Numerical Modeling and Analysis of Gas Entrainment for the Ventilated Cavity in Vertical Pipe

doi:10.1016/S1004-9541(14)60033-1

Chinese Journal of Chemical Engineering ›› 2014, Vol. 22 ›› Issue (3): 252-260.DOI: 10.1016/S1004-9541(14)60033-1

Numerical Modeling and Analysis of Gas Entrainment for the Ventilated Cavity in Vertical Pipe

向敏^1,2, 江振宇¹, 张为华¹, 屠基元^2,3

1 Collage of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China;
2 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China;
3 School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Victoria 3083, Australia

收稿日期:2012-10-25 修回日期:2013-04-23 出版日期:2014-03-28 发布日期:2014-03-05
通讯作者: XIANG Min
基金资助:
Supported by the Research Project Foundation of National University of Defense Technology (JC12-01-04) and the National Science Foundation for Post-doctoral Scientists of China (2012M520268).

Numerical Modeling and Analysis of Gas Entrainment for the Ventilated Cavity in Vertical Pipe

XIANG Min^1,2, JIANG Zhenyu¹, ZHANG Weihua¹, TU Jiyuan^2,3

1 Collage of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China;
2 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China;
3 School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Victoria 3083, Australia

Received:2012-10-25 Revised:2013-04-23 Online:2014-03-28 Published:2014-03-05
Contact: XIANG Min
Supported by:
Supported by the Research Project Foundation of National University of Defense Technology (JC12-01-04) and the National Science Foundation for Post-doctoral Scientists of China (2012M520268).

摘要/Abstract

摘要： A semi-empirical gas entrainment model was proposed for the ventilated cavity in vertical pipe, based on which, a complete numerical scheme was established by coupling with the Eulerian-Eulerian two-fluid model to predict the multiscale flow field created by ventilated cavity. Model predictions were validated against experimental measurements on void fraction and bubble size distributions. Simulations were carried out to explore the effect of ventilation rate and inlet turbulence intensity on the macroscale cavity shape and the bubbly flow downstream of the ventilated cavity. As the ventilation rate increasing, a reverse trend was observed for the void fraction and bubble size distributions. It is concluded that the average void fraction in the pipe flow region is determined by the volumetric ratio between liquid and gas. However, the bubble size evolution is dominated by the breakage effect induced by turbulence in the vortex region. Furthermore, simulations were conducted to analyze geometric scale effect based upon Froude similitude. The results imply that the velocity distributions were properly scaled. Slight scale effect was seen for the void fraction caused by faster dispersion of bubbles in the larger size model. The comparatively greater bubble size was predicted in the smaller model, implying significant scale effects in terms of turbulence and surface tension effect. It reveals that empirical correlations valid in wide range are required for the extrapolation from small-size laboratory models.

关键词: ventilated cavity, gas entrainment, bubbly flow, simulation

Abstract: A semi-empirical gas entrainment model was proposed for the ventilated cavity in vertical pipe, based on which, a complete numerical scheme was established by coupling with the Eulerian-Eulerian two-fluid model to predict the multiscale flow field created by ventilated cavity. Model predictions were validated against experimental measurements on void fraction and bubble size distributions. Simulations were carried out to explore the effect of ventilation rate and inlet turbulence intensity on the macroscale cavity shape and the bubbly flow downstream of the ventilated cavity. As the ventilation rate increasing, a reverse trend was observed for the void fraction and bubble size distributions. It is concluded that the average void fraction in the pipe flow region is determined by the volumetric ratio between liquid and gas. However, the bubble size evolution is dominated by the breakage effect induced by turbulence in the vortex region. Furthermore, simulations were conducted to analyze geometric scale effect based upon Froude similitude. The results imply that the velocity distributions were properly scaled. Slight scale effect was seen for the void fraction caused by faster dispersion of bubbles in the larger size model. The comparatively greater bubble size was predicted in the smaller model, implying significant scale effects in terms of turbulence and surface tension effect. It reveals that empirical correlations valid in wide range are required for the extrapolation from small-size laboratory models.

Key words: ventilated cavity, gas entrainment, bubbly flow, simulation

向敏, 江振宇, 张为华, 屠基元. Numerical Modeling and Analysis of Gas Entrainment for the Ventilated Cavity in Vertical Pipe[J]. Chinese Journal of Chemical Engineering, 2014, 22(3): 252-260.

XIANG Min, JIANG Zhenyu, ZHANG Weihua, TU Jiyuan. Numerical Modeling and Analysis of Gas Entrainment for the Ventilated Cavity in Vertical Pipe[J]. Chin.J.Chem.Eng., 2014, 22(3): 252-260.

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Numerical Modeling and Analysis of Gas Entrainment for the Ventilated Cavity in Vertical Pipe

Numerical Modeling and Analysis of Gas Entrainment for the Ventilated Cavity in Vertical Pipe

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