裂流和海岸环流引起的海岸变形特征研究

The present project studies the features of beach topography deformation induced by rip currents and coastal circulations. The flow field considered includes: (1) that produced by crossing waves; (2) that produced by topography perturbation on bar crest and beach bottom; (3) that produced by crossing wave field under storm wave condition. The corresponding beach topogrphy deformation patterns which can be expected and to be studied by the present project include: (1) the shoreline with large cusps; (2）transverse,oblique sand bars connected to shoreline, rhythm sand bar and rhythm shoreline; (3) three dimension shoreline erosion patterns with large cusps. The two mechanisms for beach deformation, the forced response and the topogrphy instability, and the three dimensional beach erosion patterns during storm condition will be examined.The research will be performed by conducting physical experiemnts, numerical simulations and theoretical analysis based on the linear topography instability theory. The phase-resolved numerical model and phase-averaged numerical model for computing the coupling between fluid flow and bottom deformation will be established in the study.

本项目研究裂流和海岸环流流场引起的海岸变形特征。所研究的裂流和海岸环流流场包括三类：一是海岸交叉波浪场产生的；二是沙坝或者平坡地形上沿岸方向变化的地形扰动产生的；三是风暴波况海岸交叉波浪场产生的。项目将研究海岸上这三类流场所引起的海岸变形特征，可以预见的这三类流场所产生的海岸变形分别是: (1)尖角型岸线变形; (2)海岸横向、倾斜沙坝系统，韵律型海岸沙坝，韵律型岸线;(3)类似尖角型的海岸侵蚀三维变形。本项目将研究这些海岸变形所产生的动力机制，包括强迫响应机制和地形不稳定机制，研究这些海岸变形发生的波况条件和地形条件。研究以物理模型实验，数值模拟和理论分析相结合的方式展开，探讨裂流和海岸环流流场引起的海岸变形所产生的形态特征和动力机制，探讨风暴波况裂流和海岸环流引起的海岸侵蚀变形的三维特征。

本项目以物理模型实验，数值模拟和理论分析相结合的方式研究了裂流和海岸环流流场引起的海岸变形特征。所得研究结果包括：（1）通过物理模型实验得到了海岸交叉波浪场产生的裂流和环流水平和垂向分布特征；（2）通过物理模型实验得到了海岸破碎波浪引起的海岸悬移泥沙的垂向分布特征和推移质泥沙的输移特征；（3）通过数值模拟得到了海岸上裂流和环流流场所引起的海岸变形特征，研究了地形变形的强迫响应机制和地形不稳定机制，所研究的海岸变形包括(a)尖角型海线的变形;(b)海岸横向、倾斜沙坝地形的变形；（c）韵律型海岸沙坝地形的变形。研究中建立了有关计算模型，包括:高阶 Boussinesq方程模型与地形演变耦合计算模型；基于POM模型的三维近岸环流和地形演变计算模型以及水深平均的海岸环流模型与水底变形的耦合计算模型。本项目研究成果对于海岸工程的发展具有重要实际应用价值和学术意义。