Micro-Bubbly Flows in Rotating Pipe Sections with Abrupt Expansion and Contraction∗

An investigation was carried out for swirling flow in a rotating pipe with highly viscous fluid containing micro-bubbles experimentally and numerically. In the numerical analysis, bubble trajectory of each bubble was calculated using resultant numerical flow field solutions. From experimental results, with an aid of the numerical simulation, data were obtained for the location of a stagnation point, which moves towards the inlet region as swirl ratio being increased. It was found that the position of the stagnation point had a particular convergence value in relation with Reynolds number and types of the rotating channel. In the bubble behavior, big bubbles fall into the stagnation point, and that the parabolic surface is formed by some smaller bubbles. Critical diameter of bubble, which was to be caught at the stagnation point, was also obtained numerically for the model rotating channels.