Effects of aspect ratio on rolling and twisting foils

Nasution, Andhini, Ganapathisubramani, Bharathram and Weymouth, Gabriel (2021) Effects of aspect ratio on rolling and twisting foils. Physical Review Fluids, 6 (1), [013101]. (doi:10.1103/PhysRevFluids.6.013101).

Record type: Article

Abstract

Flapping flight and swimming are increasingly studied due to both their intrinsic scientific richness and their applicability to novel robotic systems. Strip theory is often applied to flapping wings, but such modeling is only rigorously applicable in the limit of infinite aspect ratio (AR) where the geometry and kinematics are effectively uniform. This work compares the flow features and forces of strip theory and three-dimensional flapping foils, maintaining similitude in the rolling and twisting kinematics while varying the foil AR. We find the key influence of finite AR and spanwise varying kinematics is the generation of a time-periodic spanwise flow which stabilizes the vortex structures and enhances the dynamics at the foil root. An aspect-ratio correction for flapping foils is developed analogous to Prandtl finite wing theory, enabling future use of strip theory in analysis and design of finite aspect ratio flapping foils.

Text

Eﬀects of Aspect Ratio - Accepted Manuscript

Available under License University of Southampton Accepted Manuscript Licence.

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e-pub ahead of print date: 15 January 2021

Published date: 15 January 2021

Additional Information: Funding Information: We would like to thank the Indonesia Endowment Fund for Education (LPDP), the IRIDIS High Performance Computing Facility with its associated support services at the University of Southampton, and Office of Naval Research Global Award No. N62909-18-1-2091 for the completion of this work. Publisher Copyright: © 2021 American Physical Society. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.