Chinese Journal of Theoretical and Applied Mechanics ›› 2018, Vol. 50 ›› Issue (2): 427-437.DOI: 10.6052/0459-1879-17-405

• Orginal Article • Previous Articles     Next Articles

DEFORMATION AND RUPTURE OF BUBBLE WHEN THE HOLLOW DROPLET IMPACTS ON THE OIL FILM

Zhou Jianhong, Tong Baohong(), Wang Wei, Su Jialei   

  1. 1.School of Mechanical Engineering,Anhui University of Technology,Maanshan 243032,Anhui,China
    2.Institute of Tribology,Hefei University of Technology,Heifei 230009,China
  • Received:2017-12-06 Accepted:2018-02-13 Online:2018-04-16 Published:2018-04-17

Abstract:

Hollow oil droplets are easily formed by the high velocity air turbulence in the process of oil-gas lubrication. The micro bubble has an important influence on the movement process and oil film formation quality when an oil droplet impacting on the wall. The coupled level set and volume of fluid (CLSVOF) method is adopted to simulate the impact of a hollow droplet on the oil film wall. The dynamic mechanism of bubble rupture is investigated by investigating the deformation and movement of bubbles when the hollow droplets are impacted on the wall of the oil film. And the influence of bubble size, collision velocity and liquid viscosity on the characteristic parameters of bubble deformation in the process of bubble wall collision is also analyzed. The results reveal that the bubbles will deform and break up to form film droplet after the hollow droplets impact the wall of the oil film. The change of pressure and velocity gradient inside and outside the bubble is the main cause of bubble rupture. The bubble size has a great influence on the bubble rupture mode, single-point rupture occurs when the bubble is small, larger bubbles are more likely to cause multiple ruptures. The difference of force between different sizes of bubbles is larger, and there is no obvious correlation between the size of the bubble and the moment of rupture. The velocity of the collision and the viscosity of the liquid have a certain influence on the deformation, rupture and rupture time of the bubble. The larger the collision velocity, the greater the kinetic energy of the oils droplet, and the more likely the bubble deformation and rupture. When the viscosity of the liquid increases, the bubble deformation is promoted at the early stage of the movement of the oil droplet, and the rupture behavior of the bubble can be delayed in the later period of the movement.

Key words: droplet, bubble, oil film, bubble rupture, numerical simulation

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