Experimental Investigations of Three-Dimensional Flow Field around the Head of Gas-Liquid Slug Flow in Microchannels

The three-dimensional micro-particle image velocimetry (PIV) technique was used for experimentally studying three-dimensional flow field properties of slug flow in microchannels. By processing images of slug flow, three-dimensional fluorescent particles distribution and velocity flow field of the liquid around the head of slug bubble was obtained. The results show that there was two symmetrical and reverse vortices near the head of the bubble. The fluid near the bubble head had a larger velocity and flowed along the bubble surface. In the flow field far away from the bubble, the distribution of liquid velocity was parabolic in the radial direction, which was similar to a single-phase pressure driven flow. The fluid between the bubble surface and the microchannel walls had a complex motion: it might be pushed to the bubble tip if closer to the bubble surface or might be passed if closer to the walls. In addition, the gas-liquid interface was approximately rigid.