SGER: Gait Selection and Power Output in Bird Flight as Revealed Using Digital Particle Image Velocimetry, DPIV

目前对脊椎动物飞行中步态选择和机械功率输出的理解很大程度上取决于关于扑翼周围的流动特性的未经测试的假设，并且在某种程度上，动物的身体和尾巴。Tobalske将使用新技术，数字粒子图像速度测量（DPIV）来测试这些假设，并通过直接测量鸟类主要飞行肌肉的功率输出和步态选择的运动学估计来协调非定常空气动力学理论。DPIV使用强大的激光照射悬浮在空气中的小反射颗粒。 将数字视频图像采集到计算机中，并利用在视频图像中观察到的颗粒运动来计算流场中的能量。 使用DPIV和一个新的变速风洞，Tobalske将描述翅膀和身体形状不同的鸟类的流动动力学：斑马雀Taeniopygia guttata和虎皮鹦鹉Melopsittacus undulatus。尾流的几何形状和能量将被描述为整个翼拍，在间歇飞行的非扑翼阶段，并在整个速度范围内。 这将测试翅膀形状对飞行步态的影响，鸟类在飞行过程中是否以类似于地面运动中步态变化的方式改变步态，以及翅膀，身体和尾巴作为升力和阻力来源的相对贡献。 声测微法，测量运动过程中的肌肉长度，将被用来比较收缩行为与机械功率输出的斑马雀和虎皮鹦鹉在唤醒。 近年来，DPIV在推进昆虫飞行和鱼类运动研究方面发挥了重要作用。 它提供了升力产生机制的新发现，并阐明了动物在不同速度和机动过程中完成运动的机制。 15年前，研究人员使用手动数字化和立体相机测量鸟类以单一速度飞行时尾流中的能量;不幸的是，他们的结果并不支持鸟类在缓慢飞行时能够支撑体重的现成观察结果。 此外，由于之前的工作集中在自由飞行，鸟类的步态转换速度仍然未经测试。 DPIV将大大推进这项工作，因为它将自动跟踪粒子速度，从而消除了对以前工作的繁琐限制。 此外，它还可以测量鸟类在风洞中飞行时的气流，从而可以直接测试飞行速度的影响。托巴尔斯克的研究将测试长期以来纯粹基于运动学研究的预测。 它还将开发一种测量飞行鸟类机械功率输出的新方法。 鸟类飞行时的动力输出预计是巨大的，但鸟类与包括人类在内的哺乳动物共享相同的基本肌肉结构。 因此，这项研究将促进我们对高性能肌肉生理学的理解。拟议活动的更广泛影响包括对非稳态和准稳态空气动力学的意义以及动物运动中的步态选择的新理解。它还将为工程师开发自主微型飞行器提供有用的模型。最终，本研究中使用的DPIV设备将提供给所在机构其他部门的研究人员，这将加强生物学和物理学之间的联系。 本科生将协助实验的各个方面，并将在密切监督下进行论文项目。 使用这种领先技术的学生合作将提供强有力的证据，证明在本科院校进行世界一流的研究是可行的。

Current understanding of gait selection and mechanical power output in vertebrate flight largely rests on untested assumptions regarding the flow characteristics around flapping wings, and, to some extent, the animal's body and tail. Tobalske will use new technology, Digital Particle Image Velocimetry (DPIV) to test these assumptions, and seek to reconcile unsteady aerodynamic theory through direct measures of power output in the major flight muscle of birds and kinematic estimates of gait selection. DPIV uses powerful lasers to illuminate small reflective particles suspended in the air. Digital video images are captured to computer, and particle movement observed in the video images is used to calculate the energy in the flow field. Using DPIV and a new, variable-speed wind tunnel, Tobalske will describe flow dynamics over bird species that differ in wing and body shape: zebra finch Taeniopygia guttata and budgerigar Melopsittacus undulatus. Wake geometry and energy will be described for whole wingbeats, during non-flapping phases of intermittent flight, and over a full range of speeds. This will test the effects of wing shape on flight gait, whether birds change gait during flight in a manner analogous to gait change in terrestrial locomotion, and the relative contribution of the wings, body, and tail as sources of lift and drag. Sonomicrometry, which measures muscle length during locomotion, will be used to compare contractile behavior in the pectoralis muscle of zebra finch and budgerigar with mechanical power output as measured in the wake. In recent years, DPIV has been vital to advancing the study of insect flight and fish locomotion. It has furnished new discoveries of lift-producing mechanisms and clarified the mechanisms animals use to accomplish locomotion at different speeds and during maneuvering. Over fifteen years ago, researchers used manual digitizing and stereoscopic cameras to measure energy in the wake as birds flew at a single speed; unfortunately, their results did not support the ready observation that birds are able to support their weight during slow flight. Also, as this previous work focused on free flight, gait transitions across speed remain untested for birds. DPIV will significantly advance this effort because it will automate the tracking of particle velocity, thus eliminating a tedious constraint on previous work. Furthermore, it will permit measurement of flow as the birds fly in a wind tunnel so that the effects of flight speed may be tested directly.Tobalske's research will test long-standing predictions based purely on kinematic study. It will also develop a new method for measuring mechanical power output in flying birds. Power output during bird flight is predicted to be enormous, yet birds share the same basic muscular structure with mammals, including humans. Thus, this research will advance our understanding of high-performance muscle physiology. Broader impacts of the proposed activity include a new understanding of the significance of unsteady and quasi-steady aerodynamics and gait selection in animal locomotion. It will also provide engineers with a useful model for the development of autonomous, micro air vehicles. Ultimately, the DPIV equipment used in this study will be made available to researchers in other departments at the home institution, which will enhance ties between biology and physics. Undergraduate students will assist with all aspects of experiments and will pursue theses projects under close supervision. Student collaboration using this leading technology will provide strong evidence that it is feasible to conduct world-class research at an undergraduate institution.