Internal solitary wave-induced sediment resuspension and offshore infrastructure loading

内孤立波是沿海海洋中普遍存在的现象。 这些波在地下密度界面上传播，波长约为1 km，振幅约为100 m，电流大于1 m s-1;因此，从其海上发电站向岸上输送了大量能量。 在内部孤立波浅滩处，相关的近床湍流重新悬浮和重新分布底部沉积物，将有机物、营养物和污染物垂直泵入水柱。 悬浮的沉积物形成了厚达100米的云状（浑浊）层，并在海底形成了波长约为100米的巨大沙丘。 内部孤立波还对海底基础设施施加危险载荷，波浪冲击导致钻柱和锚链断裂、遥控车辆丢失和钻机倾斜，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并增加孤立波破碎区的管道壁厚。降低相关设计标准估算的不确定性将节省数千万美元。 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。 他们将：（1）建立模型，以参数化内部孤立波对沉积物再悬浮的动力学影响，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计算机模拟再现实验室生成的孤立波;（3）测量设计荷载内孤立波对海上石油和天然气基础设施（立柱和水平管道）施加的力、扭矩和应力。 这项研究将开发解决方案，以满足以下方面的关键需求：（1）海洋学家，他们需要实验室数据来预测现场的波浪再悬浮和破碎位置;（2）数值建模人员，他们需要实验室数据来验证模型;（3）管理渔业，导航和制定建筑法规的政府机构;（4）有抱负的MetOcean工程师，他们需要在海洋学和资源部门工作的高级研究生培训;以及（5）在受内孤立波影响的沃茨中管理钻井平台和铺设管道的资源和工程公司，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.