙和淤泥所覆盖，在波流作用下粉沙易于起动、悬浮和输移，且床面常伴有一定尺度的沙纹，底部水流的涡动力结构又进一步增强了泥沙的悬浮，形成动力、边界及泥沙三个过程相互反馈系统。在不同的波浪、水流、粒径组合条件下，该系统作用机制的差别导致截然不同的输沙现象，呈现较强的非线性特征。 本项目拟采用理论分析、水槽（港池）试验与现场观测相结合，开展波流共同作用下粉沙起动、底床形态变化、底部动力响应、非均匀悬沙输移过程等非线性特征研究，揭示波流共同作用下粉沙运动过程的非线性机制，建立波流共同作用下粉沙起动、沙纹预测、沙纹床面涡量、紊动动能、紊动扩散系数表达式、非均匀沙含沙量及粒径分布模式等。为河口海岸工程中深水航道泥沙骤淤问题的预测提供理论基础。

波流共同作用下粉沙输移体现为动力、边界及泥沙三个过程相互反馈系统，呈现强烈的非线性特征。系统梳理了波流共同作用下泥沙运动非线性规律的研究进展及科学问题，开展了波流共同作用下水沙精细水槽（港池）试验及现场观测，为波流作用下泥沙运动机理的认知积累基础数据。通过多普勒原理与波能流理论相结合的方法，揭示流影响下波高非线性变化机制，并提出波要素变化预测模式；从边界层泥沙起动的角度揭示了波流作用下泥沙起动非线性机制，提出适用于纯波、纯流、波流情形统一的泥沙起动临界曲线；阐明沙纹成长非线性过程，提出了基于沙纹成长过程的波流沙纹非线性预测模式；研究近底涡动力及紊动的非线性特征，提出近底涡量及紊动强度的定量表达式；基于紊动扩散和漩涡挟沙机制，建立了全水深悬沙分布及临底含沙量非线性模式。从而对波流粉沙输移非线性过程进行精细解析，并形成理论模式，丰富和发展了河口海岸动力学，为河口海岸工程泥沙预报提供科学依据。