Mechanical multiphase vibratory phenomena at very low mass ratios

当流体流动与结构物或其他流体相互作用时，不可避免地会发生流致振动。由风、管道和锅炉中的两相流以及水波激发的电缆和植物叶子只是自激振动或不稳定的几个例子。流动引起的振动可能是有害的，会导致结构故障，或者可以明智地利用来提取能量。毫无疑问，研究、描述甚至寻找模型来更好地理解和控制它们的影响是很重要的。我们的研究将为解决流致振动的基本问题提供理论和工具。拟议的研究计划集中在基本的未回答的问题上，这些问题不是目前的商业数值解所能充分处理的，也是仅从实验上难以理解的。我们将开发和使用创新的数值方法来研究具有极低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尚未回答的机械问题的物理学，这三个问题对该行业既基本又至关重要。关于死水中气泡上升的第一个轴将提供关于是什么导致等体积气泡上升缓慢或快速(上升3倍！)的答案。我们将描述气泡变形和气泡-尾迹相互作用动力学的模式内容。涡激振动幅度万能盖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情况下。研究横流中非圆柱体的旋转舞动和扭转舞动的第三个轴将有助于改进旋转舞动建模和设计实践。这些基本的振动现象以三维边界动力学引起的大位移和大变形为特征。为了实现这些目标，我们将开发新的算法，并改进基于有限元和谱元素的完全耦合的整体式任意拉格朗日-欧拉计算策略。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，我们的研究将产生新的工程工具、设计指南和科学知识。它提供了极好的成功机会，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.