NSF CAREER: Schooling

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

This program 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. There are further widespread applications of the fundamental flow physics elucidated from the proposed research. 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. Our flow facilities are equipped with state-of-the-art diagnostics to detail the flow physics and forces that occur during these interactions. 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.

Publications to date:

Kurt, M., Panah, A. E., & Moored, K. W. 2020. Flow Interactions Between Low Aspect Ratio Hydrofoils in In-line and Staggered Arrangements. Under review.

Wagenhoffer, N., Moored, K. W., & Jaworski, J. W. 2020. Unsteady propulsion and the acoustic signature of undulatory swimmers in and out of ground effect. Under review.

Baddoo, P. J., Kurt, M., Ayton, L. J., & Moored, K. W. 2020. Exact solutions for ground effect. Journal of Fluid Mechanics. Accepted.

Kurt, M., Cochran-Carney, J., Zhong, Q., Mivehchi, A., Quinn, D. B., & Moored, K. W. 2019. Swimming freely near the ground leads to flow-mediated equilibrium altitudes. Journal of Fluid Mechanics. 875, R1: 1-14. doi:10.1017/jfm.2019.540 [pdf]

Ayancik, F., Zhong, Q., Quinn, D. B., Brandes, A., Bart-Smith, H. & Moored, K. W. 2019. Scaling laws for the propulsive performance of three-dimensional pitching propulsors. Journal of Fluid Mechanics. 871, 1117-1138. doi:10.1017/jfm.2019.334 [pdf]

Kurt, M. & Moored, K. W. 2018. Unsteady performance of finite-span pitching propulsors in a side-by-side arrangement. Proceedings of the 48th AIAA Fluid Dynamics Conference, doi: 10.2514/6.2018-3732. [pdf]

Kurt, M. & Moored, K. W. 2018. Flow interactions of two- and three-dimensional networked bio-inspired control elements in an in-line arrangement. Bioinspiration and Biomimetics. 13, 045002. doi:10.1088/1748-3190/aabf4c. [pdf]

Special Issue: Fluid Dynamic Interactions in Biological and Bio-Inspired Propulsion, Guest Editors: Keith Moored & George Lauder

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