Internal solitary wave-induced sediment resuspension and offshore infrastructure loading

内孤立波是沿海海洋普遍存在的特征。这些波在亚表面密度界面上传播，波长约1 km，振幅约100 m，电流约1 m s-1；从而将大量的能源从他们的海上发电站输送到岸上。在内部孤立波浅滩的地方，相关的近床湍流重新悬浮和重新分配底部沉积物，通过水柱垂直泵送有机物、营养物质和污染物。悬浮的沉积物形成了100米厚的浊层，并在海底形成了波长约100米的巨大沙丘场。内部孤立波也会给海底基础设施带来危险载荷，海浪的冲击会导致钻柱和锚链断裂，远程操作车辆和钻机的损失，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需要昂贵的二次稳定和增加孤立波浪破碎区的管道壁厚。减少相关设计标准估计的不确定性将节省数千万美元。本研究将培养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来研究沿海海洋的内孤立波浅滩现象。他们将：(1)建立模型来参数化内孤立波对泥沙再悬浮的动态影响，并量化相关的泥沙输运；(2)确定底部粗糙度是否妨碍高分辨率计算机模拟再现实验室产生的孤立波；(3)测量内孤立波对海上油气基础设施（垂直柱和水平管道）施加的设计载荷（力、扭矩和应力）。这项研究将开发解决方案，以满足以下关键需求：(1)海洋学家，他们需要实验室数据来预测海浪的再悬浮和破碎位置；(2)需要实验室数据进行模型验证的数值建模人员；(3)管理渔业、航海和制定建筑规范的政府机构；(4)有抱负的海洋工程师，需要高级研究生培训才能在海洋学和资源部门工作；(5)资源和工程公司管理钻井平台并在内部孤立波影响水域铺设管道，使用昂贵的二次稳定和保守的管道壁厚。

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.