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The liquid-column break problem is one of the well-known validation tests for the multiphase flow computations. However, a few experimental data are available until now regarding the liquid-column break problem. In the validation process, it is necessary to consider the differences of the boundary and initial conditions between both experiment and numerical simulation. In this study, we conducted the liquid-column break experiments and measured the position of the water-front and the gravity center of the water region by using a high-speed camera and an image analyzing software. These experimental results were compared with the numerical simulation results. The water front position is usually taken as a scaling measure to evaluate the accuracy of numerical method for multiphase flows. However, when the real sizes of the liquid column changed to double without changing the aspect ratio (height/width), the non-dimensional water front positions were changed. From this fact, it is considered that the position of the waterfront cannot be used as the scaling measure for this problem. On the other hand, the gravity-center positions of the water region obtained by the experiments for both cases showed in very good agreement with the numerical results for all cases. As the conclusion, the gravity-center position should be used as the scaling measure instead of the water-front position for the two-phase numerical simulation. [ABSTRACT FROM AUTHOR]

Bubble removal in viscoelastic solution is an important challenge in both industry production and laboratory experiments. However, no effective physical bubble removal technique in viscoelastic solutions has been reported until now. In this study, the ultrasonic vibration effect on bubble removal in viscoelastic solution (300ppm-CTAC/300ppm-NaSal viscoelastic solution) was firstly observed. The ultrasonic vibration can successfully remove bubbles whose diameter is ranging from 200 μm to 1mm, and from 300ppm CTAC/NaSal at 28°C through assembling bubbles to be a large size bubble cluster in our experiments. The detailed bubble-assembling process were observed and analyzed. It is pointed out that the bubble-assembling process was directly associated with the intensity of ultrasonic vibration and the distance between bubbles in the solutions. However, the detail mechanism of the bubble-assembling behavior is still unclear, which is worth of further observation. [ABSTRACT FROM AUTHOR]