中国物理B ›› 2021, Vol. 30 ›› Issue (5): 54703-054703.doi: 10.1088/1674-1056/abd7dd

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Numerical simulation on partial coalescence of a droplet with different impact velocities

Can Peng(彭灿), Xianghua Xu(徐向华)†, and Xingang Liang(梁新刚)   

  1. Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, School of Aerospace Engineering, Tsinghua University, Beijing 100084, China
  • 收稿日期:2020-07-30 修回日期:2020-11-27 接受日期:2021-01-04 出版日期:2021-05-14 发布日期:2021-05-14
  • 通讯作者: Xianghua Xu E-mail:xxh@tsinghua.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 51876102) and the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 51621062).

Numerical simulation on partial coalescence of a droplet with different impact velocities

Can Peng(彭灿), Xianghua Xu(徐向华)†, and Xingang Liang(梁新刚)   

  1. Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, School of Aerospace Engineering, Tsinghua University, Beijing 100084, China
  • Received:2020-07-30 Revised:2020-11-27 Accepted:2021-01-04 Online:2021-05-14 Published:2021-05-14
  • Contact: Xianghua Xu E-mail:xxh@tsinghua.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 51876102) and the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 51621062).

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摘要： Partial coalescence is a complicated flow phenomenon. In the present study, the coalescence process is simulated with the volume of fluid (VOF) method. The numerical results reveal that a downward high-velocity region plays a significant role in partial coalescence. The high-velocity region pulls the droplet downward continuously which is an important factor for the droplet turning into a prolate shape and the final pinch-off. The shift from partial coalescence to full coalescence is explained based on the droplet shape before the pinch-off. With the droplet impact velocity increasing, the droplet shape will get close to a sphere before the pinch-off. When the shape gets close enough to a sphere, the partial coalescence shifts to full coalescence. The effect of film thickness on the coalescence process is also investigated. With large film thickness, partial coalescence happens, while with small film thickness, full coalescence happens. In addition, the results indicate that the critical droplet impact velocity increases with the increase of surface tension coefficient but decreases with the increase of viscosity and initial droplet diameter. And there is a maximum critical Weber number with the increase of surface tension coefficient and initial droplet diameter.

关键词: droplet impact, partial coalescence, volume of fluid (VOF) method

Abstract: Partial coalescence is a complicated flow phenomenon. In the present study, the coalescence process is simulated with the volume of fluid (VOF) method. The numerical results reveal that a downward high-velocity region plays a significant role in partial coalescence. The high-velocity region pulls the droplet downward continuously which is an important factor for the droplet turning into a prolate shape and the final pinch-off. The shift from partial coalescence to full coalescence is explained based on the droplet shape before the pinch-off. With the droplet impact velocity increasing, the droplet shape will get close to a sphere before the pinch-off. When the shape gets close enough to a sphere, the partial coalescence shifts to full coalescence. The effect of film thickness on the coalescence process is also investigated. With large film thickness, partial coalescence happens, while with small film thickness, full coalescence happens. In addition, the results indicate that the critical droplet impact velocity increases with the increase of surface tension coefficient but decreases with the increase of viscosity and initial droplet diameter. And there is a maximum critical Weber number with the increase of surface tension coefficient and initial droplet diameter.

Key words: droplet impact, partial coalescence, volume of fluid (VOF) method

中图分类号:  (Multiphase flows)

  • 47.61.Jd
47.55.df (Breakup and coalescence) 47.55.Ca (Gas/liquid flows)