Journal of the Korean Society of Visualization (한국가시화정보학회지)

The Korean Society of Visualization (한국가시화정보학회)
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Bubble and Liquid Velocities for a Bubbly Flow in an Area-Varying Horizontal Channel

유로단면이 변하는 수평관 내 기포류에서의 기포 및 액체 속도

  • Tram, Tran Thanh (Thermal Hydraulics and Severe Accident Research Division, Korea Atomic Energy Research Institute) ;
  • Kim, Byoung Jae (School of Mechanical Engineering, Chungnam National University) ;
  • Park, Hyun Sik (Thermal Hydraulics and Severe Accident Research Division, Korea Atomic Energy Research Institute)
  • Received : 2017.12.02
  • Accepted : 2017.12.15
  • Published : 2017.12.31
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Abstract

The two-fluid equations are widely used to simulate two-phase flows in a nuclear reactor. For the two-fluid momentum equation, the wall and interfacial drag terms play an important role in predicting a two-phase flow behavior. Since the bubble density is much smaller than the water density, the bubble accelerates faster than the liquid in a nozzle. As a result, the bubble phase becomes faster than the liquid phase in the nozzle. In contrast, the opposite phenomena occur in the diffuser. The purpose of our study is to experimentally show these behaviors in an area-varying channel such as nozzle and diffuser. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of the bubble and liquid phases were measured by the PIV technique. It was shown that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle; in contrast, the bubble was slower than the liquid in the diffuser. Code simulations were also performed using the MARS code. By replacing the original wall drag model in the MARS code with Kim (1)'s wall drag partition model, we obtained the simulation results being consistent with experimental observations.

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References

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