Investigation of flow structures in vertical slug flow Original Research Article

The flow structure of gas–liquid slug flow in a vertical tube has been investigated experimentally and numerically. A photochromic dye activation method was used to obtain two-dimensional liquid velocity profiles around a Taylor Bubble rising in stagnant kerosene in a vertical 25.6 mm I.D. pipe. A numerical simulation of the flow was conducted using a Volume-of-Fluid approach to predict both the shape of the Taylor Bubble and the velocity profiles in the liquid phase. In order to test the hypothesis that a trailing bubble can accelerate, catch up and coalesce with a leading bubble because of lateral motion and reduced drag force, a second experiment was performed using a solid Taylor Bubble placed in a steady downward flow of liquid. The measured drag force showed significant reduction as the bubble was moved from the tube axis towards the wall, giving support to the hypothesis.