砂质岸滩修复剖面动力演变过程及其数值模型研究

In recent years, artificial reclamation and other man-made activities are inducing and aggravating the erosion disaster along sandy coasts, causing harm to the sustainable use of coastal resources. Therefore, China launched the "Blue Bay remediation Operation" in 2016. According to the technical support requirements of the operation, this project focuses on the dynamic evolution process and numerical model of sandy beach restoration profile. A more fine wave model is constructed to describe the complex hydrodynamic processes in the nearshore area, especially in the surf zone; and a numerical model for sandy beach restoration profile evolution is established based on GPU+MPI parallel algorithm and the dynamic/morphologic coupling process. The applicability of the existing formula for calculating sediment transport rate is discussed in combination with field measurements, and the vertical distribution and correlation of suspended sediment concentration and flux along the restoration section, as well as the relationship between suspended sediment vertical concentration and synchronous velocity are investigated. The relationship among the evolution of sandy beach restoration profile, sediment transport and hydrodynamic factors and the inter-influencing mechanism are revealed, and the method and process of determining key technical indexes for the design of sandy beach restoration profile are put forward. The outputs from the present study will provide profoundly scientific and technical support for designing sandy beach restoration profile under the guidance of "natural restoration as the main".

近年来，围填海等人为活动正在诱发和加剧砂质海岸的侵蚀灾害，给海岸资源的可持续利用造成危害，为此我国在2016年启动了“蓝色海湾整治行动”。本项目根据该行动的技术支撑要求，重点围绕砂质岸滩修复剖面动力演变过程及其数值模型开展相关研究。构建更加精细的波浪模型来描述近岸区域尤其是波浪破碎后复杂的水动力过程；建立基于GPU+MPI并行算法，考虑动力耦合机制的砂质岸滩修复剖面演变数值计算模型；结合现场测量探讨现有海岸泥沙输沙率公式的适用性；揭示悬沙浓度和通量在修复剖面沿程的垂向分布及相关关系，以及悬浮泥沙垂向浓度与同步流速的关系；揭示岸滩修复剖面演化与沉积物、水动力要素的依赖关系与影响机制；提出砂质海岸修复剖面设计关键技术指标的确定方法和流程。为“以自然修复为主”砂质岸滩修复剖面设计提供更加坚实的科学和技术支撑。

项目将新型多层Boussinesq类波浪数值模型作为驱动力耦合边界层模型、输沙模型建立了基于动力过程的岸滩剖面演变数值模型，对波浪作用下沙质岸滩剖面的变形进行了数值模拟研究。基于统一计算设备架构CUDA C语言和图形处理器，实现了模型的并行加速运算。开展了潮间带水流和悬砂观测，得到了边界层内的悬沙浓度与距底高度的关系及近底床边界层内的悬沙浓度分布规律。利用岸滩剖面演化数学模型，提出的设计高水位以上剩余滩肩宽度和平均水位以上填沙侵蚀量的方法，结合养滩工程剖面设计问题，构建了规范化的设计流程。