龙凤头海滩修复工程与波流动力响应特性

Study of WaveCurrent Coupled Hydrodynamic Responses to a Beach Nourishment Project at Longfengtou Beach

摘要:

基于MIKE 21软件建立平潭龙凤头海滩修复工程海域双重嵌套二维潮流和波浪耦合数学模型，并将验证后的模型运用到工程设计方案实施前后潮流场及波浪场的模拟，比较分析水动力的变化.研究结果表明：平潭海域潮汐类型属于正规半日潮，8月大潮潮差约为5 m，潮汐强；海坛湾内潮流总体表现为往复流特征，湾口流速最大，湾内流速较小，湾顶流速最小；北端防波堤大大减少了南北水体交换，内侧落潮流调整为沿堤流；堤头处挑流作用明显，流速增加，形成明显的旋转流；南北端防波堤对其内侧一定范围海域有掩护作用，波高削减显著，受掩护岸线长度略大于防波堤长度；堤头处受波浪折射作用影响，波能辐聚，波高增大.工程后海滩中部岸段波高及流速削减不明显，建议增设离岸堤加强海滩保护.

Abstract:

A 2D wavecurrent coupled model for a beach nourishment project sea area at Longfengtou Beach was set up based on MIKE 21 by using a twolevel nested grid. The calibrated model was then adopted to simulate the flow fields and wave fields before and after the project, and the hydrodynamic responses to the nourishment project were analyzed. The simulation results show that the tide in Pingtan sea area is regular semidiurnal and the average tidal range at spring tide in August is about 5 m; the tidal current in Haitan Bay is of typical reversing current with a large flow velocity in the mouth of the bay, and a small and the smallest flow velocity in the middle and top of the bay respectively; the northern breakwater, which greatly reduces the northsouth water exchange, adjusts the ebb current along the breakwater; the flow velocity at the tip of the breakwaters increases due to the deflecting flow, and an anticlockwise circulation generates obviously; the northern and southern breakwaters only have a limited effect on the area behind the breakwaters where the wave height significantly decreases, and the influenced length of shoreline is slightly greater than that of breakwater; the wave height at the tip of breakwaters increases due to the energy convergence caused by wave refraction. Overall, the reduction of wave height and flow velocity in the middle part of the beach is negligible, thus the construction of offshore breakwater is suggested to strengthen the protection of Longfengtou Beach.