CAREER: Three-Dimensional Unsteady Flow Interactions in Flocks and Schools

这个项目的重点是扩展我们对动物群体中发生的流体动力相互作用的知识，即群体、学校和群体。该计划的主要研究目标是了解复杂排列中非稳定的三维相互作用物体之间的流动机制。教育目标是促进女性参与STEM，为中学、本科生和研究生提供工程经验，通过学校转盘鱼设计比赛，作为利哈伊大学选择项目的一部分。通过研究集体中发生的三维、不稳定的相互作用，将阐明对自然界中学校教育的能量的理解。此外，还将发现设计各种生物启发设备的基础知识，从而创造出快速、高效、灵活、安静的集体机器。对驯养动物的能量预算进行更好的估计将导致更准确的种群模型。这将帮助科学家确定生物网络对于过度捕捞、栖息地丧失和气候变化的脆弱性。对旋翼机涡旋-叶片相互作用和飞机机翼响应大气涡旋阵风的新控制是可能的。在过去的十年中，流动诊断、力传感器和非定常涡流知识的进步为描述和理解集体相互作用的流体力学打开了大门。流动物理可以看作是在涡量控制装置，即振荡推进器的影响下，高度三维的、非定常的涡体相互作用。这些流动的特点是高雷诺数、生物相关的产生推力的斯特劳哈尔数和高折减频率，使它们处于经典涡体相互作用的区域之外。具体的研究目标是：(1)描述动物典型的不同同步性和各种排列的集体运动的力、能量学和流动物理学；(2)检验自然界中看到的晶格状排列可能是由于流体介导力的假设；(3)确定个体的正则涡流拓扑如何映射到能量最优的或流体介导性的集体排列；(4)确定受生物启发的交通工具的设计的尺度定律；以及(5)详细说明自行式相互作用体的流动物理。这项拟议的研究将是实验和计算的结合。一种新的数字物理设备将被开发出来，以检查自推进相互作用的物体出现的不受约束的动力学。此外，我们将利用内部快速边界元方法的新扩展来探索大量自行式相互作用体。拟议的测量和数值将首次量化相互作用的推进器之间的三维流体介导力，从而洞察集体中个人的稳定平衡。详细的立体流动测量将捕捉到与高性能相关的机理。这一新颖的数据将解决关于动物的格子状排列是出于能量原因，还是流体介导力的副产品，还是两者都不是的争论。从这项研究中，工程师们将能够开发出高效、快速的生物启发设备。对集体相互作用的了解还可以进一步了解动物和机器人在自由表面、墙壁或地面附近飞行和游泳的动态。

This project is focused on extending our knowledge of the fluid dynamic interactions that occur in animal collectives, that is, flocks, schools and swarms. The overarching research goal of the program is to understand the flow mechanisms that occur among unsteady, three-dimensional interacting bodies in complex arrangements. The educational goal is to promote the engagement of women in STEM by providing engineering experiences for middle school, undergraduate and graduate female students through a schooling twiddle-fish design competition as a part of Lehigh University's CHOICES program. By examining the three-dimensional, unsteady interactions that occur in collectives, an understanding of the energetics of schooling in nature will be elucidated. Additionally, the fundamental knowledge to engineer schools of bio-inspired devices will be discovered leading to fast, efficient, maneuverable, agile and quiet collective machines. Better estimates of the energy budget of schooling animals will lead to more accurate population models. This will help scientists determine how fragile biological networks are to overfishing, loss of habitat and the changing climate. Novel control of rotorcraft vortex-blade interactions and of aircraft wings in response to atmospheric vortical gusts may be possible. New three-dimensional arrangements of wind and hydrokinetic turbines that use synergistic interactions may be discovered.Advances in flow diagnostics, force sensors and knowledge of unsteady, vortical flows over the past decade have opened the door to characterizing and understanding the fluid mechanics of collective interactions. The flow physics can be viewed as highly three-dimensional, unsteady, vortex-body interactions with the influence of a vorticity control device, i.e. an oscillating propulsor. These flows are characterized by high Reynolds numbers, biologically relevant thrust-producing Strouhal numbers, and high reduced frequencies placing them outside of the regime of classical vortex-body interactions. The specific research objectives are to: (1) characterize the forces, energetics and flow physics of collective locomotion for varying synchrony and various arrangements typical of animals; (2) examine the hypothesis that the lattice-like arrangements seen in nature may be due to fluid-mediated forces; (3) determine how canonical vortical wake topologies of individuals are mapped to energetically-optimal or fluid-mediated collective arrangements; (4) determine scaling laws for the design of schooling bio-inspired vehicles; and (5) detail the flow physics of self-propelled interacting bodies. The proposed research will be an integration of experiments and computations. A novel cyber-physical apparatus will be developed to examine the unconstrained dynamics that emerge from self-propelled interacting bodies. Additionally, novel extensions of our in-house fast boundary element method will be leveraged to explore large numbers of self-propelled interacting bodies. The proposed measurements and numerics will quantify for the first time the three-dimensional fluid-mediated forces between interacting propulsors giving insight into stable equilibria for individuals in a collective. The detailed stereoscopic flow measurements will capture the mechanisms associated with high performance. This novel data will settle the debate as to whether animals' lattice-like arrangements are for energetic reasons, are a by-product of fluid-mediated forces, or neither. From this research, engineers will be able to develop efficient and fast schools of bio-inspired devices. Knowledge of collective interactions also provides further insight into the dynamics of animals and robots flying and swimming near a free surface, a wall or the ground.