Multiscale computations of mass transfer from buoyant bubbles

Abstract

In the computation of multiphase flow with mass transfer, the large disparity between the length and time scale of the mass transfer and the fluid flow demand excessive grid resolution for fully resolved simulation of such flow. We have developed a subscale description for the mass transfer in bubbly flow to alleviate the grid requirement needed at the interface where the mass gets transferred from one side to the other.In this fluid dynamics video, a simulation of the mass transfer from buoyant bubbles is done using a Front Tracking method for the tracking of interface and a subscale description for the transfer of mass from the bubble into the domain. After the mass is transferred from the bubble into the domain, mass is followed by solving an advection-diffusion equation on a relatively coarse Cartesian grid. More detail about the method can be found in our paper [1]. This simulation shows 13 moving bubbles in a periodic domain,

An improved Front-Tracking technique for the simulation of mass transfer in dense bubbly flows

“…Aboulhasanzadeh et al (2012) have investigated the mass transfer of multiple rising bubbles at the same time, being able to capture the mass transfer in the bubble cluster, taking an approximation of the mass transfer near the interface using a boundary layer model. Thus, so far, mass transfer simulations in continuous bubble swarms have not yet been investigated, rather a number of different instances of bubble clusters have been reported.…”

Effect of bubble interactions on mass transfer in bubbly flow

“…Approximate solutions to (2) can be obtained in different ways. We start by considering the total amount of f in the boundary layer…”

“…Both of these studies examined only two-dimensional systems. Here, we use the multi-scale method presented in [2] and further validated with experimental data in [1] to study the mass transfer in bubble clusters, including the effect of different void fractions and Reynolds numbers.…”

“…Because of the large disparity between the length and time scale for the mass transfer compared to the momentum transfer, fully resolved three-dimensional calculations of mass transfer are challenging undertakings and those available in the literature are done for very low Schmidt number, Sc ¼ Oð1Þ, [8,22]. In order to resolve the mass transfer at the interface of moving bubbles, and make the computational requirement of simulation of high Schmidt number bubbly flows manageable, several authors have presented different approaches; [3] computed the evolution of a soluble surfactant by incorporating a singular perturbation analysis of the fluid next to the interface into a numerical solution of the interface motion for Stokes flow, [4] used the exact solution of a one-dimensional diffusion problem, fitted to the computational results close to the bubble, to find the mass flux at the surface, and [2,1] solved a mass boundary layer equation at the interface for the evolution of the mass concentration next to the bubble and transferred the mass to the surrounding fluid when the boundary layer grew over a certain limit. This approach will be discussed further in the rest of paper.…”

Reactive Mass Transfer of Single NO Bubbles and Bubble Bouncing in Aqueous Ferric Solutions – A Feasibility Study

“…In recent years, experiments focused on single mass transfer with rising bubbles to obtain a better understanding of local effects [1] such as wake shedding, bubble contamination [2][3][4][5][6], pH influence [7] and local mass transfer [1,[8][9][10][11]. With the aid of Computational-Fluid-Dynamics (CFD) simulations, local hydrodynamics can be resolved and give further information in respect to local modeling of mass transfer [12][13][14][15][16]. Koynov and Khinast [17] investigated the effect of hydrodynamics on chemically reacting bubble flows using Direct Numerical Simulations (DNS).…”