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Turbulence cascade model for viscous vortex ring-tube reconnection

Viet Dung, Duong and Van Duc, Nguyen and Van Luc, Nguyen (2021) Turbulence cascade model for viscous vortex ring-tube reconnection. Physics of Fluids, 33 (3). ISSN 1070-6631

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The reconnection of a vortex ring and a vortex tube in a viscous fluid with the effects of two vortex core sizes (σ 0 = 0.12r 0 and 0.24r 0 , where r 0 are initial ring radius) and three initial flow configurations (left-offset, center and right-offset) at Reynolds number (Re Γ) of 10000 was investigated using a high-order Vortex-in-cell method combined with a Large-eddy simulation model. For the left-offset case, a large part of the ring, slipping over the tube, associates with a small part of the tube to establish a new vortex ring, whereas the rest of the tube is reconnected by another part of the ring. For the center case, half of the ring joins with a part of the tube to construct an elliptical vortex ring while the rest connects because of viscosity. The reconnected ring and tube become more stable and are like the initial ones in the ultimate stage. For the right-offset case, both the ring and tube's reconnection occurs, and the reconnected elliptical vortex ring is rapidly distorted. The proportion of reconnected ring increases, and then this ring section loses its integrity, decaying into a complex cluster of various-scales vortex structures in different shapes. At σ 0 = 0.12r 0 , the secondary vortex structures surrounding the tube and ring appear in three cases, while they are only observed for the center case at σ 0 = 0.24r 0. For three flow configurations and two vortex core sizes, after the reconnection, the energy cascade of the flow approaches a k −5/3 slope of Kolmogorov's similarity hypotheses and a k −3 slope in the ranges of wavenumbers (k) from 3 to 10 and from 10 to 40, respectively. The highest population of small-scale coherent vortex structures is observed for the right-offset, followed by the center and left-offset. In addition, a larger number of these structures were observed for a smaller core size. This validates that the mixing performance is the best at a small vortex core and in the right-offset configuration.

Item Type: Article
Subjects: Aerospace Engineering
Engineering Mechanics
Engineering Physics
ISI-indexed journals
Divisions: School of Aerospace Engineering (SAE)
Depositing User: Duong Viet Dung
Date Deposited: 31 May 2021 11:01
Last Modified: 31 May 2021 11:01

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