| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 100 === Abstract
In this research, the Particle Image velocimetry (PIV) incorporated with a Mass Flow Controller (MFC) are utilized to observe the variations of flow filed of a Newtonian fluid and associated non-dimensional parameters, which generated by a long bubble penetration into the fluid with different fluid viscosity, within a vertical circular tube. For the sake of comparison, ten silicon oils with different viscosity and three different injection volumes are used in the present study.
At first, a high speed camera is used to capture the shape of long bubble in the circular tube. Secondly, by using the diameter of circular tube and the deduced diameter of bubble, the hollow ratio is calculated. Then, apply the flow field velocity acquired by the PIV to calculate the non-dimensional parameters: Reynolds number, Capillary number, the ratio of the diameter of recirculation and the diameter of bubble, and finally the vector velocity images incorporate with the non-dimensional parameters are used to conduct the comparison。
The results show that values of the hollow ratio of the long bubble approach to 0.61 with the increase of Capillary number in the vertical circle tube, and under the conditions of three different gas injection volumes, with the increase of the fluid viscosity, the flow fields will transformed from bypass flow to Recirculation flow. In addition, the width of the recirculation zone decreases while either the gas injection volume or the fluid viscosity increases. Consequently, the ratio of the width of recirculation zone to the diameter of bubble decreases with the decrease of the hollow ratio, and the variations of the ratio is nonlinear.
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