Numerical Studies of Bubbles in Swirling Channel Flows

The motion of bubbles in upflow in a vertical rotating closed channel is examined numerically, using a front tracking/finite volume method. The flow is driven upward by a constant pressure gradient. The Reynolds number is low enough so that the flow remains laminar and the Eötvös number is sufficiently low so the bubbles remain nearly spherical. A bubble is placed between the centerline and the walls and for low rotation rate the bubble moves to a wall, due to the lift force and the fluid shear near the walls, but for higher rotation rate the bubble moves to the center of the channel, due to the radial pressure gradient established by the rotation. For intermediate rotation rates, we find bubbles where the lift force and the pressure gradient balance and the bubbles remain between the centerline and the walls. We also examine the collective motion of a few bubbles and show that their dynamics are similar to what is observed for a single bubble.