Leading-edge flow criticality as a governing factor in leading-edge-vortex initiation in unsteady airfoil flows

Ramesh, K. , Granlund, K., Ol, M. V., Gopalarathnam, A. and Edwards, J. R. (2018) Leading-edge flow criticality as a governing factor in leading-edge-vortex initiation in unsteady airfoil flows. Theoretical and Computational Fluid Dynamics, 32(2), pp. 109-136. (doi:10.1007/s00162-017-0442-0)

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Abstract

A leading-edge suction parameter (LESP) that is derived from potential flow theory as a measure of suction at the airfoil leading edge is used to study initiation of leading-edge vortex (LEV) formation in this article. The LESP hypothesis is presented, which states that LEV formation in unsteady flows for specified airfoil shape and Reynolds number occurs at a critical constant value of LESP, regardless of motion kinematics. This hypothesis is tested and validated against a large set of data from CFD and experimental studies of flows with LEV formation. The hypothesis is seen to hold except in cases with slow-rate kinematics which evince significant trailing-edge separation (which refers here to separation leading to reversed flow on the aft portion of the upper surface), thereby establishing the envelope of validity. The implication is that the critical LESP value for an airfoil–Reynolds number combination may be calibrated using CFD or experiment for just one motion and then employed to predict LEV initiation for any other (fast-rate) motion. It is also shown that the LESP concept may be used in an inverse mode to generate motion kinematics that would either prevent LEV formation or trigger the same as per aerodynamic requirements.

Item Type:Articles
Additional Information:The authors wish to gratefully acknowledge the support of the U.S. Air Force Office of Scientific Research through Grant FA 9550-13-1-0179.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Ramesh, Dr Kiran
Authors: Ramesh, K., Granlund, K., Ol, M. V., Gopalarathnam, A., and Edwards, J. R.
College/School:College of Science and Engineering > School of Engineering > Aerospace Sciences
Journal Name:Theoretical and Computational Fluid Dynamics
Publisher:Springer
ISSN:0935-4964
ISSN (Online):1432-2250
Published Online:14 August 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Theoretical and Computational Fluid Dynamics 32(2): 109-136
Publisher Policy:Reproduced under a Creative Commons license

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