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Tip effects on three-dimensional flow structures over low-aspect-ratio plates: mechanisms of spanwise fluid transport

Published online by Cambridge University Press:  20 March 2024

Yichen Zhu Open the ORCID record for Yichen Zhu [Opens in a new window] ,
Jinjun Wang Open the ORCID record for Jinjun Wang [Opens in a new window]  and
Jiaxin Liu Open the ORCID record for Jiaxin Liu [Opens in a new window]
Yichen Zhu
Affiliation:
Fluid Mechanics Key Laboratory of Education Ministry, Beijing University of Aeronautics and Astronautics, Beijing 100191, PR China
Jinjun Wang*
Affiliation:
Fluid Mechanics Key Laboratory of Education Ministry, Beijing University of Aeronautics and Astronautics, Beijing 100191, PR China
Jiaxin Liu
Affiliation:
Fluid Mechanics Key Laboratory of Education Ministry, Beijing University of Aeronautics and Astronautics, Beijing 100191, PR China
*
†Email address for correspondence: jjwang@buaa.edu.cn
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Abstract

Three-dimensional flows over low-aspect-ratio rectangular flat plates (${A{\kern-4pt}R} = 1.00$–$1.50$) are investigated using tomographic and planar particle image velocimetry techniques. The chord-based Reynolds number is $5400$, and the angle of attack is fixed at $6^\circ$. This study reveals for the first time the interplay between spanwise fluid transport and downwash, both originating from the tip effects. Spanwise fluid transport promotes the formation and subsequent coherent development of leading-edge vortices, whereas downwash stabilizes the flow. Specifically, two mechanisms related to spanwise fluid transport are revealed. First, the spanwise fluid transport enhances the intensity of the reversed flow, promoting the shear layer roll-up and vortex shedding. Second, the near-wall spanwise flow interacts with the shed C-shape vortices, thereby strengthening the vortex heads. In particular, through these interactions, spanwise fluid transport can sustain the coherence of the C-shape vortices until the vortex heads split in a regular fashion. Consequently, the C-shape vortices are transformed into novel Þ-shape vortices for the plates of ${A{\kern-4pt}R} \leq 1.25$, which supplements the previously discovered transformation from C-shape to M-shape vortices for larger ${A{\kern-4pt}R}$ plates. Downstream of this novel vortex-splitting transformation, two fundamental processes contribute to the formation of hairpin vortices. The above comprehensive understanding of complete vortex evolution routine provides valuable insights into the tip effects on the formation of three-dimensional flows over low-${A{\kern-4pt}R}$ plates.

JFM classification

Vortex Flows: Vortex dynamics Wakes/Jets: Separated flows
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 983 , 25 March 2024 , A35
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Copyright
© The Author(s), 2024. Published by Cambridge University Press

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Typical instantaneous flowfields for AR = 1.00
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