Characterization of the swirling bubbly flow and its application to oil transportationCharacterization of the swirling bubbly flow and its application to oil transportation

We experimentally characterized the swirling bubbly flow, induced by the swirling blade, in a circular pipe with an inner diameter (D) of 70 mm. At the superficial water velocities of 0.1-2.0 m/s, we injected air (up to 20 LPM) through a sparger to generate millimeter-scale bubbles before the blade. The experiment was carried out in both vertical and horizontal pipes to examine the evolution and decay of bubble swirls under various conditions. Additionally, we tested different blade design by adjusting the rotating angle and number. In a horizontal pipe, the two-dimensional void fraction increased as the flow develops away from the blade, indicating a decrease in swirling intensity. However, after the distance of 4D, void fraction decreased because of the dominant buoyancy effect over the swirling. In a vertical pipe, void fraction notably decreased when the superficial velocity of the water exceeds a critical value (~ 0.6 m/s), which depends on the blade design and air superficial velocity. Based on the further investigation of the swirling morphology and strength, we finally introduced the oil in the pipe and examined its transportation performance with the swirling bubbly flow.