Mar
17
Giu
Seminari e Convegni
Taylor Bubbles Improve Mixing and Mass Transfer: Is It True? | with Professor Picchi
The seminar entitled "Taylor Bubbles Improve Mixing and Mass Transfer: Is It True?" will feature the participation of Davide Picchi, associate professor in the Department of Mechanical and Industrial Engineering at the University of Brescia.
It will be held on 17 June 2025 from 12:00 p.m. to 1:00 p.m. in Sala Didattica of the Department of Applied Science and Technology-DISAT of Politecnico.
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 bubbles has been the subject 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, the seminar investigates 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 clarifies 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 lead 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. Finally, we study the transport problem in the uniform film region.
It will be held on 17 June 2025 from 12:00 p.m. to 1:00 p.m. in Sala Didattica of the Department of Applied Science and Technology-DISAT of Politecnico.
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 bubbles has been the subject 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, the seminar investigates 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 clarifies 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 lead 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. Finally, we study the transport problem in the uniform film region.