Ship and Offshore Floating Platform Motions in Extreme Seas

拟议研究的目标是开发数值方法来计算船舶和海上平台在极端海域的运动。 随着深水油气田的开发，用于勘探、生产和钻井的浮式系统变得越来越重要。虽然海上浮式结构物为从海底定位和提取碳氢化合物提供了唯一安全且具有成本效益的手段，但它们可能会遇到在其位置发生的所有极端条件。船只在航行中也经常遇到极端的海浪。船舶和海上浮式结构物在极端海况下的响应预测对于它们的安全、高效运行至关重要。 在极端海域，船舶和海上结构物可能会经历高度非线性现象，如绿色水、砰击和波浪爬高，这些现象涉及自由表面破碎和多相流。相关载荷可导致局部和整体结构损坏。虽然基于势流的方法在求解船舶非线性运动问题方面取得了很大的进展，但在处理高度扭曲或破碎的自由面时仍存在很大的困难。随着高性能计算机的发展，以求解Navier-Stokes方程为基础的计算流体力学（CFD）方法可以克服这些困难。拟议的研究将侧重于开发计算流体动力学方法，用于预测船舶和海上平台在极端海洋中的运动。（1）进一步发展了一种基于约束插值剖面（CIP）的有限差分方法，用于计算考虑多相流和破断自由面的船舶和平台近场流场和运动;（2）由于CFD方法通常在远场模拟波浪的能力有限，将基于势流的Rankine方法与CIP方法耦合，以考虑远场波效应;（3）将对各种船舶和平台进行验证研究。还将在极端波浪中对船模进行模型试验。实验结果和其他已发表的数据将用于验证数值工具。 通过拟议的研究，将培养海洋流体动力学领域具有强大计算能力的高素质人员。拟议的研究将有助于国内和国际船舶和近海流体动力学领域，特别是在极端海域和打破自由表面的大幅船舶运动的数值研究。

The objective of the proposed research is to develop numerical methods to compute motions of ships and offshore platforms in extreme seas. With the oil and gas development in deepwater, floating systems for exploration, production and drilling are becoming increasingly important. While the offshore floating structures provide the only safe and cost effective means for the location and extraction of hydrocarbons from the sea bottom, they are likely to encounter all the extreme conditions that occur at their locations. Ships also often encounter extreme waves in their routes. The prediction of responses of ships and offshore floating structures in extreme seas is of vital importance to their safe and efficient operations. In extreme seas, ships and offshore structures can experience highly nonlinear phenomena such as green water, slamming and wave run-ups, which involve free-surface breaking and multi-phase flows. The associated loads can cause local and global structural damages. Although great progress has been made in solving the nonlinear ship motion problems with potential-flow based methods, there are great difficulties in treating highly distorted or breaking free surfaces. With the advance of high performance computers, these difficulties can be overcome by the computational fluid dynamics (CFD) methods based on solving the Navier-Stokes equations. The proposed research will focus on the development of a CFD method for predicting ship and offshore platform motions in extreme seas. The research is summarized as follows: (1) A constrained interpolation profile (CIP)-based finite difference method will be further developed to compute the near-field flows and motions of ships and platforms considering multi-phase flow and breaking free surfaces; (2) Since CFD methods generally have limited capability for simulating the waves in the far field, a potential-flow based Rankine method will be coupled with the CIP method to take the far-field wave effect into account; (3) Validation studies will be carried out for various ships and platforms. Model tests will also be conducted for a ship model in extreme waves. The experimental results and other published data will be used to validate the numerical tool. Through the proposed research, highly qualified personnel in the area of marine hydrodynamics with strong computational skills will be trained. The proposed research will contribute nationally and internationally to the field of ship and offshore hydrodynamics, especially the numerical studies of large-amplitude ship motions in extreme seas and breaking free surfaces.