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)

Abstract

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
• Status: Published
• Refereed: Yes
• 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: 0001-1452
• 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

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
301531		UNSflow: A low-order, open-source solver for problems that involve unsteady and nonlinear fluid dynamics	Kiran Ramesh	Engineering and Physical Sciences Research Council (EPSRC)	EP/R008035/1	ENG - Autonomous Systems & Connectivity