VOF-Simulations of Mass Transfer From Single Bubbles and Bubble Chains Rising in Aqueous Solutions

2003 ◽  
Author(s):  
Dieter Bothe ◽  
Mario Koebe ◽  
Kerstin Wielage ◽  
Hans-Joachim Warnecke
Keyword(s):  
Mass Transfer ◽  
Aqueous Solutions ◽  
Numerical Simulations ◽  
Density Ratio ◽  
Volume Changes ◽  
Two Phase ◽  
Method Transfer ◽  
High Density Ratio ◽  
Interfacial Mass Transfer ◽  
The Mathematical Model

This paper presents numerical simulations of two-phase flow with high-density ratio, taking into account mass transport of a soluble component and its interfacial mass transfer. The mathematical model and the numerical method allow for different solubility of the species in the respective fluid phases, while volume changes due to mass transfer are neglected. The discontinuous changes in species concentrations at the interface are modeled by means of Henry’s law. Simulations are carried out with an extended version of the highly parallelized code FS3D, which employs an advanced Volume-Of-Fluid (VOF) method. Transfer and transport of oxygen is examined in case of single bubbles as well as bubble chains rising in aqueous solutions. Numerical simulations show good qualitative agreement with experimental data and render the observed mass transfer phenomena correctly.

NUMERICAL SIMULATION OF ISOTHERMAL AND THERMAL TWO-PHASE FLOWS USING PHASE-FIELD MODELING

2007 ◽  
Vol 18 (04) ◽  
pp. 536-545 ◽  
Author(s):  
NAOKI TAKADA ◽  
AKIO TOMIYAMA
Keyword(s):  
Phase Field ◽  
Stokes Equations ◽  
Density Ratio ◽  
Navier Stokes ◽  
Phase Field Modeling ◽  
Two Phase Flows ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Field Modeling ◽  
High Density Ratio

For interface-tracking simulation of two-phase flows in various micro-fluidics devices, we examined the applicability of two versions of computational fluid dynamics method, NS-PFM, combining Navier-Stokes equations with phase-field modeling for interface based on the van der Waals-Cahn-Hilliard free-energy theory. Through the numerical simulations, the following major findings were obtained: (1) The first version of NS-PFM gives good predictions of interfacial shapes and motions in an incompressible, isothermal two-phase fluid with high density ratio on solid surface with heterogeneous wettability. (2) The second version successfully captures liquid-vapor motions with heat and mass transfer across interfaces in phase change of a non-ideal fluid around the critical point.

A Combined Volume of Fluid and Immersed Boundary Method for Modelling of Two-Phase Flows with High Density Ratio

2021 ◽  
Author(s):  
Qiu Jin ◽  
Dominic Hudson ◽  
W.G. Price
Keyword(s):  
Boundary Layer ◽  
Immersed Boundary Method ◽  
Density Ratio ◽  
Volume Of Fluid ◽  
High Density ◽  
Immersed Boundary ◽  
Two Phase Flows ◽  
Two Phase ◽  
Boundary Method ◽  
High Density Ratio

Abstract A combined volume of fluid and immersed boundary method is developed to simulate two-phase flows with high density ratio. The problems of discontinuity of density and momentum flux are known to be challenging in simulations. In order to overcome the numerical instabilities, an extra velocity field is designed to extend velocity of the heavier phase into the lighter phase and to enforce a new boundary condition near the interface, which is similar to non-slip boundary conditions in Fluid-Structure Interaction (FSI) problems. The interface is captured using a Volume of Fluid (VOF) method, and a new boundary layer is built on the lighter phase side by an immersed boundary method. The designed boundary layer helps to reduce the spurious velocity caused by the imbalance of dynamic pressure gradient and density gradient and to prevent tearing of the interface due to the tangential velocity across the interface. The influence of time step, density ratio, and spatial resolution is studied in detail for two set of cases, steady stratified flow and convection of a high-density droplet, where direct comparison is possible to potential flow analysis (i.e. infinite Reynold's number). An initial study for a droplet splashing on a thin liquid film demonstrates applicability of the new solver to real-life applications. Detailed comparisons should be performed in the future for finite Reynold's number cases to fully demonstrate the improvements in accuracy and stability of high-density ratio two-phase flow simulations offered by the new method.

Effect of Mild Sway on the Interfacial Mass Transfer Rate of Stored Liquids

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Dibakar Rakshit ◽  
K. P. Thiagarajan ◽  
R. Narayanaswamy
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Degrees Of Freedom ◽  
Mass Transfer Rate ◽  
Constant Amplitude ◽  
Two Phase ◽  
Interfacial Mass Transfer ◽  
Different Temperatures ◽  
Slow Moving ◽  
Liquid Vapor

An exploratory study of two-phase physics was undertaken in a slow moving tank containing liquid. This study is under the regime of conjugate heat and mass transfer phenomena. An experiment was designed and performed to estimate the interfacial mass transfer characteristics of a slowly moving tank. The tank was swayed at varying frequencies and constant amplitude. The experiments were conducted for a range of liquid temperatures and filling levels. The experimental setup consisted of a tank partially filled with water at different temperatures, being swayed using a six degrees-of-freedom (DOF) motion actuator. The experiments were conducted for a frequency range of 0.7–1.6 Hz with constant amplitude of 0.025 m. The evaporation of liquid from the interface and the gaseous condensation was quantified by calculating the instantaneous interfacial mass transfer rate of the slow moving tank. The dependence of interfacial mass transfer rate on the liquid–vapor interfacial temperature, the fractional concentration of the evaporating liquid, the surface area of the liquid vapor interface and the filling level of the liquid was established. As sway frequency, filling levels, and liquid temperature increased, the interfacial mass transfer rate also increased. The interfacial mass transfer rate estimated for the swaying tank compared with the interfacial mass transfer rate of stationary tank shows that vibration increases the mass transfer.

Comparative Study of Two-Phase Gas-Liquid Flow in the Ejector Induced Upflow and Downflow Bubble Column

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Ajay Mandal ◽  
Gautam Kundu ◽  
Dibyendu Mukherjee
Keyword(s):  
Mass Transfer ◽  
Comparative Study ◽  
Aqueous Solutions ◽  
Bubble Column ◽  
Methyl Cellulose ◽  
Stable Operation ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Mass Transfer Coefficients ◽  
Frictional Pressure Drop

A comparative study has been made on the hydrodynamics and gas-liquid mass transfer performances of upflow and downflow bubble columns. Gas-liquid distributions in the column are made by an ejector system using liquid as motive fluid and gas is used as secondary fluid for both the cases. The two-phase hydrodynamic studies have been done with water and aqueous solutions of carboxy methyl cellulose at different concentrations and air as gas phase. The volumetric mass transfer coefficients have been measured by absorbing air-carbon dioxide mixture in aqueous solutions of sodium carbonate and bicarbonate. For downflow system, experiments are carried out at natural suction of air through the ejector; whereas for upflow system, air is forced through the secondary entrance of the ejector from a high pressure tank at any desired rate. The effect of gas and liquid flowrates on gas holdup, frictional pressure drop and mass transfer coefficients have been investigated. All the experiments have been performed in the homogeneous flow regime for a stable operation.

scholarly journals Secondary breakup of a drop at moderate Weber numbers

2015 ◽  
Vol 471 (2177) ◽  
pp. 20140930 ◽  
Author(s):  
Mohit Jain ◽  
R. Surya Prakash ◽  
Gaurav Tomar ◽  
R. V. Ravikrishna
Keyword(s):  
Numerical Simulations ◽  
Lognormal Distribution ◽  
Weber Number ◽  
Drop Size ◽  
Density Ratio ◽  
Transition Regime ◽  
Number Range ◽  
High Density Ratio ◽  
Secondary Breakup ◽  
Good Agreement

We present volume of fluid based numerical simulations of secondary breakup of a drop with high density ratio (approx. 1000) and also perform experiments by injecting monodisperse water droplets in a continuous jet of air and capture the breakup regimes, namely, bag formation, bag-stamen, multibag and shear breakup, observed in the moderate Weber number range (20–120). We observe an interesting transition regime between bag and shear breakup for We =80, in both simulations as well as experiments, where the formation of multiple lobes, is observed, instead of a single bag, which are connected to each other via thicker rim-like threads that hold them. We show that the transition from bag to shear breakup occurs owing to the rim dynamics which shows retraction under capillary forces at We =80, whereas the rim is sheared away with flow at We =120 thus resulting in a backward facing bag. The drop characteristics and timescales obtained in simulations are in good agreement with experiments. The drop size distribution after the breakup shows bimodal nature for the single-bag breakup mode and a unimodal nature following lognormal distribution for higher Weber numbers.

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