Collaborative Research: Flying snakes: fluid mechanics of deforming articulated bodies

有许多飞行形式，从昆虫翅膀的自然拍打到经过改造的多旋翼直升机。在各种产生飞行力量的系统中，飞蛇体现了一种高度意想不到和非直觉的空中运动解决方案。蛇的身体是圆柱形的，没有可伸展的表面来创建或控制飞行力。尽管有这些限制，被称为“飞行”蛇的亚洲树栖物种拥有令人惊讶的复杂的滑翔能力。这些蛇从树上跳下来，压平身体，在空中以复杂的三维模式波动，产生空中运动。最令人惊讶的是，蛇可以在空中主动机动，能够在半空中根据自己的意愿转弯。了解飞蛇是如何实现这种壮举的，是在工程设备中复制这种行为的第一步，这将极大地促进复杂环境中机器人的设计，并将其重要应用于监视、搜救和灾难监测。飞蛇的空中相互作用物理--蛇作为一个铰接体的平移和旋转自由度之间的强耦合--在很大程度上是未知的。这个项目将检验这样的假设，即平移-转动耦合是通过自身变形(由波动驱动)和非定常流体力学之间的反馈来实现的。这项研究将结合动物观察、实验流体力学和计算流体力学来揭示关节形变物体的流体力学，其中飞蛇(大黄蛇属)是最好的例子。将基于自适应网格加密的浸没边界方法应用于研究滑行蛇体产生的流体流动，将有助于更有效地研究其他复杂流体问题，包括物体在较大雷诺数范围内的动态运动。所提出的实验和计算框架可能重新定义具有增强机动性的空中和水下机器人系统在流体介质中的运动形式和功能。该项目涉及一项广泛的参与计划，将使各种群体受益。首席调查员将通过与地区HBCU的方案联系，在三所合作的大学进行暑期本科生研究以及招聘研究生研究助理，从而吸引任职人数不足的学生。飞蛇激发了学生和公众的想象力，实验和计算的结果将通过专业和公开的方式传播给媒体，也将通过社交媒体直接传播给公众。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

There are numerous forms of flight ranging from the natural flapping of insect wings to engineered multi-rotor helicopters. Among the diversity of systems for producing flight forces, the flying snake embodies a highly unexpected and non-intuitive solution for aerial locomotion. With a cylindrical body, the snake has no extendable surfaces to create or control flight forces. Despite these limitations, the Asian arboreal species known as ‘flying’ snakes possess a surprisingly sophisticated ability to glide. These snakes jump from trees, flatten their body, and undulate in the air in a complex three-dimensional pattern to produce aerial locomotion. Most surprisingly, the snakes can actively maneuver in the air, capable of turning in mid-air under their own volition. Understanding how flying snakes achieve such feats is the first step toward duplicating this behavior in engineered devices, which could significantly advance design of robots in complex environments, with important applications to surveillance, search-and-rescue, and disaster monitoring. The aerial interaction physics of flying snakes - the strong coupling between the translational and rotational degrees of freedom of the snake as an articulated body - is largely unknown. This project will test the hypothesis that translational-rotational coupling is achieved through feedback between self-deformations (driven by undulation) and unsteady fluid mechanics. The research will use a combination of animal observations, experimental fluid mechanics, and computational fluid dynamics to reveal the fluid mechanics of deforming articulated bodies, of which the flying snake (genus Chrysopelea) is the prime example. The application of adaptive mesh refinement-based immersed boundary method to study fluid flows produced by gliding snakes will enable more efficient investigations on other complex fluids problems with dynamically moving objects across a wide range of Reynolds numbers. The proposed experimental and computational framework can potentially re-define the form and function of locomotion in fluid media for aerial and underwater robotic systems with enhanced mobility. The project involves a broad participation plan that will benefit a diverse range of groups. The principal investigators will engage under-represented students through programmatic connections to regional HBCUs, for summer undergraduate research as well as recruiting of graduate research assistants, at the three collaborating universities. Flying snakes excite the imagination of both students and the public, and the results of the experiments and computations will be disseminated both professionally and publicly, to media outlets and also directly to the public through social media.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.