Mechanical multiphase vibratory phenomena at very low mass ratios

当流体流动与结构或其他流体相互作用时，不可避免地会发生流致振动。电缆和植物叶片被风激发，管道和锅炉中的两相流以及水波只是自激振动或不稳定性的几个例子。流致振动可能是有害的，导致结构故障，或者可以明智地用于提取能量。毫无疑问，重要的是要研究、描述甚至找到模型，以更好地理解和控制其影响。我们的研究将提供理论和工具，以解决流致振动的基本方面。拟议的研究计划侧重于基本的悬而未决的问题，目前的商业数值解决方案没有得到充分处理，难以理解的实验。我们将开发和使用创新的数值方法来研究具有非常低的质量比和高度可变形边界的多相力学问题。拟议的研究计划旨在研究三个未回答的机械问题的物理学，这些问题对该行业来说既重要又重要。关于气泡在停滞水中上升的第一轴将提供关于是什么使相等体积的气泡上升得慢或快（3倍！）的答案。我们将描述气泡变形和气泡-尾流相互作用动力学的模态内容。通用涡激振动振幅帽上的第二个轴将进一步加强设计指南，特别是在海底应用中遇到的低质量比。本文提出的非圆柱体在横流中旋转和扭转驰振的第三轴，将有助于旋转驰振建模和设计实践的改进。这些基本的振动现象的特点是大位移和变形引起的边界动力学在3D。为了实现这些目标，我们将开发新的算法，并改善我们的完全耦合单片任意拉格朗日欧拉计算策略的基础上有限和谱元素。我们将进行特定的实验，以确定模拟中的初始条件，并验证理论或数值观测。因此，我们的研究将为工程、设计指南和科学知识带来新的工具。它提供了很好的成功机会，因为它将满足工程师在理解，建模和现有程序改进方面的需求。

Flow-induced vibrations occur inevitably when fluid flow interacts with structures or other fluids. Cables and plant leaves excited by winds, two-phase flows in pipes and boilers and water waves are just but a few examples of self-excited vibrations or instabilities. Flow-induced vibrations can be harmful leading to structural failures or can be used wisely to extract energy. Undoubtedly, it is important to study, characterize and even find models to better understand and control their effects. Our research will provide theory and tools to solve fundamental aspects of flow-induced vibrations. The proposed research program focuses on essential unanswered problems that are not handled adequately by present commercial numerical solutions and difficult to apprehend experimentally only. We will develop and use innovative numerical methods to study multiphase mechanical problems with very low mass ratios and highly deformable boundaries. The proposed research program aims at studying the physics of three unanswered mechanical problems that are both fundamental and vital for the industry. A first axis on bubble rise in stagnant water will provide answers about what makes equal volume bubbles rise slow or fast (by a factor of 3!). We will characterize the modal content of bubble deformations and bubble-wake interaction dynamics. A second axis on the universal cap of vortex-induced vibration amplitude will further reinforce design guidelines especially for the low mass ratio encountered in subsea applications. A third axis on rotational and torsional galloping of non-circular cylinders in crossflow will contribute to improve rotational galloping modeling and design practice. These fundamental vibrational phenomena are characterized by large displacements and deformations induced by boundary dynamics in 3D. To achieve these goals, we will develop new algorithms and improve our fully coupled monolithic Arbitrary Lagrangian-Eulerian computational strategies based on finite and spectral elements. We will perform specific experiments to define initial conditions in simulations and validate theories or numerical observations. Our research will thus result in new tools for engineering, design guidelines and scientific knowledge. It offers excellent chances of success because it will fill needs in understanding, modeling and existing procedure improvement engineers need.