Measurement of tiny droplets using a newly developed optical fibre probe micro-fabricated by a femtosecond pulse laser

• Published in: Measurement science & technology 2009-11, Vol.20 (11), p.114002-114002 (12)
• Main Authors: Saito, T, Matsuda, K, Ozawa, Y, Oishi, S, Aoshima, S
• Format: Article
• Language: English
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/20/11/114002

Optical fibre probing is widely applied to measurements in gas-liquid two-phase flows. We have already developed and reported a four-tip optical fibre probe (F-TOP) for millimetre-size bubbles/droplets, and a single-tip optical fibre probe (S-TOP equipped with a wedge-shaped tip) for sub-millimetre-size bubbles/droplets. However, it is difficult to measure micrometre-size bubbles/droplets by S-TOP. The main purpose of the present study was to develop a new type of optical fibre probe micro-fabricated by a femtosecond pulse laser (Fs-TOP). First, we confirmed the performance of the new probe by examining millimetre- and sub-millimetre-size droplets; the results from the Fs-TOP were compared with those obtained from the visualization of the droplets by high-speed video camera, and showed satisfactory agreement. In addition, we demonstrated the measurement of velocities and chord lengths of micrometre-size droplets (about 50 mum in diameter) using the Fs-TOP and compared them with those from the S-TOP to clarify the limits and strengths of each type of probe.