Validation of a 2D CFD Model for Hydrodynamics' Studies in CIJ Mixers

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Ricardo J. Santos ◽  
André M. Teixeira ◽  
Ertugrul Erkoç ◽  
Mohamed Sultan ◽  
Anna M Karpinska ◽  
...  
Keyword(s):  
Flow Field ◽  
Impinging Jets ◽  
Cfd Model ◽  
Operational Parameters ◽  
3D Flow ◽  
Cfd Simulations ◽  
Mixing Chamber ◽  
Validity Range ◽  
Computational Fluid Dynamics Cfd ◽  
2D Model

A 2D model of a confined impinging jets mixer having the same geometry of the mixing chamber of a Reaction Injection Moulding, RIM, machine is introduced for the flow field simulation in a Computational Fluid Dynamics, CFD, code. From the CFD simulations the flow field structures and dynamics are clearly established. In addition, the numerical parameters affecting the 2D model simulations are studied, setting for each parameter a validity range. The 2D model is validated and used in the study of some operational parameters: the Reynolds number, the Froude number and the momentum ratio between the opposed jets. The validation of the CFD simulations is also made by comparison with experimental results. The limitations of the 2D model, for simulating the actual 3D flow field, are assessed; from the 2D/3D comparison, it is clearly shown that the introduced model can predict the main flow field features.

CFD Simulations of the Cold Neutron Source at the OPAL Reactor

2020 ◽  
Author(s):  
James L Spedding ◽  
Mark Ho ◽  
Weijian Lu
Keyword(s):  
Neutron Source ◽  
Cold Neutron ◽  
Operating Conditions ◽  
Convergence Time ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Cold Neutron Source ◽  
Order Of Magnitude ◽  
Computational Fluid Dynamics Cfd ◽  
Polyhedral Mesh

Abstract The Open Pool Australian Light-water (OPAL) reactor Cold Neutron Source (CNS) is a 20 L liquid deuterium thermosiphon system which has performed consistently but will require replacement in the future. The CNS deuterium exploits neutronic heating to passively drive the thermosiphon loop and is cryogenically cooled by forced convective helium flow via a heat exchanger. In this study, a detailed computational fluid dynamics (CFD) model of the complete thermosiphon system was developed for simulation. Unlike previous studies, the simulation employed a novel polyhedral mesh technique. Results demonstrated that the polyhedral technique reduced simulation computational requirements and convergence time by an order of magnitude while predicting thermosiphon performance to within 1% accuracy when compared with prototype experiments. The simulation model was extrapolated to OPAL operating conditions and confirmed the versatility of the CFD model as an engineering design and preventative maintenance tool. Finally, simulations were performed on a proposed second-generation CNS design that increases the CNS moderator deuterium volume by 5 L, and results confirmed that the geometry maintains the thermosiphon deuterium in the liquid state and satisfies the CNS design criteria.

Vibratory Finishing of Immobilized Cylinders

2012 ◽  
Vol 565 ◽  
pp. 278-283 ◽  
Author(s):  
Stephen Wan ◽  
Takashi Sato ◽  
Andry Hartawan
Keyword(s):  
Surface Roughness ◽  
Flow Field ◽  
Granular Flow ◽  
Flow Direction ◽  
General Purpose ◽  
Vibratory Finishing ◽  
Cfd Simulations ◽  
Dense Granular Flow ◽  
The Media ◽  
Computational Fluid Dynamics Cfd

We report preliminary results from an on-going study investigating the effect of fixing workpieces within the media flow field contained in a typical vibratory finishing bowl. To this end, we studied the surface roughness evolution over the surfaces of workpieces with generic geometries such as cylinders. A granular flow dynamics model applicable to dense granular flow and a previously derived process equation were invoked in order to respectively describe the flow of the abrasive media; and the roughness distribution in terms of the granular pressure and velocity. By solving the granular flow field for the pressure and velocity distribution on a given geometry using a general purpose computational fluid dynamics (CFD) code, we were able to analyse changes in surface roughness distribution from the process equation. The immobilized cylinders were submerged in the top portion of the media flow field so as to facilitate comparison between media flow past the workpieces as experimentally observed and as predicted by the CFD simulations. We conclude with an analysis, based on both experimental and predicted results, of the way in which media flow direction biases the surface roughness distribution on an immobilized cylinder.

scholarly journals Plasmachemical Synthesis of Nanopowders in the System Ti(O,C,N) for Material Structure Modification

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Michael Filkov ◽  
Andrei Kolesnikov
Keyword(s):  
Plasma Jet ◽  
Chemical Reactor ◽  
Plasma Jets ◽  
Titanium Carbonitride ◽  
Material Structure ◽  
Operational Parameters ◽  
Synthesis Conditions ◽  
Mixing Chamber ◽  
Butane Mixture ◽  
Computational Fluid Dynamics Cfd

Refractory nanoparticles are finding broad application in manufacturing of materials with enhanced physical properties. Production of carbide, nitride, and carbonitride nanopowders in high volumes is possible in the multijet plasmachemical reactor, where temperature and velocity distributions in reaction zone can be controlled by plasma jet collision angle and mixing chamber geometry. A chemical reactor with three Direct Current (DC) arc plasma jets intersecting at one point was applied for titanium carbonitride synthesis from titanium dioxide, propane-butane mixture, and nitrogen. The influence of process operational parameters on the product chemical and phase composition was investigated. Mixing conditions in the plasma jet collision zone, particles residence time, and temperatures were evaluated with the help of Computational Fluid Dynamics (CFD) simulations. The synthesized nanoparticles have predominantly cubic shape and dimensions in the range 10–200 nm. Phase compositions were represented by oxycarbonitride phases. The amount of free (not chemically bonded) carbon in the product varied in the range 3–12% mass, depending on synthesis conditions.

scholarly journals Design and Bench-Scale Hydrodynamic Testing of Thin-Layer Wavy Photobioreactors

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1521 ◽  
Author(s):  
Monica Moroni ◽  
Simona Lorino ◽  
Agnese Cicci ◽  
Marco Bravi
Keyword(s):  
High Irradiance ◽  
Cfd Model ◽  
Operational Parameters ◽  
Concentrated Suspension ◽  
Recirculation Area ◽  
Computational Fluid Dynamics Cfd ◽  
Channel Slope ◽  
Flashing Light ◽  
Straight Flow ◽  
Thin Volume

In a thin-volume photobioreactor where a concentrated suspension of microalgae is circulated throughout the established spatial irradiance gradient, microalgal cells experience a time-variable irradiance. Deploying this feature is the most convenient way of obtaining the so-called “flashing light” effect, improving biomass production in high irradiance. This work investigates the light flashing features of sloping wavy photobioreactors, a recently proposed type, by introducing and validating a computational fluid dynamics (CFD) model. Two characteristic flow zones (straight top-to-bottom stream and local recirculation stream), both effective toward light flashing, have been found and characterized: a recirculation-induced frequency of 3.7 Hz and straight flow-induced frequency of 5.6 Hz were estimated. If the channel slope is increased, the recirculation area becomes less stable while the recirculation frequency is nearly constant with flow rate. The validated CFD model is a mighty tool that could be reliably used to further increase the flashing frequency by optimizing the design, dimensions, installation, and operational parameters of the sloping wavy photobioreactor.

Quantification of Mixing in RIM Using a Non-Diffusive Two-Phase Flow Numerical Model

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Cláudio P. Fonte ◽  
Ricardo J. Santos ◽  
Madalena M. Dias ◽  
José Carlos B. Lopes
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Linear Scale ◽  
Cfd Simulations ◽  
Two Phase ◽  
Vof Model ◽  
Mixing Chamber ◽  
Computational Fluid Dynamics Cfd

Mixing in RIM is made mainly by advective mechanisms, rather than diffusion. In this paper, the advective mechanisms that enable reducing the mixing scales down to the values required for the complete chemical reaction of the two monomers inside the RIM mixing chamber are identified and studied. From Computational Fluid Dynamics (CFD) simulations of non-diffusive two-phase flow using the Volume-of-Fluid (VOF) model, a linear scale of segregation is determined as a measure of the degree of mixing and the effect of the Reynolds number is studied.

Multiphase Computation of Cavitation Breakdown in Model and Prototype Scale Francis Turbines

2015 ◽  
Author(s):  
Daniel J. Leonard ◽  
Jules W. Lindau
Keyword(s):  
Large Scale ◽  
Scale Model ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Qualitative And Quantitative ◽  
Machine Performance ◽  
Computational Fluid Dynamics Cfd ◽  
Stage Analysis ◽  
Reduced Scale ◽  
Francis Hydroturbine

Steady-periodic multiphase Computational Fluid Dynamics (CFD) simulations were conducted to capture cavitation breakdown in a Francis hydroturbine due to large-scale vaporous structures. A reduced-scale model and a full-scale prototype were investigated to display differences in vapor content and machine performance caused by lack of Reynolds and Froude similarity. The model scale efficiencies compared favorably (within 3%) to the experimental cavitation tests. The CFD model and prototype displayed distinct qualitative and quantitative differences as σ was reduced. A stage-by-stage analysis was conducted to assess the effect of cavitation on loss distribution throughout the machine. Furthermore, a formal mesh refinement study was conducted on efficiency and volume of vapor, with three mesh levels and Richardson extrapolation, to ensure convergence.

scholarly journals Intensification of liquid mixing and local turbulence using a fractal injector with staggered conformation

2021 ◽  
Author(s):  
Shuxian Jiang ◽  
Marc-Olivier Coppens ◽  
Jia-Jun WANG
Keyword(s):  
Flow Field ◽  
Operating Conditions ◽  
Cfd Simulations ◽  
Mixing Performance ◽  
Double Ring ◽  
Spatially Distributed ◽  
Field Uniformity ◽  
Reaction Region ◽  
Dissipation Model ◽  
Computational Fluid Dynamics Cfd

Two self-similar, tree-like injectors of the same fractal dimension are compared, demonstrating that other geometric parameters besides dimension play a crucial role in determining mixing performance. In one injector, when viewed from the top, the conformation of branches is eclipsed; in the other one, it is staggered. The flow field and the fractal injector induced mixing performance are investigated through computational fluid dynamics (CFD) simulations. The finite rate/eddy dissipation model (FR/EDM) is modified for fast liquid-phase reactions involving local micromixing. Under the same operating conditions, flow field uniformity and micromixing are improved when a staggered fractal injector is used. This is because of enhanced jet entrainment and local turbulence around the spatially distributed nozzles. Compared with a traditional double-ring sparger, a larger reaction region volume and lower micromixing time are obtained with fractal injectors. Local turbulence around the spatially distributed nozzles in fractal injectors improves reaction efficiency.

scholarly journals Transient 3D CFD Simulation of a Stationary Vane, Oil Free, Rotary Compressor

2019 ◽  
Vol 63 (4) ◽  
pp. 308-318 ◽  
Author(s):  
Balázs Farkas ◽  
Jenő Miklós Suda
Keyword(s):  
Cfd Simulation ◽  
Piston Compressor ◽  
Working Fluid ◽  
Rotary Compressor ◽  
Heat Sources ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Rolling Piston ◽  
Good Agreement

The evaluation of a newly designed oil-free rotary compressor is presented based on transient 3D Computational Fluid Dynamics (CFD) simulations. The simulations are performed at low compression ratios and low pressure ratios and low rotational speeds. To place the results into context, the data presented in related literature was processed and summarized. The methods related to the CFD model of the newly designed compressor were developed, summarized and evaluated. The accessed CFD data are in good agreement with the results of the former rolling piston compressor related investigations. The oil free operation prevents the contamination of the working fluid from lubricant. Since the compressor is planned to work in open cycle within the sensitive environment of thermal heat sources contamination free operation has to be accomplished. However, oil-free operation also results in significantly lower performance based on the modelling results.

scholarly journals Aerodynamics Analysis of Speed Skating Helmets: Investigation by CFD Simulations

2021 ◽  
Vol 11 (7) ◽  
pp. 3148
Author(s):  
Guillermo Puelles Magán ◽  
Wouter Terra ◽  
Andrea Sciacchitano
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Numerical Simulations ◽  
Turbulence Model ◽  
Aerodynamic Drag ◽  
Cfd Simulations ◽  
Speed Skating ◽  
Computational Fluid Dynamics Cfd ◽  
Rans Simulations

In this work, we investigate the flow field around speed skating helmets and their associated aerodynamic drag by means of computational fluid dynamics (CFD) simulations. An existing helmet frequently used in competition was taken as a baseline. Six additional helmet designs, as well as the bare-head configuration, were analysed. All the numerical simulations were performed via 3D RANS simulations using the SST k-ω turbulence model. The results show that the use of a helmet always reduces the aerodynamic drag with respect to the bare head configuration. Besides, an optimised helmet design enables a reduction of the skaters aerodynamic drag by 5.9%, with respect to the bare-head configuration, and by 1.6% with respect to the use of the baseline Omega helmet.

scholarly journals Numerical Simulation of Internal Loop Reactor for Heavy Oil Slurry Bed Hydroprocessing

2014 ◽  
Vol 7 (1) ◽  
pp. 47-54
Author(s):  
Sun Lanyi ◽  
Wang Jian ◽  
Bai Fei ◽  
Bo Shoushi
Keyword(s):  
Flow Field ◽  
Heavy Oil ◽  
Flow Model ◽  
Scale Up ◽  
Cfd Simulations ◽  
Two Phase ◽  
Loop Reactor ◽  
Internal Loop ◽  
Commercial Code ◽  
Computational Fluid Dynamics Cfd

Computational Fluid Dynamics (CFD) simulations of internal loop reactor for heavy oil slurry bed hydroprocessing have been done in commercial code Fluent 6.3 using Euler two-phase flow model and standard k-ε turbulence model. The effects of the physical properties on the flow field in the reactor are investigated. The results show that the gas density has little effect but the liquid viscosity has a significant effect on flow field and gas hold-up. An analysis of the effect of reactor structures and scale-up on the flow field and gas hold-up are also provided, and optimal structure is obtained through simulations. The conclusions obtained in this paper have great significance for the slurry bed hydrocracking process.

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