Development and Benchmarking of Image Analysis Methods for Use in Horizontal Plug Flow
Open Access
- Author:
- Rau, Adam J
- Graduate Program:
- Nuclear Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 11, 2017
- Committee Members:
- Seungjin Kim, Thesis Advisor/Co-Advisor
- Keywords:
- Two-Phase Flow
Image Processing
Nuclear Engineering
Thermal-Hydraulics
Conductivity Probe
Horizontal Flow - Abstract:
- Accurate modeling of two-phase flow in all pipe orientations is important to the development of best-estimate systems analysis codes, which are used to assess safety margins of nuclear reactors. These codes use the flow regime approach to supply closure models to the two-phase flow field equations. The flow regime approach classifies flows into “flow regimes” based on the shape and structure of the interface between the two phases. In horizontal flow, plug flow and slug flow are two such flow regimes. Even though significant differences exist between these regimes, models capturing the differing transport characteristics of plug and slug flow have not been established. In view of this, image analysis techniques to measure two-phase parameters of the large, elongated bubbles that characterize plug flow (plug bubbles) are established in the present work. Image analysis methods have the ability to characterize the nose of the plug bubbles, which may be instrumental in studying the differences between plug and slug flow and the transport characteristics of plug bubbles. A visualization block / mirror system is designed and fabricated to allow the simultaneous visualization of two-phase flow from the top and side perspectives using a single camera, and an image processing code is written to measure plug bubble parameters from high-speed videos of two-phase flow acquired with this system. The code is capable of measuring the nose position, nose velocity, local time-averaged axial velocity, and time-averaged area-averaged void fraction of plug bubbles. Experiments are conducted in the existing horizontal two-phase flow test facility at the Advanced Multi-Phase Flow Laboratory of the Pennsylvania State University to benchmark the image analysis technique using the local four-sensor conductivity probe. Agreement within 10% is observed for the time-averaged area-averaged void fraction measured by the two techniques. For the local time-averaged axial velocity of plug bubbles, general agreement was observed within 10%. Near the top wall of the pipe, differences as up to 25% were observed.