COLLABORATIVE RESEARCH: THE BENEFICIAL AERODYNAMIC EFFECT OF BUTTERFLY SCALES

帝王蝶的翅膀有一种形态结构，具有微米量级的特征大小。这种独特的微图案化导致了表面阻力的变化，并导致在高雷诺数(Re~=10e3-10e4)下扑翼和滑翔飞行时推力和升力增加。这种能量消耗的减少对帝王来说很重要，因为帝王是所有昆虫中迁徙时间最长的。PIs的初步结果表明：(1)横穿鳞片的流动可以通过滚柱轴承效应在低Re时将局部表面阻力减少40%，(2)平行于鳞片的流动可以使局部表面阻力增加100%以上，(3)在很低的Re~5区域出现较大的阻力差，(4)前缘涡强可能根据表面阻力的变化而变化，(5)帝王蝶的初步飞行试验表明，为了保持类似的能量自由飞行，没有鳞片的蝴蝶拍打频率增加了10%。拟议的工作将通过在阿拉巴马大学亨茨维尔大学最先进的自主跟踪设施中对活的帝王标本进行飞行测试，从统计上确定具有规模的蝴蝶翅膀提高的空气动力学效率；初步结果已经显示，能够以每秒370fps的速度获得毫米级的身体和翅膀运动跟踪。REU的一名学生还将进行单翼君主前翼的自转下落测试，以测量在存在鳞片时增加的空气动力性能。阿拉巴马大学在高粘度硅油中进行的一系列动态缩放测试将使蝴蝶启发的几何模型的尺寸比实际尺寸增加10到100倍。建议的研究将(1)在具有蝴蝶图案的跌落试验中测量流线型模型上阻力系数的变化，(2)利用DPIV测量两个水槽中边界层的形成，在平板模型上进行蝴蝶图案的研究，以及(3)在俯仰板实验中基于蝴蝶图案的表面图案来评估前缘涡强的变化。第三组实验将利用TSI V3V系统对PI最近通过NSF MRI-R2奖获得的全三维体积速度流进行测量。智力价值：拟议的合作努力将导致潜在的变革性发现一种新的和独特的被动表面阻力控制方法，该方法源于蝴蝶尺度在微尺度上的作用。拟议的工作将检验我们的工作假设，即局部表面阻力变化会导致蝴蝶在拍打和滑翔飞行中对能量的需求减少。额外的工作将更好地阐明表面阻力变化和相应的涡流控制，以用于流体动力学验证提高空气动力效率的假设机制。这一基本的理解将促进将蝴蝶启发的表面图案最终用于其他工程应用的知识。广泛的影响：需要边界层控制领域的创新来为MAV提供有效的方法来减少阻力(从而增加有效载荷、射程或燃料节省)以及更高的Re应用。一种独特的、受生物启发的技术，以被动微几何的形式导致减阻，有可能通过提高节能和流动控制来影响这一研究领域的未来应用。蝴蝶鳞片的生物空气动力学功能的发现也将是结果。此外，拟议的研究还涉及其他一些有益的成果，包括对各级学生进行培训以及在期刊/会议记录和公共媒体(如《国家地理在线》)上广泛传播成果。本科生的参与将通过REU的参与进行，重点是让代表不足的群体参与。生物启发工程是一个很好的公众宣传主题，蝴蝶引起了高度的兴趣。

Lang/Slegers1335848/1335572The wings of the Monarch butterfly exhibit scales with a morphological structure that has a characteristic size on the order of micrometers. This unique micro-patterning results in a surface drag alteration, and leads to an increase in thrust and lift during flapping and gliding flight at high Reynolds numbers (Re ~= 10e3- 10e4). This reduction in energy expended would be important to the Monarch which has the longest migration of any insect. Preliminary results performed by the PIs indicate: (1) flow passing transverse to the rows of scales can decrease the local surface drag by 40% at low Re via a roller bearing effect, (2) flow passing parallel to the rows of scales can increase local surface drag by over 100%, (3) higher drag differences occur in the very low Re regime (Re ~ 5), (4) leading edge vortex strength may vary based on surface drag alteration, and (5) initial flight tests of Monarch butterflies indicate a 10% increase in flapping frequency for those without scales to maintain similar energetic free flight. Proposed work will statistically determine the increased aerodynamic efficiency of butterfly wings with scales through flight testing of live Monarch specimens in a state-of-the-art autonomous tracking facility at the University of Alabama Huntsville; preliminary results have already shown the capability to obtain mm level tracking of body and wing motion at 370 fps. Autorotating drop tests of single Monarch forewings will also be performed by a REU student to measure increased aerodynamic performance with the presence of scales. A series of dynamically scaled tests carried out in high viscosity silicone oil at the University of Alabama will allow for models of butterfly-inspired geometries with an increase in 10 to 100 times in sizing from real scales. The proposed studies will (1) measure variation in the drag coefficient over streamlined models in drop tests with butterfly-inspired surface patterning, (2) utilize DPIV measurements of boundary layer formation in tow tank studies over flat plate models with butterfly-inspired surface patterning, and (3) evaluate leading edge vortex strength variation based on surface patterning inspired by butterfly scales in pitching plate experiments. The third set of experiments will utilize the TSI V3V system for full 3-D volumetric velocity flow measurements recently acquired by the PI through a NSF MRI-R2 award.Intellectual Merit :The proposed collaborative effort will result in the potentially transformative discovery of a new and unique passive surface drag control methodology derived from butterfly scales functioning at the micro-scale level. Proposed work will test our working hypothesis that local surface drag alteration results in reduced energy requirements for butterflies in flapping and gliding flight. Additional work will better elucidate the surface drag alteration and corresponding vortex control for fluid dynamic confirmation of the hypothesized mechanisms for increased aerodynamic efficiency. This fundamental understanding will advance knowledge for the ultimate use of a butterfly-inspired surface patterning for other engineering applications.Broader Impacts :Innovations in the field of boundary layer control are needed to provide efficient methodologies to decrease drag (resulting in increased payload, range or fuel savings) for MAVs as well as higher Re applications. A unique, bioinspired technology in the form of a passive microgeometry leading to drag reduction has the potential to impact this area of research with future applications with increased energy conservation and flow control. The discovery of the biological aerodynamic function of butterfly scales would also result. In addition, the proposed study involves a number of other beneficial outcomes including the training of students at all levels and broad dissemination of results in journals/conference proceedings and the public media (e.g. National Geographic Online). Undergraduate student involvement will take place through REU participation with a focus on involving underrepresented groups. Bio-inspired engineering is an excellent topic for public outreach, and butterflies generate a high level of interest.