Deformation and break-up of a bubble in a horizontal solid-body rotation flow*

We study the dynamics of a bubble released inside a horizontal

solid-body rotating flow. When the rotational velocity of the tank increases, the bubble moves close to the axis of the cell, and stretches along the horizontal axis.

We show that the bubble aspect ratio can be predicted by the model of Rosenthal JFM 1962 provided an appropriate correction due to the impact of buoyancy is included.  We also show that the bubble can break up: this occurs through a resonance mechanism when the rotational velocity of the tank becomes of the order of the eigenfrequency of the bubble. We also deduce the drag and lift coefficients from the mean bubble position and discuss their values in comparison with existing models.

 

Eventually, we explore the effects of surfactants on the dynamics and shape of the bubble. We have studied two surfactant concentrations: one lower than the CMC (0.33 CMC) and one higher than the CMC (2 CMC). The results reveal that as expected the deformation of the can still be modelled by the model of Rosenthal 1962 in the case of the 2 CMC solution. In the case of the 0.33 CMC solution, the bubble behaves as if it was seeing an effective surface tension. We finally discuss the impact of the surfactant on the lift and drag coefficients, and on the shape of the bubble.