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Vortex dynamics for flow around the slat cove at low Reynolds numbers

Published online by Cambridge University Press:  26 May 2021

Jiang-Sheng Wang  and
Jin-Jun Wang Open the ORCID record for Jin-Jun Wang [Opens in a new window]
Jiang-Sheng Wang
Affiliation:
Fluid Mechanics Key Laboratory of Education Ministry, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Jin-Jun Wang*
Affiliation:
Fluid Mechanics Key Laboratory of Education Ministry, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
*
†Email address for correspondence: jjwang@buaa.edu.cn
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Abstract

Time-resolved particle image velocimetry (TR-PIV) is employed to investigate the vortex dynamics around the slat cove of a 30P30N multi-element airfoil at a fixed geometric angle of attack of 4 ° within the stowed chord Reynolds number range of 9.3 × 103 ≤ Rec ≤ 5.2 × 104. The results link the frequency properties to the vortex shedding patterns of the slat cusp shear layer. With increasing Rec, three types of vortex dynamics are identified: (i) no vortex shedding from the slat cusp shear layer and the absence of hydrodynamic feedback in the slat cove (9.3 × 103 ≤ Rec ≤ 1.27 × 104); (ii) impingement of shed vortices on the underside of the slat trailing edge at a steady location (1.38 × 104 ≤ Rec ≤ 1.83 × 104); (iii) impingement of shed vortices on the underside of the slat trailing edge at unsteady locations (2.41 × 104 ≤ Rec ≤ 5.2 × 104). The fluctuations generated by shed vortices link the slat cusp and trailing edge by the hydrodynamic feedback in the slat cove. Besides the fundamental frequency and its harmonics, subharmonics and fractional harmonics occur to the slat cusp shear layer in the Rec range of 2.41 × 104–5.2 × 104. Subharmonics make the impingement locations of shed vortices unsteady. Fractional harmonics trigger the secondary instability of the braid region between two consecutive vortices to generate more shed vortices. The vortex dynamics in this Rec range is found to persist to Rec ~ 106.

JFM classification

Vortex Flows: Vortex interactions Vortex Flows: Vortex dynamics Vortex Flows: Vortex shedding

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Type
JFM Papers
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Journal of Fluid Mechanics , Volume 919 , 25 July 2021 , A27
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© The Author(s), 2021. Published by Cambridge University Press

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