The Effects of Hydrodynamics Characteristics on Mass Transfer During Droplet Formation Using Computational Approach

2006 ◽  
Author(s):  
A. Javadi ◽  
M. Taeibi-Rahni ◽  
D. Bastani ◽  
K. Javadi
Keyword(s):  
Mass Transfer ◽  
Stokes Equations ◽  
Computational Simulation ◽  
Mass Transfer Rate ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Two Phases ◽  
Expansion Model

For the reason that flow expansion model (developed in our previous work) for evaluating mass transfer during droplet formation involves with manifest hydrodynamic aspects, in this research computational simulation of this phenomenon was done for characterization of hydrodynamics effects on the mass transfer during droplet formation. For this purpose, an Eulerian volume tracking computational code based on volume of fluid (VOF) method was developed to solve the transient Navier-Stokes equations for the axisymmetric free-boundary problem of a Newtonian liquid that is dripping vertically and breaking as drops into another immiscible Newtonian fluid. The effects of hydrodynamics effects on the mass transfer during droplet formation have been discussed in the three features, including: 1- The intensity of the interaction between two phases 2-The strength and positions of the main vorticities on the nozzle tip 3-The effects of local interfacial vorticities (LIV). These features are considered to explain the complexities of drop formation mass transfer between Ethyl Acetoacetate (presaturated with water) as an organic dispersed phase and water as continuous phase for two big and small nozzle sizes (0.023 and 0.047 cm, ID) which have different level of mass transfer rate particularly in first stages of formation time.

Optimization of Propulsion Kinematics of a Flexible Foil Using Integrated CFD-CSD Simulations

2012 ◽  
Author(s):  
Jiho You ◽  
Jinmo Lee ◽  
Donghyun You
Keyword(s):  
Structural Dynamics ◽  
Immersed Boundary Method ◽  
Stokes Equations ◽  
Computational Simulation ◽  
Moving Boundaries ◽  
Navier Stokes ◽  
Immersed Boundary ◽  
Navier Stokes Equations ◽  
Simulation Methodology ◽  
Computational Structural Dynamics

A computational simulation methodology, which combines a computational fluid dynamics technique and a computational structural dynamics technique, is employed to design a deformable foil of which kinematics is inspired by the propulsive motion of a fin or a tail of fish and cetacean. The unsteady incompressible Navier-Stokes equations are solved using a second-order accurate finite-difference method and an immersed-boundary method to effectively impose boundary conditions on complex moving boundaries. A finite-element-based structural dynamics solver is employed to compute the deformation of the foil due to interaction with fluid. A phase angle between pitching and heaving motions as well as the flexibility of the foil, which is represented by the Youngs modulus are varied to find out how these factors affect the propulsion efficiency.

Experiment and Computer Modelling of the Filling Flows in Pressure Die Casting

1992 ◽  
Author(s):  
J. Hu ◽  
S. Ramlingam ◽  
G. Meyerson ◽  
E. R. G. Eckert ◽  
R. J. Goldstein
Keyword(s):  
Flow Visualization ◽  
Stokes Equations ◽  
Computer Modelling ◽  
Die Casting ◽  
Continuous Phase ◽  
Navier Stokes ◽  
Liquid Droplets ◽  
Navier Stokes Equations ◽  
Free Surfaces ◽  
Pressure Die Casting

Abstract Until recently, computer simulation of filling flows in die casting have been focused on the determination of the free surfaces of injected liquid and has had difficulties to relate the flows with the formation of casting porosity. Flow visualization in scaled experiments indicates that the liquid has very complicated surfaces and that, in many cases, the surfaces break up and create a mixture zone with liquid droplets and air. This is especially true in pressure die casting where liquid metal is injected at a speed in order of 100 m/s and at a pressure up to 100 atm. The Reynolds number in the process could be above 105 and the Weber number above 102. Surface tension is far from sufficiently strong to sustain disturbance growth due to various instabilities. It is hard to keep the liquid as a separate continuous phase. Based on flow visualization experiments, a mathematical model is proposed as an alternative and effective simplification to the traditional tracing methods. Instead of determining the continuous free surfaces, the model tries to predict distributions of mass fraction of the injected liquid by solving a partial differential equation of mass transport together with the Navier-Stokes equations. Appropriate unsteady schemes of a finite difference analysis have been developed and are described in the paper. Results with an uniform straight injection into a die cavity are presented, which have re-created the filling patterns of the flows in experiments.

LARGE EDDY SIMULATION OF SEDIMENT-LADEN TURBULENT FLOW IN AN OPEN CHANNEL

2008 ◽  
Vol 22 (16) ◽  
pp. 2517-2527 ◽  
Author(s):  
ZHANHONG WAN ◽  
ZHILIN SUN ◽  
ZHENJIANG YOU ◽  
QIYAN ZHANG
Keyword(s):  
Large Eddy Simulation ◽  
Open Channel ◽  
Stokes Equations ◽  
Sediment Concentration ◽  
Continuous Phase ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Concentration Equation

Sediment transport in fully developed turbulent open channel flow has been investigated using large eddy simulation (LES) of the incompressible Navier–Stokes equations. The scalar transport equation of the sediments concentration, which is based on the continuous-phase approach, is adopted. The settling process is taken into account with a modified settling velocity appearing in the sediment concentration equation. A Smagorinsky model allowing for the interaction between the fluid flow and the suspended sediment is used to simulate the unresolved, subgrid scale terms. The LES results are compared with the experimental data, and good general agreement is achieved.

scholarly journals Transport coefficients for low and high-rate mass transfer along a biological horizontal cylinder

2006 ◽  
Vol 10 (2) ◽  
pp. 441-447
Author(s):  
Alberto A. Barreto ◽  
Mauri Fortes ◽  
Wanyr R. Ferreira ◽  
Luiz C. A. Crespo
Keyword(s):  
Mass Transfer ◽  
Stokes Equations ◽  
Transport Coefficients ◽  
Horizontal Cylinder ◽  
Transport Processes ◽  
High Rate ◽  
Navier Stokes ◽  
Transfer Coefficients ◽  
Navier Stokes Equations ◽  
Drying Conditions

Knowledge of heat and mass transfer coefficients is essential for drying simulation studies or design of food and grain thermal processes, including drying. This work presents the full development of a segregated finite element method to solve convection-diffusion problems. The developed scheme allows solving the incompressible, steady-state Navier-Stokes equations and convective-diffusive problems with temperature and moisture dependent properties. The problem of simultaneous energy, momentum and species transfer along an infinite, horizontal cylinder under drying conditions in forced convection is presented, considering conditions normally found in biological material thermal treatment or drying. Numerical results for Nusselt and Sherwood numbers were compared against available empirical expressions; the results agreed within the associated experimental errors. For high rate mass transport processes, the proposed methodology allows to simulate drying conditions involving wall convective mass flux by a simple inclusion of the appropriated boundary conditions.

scholarly journals Computational simulation of a single Taylor bubble rising in a vertical column with stagnant liquid

2021 ◽  
Vol 9 (2B) ◽  
Author(s):  
Francisco Rogerio Teixeira Nascimento
Keyword(s):  
Open Source Software ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Computational Simulation ◽  
Navier Stokes ◽  
Vertical Column ◽  
Navier Stokes Equations ◽  
Taylor Bubble ◽  
Two Fluids ◽  
Bubble Rising

This work presents a computational simulation of a single Taylor bubble rising in a vertical column of stagnant liquid. The computational simulation was based on the Navier-Stokes equations for isothermal, incompressible, and laminar flow, solved by using the open source software OpenFOAM. The two fluids were assumed immiscible. The governing equations were discretized by the volume-of-fluid (VOF) method and solved using the Gauss iteration method. Parametric mesh was used in order to improve the modeling of curvilinear geometry. Numerical solutions were obtained for the rise velocities and shapes of the bubbles which are in excellent agreement with experimental data and correlations from literature.

Computational Mass Transfer Based on CFD with OpenFOAM in Single-Phase Flow

2011 ◽  
Vol 145 ◽  
pp. 134-137
Author(s):  
Xiao Guang Yang ◽  
Hong Xing Dong ◽  
Xing Hua Zhang
Keyword(s):  
Mass Transfer ◽  
Single Phase ◽  
Chemical Engineering ◽  
Stokes Equations ◽  
Conservation Equation ◽  
Navier Stokes ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Navier Stokes Equations ◽  
Computational Fluid Dynamics Cfd

In this work computational mass transfer was investigated based on computational fluid dynamics (CFD) in single-phase flow with the open-source software, OpenFOAM. OpenFOAM supplied a kind of open structure, which made it convenient that a suitable physical model was added with CFD equations according to the problem. In order to compute mass transfer with fluid flow, the component conservation equation was listed with Navier-Stokes equations. With the equations, a pipe flow with mass transfer was simulated on the assumption that the fluid density is constant by our solver which was developed based on OpenFOAM. By the simulation, the pressure, velocity and component mass fraction can be easily obtained at different time and position, which is very important for the analysis of equipments in chemical engineering. Although some details need to be considered such as the change of density with composition, the boundary conditions and the affect of complex shape, computational mass transfer with OpenFOAM has showed very large potential to be applied in industry.

scholarly journals Growth and spectra of gravity–capillary waves in countercurrent air/water turbulent flow

2015 ◽  
Vol 777 ◽  
pp. 245-259 ◽  
Author(s):  
Francesco Zonta ◽  
Alfredo Soldati ◽  
Miguel Onorato
Keyword(s):  
Stokes Equations ◽  
Capillary Waves ◽  
Turbulence Theory ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Generation Process ◽  
Navier Stokes Equations ◽  
Interface Waves ◽  
Two Phases ◽  
Wave Induced

Using direct numerical simulation of the Navier–Stokes equations, we analyse the dynamics of the interface between air and water when the two phases are driven by opposite pressure gradients (countercurrent configuration). The Reynolds number ($\mathit{Re}_{{\it\tau}}$), the Weber number ($\mathit{We}$) and the Froude number ($\mathit{Fr}$) fully describe the physical problem. We examine the problem of the transient growth of interface waves for different combinations of physical parameters. Keeping$\mathit{Re}_{{\it\tau}}$constant and varying$\mathit{We}$and$\mathit{Fr}$, we show that, in the initial stages of the wave generation process, the amplitude of the interface elevation${\it\eta}$grows in time as${\it\eta}\propto t^{2/5}$. The wavenumber spectra,$E(k_{x})$, of the surface elevation in the capillary range are in good agreement with the predictions of wave turbulence theory. Finally, the wave-induced modification of the average wind and current velocity profiles is addressed.

scholarly journals Numerical study of the thermosolutal convection in a 3-D cavity submitted to cross gradients of temperature and concentration

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1923-1933
Author(s):  
Meriem Ouzaouit ◽  
Btissam Abourida ◽  
Lahoucine Belarche ◽  
Hicham Doghmi ◽  
Mohamed Sannad
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Stokes Equations ◽  
Numerical Study ◽  
Thermosolutal Convection ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Wide Range ◽  
Conservation Of Momentum ◽  
Prandtl Numbers

This study is a contribution to the numerical study of the thermosolutal convection in a 3-D porous cavity filled with a binary fluid submitted to cross gradients of temperature and concentration. The Navier-Stokes equations, mass and energy governing the physical problem are discretized by the finite volume method. The equations of conservation of momentum coupled with the continuity equation are solved using the SIMPLEC algorithm, then the obtained system is solved using the implicit alternating directions method. The numerical simulations, presented here, correspond to a wide range of thermal Rayleigh number (103< Ra < 106) and buoyancy ratio (1 < N < 12). The Lewis and Prandtl numbers were fixed respectively at 5 and 0.71 and the sections dimension ? = D / H = 0.4. The temperature distribution, the flow pattern and the average heat and mass transfer are examined. The obtained results show significant changes in terms of heat and mass transfer, by proper choice of the governing parameters.

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