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Vortex formation on a pitching aerofoil at high surging amplitudes

Published online by Cambridge University Press:  27 October 2020

Luke R. Smith Open the ORCID record for Luke R. Smith [Opens in a new window]  and
Anya R. Jones Open the ORCID record for Anya R. Jones [Opens in a new window]
Luke R. Smith*
Affiliation:
Department of Aerospace Engineering, University of Maryland, College Park, MD 20742, USA
Anya R. Jones
Affiliation:
Department of Aerospace Engineering, University of Maryland, College Park, MD 20742, USA
*
†Email address for correspondence: lsmith1@umd.edu
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Abstract

In many applications, conventional aerofoils are subject to a number of simultaneous motions that complicate the prediction of flow separation. The purpose of this work is to evaluate the impact of a large-amplitude free-stream oscillation on the timing of vortex formation for a simultaneously surging and pitching wing. Experimental flow field measurements were obtained on a NACA 0012 aerofoil over a wide range of surge amplitudes ($1.50 \leq \lambda \leq 2.25$) and reduced frequencies ($0.1 \leq k \leq 0.3$). Particular attention was paid to how various mechanisms of flow separation, specifically the velocity induced by the trailing wake and unsteady effects in the boundary layer, were impacted by a change in the properties of the surge motion. In the regime where $k \leq 0.3$, a change in the surge kinematics primarily manifested as a change in the relative strength of the trailing wake. Boundary layer unsteadiness was found to have a negligible influence on the timing of vortex formation in the same flow regime. Thus, the timing of leading-edge vortex formation was well predicted by a combination of an unsteady inviscid flow solver and a quasi-steady treatment of the boundary layer, a promising result for low-order predictions of vortex behaviour in unsteady aerofoil flows.

JFM classification

Wakes/Jets: Separated flows Vortex Flows: Vortex dynamics Boundary Layers: Boundary layer separation

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Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 905 , 25 December 2020 , A22
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Copyright
© The Author(s), 2020. Published by Cambridge University Press

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