Who: Associate professor Davide Picchi from the University of Brescia, Italy
When: Wednesday 25 June, between 11:00 and 12:00 CET (Norway time). Note that it is at 11 instead of the usual 13:00
Where: The lecture will be in-person in the common room (PoreLab Trondheim). From anywhere else, you will be able to join via the following Zoom link: zoom here Https://uio.zoom.us/j/65837085049?pwd=WjZianUyN3FJa2liQkxBbzQrOCtGdz09
Title: Taylor bubbles improve mixing and mass transfer — is it true?
Summary: The motion of Taylor bubbles in capillaries is typical of many engineering and biological systems, ranging from subsurface flows to small-scale reactors. Although the hydrodynamics of elongated bubble has been object of several studies, the case where a solute is transported in the surrounding liquid and surface mass-transfer mechanisms act on the solid wall or the bubble-fluid interface is much less understood. To fill this gap, we investigate the transport problem around a confined Taylor bubble to access the competition between advection, diffusion, and surface mass-transfer in the different regions of the bubble. To this aim, we derive a one dimensional Advection-Diffusion-Mass-Transfer equation where the transport mechanisms are described through an effective velocity, an effective diffusion coefficient, and an effective Sherwood number. Our model generalises the Aris-Taylor dispersion to the case of a Taylor bubble and clarify the impact of surface mass-transfer in the advection and diffusion dominated regimes for both the front and rear menisci. Interestingly, the effective diffusion coefficient scales with the square of the Péclet number based on the film thickness and, when the Péclet number balances with the Sherwood number, there exist conditions that leads to the formation of hot spots of concentration. We also show that the typical shape oscillations of the bubble rear locally enhance superficial mass-transfer.