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Measurement and Modeling of the Liquid-phase Turbulence in Adiabatic Air-water Two-phase Flows with a Wide Range of Void Fractions

Zhou, Xinquan
http://rave.ohiolink.edu/etdc/view?acc_num=osu1406210359

Abstract Details

2014, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
The current work focuses on the measurement and modeling of liquid-phase turbulence in adiabatic air-water two-phase flow with a relatively wide range of void fractions. The purpose of this research work is to understand and accurately predict two-phase flow behavior. Emphasis is placed on the liquid-phase turbulence characteristics for different flow regimes. A state-of-the-art particle image velocimetry (PIV) was used to perform liquid-phase turbulence measurements on two flow channels, a circular pipe with an inner diameter (ID) of 50 mm at OSU and a rectangular channel with a cross section dimension of 30 mm x 10 mm at Virginia Tech, respectively. Three local measurement ports were used to study the flow development along the test section. An advanced optical phase separation method, namely planar laser-induced fluorescence (PLIF), was applied to separate the liquid-phase particles from bubbles in the flow. An image pre-processing scheme was developed and imposed on the two-phase flow PIV images to remove remaining noise and therefore improve phase separation. The combination of the optical phase separation method and image pre-processing scheme proved capable of effectively reducing the noise in the two-phase flow PIV images and therefore increasing the measurement accuracy. The PIV measurement uncertainty analysis, as an integral part of the measurements, was conducted to assess the confidence in the measurement results. Different approaches were adopted to address different important uncertainty sources in the measurements. In addition, multiple benchmark tests were performed to assess the measurements and to explore the feasibility of the PIV measurements in high void fraction flow conditions. The measured liquid-phase velocity associated with the void fraction distribution measured by a four-sensor conductivity was used to calculate the superficial liquid velocity, which was benchmarked by the flow rate reading from a magnetic flow meter. The results obtained by using the PIV system were quantitatively and qualitatively compared with those obtained in the literature which used different instruments at similar flow conditions. Reasonable agreement was found between the present data and those found in the literature. Extensive data of the liquid-phase turbulence in air-water two-phase flow was acquired using the PIV-PLIF system. The void fraction of the flow conditions varied from 0 to 40% for the circular pipe at OSU and approximately to 60% for the rectangular channel at VT. The flow regimes studied include single-phase, bubbly, cap-bubbly, slug, and churn-turbulent flows with the superficial liquid velocity ranging from 0.5 to 3.4 m/s. The turbulence characteristics include the axial mean velocity, turbulence intensity, axial and radial velocity fluctuation, Reynolds stress, and relative velocity. A liquid-phase turbulence model for two-phase bubbly flows was developed based on the two-phase extension of the single-phase k-e model. Similar to the single-phase k-e model, the two-phase k-e model has all the counterparts except an extra interfacial transfer term, which indicates additional turbulence generated due to the interaction between the two phases. To assess the liquid-phase turbulence model, numerical simulations were performed using Fluent 14.0 and the results were compared against the experimental data. A reasonable agreement of the kinetic energy prediction was found in several bubbly flow runs.
Xiaodong Sun, Dr. (Committee Chair)
Marcello Canova, Dr. (Committee Member)
Richard Christensen, Dr. (Committee Member)
Jeffrey Sutton, Dr. (Committee Member)
213 p.
Mechanical Engineering
Two-phase flow; PIV; Turbulence; Void fraction; Measurement; Modeling; Nuclear Engineering

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Citations

  • Zhou, X. (2014). Measurement and Modeling of the Liquid-phase Turbulence in Adiabatic Air-water Two-phase Flows with a Wide Range of Void Fractions [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406210359

    APA Style (7th edition)

  • Zhou, Xinquan. Measurement and Modeling of the Liquid-phase Turbulence in Adiabatic Air-water Two-phase Flows with a Wide Range of Void Fractions. 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1406210359.

    MLA Style (8th edition)

  • Zhou, Xinquan. "Measurement and Modeling of the Liquid-phase Turbulence in Adiabatic Air-water Two-phase Flows with a Wide Range of Void Fractions." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406210359

    Chicago Manual of Style (17th edition)

osu1406210359
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This open access ETD is published by The Ohio State University and OhioLINK.