Computational Modeling of Bubbles Growth Using the Coupled Level Set-Volume of Fluid Method.

Yuxuan Liu,Amir Taqieddin,Akram N Alshawabkeh,Michael R Allshouse

doi:10.3390/fluids5030120

Abstract

Understanding the generation, growth, and dynamics of bubbles as they absorb or release dissolved gas in reactive flows is crucial for optimizing the efficiency of electrochemically gas-evolving systems like alkaline water electrolysis or hydrogen production. To better model these bubbly flow systems, we use a coupled level set and volume of fluid approach integrated with a one-fluid transport of species model to study the dynamics of stationary and rising bubbles in reactive two-phase flows. To accomplish this, source terms are incorporated into the continuity and phase conservation equations to allow the bubble to grow or shrink as the species moves through the interface. Verification of the hydrodynamics of the solver for non-reactive systems demonstrates the requisite high fidelity interface capturing and mass conservation necessary to incorporate transport of species. In reactive systems where the species impacts the bubble volume, the model reproduces the theoretically predicted and experimentally measured diffusion-controlled growth rate (i.e., R(t) ∝ t0.5). The model is then applied to rising bubbles to demonstrate the impact of transport of species on both the bubble velocity and shape as well as the concentration field in its wake. This improved model enables the incorporation of electric fields and chemical reactions that are essential for studying the physicochemical hydrodynamics in multiphysics systems.

Highlights

Multiphase flows are encountered in many different scientific and industrial applications such as atomization in combustion [1], boiling in power generators [2], sedimentation flows [3], ocean waves [4], and electrochemically gas-evolving systems [5,6]
We have presented a one-fluid approach based on the s-CLSVOF method to simulate bubbles in systems where the transport of species has the potential to change the volume of the bubble
The s-CLSVOF method takes advantage of the sharp interfaces produced by the level set method and the volume conservation of the volume of fluid approach

Summary

Introduction

Multiphase flows are encountered in many different scientific and industrial applications such as atomization in combustion [1], boiling in power generators [2], sedimentation flows [3], ocean waves [4], and electrochemically gas-evolving systems [5,6]. Understanding the dynamics of bubble-liquid multiphase flows is difficult due to the nonlinear, multiscale, and interconnected interactions between the two phases [7]. These systems become more complicated with flows that involve chemical reactions that result in reactive flows, such as bubbly flows in electrochemically gas-evolving systems that contain dissolved gas in the liquid phase. In these systems, the electrochemical reactions that occur at the electrode are responsible for the bubble formation, growth, and detachment at the electrode surface. While the presence of bubbles enhances the system efficiency by inducing flow circulation due to the bubble rising within the cell, it has the unwanted effects of changing the conductivity of the bulk electrolyte and reducing the liquid-solid

Methods

Results

Conclusion