This paper aims at the effect of gas flow and viscosity of the fluid on the profile of a long bubble. The gas flow controlled by a mass flow controller is injected into a tube filled with liquid silicon oil. The images of bubble profile are captured by a high-speed camera. The fractional converge of the liquid and the hollow ratio of the bubble is estimated by measuring the width of these images. The result shows that the values of Capillary number and Reynolds number increase as the gas flow rate increase under a constant viscosity. However, the hollow ratio decreases while the flow rate increases. The value of fractional converge is 0.6 while the value of Capillary number approaches to 10 for the 500cs silicon oil, the results are consistent with the projections of Cox

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