Drag and lift forces on bubbles in a rotating flow

Abstract

The motion of small air bubbles in a horizontal solid-body rotating flow is investigated experimentally. Bubbles with a typical radius of 1 mm are released in a liquid-filled horizontally rotating cylinder. We measure the transient motion of the bubbles in solid-body rotation and their final equilibrium position from which we compute drag and lift coefficients for a wide range of dimensionless shear rates 0.1< Sr <2 ( Sr is the velocity difference over one bubble diameter divided by the slip velocity of the bubble) and Reynolds numbers 0.01< Re <500 ( Re is based on the slip velocity and bubble diameter). For large Sr , we find that the drag force is increased by the shear rate. The lift force shows strong dependence on viscous effects. In particular, for Re <5, we measure negative lift forces, in line with theoretical predictions. The motion of small air bubbles in a horizontal solid-body rotating flow is investigated experimentally. Bubbles with a typical radius of 1 mm are released in a liquid-filled horizontally rotating cylinder. We measure the transient motion of the bubbles in solid-body rotation and their final equilibrium position from which we compute drag and lift coefficients for a wide range of dimensionless shear rates 0.1< Sr <2 ( Sr is the velocity difference over one bubble diameter divided by the slip velocity of the bubble) and Reynolds numbers 0.01< Re <500 ( Re is based on the slip velocity and bubble diameter). For large Sr , we find that the drag force is increased by the shear rate. The lift force shows strong dependence on viscous effects. In particular, for Re <5, we measure negative lift forces, in line with theoretical predictions.