COLLABORATIVE RESEARCH: THE BENEFICIAL AERODYNAMIC EFFECT OF BUTTERFLY SCALES

Lang/Slegers 1335848/1335572帝王蝶的翅膀显示出具有微米量级特征尺寸的形态结构的鳞片。 这种独特的微图案导致表面阻力改变，并导致在高雷诺数（Re ~= 10 e3 - 10 e4）下的扑动和滑翔飞行期间的推力和升力增加。这种能量消耗的减少对帝王蝶很重要，因为帝王蝶是所有昆虫中迁徙时间最长的。PI执行的初步结果表明：（1）在低雷诺数下，通过滚柱轴承效应，横向于鳞片行的流动可使局部表面阻力降低40%，（2）平行于鳞片行的流动可使局部表面阻力增加100%以上，（3）在很低雷诺数区（Re ~ 5）出现较大的阻力差，（4）前缘涡流强度可能根据表面阻力的变化而变化，（5）帝王蝶的初始飞行试验表明，对于那些没有鳞片的蝴蝶，为了保持类似的能量自由飞行，扑翼频率增加了10%。拟议的工作将通过在亚拉巴马大学亨茨维尔分校最先进的自主跟踪设施中对活帝王蝶标本进行飞行测试，从统计学上确定带有鳞片的蝴蝶翅膀的空气动力学效率的增加;初步结果已经表明，能够以370 fps的速度获得对身体和翅膀运动的毫米级跟踪。单个帝王蝶前翼的自转跌落试验也将由一名REU学生进行，以测量在鳞片存在下增加的空气动力学性能。亚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允许蝴蝶灵感几何形状的模型在尺寸上比真实的比例增加10到100倍。拟议的研究将（1）在具有蝴蝶启发的表面图案的下落试验中测量流线型模型的阻力系数的变化，（2）在具有蝴蝶启发的表面图案的平板模型的拖曳水池研究中利用DPIV测量的边界层形成，（3）在俯仰板试验中根据蝴蝶尺度启发的表面图案评估前缘涡强度变化。第三组实验将利用TSI V3 V系统进行完整的三维体积速度流测量，PI最近通过NSF MRI-R2 award.Intellectual Merit获得了该系统。拟议的合作努力将导致一种新的和独特的被动表面阻力控制方法的潜在变革性发现，该方法来自蝴蝶尺度在微观尺度上的功能。建议的工作将测试我们的工作假设，局部表面阻力改变的结果，减少能量需求的蝴蝶在扑翼和滑翔飞行。额外的工作将更好地阐明表面阻力的变化和相应的涡流控制，以流体动力学确认增加气动效率的假设机制。这种基本的理解将推进知识的最终使用的蝴蝶启发的表面图案为其他工程应用。更广泛的影响：在边界层控制领域的创新需要提供有效的方法来减少阻力（从而增加有效载荷，范围或节省燃料）的微型飞行器以及更高的Re应用。一种独特的生物启发技术，以被动微几何形状的形式导致减阻，有可能影响这一研究领域，未来的应用将增加节能和流量控制。蝴蝶鳞片的生物空气动力学功能的发现也将随之而来。此外，拟议的研究还涉及一些其他有益的成果，包括对各级学生的培训，以及在期刊/会议记录和公共媒体（如国家地理在线）上广泛传播研究结果。本科生的参与将通过REU参与，重点是涉及代表性不足的群体。生物启发工程是一个很好的主题，为公众宣传，蝴蝶产生了很高的兴趣。

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.