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工科系奈微米生醫流體實驗室
工科系奈微米生醫流體實驗室
Bubble dynamics

Microbubble in trapezoid microchannel (IJHMT 2004, IJMF 2005)

In this serials work, we explore the design of micro channel with different shape and geometry to accommodate better efficiency and performance for solution transportation and heat transfer (3-1-3-3), and the bubble dynamics when they encountered to one another (3-4-3-5). These work have been cited more than 140 times for their contribution on the understanding of the fundamental issues of two phase flow in micro channel and micro bubble interactions. The work 3-1 and 3-2 explores experimentally bubble dynamics in a single and double trapezoid microchannel with a hydraulic diameter of 41.3lm. Bubble nucleation, growth, departure size, and frequency are observed using a high speed digital camera and analyzed by the Image-Pro. The results of the study indicates that the bubble nucleation in the microchannel may be predicted from the classical model with microsized cavities and the bubble typically grows with a constant rate from 0.13 to 7.08lm/ms. Some cases demonstrate an extraordinarily high growth rate from 72.8 to 95.2lm/ms. The size of bubble departure from the microchannel wall is found to be governed by surface tension and drag of bulk flow and may be fairly correlated by a modified form of Levy equation. The bubble frequency in the microchannel is comparable to that in an ordinary sized channel. The traditional form of frequency–departure-diameter relationship seems to be inexistent in the microchannel of this study.

 

Explosive Micro Bubble generation (MNF2010, JMM 2012)

The triple-bubble interaction controlled by a precise time-delayed technique was investigated in detail with respect to different ignition times, heater spaces and sequential firing modes to promote efficient energy cascading and concentration. The target bubble, which was generated under a specific delay time with two auxiliary bubbles, can have a volume that is two or almost three times larger than that of a single bubble. This result overcomes the limitation of energy usage on an explosive microbubble under a constant heat flux. As the heater space decreases, stronger bubble–bubble interactions were obtained due to the hydrodynamic effect and the intensive pressure wave emission, resulting in highly enhancing and depressing bubble dynamics. Other interesting phenomena, such as bubble shifting, mushroom-shape bubble, rod-shape bubble and bubble extension among heaters, were also recorded by a high-speed phase-averaged stroboscopic technique, displaying special non-spherical bubble dynamics. Artificial manipulation of bubble behavior was further conducted in a two-level sequential firing process. Using various volumetric combinations, the adjustable multi-level fluid transportation can be realized by a digital time-delayed control. The above-mentioned information can be applied to not only the design and operation of inkjet printheads but also cavitation research and fluid pumping in microdevices