Collaborative Research: The aerodynamic and metabolic costs and benefits of flow interactions in bird flight

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

Recent field studies of flight mechanics in birds of several types and sizes have revealed more use of environmental energy (e.g. gusts, wakes and updrafts) to power flight than was previously believed to be the case. However, because the detailed studies of the aerodynamics, flight costs and flight mechanics of birds have been carried out in wind tunnels with smooth, steady air flow, little is known about how birds take advantage of unsteady flow patterns. In this project the researchers will fill this gap in understanding by measuring the energetic cost of flight, the aerodynamics, and the flapping motion of birds in a wind tunnel, comparing smooth flow conditions to 4 different unsteady flow cases. This study will also test the use of body-mounted accelerometers to serve as a proxy measure of the energetic cost of flight over the same wide range of flow conditions, enabling more accurate field studies. This research will add to basic understanding of aerodynamics in unsteady flows and the ecology and evolution of small birds. Pursuing this project requires an interdisciplinary combination of biology and engineering. To further the educational goals of this project, it includes a Research Experience for Undergraduates component. In this sub-program, Biology and Engineering undergraduates from around the nation apply for a summer research fellowship to work on the project. Selected students will assist with the main project and pursue a sub-project of their own design with the assistance of the rest of the project team. In this project the PI and Co-PIs will apply state-of-the-art metabolic aerodynamic and accelerometry measurements to understand the energetic costs or benefits for interactions between birds and potentially beneficial flow structures, along with the underlying aerodynamic mechanisms that give rise to the metabolic outcomes. Flow patterns will be generated using an actuated airfoil capable of producing organized non-steady flows with independently variable frequency, magnitude and direction, allowing us to precisely delineate potentially beneficial environmental flows. Accelerometry results will be compared to aerodynamic and metabolic results to investigate the feasibility of using accelerometry as a proxy for energy expenditure in flight across a wide range of flight speeds and airflow patterns. Broader impacts from this study focus on a Research Experience for Undergraduates program whereby nationally recruited Biology and Engineering or Physics undergraduates will be trained in interdisciplinary research and collaboration while they assist with the main project goals and, in consultation with the rest of the team, design and execute their own sub-project. This award is co-funded by the BIO-IOS-Physiological Mechanisms and Biomechanics Program and the ENG-CBET-Fluid Dynamics Program. 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.