Bubble Measurement in Breaking Waves: Photograph and Optical Fiber Probe Approach.

Liu, F.; Chen, Z.; Meng, X., and Xing, B., 2026. Bubble measurement in breaking waves: Photograph and optical fiber probe approach. Journal of Coastal Research, 42(1), 50–60. Charlotte (North Carolina), ISSN 0749-0208. An image-based method has emerged as the primary technique for measuring bubble size distribution in bubble plumes beneath breaking waves. However, this technique encounters considerable measurement inaccuracies when applied to high void fraction bubble plumes containing a significant number of coalesced and overlapping bubbles. To overcome this limitation, the present study investigates the development of an optical fiber probe enabling integrated measurement of highly concentrated bubble plumes in conjunction with image analysis techniques. Following a structured development protocol that integrates probe structure simulation, fabrication of sensing elements, critical circuit design, and combined observation simulation experiments, this study validates the feasibility of employing the probe for high void fraction bubble plume detection. Subsequently, a correlation model is derived to establish quantitative relationships between the probe's measurement outputs and the image analysis results. The experimental results demonstrate that the proposed probe achieves effective detection of bubble plumes generated at a gas bubbling rate of 60 cm/s. When implemented in conjunction with image analysis for combined observations, the measurement datasets from both methods exhibit a statistically significant linear correlation, as characterized by the derived model. By integrating the optical fiber probe with the image-based method through sensor packaging design, this probe could serve as a robust complementary approach for characterizing bubble plumes with a high void fraction. [ABSTRACT FROM AUTHOR]