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Research Papers: Multiphase Flows

Numerical Simulation of Bubble Cluster Induced Flow by Three-Dimensional Vortex-in-Cell Method

[+] Author and Article Information
Bin Chen

State Key Laboratory of Multiphase Flow
in Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: chenbin@mail.xjtu.edu.cn

Zhiwei Wang

State Key Laboratory of Multiphase Flow
in Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049,China
Shenzhen Institutes of Advanced Technology,
Chinese Academy of Sciences,
Xueyuan Avenue 1068,
Shenzhen 518035,China

Tomomi Uchiyama

EcoTopia Science Institute,
Nagoya University,
Furo-cho, Chikusa-ku,
Nagoya 464-8603, Japan

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 8, 2013; final manuscript received February 24, 2014; published online May 12, 2014. Assoc. Editor: Zhongquan Charlie Zheng.

J. Fluids Eng 136(8), 081301 (May 12, 2014) (16 pages) Paper No: FE-13-1416; doi: 10.1115/1.4026968 History: Received July 08, 2013; Revised February 24, 2014

The behavior of air bubble clusters rising in water and the induced flow field are numerically studied using a three-dimensional two-way coupling algorithm based on a vortex-in-cell (VIC) method. In this method, vortex elements are convected in the Lagrangian frame and the liquid velocity field is solved from the Poisson equation of potential on the Eulerian grid. Two-way coupling is implemented by introducing a vorticity source term induced by the gradient of void fraction. Present simulation results are favorably compared with the measured results of bubble plume, which verifies the validity of the proposed VIC method. The rising of a single bubble cluster as well as two tandem bubble clusters are simulated. The mechanism of the aggregation effect in the rising process of bubble cluster is revealed and the transient processes of the generation, rising, strengthening, and separation of a vortex ring structure with bubble clusters are illustrated and analyzed in detail. Due to the aggregation, the average rising velocity increases with void fraction and is larger than the terminal rising velocity of single bubble. For the two tandem bubble cluster cases, the aggregation effect is stronger for smaller initial cluster distance, and both the strength of the induced vortex structure and the average bubble rising velocity are larger. For the 20 mm cluster distance case, the peak velocity of the lower cluster is about 2.7 times that of the terminal velocity of the single bubble and the peak average velocity of two clusters is about 2 times larger. While for the 30 mm cluster distance case, both the peak velocity of the lower cluster and two clusters are about 1.7 times that of the terminal velocity of the single bubble.

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References

Figures

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Fig. 1

Interpolation of velocity from the neighboring mesh nodes

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Fig. 2

Redistribution of vortex elements using the M4' function

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Fig. 8

Bubble distribution of the rising of single bubble cluster (αg = 0.0135, QD/UT = 0.1)

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Fig. 7

Initial distribution of the bubble clusters

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Fig. 6

Variation of plume centerline velocity on gas flow rate at 50 mm above plume source

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Fig. 5

Comparison between present simulation and experimental observation of bubble plume (i: experimental observation of Alam and Arakeri [51]; ii: present simulation)

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Fig. 4

Terminal rising velocity of single bubble

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Fig. 3

Average position of bubbles in z direction at different grid resolutions

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Fig. 9

Liquid Q value field of the rising of single bubble cluster (αg = 0.0135,QD/UT = 0.1)

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Fig. 10

Liquid velocity field of the rising of single bubble cluster on the x = 0.1 m plane (αg = 0.0135)

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Fig. 11

Liquid vorticity field of the rising of single bubble cluster on the x = 0.1 m plane (αg = 0.0135, ωx* = ωxD/UT)

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Fig. 12

Effect of void fraction on flow field of the rising of single bubble cluster on the x = 0.1 m plane (ωx* = ωxD/UT, t*= 16.0)

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Fig. 13

Comparison of the evolution of average bubble rising velocity of single bubble cluster

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Fig. 14

Liquid velocity field of the rising of two tandem bubble clusters on the x = 0.1 m plane (cluster distance: 30 mm)

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Fig. 15

Liquid vorticity field of the rising of two tandem bubble clusters on the x = 0.1 m plane (cluster distance: 30 mm, ωx* = ωxD/UT)

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Fig. 16

Merging of the two vortex ring structures in the rising process of two tandem bubble clusters (cluster distance: 30 mm, QD/UT = 0.3)

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Fig. 17

Effect of initial cluster distance on the flow field on the x = 0.1 m plane on the rising process of two tandem bubble clusters (cluster distance: 20 mm, ωx* = ωxD/UT)

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Fig. 18

Effect of initial cluster distance on the flow field on the x = 0.1 m plane on the rising process of two tandem bubble clusters (cluster distance: 30 mm, ωx* = ωxD/UT)

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Fig. 19

Comparison of the evolution of average bubble rising velocity of two tandem bubble clusters

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