Determination of epsilon for Omega vortex identification method

Dong, Xiangrui; Wang, Yiqian; Chen, Xiaoping; Dong, Yinlin; Zhang, Yuning; Liu, Chaoqun

doi:10.1007/s42241-018-0066-x

Cited by 136 publications

(32 citation statements)

References 24 publications

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“…microjet formation) and the complex fluid flow (e.g. vortex [28][29][30]). For related reviews on the cavitation and bubble dynamics based on high-speed camera, Lauterborn and Kurz [31] and Wang et al [32] are suggested.…”

Section: Resultsmentioning

confidence: 99%

“…As shown in the above figure, the agreement between the theoretical predictions and the experimental data is fairly good. As a future work, an experimental system based on the high speed photography [27] will be employed to further reveal the interesting bubble phenomenon (e.g., micro-jet formation) and the complex fluid flow (e.g., vortex [28][29][30]). For related reviews on the cavitation and bubble dynamics based on high-speed camera, Lauterborn and Kurz [31] and Wang et al [32] are suggested.…”

Section: Discussionmentioning

confidence: 99%

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Rectified Diffusion of Gas Bubbles in Molten Metal during Ultrasonic Degassing

Zhang

2019

Symmetry

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In the present paper, an analytical solution of rectified diffusion of processes of gas bubbles in molten metal is derived for the purpose of predicting the diffusion behaviors of gas bubbles during ultrasonic degassing. In the present model, a theoretical threshold (in terms of the amplitude of the applied ultrasonic field) is determined for the evaluation of the ultrasonic degassing effects. The diffusion of hydrogen bubbles in molten aluminum is predicted, so as to provide examples to illustrate the important findings of the present work.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Rectified Diffusion of Gas Bubbles in Molten Metal during Ultrasonic Degassing

Zhang

2019

Symmetry

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“…These complex scenarios will be further considered in future work, together with non-spherical bubble oscillations [41]. Furthermore, the cavitation-induced vortex generations are of great interest for many industrial flows, which could also be revealed with the aid of the newly developed vortex identification method [42,43].…”

Section: Physical Interpretation Of the Phenomenonmentioning

confidence: 99%

Retardant Effects of Collapsing Dynamics of a Laser-Induced Cavitation Bubble Near a Solid Wall

Li¹,

Duan²,

Zhang³

et al. 2019

Symmetry

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In the present paper, the dynamic behavior of cavitation bubbles near a wall is experimentally investigated with a focus on the retardant effects of the wall on the collapsing dynamics of the bubble. In the present experiments, a cavitation bubble is generated by a focused laser beam with its behavior recorded through high-speed photography. During the data analysis, the influences of non-dimensional bubble–wall distance on the bubble collapsing dynamics are qualitatively and quantitatively investigated in terms of the interface evolution, the velocities of the poles, and the movement of the bubble centroid. Our results reveal that the presence of the wall could significantly affect the collapsing characteristics, leading to a dramatic difference between the moving velocities of interfaces near and away from the wall. With the decrease of the bubble–wall distance, the effects will be gradually strengthened with a rapid movement of the bubble centroid during the final collapse. Finally, a physical interpretation of the phenomenon is given based on the bubble theory, together with a rough estimation of the induced water hammer pressure by the bubble collapse.

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“…Attempting to remedy the problems of vorticity based methods, 2G vortex identification criteria such as ∆ (Chong and Perry,1990) [8,9] , Q (Hunt et al, 1988) [10] , 2 (Jeong, J., and Hussain, F., 1995) [11] , ci (Zhou et al, 1999) [12] , Ω (Liu et al, 2016; Dong et al, 2018) [13][14] , etc., have been introduced and extensively applied in visualizing vortex structures over the past three decades. Although the 2G-schemes have been able to judge the presence of the local rotational motion, these methods need an adjustment of threshold to visualize the isosurface plot accurately.…”

Section: Introductionmentioning

confidence: 99%

Stretching and Shearing Contamination Analysis for Liutex and Other Vortex Identification Methods

Shrestha

Nottage

et al. 2020

Preprint

Self Cite

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The newly developed vortex-identification method, Liutex, has provided a new systematic description of the local fluid rotation, which includes scalar, vector, and tensor forms. However, the advantages of Liutex over the other widely used vortex-identification methods such as Q, Δ, λ2 , and λci have not been realized. These traditional methods count on shearing and stretching as a part of vortex strength. But, in the real flow, shearing and stretching do not contribute to fluid rotation. In this paper, the decomposition of the velocity gradient tensor is conducted in the Principal Coordinate for uniqueness. Then the contamination effects of stretching and shearing of the traditional methods are investigated and compared with the Liutex method in terms of mathematical analysis and numerical calculations. The results show that the Liutex method is the only method that is not affected by either stretching or shear, as it represents only the local fluid rigid rotation. These results provide supporting evidence that Liutex is the superior method over others.

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Determination of epsilon for Omega vortex identification method

Cited by 136 publications

References 24 publications

Rectified Diffusion of Gas Bubbles in Molten Metal during Ultrasonic Degassing

Rectified Diffusion of Gas Bubbles in Molten Metal during Ultrasonic Degassing

Retardant Effects of Collapsing Dynamics of a Laser-Induced Cavitation Bubble Near a Solid Wall

Stretching and Shearing Contamination Analysis for Liutex and Other Vortex Identification Methods

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