Flow patterns in gas-assisted injection molding process in a channel

  • Cheng-Hsing Hsu
  • Po-Chuang Chen
  • Kuang-Yuan KungEmail author
  • Chuan Lai
Original article


The flow field of a long bubble steadily expelling a viscous fluid confined by two closely located parallel plates is examined. In order to investigate the influence of bubble size on the flow field, a theoretical bubble profile is used to replace the complicated procedure for computing simultaneously the interface between the gas surface and fluid flows. The present study showed the two typical flow patterns and also a third flow pattern of the stagnation point moving in the region of the bubble tip front during transformation of the two typical flow patterns. The vorticity patterns are also drawn for various bubble profiles and are examined for their effect on the flow. The velocity field is also presented from two different viewpoints and the phenomena is examined. The stagnation point located on the center line between the bubble tip to the upstream is only found in the small range of \(2/3 <\lambda < 0.685\) in a channel, where λ is ratio of the bubble width to the distance between two parallel plates.


Gas-assisted Expelled fluid flow Stagnation point Two-phase flow 



Half distance between the two parallel plates


Constant velocity of the bubble




Fractional converge


The normal unit vector on the bubble interface


Pressure in the fluid expelled by bubble


The tangential unit vector on the bubble interface


The velocity of the fluid expelled by the bubble


The axial direction in coordinate system


The radial direction in coordinate system


The over-relaxation factor


The angle between the normal of the interface and the axial direction


The ratio of asymptotic bubble width to half distance of the two parallel plates


Kinematic viscosity




Stream function




Iterative time


Dimensionless form


Capillary number (dimensionless parameter)


The number of grid in the axial direction


The number of grid in the radial direction


The grid index in the y-direction on the wall


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Copyright information

© Springer-Verlag London Limited 2006

Authors and Affiliations

  • Cheng-Hsing Hsu
    • 1
  • Po-Chuang Chen
    • 1
  • Kuang-Yuan Kung
    • 2
    Email author
  • Chuan Lai
    • 1
  1. 1.Department of Mechanical EngineeringChung-Yuan Christian UniversityChung-LiTaiwanRepublic of China
  2. 2.Department of Mechanical EngineeringNanya Institute of TechnologyChung-LiTaiwanRepublic of China

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