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.

流固耦合在一系列工程应用中无处不在，从空气动力学中的颤振和发散，到核反应堆中燃料棒的振动、海上平台中的张力腿、风力涡轮机塔架和流体动能收集。这项工作的主要目的是证明，在钝体内部使用特意设计的非线性振荡器，可以被动抑制涡流引起的振动 - VIV，部分稳定经过身体的尾流，并减少周围流体施加的阻力，而无需任何外部修改。这项研究可以在不同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钝体上的阻力可能会通过提高未来飞行器和船只的性能、扩大其运行范围和降低燃料消耗来显着影响其设计。此外，通过对经历 VIV 的体内内部非线性振荡器进行适当设计和优化，可以实现增强且经济的流体动力振动能量收集。在这项研究中，强非线性有限维振荡器与无限维流体流的动态相互作用将被研究。这不仅对于理解各种背景下的流体-结构相互作用很重要，而且在更广泛的意义上也很重要，因为它可以作为理解涉及非线性的各种其他机械（和非机械）系统的非线性动力学行为的测试平台。耦合的有限维和无限维部分的相互作用。处理中高范围的雷诺数（Re）的根本重要性在于我们的初步结果表明，二维层流情况下吸引子的维数小于四，而在二维层流情况下，吸引子的维数小于四。在动荡的情况下，预计 Re 会增长到 9/4 次方。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，其中吸引子的尺寸从 1（对于周期性响应）到更大的值。我们还将研究迄今为止尚未探索的角动量在 VIV 中的作用。最后，将探讨强非线性内部振荡元件在中等和较高 Re 条件下大幅改变钝体尾流并降低其阻力系数的能力。该研究将使用慢/快动态分解、不变慢流形考虑、非线性系统识别和降阶建模技术来进行。高保真流固耦合计算将在层流、过渡和湍流状态下进行。