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

流固耦合（FSI）对许多工程系统的设计至关重要。从适航性到飞机机动性，几乎所有的机械系统都涉及到结构和流体流动之间一定程度的耦合。在Ecole Polytechnique de montral，我们开发了有效的单片全耦合算法，用于具有三维非定常结构的柔性结构的通用FSI。我们的工作产生了足够的兴趣，一些公司已经资助了我们的研究扩展（Gaz Transport & Technigaz, Commissariat <e:1> ' Énergie Atomique, TOTAL SA）。我们提出的研究是我们之前对FSI模拟研究的自然延伸。它将侧重于基本的公式和计算问题（接触，谱元方法），以准确和一致的有限元模拟结构，经历由不可压缩流体流动引起的大位移和变形。我们的目标是扩展FSI配方，以解决海上工业中突出而典型的挑战：非常低（零）质量比的海上结构的流动诱发振动，符合隔水管的流动安排和隔水管塔的快速移动。通常的解耦算法在这些问题上失败得很惨。此外，目前的趋势是在更深的水域钻井，这意味着将石油从海底输送到海面的立管管线现在跨越了2000多米，这就需要设计新的浮力装置和新的立管概念。立管、浮筒和立管塔的动力行为是由强烈的流激振动引起的，而传统的松耦合算法很难处理这种振动。我们相信，我们的全耦合方法可以克服这些新的极端FSI所带来的许多困难。为了实现我们的目标，我们确定了以下目标：改进我们的全耦合单片计算方法，提高其精度和计算效率。我们将把我们的有限元公式扩展到等参数、高阶谱元，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更高的计算效率中获益。这是我们方法的自然延伸。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。我们倾向于使用拉格朗日乘数来处理不等式，因为它们不受例如惩罚方法引入的近似的影响。将该公式应用于与海上应用相关的质量比非常低的问题。通过低雷诺数通道的实验室de msamicique的流体和结构相互作用实验室之间的实验协作工作验证École de montracial的理工大学。我们已经确定了以下具有实际意义的问题：立管塔的扭转和动驰，b。浮力行为可以，c。该研究具有创新性，因为它将促进计算模型的开发和验证，从而深入了解海上机械中典型的流体诱发振动问题。对低质量比的关注构成了一个真正的附加价值，因为这是当前CFD/CSD软件的一个明确的弱点。我们的工作动机是开发行业所需的工具，以安全操作加拿大超深水的未来海上油田开发。我们的方法提供了极好的成功前景，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.