Detailed 3D modelling of mass transfer processes in two phase flows with dynamic interfaces

We developed a method that will enable us to determine mass transfer coefficients for a\ud large number of two phase flow conditions based on numerical simulation. A three-dimensional\ud direct numerical simulation based on the Front Tracking technique taking into account the mass\ud transfer process was chosen for this purpose. The dissolved species concentration in the liquid\ud phase is tracked using a scalar mass balance while the value of the concentration at the interface\ud is determined via an immersed boundary technique. In the present study, simulations are carried\ud out to investigate the effect of the bubble shape on the dissolved species concentration fiel

Detailed modeling of hydrodynamics mass transfer and chemical reactions in a bubble column using a discrete bubble model

A 3D discrete bubble model is adopted to investigate complex behavior involving hydrodynamics, mass transfer and chemical reactions in a gas¿liquid bubble column reactor. In this model a continuum description is adopted for the liquid phase and additionally each individual bubble is tracked in a Lagrangian framework, while accounting for bubble¿bubble and bubble¿wall interactions via an encounter model. The mass transfer rate is calculated for each individual bubble using a surface renewal model accounting for the instantaneous and local properties of the liquid phase in its vicinity. The distributions in space of chemical species residing in the liquid phase are computed from the coupled species balances considering the mass transfer from bubbles and reactions between the species. The model has been applied to simulate chemisorption of CO2 bubbles in NaOH solutions. Our results show that apart from hydrodynamics behavior, the model is able to predict the bubble size distribution as well as temporal and spatial variations of each chemical species involved

A hybrid discrete bubble-lattice Boltzmann–discrete element model for gas-charged sediments

This paper presents a hybrid discrete bubble-lattice Boltzmann–discrete element modelling framework for simulating gas-charged sediments, especially in the seabed. A discrete bubble model proposed in chemical engineering is adapted in the coupled discrete element/lattice Boltzmann method to model the migration of gas bubbles in saturated sediments involving interactions between gas bubbles and fluid/solid phases. Surface tension is introduced into the discrete bubble model in this work, so that it can handle the complex gas–fluid–solid interface. The lattice Boltzmann and discrete element methods are, respectively, employed to simulate fluid flows and mechanical behaviours of sediments. A velocity interpolation-based immerse boundary method is utilised to resolve the coupling between the fluid flow and the solid/gas phase. The proposed technique is preliminarily validated using simulations of bubble migration in fluids, which is followed by high-resolution investigations of the transport of a gas bubble in seabed sediments. It is demonstrated that this hybrid method can reproduce, to a certain degree, the characters of bubbles moving in seabed sediment tests

Parallelization of an Euler-Lagrange model using a mixed domain decomposition and mirror domain technique: application to dispersed gas-liquid two-phase flow

We report a parallel algorithm applicable to a Euler–Lagrange model embedding four-way coupling. The model describing the dispersed phase dynamics accounts for bubble–bubble collisions and is parallelized using a mirror domain technique while the pressure Poisson equation for the continuous phase is solved using a domain decomposition technique implemented in the PETSc library [S. Balay, K. Buschelman, W.D. Gropp, D. Kaushik, M.G. Knepley, L.C. McInnes, B.F. Smith, H. Zhang, PETSc Web page: http://www.mcs.anl.gov/petsc, 2001]. The parallel algorithm is verified and it is found that it gives the same results for both phases as compared to the serial algorithm. Furthermore the algorithm shows good scalability up to 32 processors. Using the proposed method, a homogeneous bubbly flow in a laboratory scale bubble column can be simulated at very high gas hold-up (37%) while consuming a reasonable amount of calculation wall time