Dynamics of Bluff Bodies with Internal Nonlinear Oscillators: Vortex-Induced Vibration Suppression, Partial Wake Stabilization, and Drag Reduction

具有内部非线性振荡器的钝体动力学：涡激振动抑制、部分尾流稳定和减阻

• 批准号: 1363231
• 负责人: Alexander Vakakis
• 金额: $ 32.5万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1363231&HistoricalAwards=false
• 关键词: Dynamics; Bluff; Bodies; Internal; Nonlinear

Fluid-structure interaction is ubiquitous across a range of engineering applications, from flutter and divergence in aerodynamics, to vibration of fuel rods in nuclear power reactors, tension legs in offshore platforms, wind turbine towers, and hydrokinetic energy harvesting. A major aim of this work is to demonstrate that using intentionally designed nonlinear oscillators inside a bluff body it is possible to passively suppress vortex induced vibrations - VIVs, partially stabilize the wake past the body, and reduce the drag force exerted by the surrounding fluid without any external modification. This research can have broad and significant impact in diverse fields. For example, the reduction of the drag forces on a bluff body through the action of internal nonlinear oscillators might significantly affect the design of future air vehicles and boats by enhancing their performance, enlarging their range of operation and decreasing fuel consumption. Also, enhanced and economical hydrodynamic vibration energy harvesting could be achieved by appropriate design and optimization of internal nonlinear oscillators inside a body undergoing VIVs.In this research, the dynamic interactions of a strongly nonlinear finite-dimensional oscillator with an infinite-dimensional fluid flow will be studied. This is important in understanding not only fluid-structure interaction in a variety of contexts, but also, in a broader sense, because it serves as a testbed for understanding the nonlinear dynamical behavior of a variety of other mechanical (and nonmechanical) systems involving nonlinear interactions of coupled finite- and infinite-dimensional parts. The fundamental importance of dealing with an intermediate-to-high range of Reynolds number -- Re -- lies in the fact that our preliminary results show that the dimension of the attractor in the two-dimensional laminar case is less than four, while in the turbulent case, it is expected to grow as Re to the 9/4 power. This system thus provides a unique opportunity to understand the dynamics of fluid-structure interaction, where the dimension of the attractor varies from one (for periodic response) to much larger values. We will also study the heretofore unexplored role of angular momentum in VIV. Finally, the capacity of strongly nonlinear internal oscillating elements to drastically modify the wake of a bluff body and reduce its drag coefficient at both intermediate and higher Re will be explored. The research will be performed using slow/fast dynamical decompositions, invariant slow manifold considerations, nonlinear system identification, and reduced-order modeling techniques. High-fidelity fluid-structure interaction computations will be performed in the laminar, transition, and turbulent regimes.

在各种工程应用中，流体结构的相互作用无处不在，从空气动力学的颤动和差异到核电反应器中的燃油杆的振动，离岸平台上的张力腿，风力涡轮机塔和水力学能量收获。这项工作的一个主要目的是证明，使用故意设计的无线性振荡器在虚张声势体内，可以被动地抑制涡旋诱导的振动 - 体内，部分稳定尾流，并减少周围流体施加的阻力，而无需任何外部修饰。这项研究可能对各种领域产生广泛而重大的影响。例如，通过内部非线性振荡器的作用减少了悬崖车身上的阻力力，可能会通过提高其性能，扩大其运行范围并减少燃油消耗，从而显着影响未来的空中车辆和船只的设计。同样，通过适当的设计和优化了正在进行VIV的体内的内部非线性振荡器可以实现增强和经济的流体动力振动能量。在这项研究中，将研究强烈的非线性有限维振荡器的动态相互作用与无限维流动的强度相互作用。这对于理解各种情况下的流体结构相互作用很重要，而且从更广泛的意义上讲，它是一种测试床，用于理解涉及涉及有限有限的和无限二维部分非线性相互作用的各种其他机械（和非机械）系统的非线性动力学行为。处理中间至高度的雷诺数字的基本重要性 - re-在于我们的初步结果表明，在二维层层层层中，吸引子的维度小于四，而在动荡的情况下，它可以随着9/4的功率而增长。因此，该系统提供了一个独特的机会来了解流体结构相互作用的动力学，其中吸引子的维度从一个（定期响应）到更大的值不等。我们还将研究VIV中角动量的迄今未开发的作用。最后，将探索强烈非线性的内部振荡元件的能力大大修改虚张声势的尾巴，并探索中级和更高RE的阻力系数。该研究将使用缓慢/快速的动态分解，不变的慢速歧管考虑，非线性系统识别和减少阶层建模技术进行。高保真流体结构的相互作用计算将在层流，过渡和湍流方案中进行。