Behavior and Surrounding Liquid Motion of a Single Bubble Rising in Water-Surfactant Solutions

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The effects of a surfactant on a single ascending bubble motion and its surrounding liquid motion were investigated using 1-pentanol and purified water systems. An ellipsoidal bubble (2.8 mm in equivalent diameter) was examined in a quiescent liquid. The bubble motion was visualized using a high-speed video camera. As a result, changes of the amplitude and frequency of the bubble trajectory were observed at a 1-pentanol concentration of 150ppm. At 500ppm, "small initial deformation" due to the strong damping effect was caused by adsorption of the surfactant on the bubble surface. The bubble velocity became low as reported by the other researchers. Furthermore, the liquid motion in the vicinity of the bubble was visualized via PIV method (Particle Image Velocimetry) with recursive cross correlation PIV algorithm. As a result, the difference in vorticity associated with the strength of the shed vortex was observed at the inversion points at which the bubble changes the direction of the zigzag motion. The difference affects the change of the amplitude and frequency of the bubble trajectory. An effect of the boundary condition changing from free-slip to no-slip in the contaminated system yields this difference.
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