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Active Control Of Wingtip Vortices Using Piezoelectric Actuated Winglets

机译：主动控制翼梢小翼主动控制翼尖涡流

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摘要

Wingtip vortices develop at the tips of aircraft wings due to a pressure imbalance during the process of generating lift. These vortices significantly increase the total aerodynamic drag of an aircraft at high-lift flight conditions such as during take-off and landing. The long trailing vortices contain strong circulation and may induce rolling moments and lift losses on a trailing aircraft, making them a major cause for wake turbulence. A mandatory spacing between aircraft is administered by civil aviation agencies to reduce the probability of hazardous wake encounters. These measures, while necessary, restrict the capacity of major airports and lead to higher wait times between take-off and landing of two aircraft. This poses a major challenge in the face of continuously increasing air traffic volume. Wingtip vortices are also known as a potent source of aerodynamic vibrations and noise. These negative effects have made the study of wingtip vortex attenuation a critical area of research. The problem of induced drag has been addressed with the development of wingtip device, like winglets. Tip devices diffuse the vortex at its very onset leading to lower induced drag. The problem of wake turbulence has been addressed in studies on vortex interactions and co-operative instabilities. These instabilities accelerate the process of vortex breakdown, leading to a lower lifetime in the wake. A few studies have tried to develop active mechanisms that can artificially excite these instabilities.;The aim of the present study is to develop a device that can be used for both reducing induced drag and exciting wake instabilities. To accomplish this objective, an active winglet actuator has been developed with the help of piezoelectric Macro-Fiber Composite (MFC). The winglet is capable of oscillating about the main wing-section at desired frequency and amplitude. A passive winglet is a well-established drag reducing device. An oscillating winglet can introduce perturbations that can potentially lead to instabilities and accelerate the process of vortex breakdown. A half-body model of a generic aircraft configuration was fabricated to characterize and evaluate the performance of actuated winglets. Two winglet models having mean dihedral orientations of 0° and 75° were studied. The freestream velocity for these experiments was 20 m/s. The angle of incidence of the wing-section was varied between 0° and 8°. The Reynolds number based on the mid-chord length of the wing-section is 140000. The first part of the study consisted of a detailed structural characterization of the winglets at various input excitation and pressure loading conditions. The second part consisted of low speed wind tunnel tests to investigate the effects of actuation on the development of wingtip vortices at different angles of incidence. Measurements included static surface pressure distributions and Stereoscopic (ensemble and phase-locked) Particle Image Velocimetry (SPIV) at various downstream planes. Modal analysis of the fluctuations existing in the baseline vortex and those introduced by actuation is conducted with the help of Proper Orthogonal Decomposition (POD) technique.;The winglet oscillations show bi-modal behavior for both structural and actuation modes of resonance. The oscillatory amplitude at these actuation modes increases linearly with the magnitude of excitation. During wind tunnel tests, fluid structure interactions lead to structural vibrations of the wing. The effect of these vibrations on the winglet oscillations decreases with the increase in the strength of actuation. At high input excitation, the actuated winglet is capable of generating controlled oscillation s suitable for perturbing the vortex. The vortex associated with a winglet is stretched along its axis with multiple vorticity peaks. The center of the vortex core is seen at the root of the winglet while the highest vorticity levels are observed at the tip.;The vortex core rotates and becomes more circular in shape while diffusing downstream. The shape, position, and strength of the vorticity peaks are found to vary periodically with winglet oscillation. Actuation is even capable of disintegrating the single vortex core into two vortices. The most energetic POD fluctuation modes, at the center of the baseline vortex core, correspond to vortex wandering at the initial downstream planes. At the farthest planes, the most energetic modes can be associated with core deformation. High energy fluctuations in the actuated vortex correspond to spatial oscillations and distortions produced by the winglet motion.
机译：由于产生升力过程中的压力不平衡，在飞机机翼的顶端会形成翼尖涡流。这些旋涡显着增加了飞机在高空飞行条件下（例如起飞和着陆期间）的总空气动力学阻力。较长的尾随涡流具有较强的环流，并可能在尾随的飞机上引起侧倾力矩和升力损失，从而使它们成为尾流湍流的主要原因。飞机之间的强制间距由民航机构管理，以减少发生危险的尾波的可能性。这些措施在必要时限制了主要机场的容量，并导致两架飞机起降之间的等待时间更长。面对不断增加的空中交通量，这构成了重大挑战。翼尖涡流也被称为气动振动和噪声的强大来源。这些负面影响使对翼尖涡流衰减的研究成为研究的关键领域。翼尖装置（如小翼）的发展已解决了诱导阻力的问题。尖端装置在涡流的最开始处扩散，导致较低的诱导阻力。尾流湍流的问题已经在涡旋相互作用和合作不稳定性的研究中得到解决。这些不稳定性加速了涡旋破坏的过程，导致尾流寿命降低。一些研究试图开发出可以人为地激发这些不稳定性的主动机制。本研究的目的是开发一种既可用于减少诱发阻力又可以激发兴奋性不稳定性的装置。为了实现这个目标，已经在压电宏观纤维复合材料（MFC）的帮助下开发了主动小翼致动器。小翼能够以所需的频率和振幅围绕主翼部分振荡。被动式小翼是成熟的减阻装置。振荡的小翼可能会引入扰动，这可能会导致不稳定性并加速涡旋破裂的过程。制造了通用飞机配置的半身模型，以表征和评估致动小翼的性能。研究了平均二面角方向为0°和75°的两个小翼模型。这些实验的自由流速度为20 m / s。机翼部分的入射角在0°和8°之间变化。基于机翼截面中弦长度的雷诺数为140000。研究的第一部分包括在各种输入激励和压力载荷条件下小翼的详细结构特征。第二部分包括低速风洞测试，以研究在不同入射角下驱动对翼尖涡流发展的影响。测量包括在各个下游平面的静态表面压力分布和立体（合奏和锁相）粒子图像测速（SPIV）。借助适当的正交分解（POD）技术，对基线涡旋中存在的波动以及由驱动引起的波动进行了模态分析。;小翼振动在共振的结构和驱动模式下均表现出双峰行为。这些激励模式下的振荡幅度随激励幅度线性增加。在风洞测试期间，流体结构的相互作用会导致机翼的结构振动。这些振动对小翼振动的影响随着致动强度的增加而减小。在高输入激励下，被致动的小翼能够产生适于扰动涡旋的受控振荡。与小翼相关的旋涡沿其轴拉伸，并带有多个旋涡峰。在小翼的根部可以看到涡流核心的中心，而在尖端则可以看到最高的涡度。涡流核心旋转并变得更圆，同时向下游扩散。发现旋涡峰的形状，位置和强度会随着小翼振荡而周期性变化。致动甚至能够将单个涡旋核分解为两个涡旋。在基线涡旋核中心的能量最高的POD波动模式对应于初始下游平面的涡旋漂移。在最远的平面上，最活跃的模式可能与岩心变形有关。被驱动的涡旋中的高能量波动对应于由小翼运动产生的空间振荡和畸变。

著录项

  • 作者

    Guha, Tufan Kumar.;

  • 作者单位

    The Florida State University.;

  • 授予单位 The Florida State University.;
  • 学科 Mechanical engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 180 p.
  • 总页数 180
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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