多波浪冲流事件作用下波浪冲流带地形演变规律研究

Being able to predict beachface evolution is of great importance for the development and protection of the nearshore region. The beach evolution in the swash zone has been recognized as one of the key factors for the beachface evolution in the nearshore region. Considerable work-observational, experimental and numerical-has been done in this area to try to understand and predict beach behaviour; however, most of the numerical work carried out so far has focused primarily on the beach evolution under one single swash event. In reality, multiple swash events interact, and these swash interactions have been recognised important in the beachface evolution. Thus, this proposal is aimed to develop a numerical model based on the Method of Characteristics, which can solve bores accurately, simulating the beachface evolution under multiple swash events. The swash interactions will be examined by investigating dam-break flows. The existing experimental and measured multiple swash events data will be used to verify and improve the model. The effects of swash interactions on swash flow and beachface evolution will be examined. High accuracy is one of the characteristics of the developed model, and the model will serve as benchmark for the future development of morphodynamic models that are easy to use but not able to achieve high accuracy for multiple swash events. It will provide great insight into the swash morphodynamics. Laser scanners, that are able to precisely and rapidly measure changes in the beach surface will be used to take measurements of multiple swash events on Xiangshan Beach. It will give fundamental data for swash zone research, and the applicability and superiority of laser scanners in swash zone measurements will be further explored.

海岸地形变化的预测是海岸开发及保护的重要基础；而波浪冲流带的地形演变，则是影响海岸地形变化的重要因素。众多的实验及现场实测资料显示，相邻波浪冲流事件之间的相互作用对波浪冲流带地形演变具有重要作用。然而，现有数学模型只能模拟单个波浪冲流事件，无法模拟冲流事件的相互作用，结果不甚理想。因此，本项目拟通过研究溃坝问题，进行相邻波浪冲流事件之间的相互作用研究，利用特征曲线法建立高精度地形演变模型，并通过模型模拟来探讨波浪冲流事件间的相互作用对水流、泥沙运动、地形变化的作用机理。本课题所开发的精细模型，将为未来其他适用性强但精度有限的多波浪冲流事件地形演变模型的开发提供参考和验证依据，有助于进一步掌握波浪冲流带的地形演变规律。同时，本项目拟利用高精度的激光扫描仪，在宁波象山岸滩采集多波浪冲流事件中的水流和地形资料，探索激光扫描仪在波浪冲流带研究中的应用前景，并为研究提供基础数据。

海岸地形变化的预测是海岸开发及保护的重要基础；而波浪冲流带的地形变化则是影响海岸地形变化的重要因素。在项目组已有的单个波浪冲流事件作用下地形变化研究的基础上，本项目重点研究了相邻两个波浪冲流事件之间的相互作用这一物理过程，在此基础上该项目利用特征曲线法建立了精度较高的多波浪冲流事件作用下波浪冲流带的地形演变模型。本项目进一步通过模型模拟来探讨波浪冲流事件间的相互作用对水流、泥沙运动、地形变化的作用机理。.首先，本项目通过溃坝问题的解析求解，加深了对波浪冲流带涌波与涌波的相互作用的理解。另外，该项目建立了涌波传播过程中的能量耗散和形成的湍流之间的关系，并在模型中引入由此项导致泥沙悬浮，进而通过模型模型研究了涌波湍流对地形变化的影响。该研究结果显示涌波湍流有助于将冲流带下部的泥沙带到冲流带上部形成堆积。最后，本项目数值模拟了两个孤立波引起的波浪冲流事件作用下的地形变化，研究结果显示两个冲流事件的强相互作用会形成泥沙在冲流带上部堆积，然而相对独立（弱相互作用）的冲流事件使得冲流带中上部泥沙被侵蚀，随着水流运动到冲流带下部形成堆积。由此可见，相邻冲流事件的相互作用强度对冲流带地形变化的模式有较大的影响。本项目的研究进一步加深了我们对波浪冲流带关键物理过程的理解，并揭示了这些物理过程在地形演变过程中的作用机理，此研究成果对简化的海岸地形演变模型的改进具有重要的指导意义。