Measurements in the wake of a ventilated hydrofoil: a step towards improved turbine aeration techniques

27th IAHR Symposium on Hydraulic Machinery and Systems

Ellis, C.^1 ; Karn, A.^1 ; Hong, J.^1 ; Lee, S.-J.^2 ; Kawakami, E.^3 ; Scott, D.^4 ; Gulliver, J.^1 ; Arndt, R.E.A.^1

St. Anthony Falls Laboratory, University of Minnesota, United States^1

Research Institute of Marine Systems Engineering, Seoul National University, Korea, Republic of^2

3M Corporate Research Process Laboratory, United States^3

ALSTOM Renewable Power Canada Inc., United States^4

关键词: Background illumination;    Bubble detection;    Bubble size distributions;    Bubble velocities;    Edge detection methods;    High speed water;    Tracking algorithm;    University of Minnesota;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/6/062009/pdf
DOI  :  10.1088/1755-1315/22/6/062009

来源: IOP

【 摘 要 】

The purpose of this study is to develop the necessary algorithms to determine the bubble size distribution and velocity in the wake of a ventilated or cavitating hydrofoil utilizing background illumination. A simplified experiment was carried out to validate the automatic bubble detection algorithm at the Saint Anthony Falls Laboratory (SAFL) of the University of Minnesota. The experiment was conducted in the SAFL high-speed water tunnel. First, particle shadow velocimetry (PSV) images of a bubbly flow were collected. Bubbles were identified in the images using an edge detection method based on the Canny algorithm. The utilized algorithm was designed to detect partly overlapping bubbles and reconstruct missing parts. After all images were analyzed, the bubble velocity was determined by applying a tracking algorithm. This study has shown that the algorithm enables reliable analysis of irregularly shaped bubbles even when bubbles are highly overlapped in the wake of the ventilated hydrofoil. It is expected that this technique can be used to determine the bubble velocity field as well as the bubble size distributions.