Transport of oxygen in the wake of a high-Re bubble rising in a thin-gap cell
I will present new experimental results concerning mass transfer at the interface of an isolated bubble rising in a liquid at rest, the bubble being confined in a vertical thin-gap cell of thickness w smaller than the capillarity length. Considered bubbles have a diameter d greater than w and therefore look like ‘pancakes’ separated from the walls by thin liquid films. The flow regime is inertial, and there exists a strong coupling between the bubble motion and its wake dynamics. The mass transfer leads to the transport of oxygen in the flow perturbation generated by the bubble motion. Understanding the gas-liquid interactions in bubble wakes is crucial for discussing yield and selectivity when implementing a reaction in which a gaseous reactant is transferred through the fluid interfaces. Therefore, focus will be paid on the role of the 3D velocity field in the oxygen transport through the liquid. The questions that are addressed concern : (i) the characterization of the 3D velocity field in the vicinity of the bubble ; (ii) the occurrence of contrasted mass transfers in the films and at the bubble interface surrounded by high-Reynolds number external flow ; (iii) the locations of intense mass transfer sources and the times at which they are activated ; (iv) the modes of concentration transport before oxygen is finally deposed in the far wake of the bubbles.
Contact Nathanaël Machicoane for more information or to schedule a discussion with the seminar speaker.