Usefulness of inviscid linear unsteady lifting-line theory for viscous large-amplitude problems

Bird, H. J.A., Ramesh, K. , Ōtomo, S. and Maria Viola, I. (2022) Usefulness of inviscid linear unsteady lifting-line theory for viscous large-amplitude problems. AIAA Journal, 60(2), pp. 598-609. (doi: 10.2514/1.J060808)

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Unsteady lifting-line theory (ULLT) is a low-order method capable of modeling interacting unsteady and finite wing effects at low computational cost. Most formulations of the method assume inviscid flow and small amplitudes. Although these assumptions might be suitable for small-amplitude aeroelastic problems at high Reynolds numbers, modern engineering applications increasingly involve lower Reynolds numbers, large-amplitude kinematics, and vortex structures that lead to aerodynamic nonlinearities. This paper establishes that ULLT still provides a useful solution for low-Reynolds-number, large-amplitude kinematics problems, by comparing ULLT results against those of experimentally validated computational fluid dynamics simulations at Re=10,000. Three-dimensional effects stabilize leading-edge vortex (LEV) structures, resulting in a good prediction of whole wing force coefficients by ULLT. Although the inviscid spanwise force distributions are accurate for small-amplitude kinematics, the ULLT cannot model three-dimensional vortical structures, and thus it cannot correctly predict the force distribution due to the LEV. It can, however, predict the shedding of LEVs to a limited extent via the leading-edge suction parameter criterion. This can then be used as an indicator of the usefulness of the force distribution results.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Ramesh, Dr Kiran and Bird, Hugh
Authors: Bird, H. J.A., Ramesh, K., Ōtomo, S., and Maria Viola, I.
College/School:College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
Journal Name:AIAA Journal
Publisher:American Institute of Aeronautics and Astronautics
ISSN (Online):1533-385X
Published Online:25 September 2021
Copyright Holders:Copyright © 2021 The Authors
First Published:First published in AIAA Journal 60(2): 598-609
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
301531UNSflow: A low-order, open-source solver for problems that involve unsteady and nonlinear fluid dynamicsKiran RameshEngineering and Physical Sciences Research Council (EPSRC)EP/R008035/1ENG - Autonomous Systems & Connectivity