Advanced FEM for Strongly Coupled Fluid-Structure Interactions in Offshore Applications Including Low and Zero Mass Ratios

流体-结构相互作用（FSI）是许多工程系统设计的关键。从适航性到飞机操纵性，几乎所有的机械系统都涉及结构和流体流动之间一定程度的耦合。在Ecole Polytechnique de Montréal，我们已经开发了有效的单片完全耦合算法，用于具有柔性结构的通用FSI的三维非定常配置。我们的工作已经引起了足够的兴趣，几家公司已经资助了我们的研究扩展（Gaz Transport & Technigaz，Commissédél 'Énergie Atomique，TOTAL SA）。我们提出的研究是一个自然的扩展，我们以前的研究模拟流固耦合。它将集中在基本的配方和计算问题（接触，谱元法）进行大位移和不可压缩流体的流动引起的变形结构的准确和一致的有限元模拟。我们的目标是扩展FSI公式，以解决海洋工程行业中突出而典型的挑战：具有非常低（零）质量比的海洋结构物的流致振动，与隔水管塔的湍流和驰振的流动布置一致。通常的解耦算法在这些问题上失败得很惨。此外，在越来越深的沃茨中钻探的当前趋势意味着将石油从洋底运送到表面的立管管线现在跨越超过2000米，这需要设计新的浮力装置和新的立管概念。立管、浮标和立管塔的动力学行为是由传统的松散耦合算法处理不好的强流致振动引起的。我们相信，我们的完全耦合的方法可以克服这些新的极端FSI提出的许多困难。为了实现我们的目标，我们确定了以下目标：1。完善我们的全耦合单片计算方法，以提高其精度和计算效率。我们将我们的FE公式扩展到等参，高阶谱元素，以提高空间精度，并通过结合时间步长和网格自适应策略从其更高的计算效率中受益。这是我们方法的自然延伸。2.实现刚体动力学的接触算法，这将保持我们的高阶时间精度方法。我们赞成使用拉格朗日乘子不等式，因为他们是免费的，从近似引入的惩罚方法，例如。3.将公式应用于与海上应用相关的质量比非常低的问题。通过流体机械学院低雷诺数通道和蒙特利尔理工学院流体-结构相互作用实验室之间的实验合作进行验证。我们已经确定了以下具有实际意义的问题：a.立管塔扭转和平移驰振，B。浮力的行为可以，C。将立管组件汇聚到海上平台，这一通用研究具有创新性，因为它将导致计算模型的开发和验证，从而深入了解海上力学中典型的流激振动问题。对低质量比的关注构成了一个真实的附加值，因为它是目前CFD/CSD软件的一个公认的弱点。我们的工作是出于开发该行业所需的工具的需要，以便在加拿大超深沃茨安全地操作未来的海上油田开发。我们的方法提供了很好的成功前景，因为它是现有工程设计程序的自然延伸。

Fluid-Structure Interactions (FSI) are critical to the design of many engineering systems. From sea-worthiness to airplane maneuverability, nearly all mechanical systems involve a certain degree of coupling between structures and fluid flows. At the Ecole Polytechnique de Montréal, we have developed effective monolithic fully coupled algorithms for generic FSI with flexible structures for 3D unsteady configurations. Our work has generated sufficient interest that several companies have funded extensions of our research (Gaz Transport & Technigaz, Commissariat à l’Énergie Atomique, TOTAL SA). The research we propose is a natural extension of our previous research on simulation of FSI. It will focus on fundamental formulation and computational issues (contact, spectral element method) for accurate and consistent finite element simulation of structures undergoing large displacements and deformations induced by the flow of incompressible fluids. Our goal is to extend FSI formulations to tackle outstanding while typical challenges in the offshore industry: flow induced vibrations of offshore structures with very low (zero) mass ratios, in-line with the flow arrangements of risers and galloping of riser towers. The usual decoupled algorithms fail miserably on these problems. Also, the current trend to drill in ever deeper waters implies that riser lines carrying the oil from the ocean floor to the surface now span more than 2000 m which requires that new buoyancy devices and new riser concepts be designed. Risers, buoys and riser towers dynamical behaviors result from strong Flow Induced Vibrations that are poorly handled by traditional loosely coupled algorithms. We believe that our fully coupled approach can overcome many of the difficulties presented by these new extreme FSI. To achieve our goal we have identified the following objectives: 1. REFINE our fully coupled monolithic computational method to improve its accuracy and computational efficiency. We will extend our FE Formulation to isoparametric, higher order spectral elements to improve spatial accuracy and benefit from their higher computational efficiency by combining time-step and mesh adaptation strategies. This constitutes a natural extension of our methodology. 2. IMPLEMENT contact algorithms for rigid-body dynamics that will preserve our high-order temporal accuracy method. We favor using Lagrange multipliers for inequalities since they are free from approximations introduced by penalty methods for instance. 3. APPLY the formulation to problems with very low mass ratios that are relevant to offshore applications. Validation through experimental collaborative work between the low Reynolds number chanel of the Laboratoire de Mécanique des Fluides and Fluid-Structure Interaction Laboratory of the École Polytechnique de Montréal. We have identified the following problems of practical relevance: a. Riser tower torsional and translational galloping, b. Behavior of buoyancy can, c. Riser assemblies converging to an offshore platform, This generic research is innovative, as it will lead to the development and validation of computational models to shed insight into flow-­induced vibration problems typical to offshore mechanics. The focus on low mass ratio constitutes a real added value since it is an identified weakness of present CFD/CSD softwares. Our work is motivated by the need to develop the tools required by the industry to operate safely future oil offshore field developments in Canadian ultra-deep waters. Our approach offers excellent perspectives of success because it is a natural extension of existing engineering design procedures.