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。

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.