scholarly journals CFD-based numerical simulation of cyclone separator for separating stigmas from petals of saffron

2020 ◽  
Author(s):  
Javad Nemati ◽  
Babak Beheshti ◽  
Ali Mohammad Borghei
Keyword(s):  
Separation Efficiency ◽  
Solid Phase ◽  
Equations Of Motion ◽  
Fluid Phase ◽  
Reynolds Stress Model ◽  
Continuous Phase ◽  
Solid Particles ◽  
Inlet Section ◽  
Ansys Fluent ◽  
Discrete Phase

This study numerically modeled the flow of a fluid (air) and solid particles (saffron flower) inside a cyclone using the finite volume method (FVM) in ANSYS Fluent. The continuous phase was simulated under steady state conditions, as the initial condition, using the Reynolds Stress Model (RSM) for turbulence at three constant inlet air velocities of 1.5 m/s, 2.5 m/s, and 3.5 m/s over the inlet section. One-way coupling was assumed to govern all numerical analyses. The fluid phase and particles were treated as the continuous medium (within a Eulerian framework) and discrete phase (within a Lagrangian framework), respectively. The equations governing the gas phase included the compressible Navier–Stokes and the conservation of mass. The discrete phase equations included the equations of motion for three different particles including petals, stigmas, and anthers. According to the numerical results, the cyclone separation efficiency was calculated, and the static pressure and velocity contours were plotted. The results showed the capability of the CFD-based simulation for an accurate demonstration of the behavior of the fluid–solid phase. Accordingly, it can be used to predict the efficiency of stigma separation from petals of saffron using airflow in the cyclone. According to the results, the highest cyclonic separation efficiency of 89% was achieved at an inlet air velocity of 3.5 m/s, which was very close to the experimental data.

Comparative Assessment of Turbulence Models for Prediction of Flow-Induced Corrosion Damages

2011 ◽  
Author(s):  
Kaushik Das ◽  
Debashis Basu ◽  
Todd Mintz
Keyword(s):  
Corrosion Rate ◽  
Cross Sections ◽  
Volume Fraction ◽  
Solid Phase ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Continuous Phase ◽  
Comparative Assessment ◽  
Solid Particles ◽  
Protective Film

The present study makes a comparative assessment of different turbulence models in simulating the flow-assisted corrosion (FAC) process for pipes with noncircular cross sections and bends, features regularly encountered in heat exchangers and other pipeline networks. The case study investigates material damage due to corrosion caused by dissolved oxygen (O2) in a stainless steel pipe carrying an aqueous solution. A discrete solid phase is also present in the solution, but the transport of the solid particles is not explicitly modeled. It is assumed that the volume fraction of the solid phase is low, so it does not affect the continuous phase. Traditional two-equation models are compared, such as isotropic eddy viscosity, standard k-ε and k-ω models, shear stress transport (SST) k-ω models, and the anisotropic Reynolds Stress Model (RSM). Computed axial and radial velocities, and turbulent kinetic energy profiles predicted by the turbulence models are compared with available experimental data. Results show that all the turbulence models provide comparable results, though the RSM model provided better predictions in certain locations. The convective and diffusive motion of dissolved O2 is calculated by solving the species transport equations. The study assumes that solid particle impingement on the pipe wall will completely remove the protective film formed by corrosion products. It is also assumed that the rate of corrosion is controlled by diffusion of O2 through the mass transfer boundary layer. Based on these assumptions, corrosion rate is calculated at the internal pipe walls. Results indicate that the predicted O2 corrosion rate along the walls varies for different turbulence models but show the same general trend and pattern.

CFD Study on must of Grapes Separation in a Hydrocyclone

2013 ◽  
Vol 837 ◽  
pp. 645-650
Author(s):  
Petru Cârlescu ◽  
Ioan Tenu ◽  
Marius Baetu ◽  
Radu Rosca
Keyword(s):  
Cfd Simulation ◽  
Reynolds Stress Model ◽  
Continuous Phase ◽  
Solid Particles ◽  
Advanced Degree ◽  
Separation And Purification ◽  
Discrete Phase Model ◽  
Flow Rates ◽  
Discrete Phase ◽  
Simulation And Experiment

Abstract. Hydrocyclones are increasingly used in the food industry for various separation and purification. In this paper, an optimization was made to design a hydrocyclone model using CFD (Computational Fluid Dynamics). CFD simulation is performed with FLUENT software by coupling the Reynolds Stress Model (RSM) for must of grapes flow with Discrete Phase Model (DPM) for solid particles trajectory. Coupling of discrete phase (particles) and continuous phase (must of grapes) in the mathematical model is set so that the continuous phase to influence discrete phase. Tracking particles traiectory in this hydrocyclone allows advanced degree is separation so obtained to the maximum particle size approaching the size of a yeast cell 10 μm, without separating them. Hydrocyclone dimensional designed simulation was performed and analyzed on an experimental pilot plant for three different must flow rates supply. Introduced particle flow rates simulation and experiment does not exceed 10% of the must flow rates. The degree of separation obtained is in agreement with experimental data.

scholarly journals MODELING COMPUTATIONAL FLUID DYNAMICS OF MULTIPHASE FLOWS IN ELBOW AND T-JUNCTION OF THE MAIN GAS PIPELINE

Transport ◽  
2019 ◽  
Vol 34 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Yaroslav Doroshenko ◽  
Julia Doroshenko ◽  
Vasyl Zapukhliak ◽  
Lyubomyr Poberezhny ◽  
Pavlo Maruschak
Keyword(s):  
Natural Gas ◽  
Multiphase Flows ◽  
Linear Part ◽  
Erosive Wear ◽  
Gas Pipeline ◽  
Solid Particles ◽  
Ansys Fluent ◽  
Gas Main ◽  
Discrete Phase ◽  
Main Gas Pipeline

The research was performed in order to obtain the physical picture of the movement of condensed droplets and solid particles in the flow of natural gas in elbows and T-junctions of the linear part of the main gas pipeline. 3D modeling of the elbow and T-junction was performed in the linear part of the gas main, in particular, in places where a complex movement of multiphase flows occurs and changes its direction. In these places also occur swirls, collisions of discrete phases in the pipeline wall, and erosive wear of the pipe wall. Based on Lagrangian approach (Discrete Phase Model – DPM), methods of computer modeling were developed to simulate multiphase flow movement in the elbow and T-junction of the linear part of the gas main using software package ANSYS Fluent R17.0 Academic. The mathematical model is based on solving the Navier–Stokes equations, and the equations of continuity and discrete phase movement closed with Launder–Sharma (k–e) two-parameter turbulence model with appropriate initial and boundary conditions. In T-junction, we simulated gas movement in the run-pipe, and the passage of the part of flow into the branch. The simulation results were visualized in postprocessor ANSYS Fluent R17.0 Academic and ANSYS CFD-Post R17.0 Academic by building trajectories of the motion of condensed droplets and solid particles in the elbow and T-junction of the linear part of the gas main in the flow of natural gas. The trajectories were painted in colors that match the velocity and diameter of droplets and particles according to the scale of values. After studying the trajectories of discrete phases, the locations of their heavy collision with the pipeline walls were found, as well as the places of turbulence of condensed droplets and solid particles. The velocity of liquid and solid particles was determined, and the impact angles, diameters of condensed droplets and solid particles in the place of collision were found. Such results provide possibilities for a full and comprehensive investigation of erosive wear of the elbow and T-junction of the linear part of the gas main and adjacent sections of the pipeline, and for the assessment of their strength and residual life.

Dispersion of Particles Coming Out of the Mouth While Speaking in a Ventilated Indoor Environment

2021 ◽  
Author(s):  
Morteza Ali Masoomi ◽  
Mazyar Salmanzadeh ◽  
Goodarz Ahmadi
Keyword(s):  
Coming Out ◽  
Indoor Environment ◽  
Distribution Systems ◽  
Ventilation System ◽  
Field Studies ◽  
Continuous Phase ◽  
Ansys Fluent ◽  
Air Mixing ◽  
Long Time ◽  
Discrete Phase

Abstract Breathing air that contains virus-infected droplets is the leading cause of Covid-19 transmission. Sneezing, coughing, breathing, and talking of an infected person would generate aerosolized droplets that carry the coronavirus. Earlier research efforts have focused on sneezing and coughing as the primary transmission sources. New experiments and field studies have shown that breathing and talking are also effective mechanisms in spreading viruses. In this article, the dispersion of particles/droplets during speaking is studied. COVID-19 virus is about 120 nanometers and is suspended in saliva or mucus droplets emitted by an injected person. These droplets evaporate in a fraction of a second as they enter the environment and reduce in size. However, the droplets’ viral content remains the same as they move by the room’s airflow. The particles from sneezing and coughing are larger than those released by speaking. As the particles/droplets are small, the effect of gravity is small, and they remain suspended in the air for a long time. Also, being small makes them more easily penetrate the respiratory passages. Using the computational fluid dynamics method in conjunction with the ANSYS-Fluent software, the particle transport and dispersion were simulated. The Eulerian approach modeled the airflow (continuous phase), and the Lagrangian approach modeled the particle (discrete phase) movements. This study also investigated the ventilation system’s effects on the distribution of particles in the indoor environment. The displacement and mixing air distribution systems were considered. Simulation results showed that droplets remain suspended in the room for a relatively long time after evaporation. Large particles were deposited quickly, and a significant percentage of smaller particles were removed by the ventilation system. The concentration of particles in the upper half of the room was also quite low for the mixing ventilation system. This was due to the fact that the room air mixing system is relatively uniform; this uniformity of airflow caused the particles to get trapped quickly. Also, for the displacement system, the room airflow was not uniform; these particles were then dispersed in the room and spent more time in the indoor environment.

scholarly journals CFD Modeling of Hydrocyclones—A Study of Efficiency of Hydrodynamic Reservoirs

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 118 ◽  
Author(s):  
Marvin Durango-Cogollo ◽  
Jose Garcia-Bravo ◽  
Brittany Newell ◽  
Andres Gonzalez-Mancera
Keyword(s):  
Pressure Drop ◽  
Separation Efficiency ◽  
Collection Efficiency ◽  
Saddle Points ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Cfd Modeling ◽  
Eddy Simulation ◽  
Discrete Phase ◽  
Rsm Model

The dynamics of hydrocyclones is complex, because it is a multiphase flow problem that involves interaction between a discrete phase and multiple continuum phases. The performance of hydrocyclones is evaluated by using Computational Fluid Dynamics (CFD), and it is characterized by the pressure drop, split water ratio, and particle collection efficiency. In this paper, a computational model to improve and evaluate hydrocyclone performance is proposed. Four known computational turbulence models (renormalization group (RNG) k- ε , Reynolds stress model (RSM), and large-eddy simulation (LES)) are implemented, and the accuracy of each for predicting the hydrocyclone behavior is assessed. Four hydrocyclone configurations were analyzed using the RSM model. By analyzing the streamlines resulting from those simulations, it was found that the formation of some vortices and saddle points affect the separation efficiency. Furthermore, the effects of inlet width, cone length, and vortex finder diameter were found to be significant. The cut-size diameter was decreased by 33% compared to the Hsieh experimental hydrocyclone. An increase in the pressure drop leads to high values of cut-size and classification sharpness. If the pressure drop increases to twice its original value, the cut-size and the sharpness of classification are reduced to less than 63% and 55% of their initial values, respectively.

DYNAMIC SIMULATION OF PRESSURE DRIVEN FLOW OF FLUIDS WITH SUSPENDED FERROUS PARTICLES IN A MICRO CHANNEL UNDER MAGNETIC FIELD

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4890-4897
Author(s):  
SINAN OZCAN ◽  
CAHIT A. EVRENSEL ◽  
MARK A. PINSKY ◽  
ALAN FUCHS
Keyword(s):  
Magnetic Field ◽  
Pressure Gradient ◽  
Uniform Magnetic Field ◽  
Computational Study ◽  
Fluid Phase ◽  
Continuous Phase ◽  
Micro Channel ◽  
Carrier Fluid ◽  
Discrete Phase ◽  
Pressure Driven Flow

This computational study focuses on the dynamics of individual ferrous particles and the flow of the incompressible Newtonian fluid under the effect of an externally applied magnetic field and pressure gradient in a two-dimensional micro channel with smooth walls. The particle dynamics is simulated as a discrete phase using MATLAB code and the fluid flow is solved as a continuous phase using Computational Fluid Dynamics Software FLUENT. Interaction between the particle and fluid phases are included as hydrodynamic forces predicated by the fluid phase simulation and updated particle locations determined by the particle phase solution under non-uniform magnetic field. Non-uniform magnetic field forces the particles to move to poles of the magnet, and results in their accumulation. This causes drastic change on the continuous phase flow and pressure distribution, which in turn influences the particle motion. Predicted dynamics of the suspended ferrous particles under magnetic field and flow of the carrier fluid with pressure gradient is in reasonably well agreement with previous work. The results show that non-uniform magnetic field generated by externally placed magnets can be used to control the locations of the particles and flow of the fluid in a micro channel.

Equations of Motion of Two-Phase Variable Mass Systems With Solid Base

1994 ◽  
Vol 61 (4) ◽  
pp. 855-860 ◽  
Author(s):  
F. O. Eke ◽  
Song-Min Wang
Keyword(s):  
Solid Phase ◽  
Equations Of Motion ◽  
Variable Mass ◽  
Fluid Phase ◽  
Solid Base ◽  
Phase Variable ◽  
Dynamical Equations ◽  
Two Phase ◽  
Attitude Stability ◽  
Variable Mass Systems

This paper develops dynamical equations for variable mass systems that can be viewed, at any given instant, as comprising a solid phase and a fluid phase. The equations of translational and rotational motion are presented, and several versions of each are given. It is shown that some versions have major advantages over others because they involve parameters that are relatively easy to estimate in practical problems, and make close-form solutions possible without the usual penalty of drastic simplifying assumptions. A simple rocket example is presented, and shows that instability cannot be ruled out for such systems. It is shown that system and combustion chamber geometry play a crucial role in the attitude stability of such systems.

Development and Validation of Two-Way Fluid-Particle Coupling in Turbulent Flows for a CFD Code

2013 ◽  
Author(s):  
Jianjun Xiao ◽  
Anatoly Svishchev ◽  
Thomas Jordan
Keyword(s):  
Experimental Data ◽  
Turbulent Flows ◽  
Gas Flow ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Continuous Phase ◽  
Particle Dispersion ◽  
Solid Particles ◽  
Particle Volume ◽  
Discrete Phase

A Lagrangian approach was used in CFD code GASFLOW to describe particle dispersion in turbulent flows. One-way coupling between fluid and particle is often used due to its simplicity of implementation. However, in case of higher particle volume fraction or mass loading in the continuous phase, one-way coupling is not sufficient to simulate the interaction between fluid and particles. For instance, the liquid droplets released by a spray nozzle in the nuclear power plant will lead to a strong gas entrainment, and consequently impact the gas flow field. When the volume fraction of the discrete phase is not negligible compared to the continuous phase, the interaction between the continuous fluid and dispersed phase becomes significant. Two-way momentum coupling between fluid and solid particles was developed in CFD code GASFLOW. The dynamics of the discrete particles was solved by an implicit algorithm to ensure the numerical stability. The contribution of all particles to a fluid cell was treated as the source term to the continuous phase which was solved with Arbitrary-Lagrangian-Eulerian (ALE) methodology. In order to verify and validate the code, the calculation results were then compared to theoretical results, predictions of other CFD codes and experimental data. Predictions compared favorably with the experimental data. It indicates that the effect of two-way coupling is significant when the volume fraction of discrete phase is not negligible. Two-way coupling of mass, energy and turbulence will be implemented in the future development of the GASFLOW code.

Modeling Welding by Surface Heating

1992 ◽  
Vol 114 (4) ◽  
pp. 439-449 ◽  
Author(s):  
I. C. Sheng ◽  
Y. Chen
Keyword(s):  
Energy Equation ◽  
Solid Phase ◽  
Equations Of Motion ◽  
Fluid Phase ◽  
Equation Of Motion ◽  
Avrami Equation ◽  
Moving Heat Source ◽  
Stress Evolution ◽  
Fluid Mixture ◽  
Traction Boundary Conditions

A mathematical model has been developed in describing the temperature distribution, the flow of the molten fluid and the stress field in the solid during welding. In modeling the properties of the material during welding, the solid phase is assumed to behave as a thermoviscoplastic solid obeying Bodner-Partom/Walker type constitutive equation, whereas the fluid phase as a thermoviscous incompressible fluid. Three regions exist: pure solid, pure fluid, and the transition (solid-fluid mixture). In the formulation of the boundary value problem, the energy equation is coupled to the equation of motion through the terms of mechanical work and the latent heat of the phases, whereas the equations of motion of the solid and the fluid are decoupled. Appropriate thermal and traction boundary conditions are detailed in the text. Phase transformation activities during cooling are monitored by CCT diagram and Avrami equation. An arbitrary Lagrangian and Eulerian method is used to accommodate the kinematic description of both the solid and the fluid phases. A representative plane perpendicular to the moving heat source is analyzed. Results of sample calculations are presented to show the temperature and the stress evolution in time. Residual stress and microstructure patterns are presented.

scholarly journals Numerical Prediction of Collection Efficiency of a Personal Sampler Based on Cyclone Principle

2014 ◽  
Author(s):  
Antara Badhan ◽  
Luz Bugarin ◽  
Shaolin Mao
Keyword(s):  
Fluid Dynamics ◽  
Boundary Condition ◽  
Collection Efficiency ◽  
Numerical Approach ◽  
Reynolds Stress Model ◽  
Continuous Phase ◽  
Design Parameters ◽  
Ansys Fluent ◽  
Outflow Boundary Condition ◽  
High Efficient

A personal bio-aerosol sampler is a self-contained, operation flexible, high-efficient device for indoor air quality (IAQ) and health risk exposure monitoring and measurement. Bio-aerosols such germ-laden viruses, microbial species, airborne microorganisms and volatile organic compounds (VOC) are sucked into the sampler and are deposited on the inner wall surface based on cyclone principal. The major concern with bio-aerosol samplers is the collection efficiency. In this study, we use computational fluid dynamics (CFD) tools to evaluate key design parameters, specifically the inlet tube angle and collection tube inner wall roughness. 3D incompressible turbulent flow is simulated using commercial software ANSYS FLUENT. Reynolds stress model (RSM) is used to investigate the turbulence effect with the following boundary conditions (velocity-inlet boundary condition at inlet, outflow boundary condition at outlet and no slip at walls). The numerical approach for air-aerosol interaction is based on an Eulerian-Lagrangian fluid dynamics framework, where the particles or droplets trajectories are computed in a Lagrangian method (discrete phase element) and then conjugate these particles to the continuous phase in the Eulerian frame. The variation of inlet angle affects the collection efficiency of the cyclone separator. In addition, the flow characterizations with different velocity fluctuation profiles validate the continuous phase model. The development and evolution of the vortex core region for the axial velocity are obtained and evaluated in the simulation of the cyclonic flow.

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