Event
【GIR Open Seminar】 Dr. Ching-Yao Chen / National Yang Ming Chiao Tung University (Taiwan)
| Date | 2023.6.21 (15：00 - 16：00) |
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| Venue | |
| Speaker | Dr. Ching-Yao Chen |
| Affiliation | National Yang Ming Chiao Tung University (Taiwan) |
| Title | "Characteristics and Applications of Magnetohydrodynamic (MHD) Bubbly Jet" ＜Abstract＞ Magnetohydrodynamic (MHD) jet induced by the Lorentz force in saltwater possesses potential applications to improve marine vehicle propulsion and hydrogen collection. Recent development of a small scale marine unmanned surface vehicle (USV) based on MHD propulsion will be introduced. To further optimize the energy efficiency and propulsion enhancement, pattern and flow transition of MHD bubbly jets are studied. In addition, bubbles of oxygen and hydrogen are produced by the associated electrolysis. For better implementations to hydrogen production or drag reduction, typical characteristics of the MHD bubbly jet, such as the size distribution and motion of oxygen and hydrogen bubbles, need to be well realized. A Lorentz-force based Reynolds number Re_L is proposed to categorize the transition of flow regimes from laminar to turbulent. For a jet of lower Re_L, the pattern of the bubbly jet appears as a continuous, wavy and laminar stream. Turbulent breakups start to evolve at farther downstream of the bubbly jet once the Re_L exceeds a critical value. The critical value of Re_L ~ 1500 is verified both by visual observation and relevant quantitative measures of the bubbly jet. In addition, dependence of the mean size of bubble on the current density is generally verified. Two regimes regarding the bubble sizes are distinguished. For Re_L < 2000, size of bubble monotonically increases with current density, so that referred to as the electrochemistry regime. Nevertheless, the size of bubble remains nearly unchanged for Re_L > 2000, referred to as the flow regime in which the turbulent breakup of the bubbly jet core starts to evolve. The proposed mechanisms of these two regimes are supported by the pattern of bubbly jet. |
| Language | English |
| Intended for | Everyone is welcome to join. |
| Co-Organized by | Institute of Global Innovation Research "LIFE SCIENCE" Tagawa Team Excellent Leader Development for Super Smart Society by New Industry Creation and Diversity |
| Contact | Institute of Global Innovation Research, Institute of Engineering Prof. Yuichiro Nagatsu e-mail: nagatsu（at）cc.tuat.ac.jp |
| Remarks | ＜Reference＞ |
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