NONLINEAR DYNAMICS OF BLUFF-BODY WAKES AND FLUID-STRUCTURE INSTABILITIES: A SYMMETRY-GROUP BASED APPROACH

钝体尾流和流结构不稳定性的非线性动力学：基于对称群的方法

• 批准号: RGPIN-2015-06604
• 负责人: Mureithi, Njuki
• 金额: $ 1.82万
• 依托单位: École Polytechnique de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=680956
• 关键词: NONLINEAR; DYNAMICS; BLUFF; BODY; WAKES

The subject of interest is fluid-structure interaction (FSI) involving large and/or complex systems with inherent symmetry. Such systems are ubiquitous in nature and in engineering. Typical examples include mechanical and civil engineering structures such truss structures, dome structures, space structures as well as machines jet engines etc.******Symmetry in many cases leads to highly simplified behavior, even for large complex systems. At the same time, symmetry may lead to unexpected and counter-intuitive behavior which can be difficult to explain or fully understanding without delving into the details of system dynamics under the influence of symmetry. ******There has been increasing interest in symmetry group theory and its application to large complex engineering systems ranging from space structures to high speed trans and jet engines. However, systematic exploitation remains limited. Yet there are many problems where symmetry theory provides deep insight into the dynamics of complex systems. The problem of mode localization in rotating machines is now well known and understood. This problem, which perplexed engineers in the 50s can very conveniently, explained using symmetry group theory. ******In the proposed research program the additional effects associated with the presence of fluid flow interacting with the structures will be investigated. Mode localization / symmetry-breaking drastically changes the effective vibration modes. This is expected to significantly modify the stability behavior of tubes subjected to axial flow. To address the challenge of complexity in large systems the proposed research program employs symmetry group theory to develop feasible reduced order models (ROMs) for large and complex systems. The specific problems addressed are in the area of fluid-structure interactions for (i) complex flows such as wake flows behind circular cylinders and (ii) or large flow-structure systems such as cylinder arrays undergoing flow-induced instabilities. ******Besides the predicting the observed dynamical behavior, a potentially more important contribution of the symmetry based model is the demonstration of the link between the wake flow dynamics and the dynamics of the general class of physical and mathematical systems having the same symmetry. As a specific example, the Karman wake undergoes a period-doubling bifurcation for high amplitude forcing. ******The period-doubling bifurcation of the Karman wake is intimately related to the relative symmetry between the forcing perturbation and the symmetry of the Karman wake flow. Other physical systems having the same relative symmetries include pendulums with periodically oscillating support, and fluid-filled vessels under vertical excitation. The systems also exhibit period-doubling instabilities due to the same symmetry breaking instability. ***********

感兴趣的主题是涉及具有固有对称性的大型和/或复杂系统的流体-结构相互作用（FSI）。这样的系统在自然界和工程中普遍存在。典型的例子包括机械和土木工程结构，如桁架结构、穹顶结构、空间结构以及机器喷气发动机等。******在许多情况下，对称性会导致行为高度简化，即使对于大型复杂系统也是如此。同时，对称性可能会导致意想不到的、反直觉的行为，如果不深入研究对称性影响下的系统动力学细节，这些行为就很难解释或完全理解。 ******人们对对称群理论及其在从空间结构到高速传输和喷气发动机等大型复杂工程系统中的应用越来越感兴趣。然而，系统性的利用仍然有限。然而，对称理论在许多问题上提供了对复杂系统动力学的深入洞察。旋转机器中的模式定位问题现在已众所周知并被理解。这个困扰20世纪50年代工程师的问题可以很方便地用对称群理论来解释。 ******在拟议的研究计划中，将研究与结构相互作用的流体流动的存在相关的额外影响。模式局部化/对称性破缺极大地改变了有效振动模式。预计这将显着改变承受轴向流的管的稳定性行为。为了解决大型系统复杂性的挑战，拟议的研究计划采用对称群理论来为大型复杂系统开发可行的降阶模型（ROM）。所解决的具体问题是在流固相互作用领域：(i) 复杂的流动，例如圆柱体后面的尾流，以及 (ii) 或大型流结构系统，例如经历流动引起的不稳定性的圆柱体阵列。 ******除了预测观察到的动力学行为之外，基于对称性的模型的一个潜在更重要的贡献是证明尾流动力学与具有相同性质的一般类物理和数学系统的动力学之间的联系对称。作为一个具体示例，卡门尾流经历倍周期分岔以实现高振幅强迫。 ******卡门尾流的倍周期分岔与强迫扰动和卡门尾流的对称性之间的相对对称性密切相关。具有相同相对对称性的其他物理系统包括具有周期性振荡支撑的摆，以及在垂直激励下充满流体的容器。由于相同的对称性破缺不稳定性，该系统还表现出倍周期不稳定性。 **********