Internal solitary wave-induced sediment resuspension and offshore infrastructure loading

内孤立波是近岸海洋普遍存在的特征。这些波在次表层密度界面上传播，波长约1公里，振幅约100m，并有1m的S-1流，从而将大量的能量从近海发电站输送到岸边。在内部孤立波浅滩的地方，相关的近床湍流重新悬浮并重新分配海底沉积物，将有机质、营养物质和污染物垂直抽送到水柱中。悬浮沉积物形成了100米厚的云状物(浑浊层)，并在海底形成了波长约100米的巨大沙丘场。内部孤立波还对海底基础设施施加危险负荷，海浪冲击导致钻柱和锚链断裂，遥控车辆丢失，钻井平台倾倒，造成数百万美元的重新定位成本和收入损失。此外，目前的海底管道设计标准要求在孤立波破碎区进行昂贵的二次稳定和增加管道壁厚。减少相关设计标准估计的不确定性将节省数千万美元。 这项拟议的研究将培养4名博士、6名硕士和5名本科生，他们将进行实验室实验和数值模拟，以研究沿海海洋中的内孤立波浅滩。这些项目将：(1)开发模型，使内孤立波对沉积物再悬浮的动态影响参数化，并量化相关的沉积物输运；(2)确定海底粗糙度是否妨碍高分辨率的计算机模拟再现实验室产生的孤立波；(3)测量内孤立波对近海石油和天然气基础设施(垂直柱和水平管道)施加的设计荷载(力、扭矩和应力)。 这项研究将制定解决方案，以满足下列关键需求：(1)海洋学家，需要实验室数据来预测海浪在野外的再悬浮和破裂位置；(2)数值模型师，需要实验室数据进行模型验证；(3)管理渔业、导航和制定建筑规范的政府机构；(4)有抱负的MetOcean工程师，他们需要高级研究生培训才能在海洋学和资源部门工作；(5)资源和工程公司，专门管理钻机和在受内部孤立波影响的水域铺设管道，使用昂贵的二次稳定措施和保守的管道壁厚。

Internal solitary waves are ubiquitous features of the coastal ocean. Propagating on subsurface density interfaces, these waves have ~1 km wavelengths, ~100 m amplitudes and >1 m s-1 currents; thereby transporting significant energy shoreward from their offshore generation sites. Where the internal solitary waves shoal, the associated near-bed turbulence re-suspends and re-distributes bottom sediment, pumping organic matter, nutrients and contaminants vertically through the water-column. The suspended sediment creates nepheloid (turbidity) layers that are 100s of m thick and forms immense dune fields with ~100 m wavelengths on the ocean floor. Internal solitary waves also apply hazardous loads to subsea infrastructure, with wave impacts leading to broken drill strings and anchor chains, lost remote operated vehicles and listing of rigs, causing millions of dollars in repositioning costs and lost revenue. Moreover, present subsea pipeline design criteria require costly secondary stabilization and increased pipeline wall thickness in solitary wave breaking zones. Reduced uncertainty in estimation of the associated design criteria will save $10s of millions. The proposed research will train 4 PhD, 6 MSc and 5 undergraduate students, who will perform laboratory experiments and numerical simulations to investigate internal solitary wave shoaling in the coastal ocean. They will: (1) develop models to parameterize the dynamic effects of internal solitary waves on sediment resuspension and quantify the associated sediment transport; (2) determine whether bottom roughness is preventing high-resolution computer simulations from reproducing laboratory-generated solitary waves; (3) measure the design loads (force, torque and stress) applied by internal solitary waves to offshore oil and gas infrastructure (vertical columns and horizontal pipelines). This research will develop solutions to address critical needs of (1) Oceanographers, who require laboratory data to predict wave resuspension and breaking locations in the field; (2) Numerical Modellers, who require laboratory data for model validation; (3) Government Agencies that manage fisheries, navigation and develop building codes; (4) aspiring MetOcean engineers, who require advanced graduate training to work in the oceanography and resource sectors; and (5) Resource and Engineering Companies that manage rigs and lay pipeline in internal solitary wave impacted waters, using costly secondary stabilization and conservative pipeline wall thicknesses.