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Characteristics of air bubble rising in low concentration polymer solutions
The bubble rise phenomena in different low concentration polymer solutions for higher Reynolds number are presented in this paper. The main characteristics, namely, the bubble velocity, the bubble trajectory and the drag relationship are investigated. The experiments were conducted in two different cylindrical columns at various liquid heights by introducing different bubble volumes (from 0.1mL to 20.0mL) corresponding to each height. The bubble rise velocity, bubble size and bubble trajectory were measured using a combination of non-intrusive-high speed photographic method and digital image processing. The parameters that significantly affect the rise of air bubble are identified. The bubble rise velocity of different volumes and the effect of liquid heights on the bubble rise velocity are analysed and discussed. The results show that the average bubble rise velocity increases with the increase in bubble volume for different low concentration polymer solutions and the bubble velocity is not dependant on the size of the test rig. The results of bubble trajectory for various bubbles are compared and discussed. In trajectory analysis, it is seen that the smaller bubbles show helical or zigzag motion and larger bubbles follow spiral motion. A new set of data of the drag coefficient for air bubble for higher Reynolds number are reported and compared with the results of other analytical and experimental studies available in the literature. The bubble rise characteristics, i.e., bubble velocity, trajectory and drag coefficient produced acceptable and consistent results.