| As wide application in micro electro mechanical system (MEMS) and super cavitation in recent years, the control of bubble has become an ultimate goal on bubble dynamic characteristics. However, bubble is messy and less controlled at most time in application due to the poor understand on bubble dynamic characteristics. It directly affect the efficiency of bubble. This paper, molecular dynamic simulation and experiment are use to study the dynamic characteristics of cavitation bubble, thermal bubble and gas-liquid bubble respectively.Cavitation occurs in canonical ensemble is studied by molecular dynamics simulation. The simulation result shows that there is a range of value for both temperature and numerical density. Cavitation could occur only the temperature or numerical density is equal or lesser than the range of value. In that case, stable and lager bubbles will form when temperature or numerical density is lesser than the range of value. Otherwise, unstable and smaller bubbles will form in liquid.Similarly, the research on growth and collapse of cavitation bubble in canonical ensemble is also carried out by molecular dynamics simulation. It indicates bubble could be intact in lower temperature. As the increase of temperature, it becomes more and more difficult for bubble to keep its stability. The higher the temperature, the faster the bubble collapse. It finds that the collapse time of bubble could be reduced by 60%, and the shock wave fall by 35% with temperature varies from 0.62 to 0.80. However, stability of bubble could be improved by reducing the numerical density, and also reaches a larger volume. Moreover, the effect of numerical density on bubble stability becomes more and more weak as the increase of temperature.A single thermal bubble nucleating and growing on micro electrode is studied by experiment. The results indicate that it takes less time for bubble nucleating on micro electrode with higher heat flux and in lower ambient pressure. The nucleation time will reduce by 17% and 3% respectively as the heat flux increase from 0.140 MW-m-2 to 0.169 MW-m-2 and the ambient pressure decrease from 5 kPa to 0 kPa. The growth of thermal bubble includes the stages of rapid growth and dynamic equilibrium, with the velocity being from fast to slow. In the former part of rapid growth, heat flux plays a dominant role in bubble growth. While, the effect of ambient pressure on bubble growth becomes significant in the latter part of rapid growth. And the final diameter of thermal bubble is both affected by heat flux and pressure.The moving of liquid-gas bubble on electrode in micro channel is also researched in experiment. It is obtained that the velocity of bubble moving on the hydrophobic electrode is 1.13 times than the bubble on the hydrophilic electrode. Moreover, the velocity will decrease by 2% when current is input on the hydrophobic electrode for 90 s and the heat flux is 5 x 102 kW-m-2. Oppositely, current input on the hydrophilic electrode could increase the velocity of bubble. And that, bubble moving faster as the increase of heat flux and heating time on the electrode. When the heat flux varies from 0 kW·m-2 to 5 x 102 kW·m-2, and the heating time changes from 0 s to 150 s, the velocity of bubble will be raised 5%. However, it accelerates and becomes more and more slowly as the increase of heat flux and heating time of electrode. |
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