Flow Past Two Cylinders Arranged in Tandem Within a Microbubble Plume

This study investigates the flow past two cylinders arranged in tandem within a microbubble plume inside a tank. Microbubbles with a mean diameter of 0.055 mm are released by water electrolysis from electrodes placed at the bottom of the tank. Upon rising, these microbubbles induce an upward water flow around them due to buoyancy. Orthogonally to the axis of this microbubble plume, two cylinders with a diameter D of 30 mm are arranged in tandem. The distance between the cylinders, L, ranges between 1.5D and 3D. The bubbles and the water flow around the cylinders are visualized, and the bubble velocity distribution is measured. The experiments reveal the water and bubble shear layers originating at the sides of the lower cylinder, and allow the elucidation of their behavior around the upper cylinder. Furthermore, this study makes clear the effects of L on the flow around the two cylinders, such as the stagnant bubbly flow and the bubbly wake.