Mathematical modeling of the fluid flow in a mixing device for melting/dissolving solid particles in a liquid alloy

2014 ◽  
Vol 1611 ◽  
pp. 19-24
Author(s):  
J. A. Delgado-Álvarez ◽  
J. G. Perea-Zurita ◽  
A. Antonio-Morales ◽  
C. González-Rivera ◽  
M. A. Ramírez-Argáez
Keyword(s):  
Mathematical Model ◽  
Fluid Flow ◽  
Residence Time ◽  
Stokes Equations ◽  
Volume Of Fluid ◽  
Momentum Conservation ◽  
Operating Conditions ◽  
Solid Particles ◽  
Alloying Elements ◽  
Ansys Fluent

ABSTRACTA study of the fluid flow in a mixing device proposed to dissolve alloying elements in iron baths is performed through a mathematical model in order to predict the best operating conditions for a proper melting/dissolution of solid alloying particles. The mathematical model consists in the mass and momentum conservation equations (continuity and Turbulent Navier-Stokes equations), and the standard two k-epsilon turbulence model. The model is numerically solved in transient regime with the Volume of Fluid algorithm (VOF) to calculate the vortex shape. VOF is built-in the CFD (Computational Fluid Dynamics) software ANSYS FLUENT 14. A flow of metal enters tangentially in the mixing chamber of the proposed mixing device (taken from an open patent) to generate a vortex. The shape and height of the vortex reached in this chamber depends on several design variables, but in this work only the presence or absence of a barrier in the device is analyzed. Results are obtained on the vortex sizes and shapes, liquid flow patterns, turbulent structure, residence times of the particles of alloying elements added to the melt and mixing times (Residence time distribution curves) of two devices: one with a barrier and the other without this barrier. It is found that the presence of the barrier in the device increases turbulence, destroys the vortex, decreases the residence time of the particles, and decreases the volume of fluid in the device. Most of the features of the barrier are detrimental for mixing and inhibits melting/dissolution of the alloying elements. Then, it is suggested a device without the presence of barrier for better performance.

Geometrical Effects of Channel Configuration on the Performance of Membraneless Fuel Cells

2017 ◽  
Author(s):  
Hector Gomez ◽  
Usama Tohid ◽  
Arturo Pacheco-Vega
Keyword(s):  
Mathematical Model ◽  
Fuel Cell ◽  
Stokes Equations ◽  
Single Channel ◽  
Numerical Data ◽  
Operating Conditions ◽  
Straight Channel ◽  
Wavy Channel ◽  
Channel Configuration ◽  
The Impact

In this study, numerical simulations were performed to find the current-voltage distribution for a laminar flow-based membraneless fuel cell (LFFC). The system uses formic acid and oxygen as the fuel and oxidant, respectively, and has a Y-shaped geometry with two separate inlets that merge into a single channel. The main objective of this work is to analyze the impact of geometry and operating conditions on the performance of these devices. This is done by proposing a novel wavy-channel-based geometry for the side walls, along with planar top and bottom walls, and comparing the behavior of the corresponding system to that of LFFCs based on straight-channel walls. Special attention is placed on the effect of both the amplitude of the sinusoid and its wavelength on the performance of the device. The effect of flow rates — in the range of [200, 350] μL/min — is also studied. The mathematical model is formulated by considering the Navier-Stokes equations along with Butler-Volmer and Fick’s law. For each fuel-cell configuration, the governing equations are discretized and solved using finite elements, and the solutions given in terms of the polarization curves. The model was first verified using published numerical data for a straight-channel-based LFFC. The simulations show that the performance achieved by the device, based on the proposed wavy channel geometry, is slightly better than that of the LFFC with straight channel walls. On the other hand, higher flowrates significantly improve the power density of the device. Although the current mathematical model may be useful in a variety of applications, improvements on it are currently underway to account for the effects of potential distributions on ions within the flow channel, and results from it will be reported in the future.

3-D Numerical Simulation for Fuel Cell Performance

2002 ◽  
Author(s):  
Tien-Chien Jen ◽  
S. H. Chan ◽  
T. Z. Yan
Keyword(s):  
Fluid Flow ◽  
Fuel Cell ◽  
Stokes Equations ◽  
Current Density Distribution ◽  
Mass Transfer Process ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Fuel Cell Performance ◽  
Gas Channel

A 3-D mathematical model for the PEM fuel cell including gas channel has been developed to simulate fluid flow, current density distribution, and multi-component transport. In order to understand the developing fluid flow and mass transfer process inside the fuel cell channels, the conventional Navier-Stokes equations for gas channel, and volume-averaged Navier-Stokes equations for porous gas diffusers and catalyst layer are adopted individually in this study. A set of conservation equations and species concentration equations are solved numerically in a coupled gas channel and porous media domain using the vorticity-velocity method with power law scheme. Detailed development axial velocity and secondary flow fields at various axial positions in the entrance region are presented. Polarization curves under various operating conditions are demonstrated by solving the equations for electrochemical reactions and the membrane phase potential. Compared with experimental data from published literatures, numerical results of this model agree closely with experimental results. Finally, mass transport equations are solved at a preset condition of electrochemical reaction, and oxygen and hydrogen mole fraction distribution fields are displayed.

Design of a rotor for aluminum degassing assisted by physical and mathematical modeling

MRS Advances ◽  
2017 ◽  
Vol 2 (61) ◽  
pp. 3759-3764
Author(s):  
M. Ramírez-Argáez ◽  
D. Abreú López ◽  
C. González Rivera
Keyword(s):  
Mathematical Modeling ◽  
Physical Model ◽  
First Principles ◽  
Gas Flow ◽  
Momentum Conservation ◽  
Operating Conditions ◽  
Ansys Fluent ◽  
Improved Design ◽  
Water Saturated

ABSTRACTRecent studies on aluminum degassing [1, 2] show that although the impeller speed and the gas flow rate are important process variables in terms of the productivity and operational costs, the impeller design is also a key design parameter influencing the productivity and the quality of the aluminum in foundry shops. In this work, an improved design of an impeller is tested through a water physical model and mathematical modeling and its performance is compared against commercial designs of impellers. A full-scale water physical model of a batch aluminum degassing unit was used to test the impellers by using the same operating conditions (580 rpm and 40 liters per minute) and by performing deoxidation from water by purging nitrogen into the water saturated with oxygen (similar to the dehydrogenation). A mathematical model based on first principles of mass and momentum conservation equations was developed and solved numerically in the commercial CFD code ANSYS Fluent to describe the hydrodynamics of the system with the objective of explaining the deoxidation kinetics observed in the experiments. It has been found that the new impeller design shows a better performance than the commercial designs in terms of degassing kinetics for the conditions used in this study, which is explained since the new design promotes a flow dynamics that increases the pumping effect, creating a bigger pressure drop and fluid flow patterns which help to drag and distribute more evenly the bubbles in the entire ladle than the commercial designs.

scholarly journals Modeling of fiber bridging in fluid flow for well stimulation applications

2019 ◽  
Vol 17 (3) ◽  
pp. 671-686 ◽  
Author(s):  
Mehdi Ghommem ◽  
Mustapha Abbad ◽  
Gallyam Aidagulov ◽  
Steve Dyer ◽  
Dominic Brady
Keyword(s):  
Fluid Flow ◽  
Numerical Model ◽  
New Product Development ◽  
Flow Rate ◽  
Empirical Studies ◽  
Operating Conditions ◽  
Solid Particles ◽  
Fluid Viscosity ◽  
Design Guideline ◽  
Fiber Loading

AbstractAccurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated. Degradable materials (fibers and solid particles) have recently shown a good capability as fluid diversion to overcome the issues related to matrix stimulation. Despite the success achieved in the recent acid stimulation jobs stemming from the use of some products that rely on fiber flocculation as the main diverting mechanism, it was observed that the volume of the base fluid and the loading of the particles are not optimized. The current industry lacks a scientific design guideline because the used methodology is based on experience or empirical studies in a particular area with a particular product. It is important then to understand the fundamentals of how acid diversion works in carbonates with different diverting mechanisms and diverters. Mathematical modeling and computer simulations are effective tools to develop this understanding and are efficiently applied to new product development, new applications of existing products or usage optimization. In this work, we develop a numerical model to study fiber dynamics in fluid flow. We employ a discrete element method in which the fibers are represented by multi-rigid-body systems of interconnected spheres. The discrete fiber model is coupled with a fluid flow solver to account for the inherent simultaneous interactions. The focus of the study is on the tendency for fibers to flocculate and bridge when interacting with suspending fluids and encountering restrictions that can be representative of fractures or wormholes in carbonates. The trends of the dynamic fiber behavior under various operating conditions including fiber loading, flow rate and fluid viscosity obtained from the numerical model show consistency with experimental observations. The present numerical investigation reveals that the bridging capability of the fiber–fluid system can be enhanced by increasing the fiber loading, selecting fibers with higher stiffness, reducing the injection flow rate, reducing the suspending fluid viscosity or increasing the attractive cohesive forces among fibers by using sticky fibers.

Fluid Flow and Heat Transfer Simulations of the Cooling-Water Channel in a Tera-Hertz Radiation Detector

2012 ◽  
Author(s):  
Usama Tohid ◽  
Arturo Pacheco-Vega ◽  
Rodion Tikhoplav ◽  
Marcos Ruelas
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Laser Irradiation ◽  
Stokes Equations ◽  
Cooling System ◽  
Rectangular Channel ◽  
Operating Conditions ◽  
Channel Height ◽  
Flow And Heat Transfer ◽  
Direct Laser

Detailed numerical simulations have been carried out to find the velocity and temperature fields of a rectangular channel with large aspect-ratio. The channel under analysis is aimed to cool a thermo-chromic liquid crystal material (TLC) that is able to capture laser irradiation in the terahertz range. The overall objective of the cooling system is to maintain a nearly-homogeneous temperature of the TLC layer that is not exposed to the direct laser irradiation. The fluid flow and heat transfer simulations are carried out on the basis of three-dimensional versions of the Navier-Stokes equations, along with the energy equation, for an incompressible flow, to determine values of velocity, pressure and temperature inside the channel under different operating conditions. These values are then used to find, from a specific set, the value of the channel height that allows for the most uniform temperature distribution within the expected operating conditions. Results from this analysis indicate that, for all the inlet velocities considered, there is a common value of the channel height, that represents the optimum.

Quantification of Stator Blade Shape Influence on Non-Equilibrium Condensation in Low-Pressure Steam Turbine

2017 ◽  
Author(s):  
Giteshkumar Patel ◽  
Yogini Patel ◽  
Teemu Turunen-Saaresti ◽  
Aki Grönman
Keyword(s):  
Steam Turbine ◽  
Stokes Equations ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Droplet Growth ◽  
Condensation Process ◽  
Trailing Edge ◽  
Ansys Fluent ◽  
Pressure Surface ◽  
Blade Shape

The expansion of steam flow and the condensation phenomena in an LP turbine depend on both the flow passage shape and the operating conditions. This paper presents the quantification of the influence of local geometrical details of the steam turbine blade including blade surface tapering, dimple inclusion and trailing edge shapes on flow expansion and condensation phenomena. For this purpose, the wet-steam model of ANSYS FLUENT, based on the Eulerian-Eulerian approach, was used. The mixture of vapor and liquid phases was solved by compressible Reynolds-averaged Navier-Stokes equations. The low inlet superheat case of White et al. [1] which is conducted with planar stator cascade was used as reference for this study. Various modifications including blade trailing edge shapes, blade shape modification via blade pressure and suction surfaces’ tapering, and addition of dimple feature to the blade pressure surface were applied to the blade profile. The presented results revealed that the applied blade shape modifications affected nucleation and droplet growth processes, shock wave structures and entropy generation rates. The influence of blade shape on loss generation was presented by calculating the Markov energy loss coefficients. The presented analysis exhibits that the blade shape alteration influences the overall loss generation that occur due to the irreversible heat and mass transfer during the condensation process.

Modelling of the Influence of Vegetative Barrier on Concentration of PM10 and PM2,5 from Highway

2016 ◽  
Vol 821 ◽  
pp. 97-104
Author(s):  
Hynek Řezníček ◽  
Luděk Beneš
Keyword(s):  
Mathematical Model ◽  
Fluid Flow ◽  
Stokes Equations ◽  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Turbulent Fluid Flow ◽  
Vegetative Barrier ◽  
Orthogonal Grid ◽  
Different Types

The influence of different types of the vegetative barrier near a highway on dustiness was studied. Transport, dispersion and sedimentation of pollutants PM10 and PM2.5 emitted from the highway was numerically simulated. Mathematical model was based on the Navier-Stokes equations for turbulent fluid flow in Boussinesq approximation. The AUSM-MUSCL scheme in finite volume formulation on structured orthogonal grid was used.The influence of the shape of the barrier and of its obstructing properties on the concentration of pollutants was studied.

scholarly journals Effect of Mesh Type on Numerical Computation of Aerodynamic Coefficients of NACA 0012 Airfoil

2021 ◽  
Vol 87 (3) ◽  
pp. 31-39
Author(s):  
Mostafa Abobaker ◽  
Sogair Addeep ◽  
Lukmon O Afolabi ◽  
Abdulhafid M Elfaghi
Keyword(s):  
Numerical Computation ◽  
Unstructured Mesh ◽  
Subsonic Flow ◽  
Momentum Conservation ◽  
Operating Conditions ◽  
Computational Method ◽  
Governing Equations ◽  
Ansys Fluent ◽  
Lift And Drag ◽  
Naca 0012

Mesh type and quality play a significant role in the accuracy and stability of the numerical computation. A computational method for two-dimensional subsonic flow over NACA 0012 airfoil at angles of attack from 0o to 10o and operating Reynolds number of 6×106 is presented with structured and unstructured meshes. Steady-state governing equations of continuity and momentum conservation are solved and combined with k-v shear stress transport (SST-omega) turbulence model to obtain the flow. The effect of structured and unstructured mesh types on lift and drag coefficients are illustrated. Calculations are done for constant velocity and a range of angles of attack using Ansys Fluent CFD software. The results are validated through a comparison of the predictions and experimental measurements for the selected airfoil. The calculations showed that the structured mesh results are closer to experimental data for this airfoil and under studied operating conditions.

scholarly journals Application of modified Navier-Stokes equations to determine the unsteady force effects of a heterogeneous liquid

2019 ◽  
Vol 213 ◽  
pp. 02068
Author(s):  
František Pochylý ◽  
Roman Klas ◽  
Simona Fialová
Keyword(s):  
Stokes Equations ◽  
Tube Wall ◽  
Solid Particles ◽  
Navier Stokes ◽  
Liquid Volume ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Compliant Wall ◽  
Unsteady Force ◽  
Flexible Wall

The article is focused on calculating the force effects of a heterogeneous liquid on pipe walls. The solution is based on the concentration of solid particles. The base fluid is assumed to be incompressible. The solution will apply Euler-Lagrange's solution principle. Two tasks will be solved; with a rigid and a flexible tube wall. The solution will be carried out with non-stationary boundary conditions that were determined experimentally. Interaction of a heterogeneous fluid with a flexible wall assumes its deformation. The force effects will be solved by two methods; FSI simulation using ANSYS FEA solvers and CFD solvers ANSYS Fluent and using Navier-Stokes equations by direct integration through liquid volume. In this case, the unsteady term of the Navier-Stokes equations will be modified so that the Gauss Ostrogradsky theorem can be used to calculate the force. At the end, the force effects on the rigid and compliant wall will be compared with the unsteady turbulent flow of the heterogeneous liquid.

Simulation of free surface flows using volume of fluid method and genetic algorithm

2014 ◽  
Vol 16 (5) ◽  
pp. 1110-1124 ◽  
Author(s):  
N. Soleiman Beygi ◽  
H. Hakimzadeh ◽  
M. R. Chenaglou
Keyword(s):  
Genetic Algorithm ◽  
Fluid Flow ◽  
Free Surface ◽  
Stokes Equations ◽  
Volume Of Fluid ◽  
Free Surface Flows ◽  
Computational Domain ◽  
Tracking Method ◽  
Surface Tracking ◽  
Donor And Acceptor

In this paper, details of a numerical model development for simulation of fluid flows with moving free surface are presented. The unsteady incompressible Navier–Stokes equations on a fixed grid system are used to obtain velocity and pressure values in the computational domain and volume of fluid (VOF) method is used to determine free surface location. In order to reduce numerical smearing and increase accuracy of numerical modeling of fluid flow with moving free surface, a new free surface-tracking method is proposed. The proposed method is a combination of genetic algorithm and free surface tracking method based on donor and acceptor scheme. The specification of the new combinational method can be summarized in determining orientation vector and plane constant to represent the free surface orientation in each cell. The proposed algorithm can be easily used in any unstructured grids. In this method, the fluid flow equations are explicitly discretized with the finite volume method and the projection method is used to determine the velocity and pressure magnitude in computational domain. Validity of the new solution algorithm is demonstrated through its application to the dam break and the bore motion examples.

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