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Numerical simulation of two-dimensional spouted bed with draft plates by discrete element method

ZHAO Yongzhi, JIANG Maoqiang, CHENG Yi, JIN Yong

《化学科学与工程前沿(英文)》 2008年 第2卷 第1期   页码 5-9 doi: 10.1007/s11705-008-0009-0

摘要: A discrete element method (DEM)-computational fluid dynamics (CFD) two-way coupling method was employed to simulate the hydrodynamics in a two-dimensional spouted bed with draft plates. The motion of particles was modeled by the DEM and the gas flow was modeled by the Navier-Stokes equation. The interactions between gas and particles were considered using a two-way coupling method. The motion of particles in the spouted bed with complex geometry was solved by combining DEM and boundary element method (BEM). The minimal spouted velocity was obtained by the BEM-DEM-CFD simulation and the variation of the flow pattern in the bed with different superficial gas velocity was studied. The relationship between the pressure drop of the spouted bed and the superficial gas velocity was achieved from the simulations. The radial profile of the averaged vertical velocities of particles and the profile of the averaged void fraction in the spout and the annulus were statistically analyzed. The flow characteristics of the gas-solid system in the two-dimensional spouted bed were clearly described by the simulation results.

关键词: annulus     BEM-DEM-CFD simulation     gas-solid     two-dimensional     relationship    

Multiscale mechanical modeling of hydrated cement paste under tensile load using the combined DEM-MD

Yue HOU, Linbing WANG

《结构与土木工程前沿(英文)》 2017年 第11卷 第3期   页码 270-278 doi: 10.1007/s11709-017-0408-8

摘要: In this paper, a combined DEM-MD method is proposed to simulate the crack failure process of Hydrated Cement Paste (HCP) under a tensile force. A three-dimensional (3D) multiscale mechanical model is established using the combined Discrete Element Method (DEM)-Molecular Dynamics (MD) method in LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). In the 3D model, HCP consists of discrete particles and atoms. Simulation results show that the combined DEM-MD model is computationally efficient with good accuracy in predicting tensile failures of HCP.

关键词: hydrated cement paste     multiscale     MD simulation     DEM    

CFD simulation on membrane distillation of NaCl solution

Zhaoguang XU, Yanqiu PAN, Yalan YU

《化学科学与工程前沿(英文)》 2009年 第3卷 第3期   页码 293-297 doi: 10.1007/s11705-009-0204-7

摘要: A computational fluid dynamics (CFD) simulation that coupled an established heat and mass transfer model was carried out for the air-gap membrane distillation (AGMD) of NaCl solution to predict mass and heat behaviors of the process. The effects of temperature and flowrate on fluxes were first simulated and compared with available experimental data to verify the approach. The profiles of temperature, temperature polarization factor, and mass flux adjacent to the tubular carbon membrane surface were then examined under different feed Reynolds number in the computational domain. Results show that the temperature polarization phenomena can be reduced, and mass flux can be enhanced with increase in the feed Reynolds number.

关键词: membrane distillation     computational fluid dynamics (CFD) simulation     temperature polarization     carbon membrane    

Computational simulation methods for fiber reinforced composites

Vladimír KOMPI, Zuzana MURINKOV, Sergey RJASANOW, Richards GRZIBOVSKIS, Qinghua QIN,

《结构与土木工程前沿(英文)》 2010年 第4卷 第3期   页码 396-401 doi: 10.1007/s11709-010-0079-1

摘要: Trefftz-finite element method (Trefftz-FEM), adaptive cross approximation BEM (ACA BEM) and continuous source function method (CSFM) are used for the simulation of composites reinforced by short fibers (CRSF) with the aim of showing the possibilities of reducing the problem of complicated and important interactions in such composite materials.

关键词: Trefftz-finite element method (Trefftz-FEM)     adaptive cross approximation BEM (ACA BEM)     method of continuous source functions     composite materials     short fibers    

Experimental study on bubble behavior and CFD simulation of large-scale slurry bubble column reactor

Haoyi SUN, Tao LI, Weiyong YING, Dingye FANG

《化学科学与工程前沿(英文)》 2010年 第4卷 第4期   页码 515-522 doi: 10.1007/s11705-010-0516-7

摘要: Slurry bubble column reactors (SBCR) is a three-phase fluidized reactor with outstanding advantages compared with other reactors and is difficult to scale-up due to lack of information on hydrodynamics and mass transfer over a wide range of operating conditions of commercial interest. In this paper, an experiment was conducted to investigate the bubble behavior in SBCR with a height of 5600 mm and an interior diameter of 480 mm. Bubble rise velocity, bubble diameter, and gas holdup in different radial and axial positions are measured in SBCR using four-channel conductivity probe. Tap water, air, and glass beads (mean diameter 75–150 μm) are used as liquid, gas, and solid phases, respectively. It shows that hydrodynamic parameters have good regularity in SBCR. Moreover, a commercial computational fluid dynamics (CFD) package, Fluent, was used to simulate the process in SBCR. The simulations were carried out using axi-symmetric 2-D grids. Data obtained from experiment and CFD simulation are compared, and results show that the tendency of simulation is almost uniform with the experiment, which can help to obtain further understanding about multiphase flow process and establish a model about the synthesis of alcohol ether fuel in SBCR.

关键词: SBCR     four-channel conductivity probe     hydrodynamics     CFD    

Combustion mechanism development and CFD simulation for the prediction of soot emission during flaring

Anan Wang,Helen H. Lou,Daniel Chen,Anfeng Yu,Wenyi Dang,Xianchang Li,Christopher Martin,Vijaya Damodara,Ajit Patki

《化学科学与工程前沿(英文)》 2016年 第10卷 第4期   页码 459-471 doi: 10.1007/s11705-016-1594-y

摘要: Industrial Flares are important safety devices to burn off the unwanted gas during process startup, shutdown, or upset. However, flaring, especially the associated smoke, is a symbol of emissions from refineries, oil gas fields, and chemical processing plants. How to simultaneously achieve high combustion efficiency (CE) and low soot emission is an important issue. Soot emissions are influenced by many factors. Flare operators tend to over-steam or over-air to suppress smoke, which results in low CE. How to achieve optimal flare performance remains a question to the industry and the regulatory agencies. In this paper, regulations in the US regarding flaring were reviewed. In order to determine the optimal operating window for the flare, different combustion mechanisms related to soot emissions were summarized. A new combustion mechanism (Vsoot) for predicting soot emissions was developed and validated against experimental data. Computational fluid dynamic (CFD) models combined with Vsoot combustion mechanism were developed to simulate the flaring events. It was observed that simulation results agree well with experimental data.

关键词: flare     soot emission     combustion mechanism     CFD simulation    

Vortex-induced vibration of stay cable under profile velocity using CFD numerical simulation method

Wenli CHEN, Hui LI,

《结构与土木工程前沿(英文)》 2009年 第3卷 第4期   页码 357-363 doi: 10.1007/s11709-009-0060-z

摘要: Vortex-induced vibration (VIV) of a stay cable subjected to a wind profile is numerically simulated through combining computational fluid dynamics (CFD) code CFX 10.0 and computational structural dynamics (CSD) code ANSYS 10.0. A stay cable with the inclined angle of 30° is used as the numerical model. Under a profile of mean wind speed, unsteady aerodynamic lift coefficients of the cable have been analyzed in both time domain and frequency domain when VIV occurs. The results indicate that the lift coefficient wave response of the stay cable under a wind profile is different from that of an infinitely long cable under a uniform flow in water (i.e., without consideration of profile) obtained by direct numerical simulation. Cable oscillations can severely affect the unsteady aerodynamic frequencies, change flow field distribution near the cable and affect the vortex shedding in the wake.

关键词: stay cable     fluid-structure interaction     numerical simulation     vortex-induced vibration    

CFD simulation on shell-and-tube heat exchangers with small-angle helical baffles

Minhua ZHANG,Fang MENG,Zhongfeng GENG

《化学科学与工程前沿(英文)》 2015年 第9卷 第2期   页码 183-193 doi: 10.1007/s11705-015-1510-x

摘要: Shell-and-tube heat exchanger with helical baffles is superior to that with segmental baffles in reducing pressure drop, eliminating dead zone and lowering the risks of vibration of tube bundle. This paper focused on the small-angle helical baffles that have been merely reported in open literature. These baffles are noncontinuous helical baffles with a helix angle of 10° to 30°, and their shapes are 1/4 ellipse, 1/4 sector and 1/3 sector. To assess the integrative performance, /? is employed, and the calculated results show that among the three baffle shapes the heat exchangers with a 1/4 sector helical baffle have the lowest pressure drop. At = 10° and 20°, 1/4 sector helical baffle heat exchangers show the best integrative performance; at = 30°, 1/4 ellipse and 1/4 sector helical baffle heat exchangers perform almost the same. For the study of helix angles, we found that 30° has the best integrative performance at low mass flow rate, almost the same as 20° at high mass flow rate.

关键词: heat transfer     pressure drop     helical baffle     CFD    

CFD simulation of the hydrodynamics in an internal air-lift reactor with two different configurations

Mona EBRAHIMIFAKHAR, Elmira MOHSENZADEH, Sadegh MORADI, Mostafa MORAVEJI, Mahmoud SALIMI

《化学科学与工程前沿(英文)》 2011年 第5卷 第4期   页码 455-462 doi: 10.1007/s11705-011-1116-x

摘要: Computational fluid dynamics (CFD) was used to investigate the hydrodynamic parameters of two internal airlift bioreactors with different configurations. Both had a riser diameter of 0.1 m. The model was used to predict the effect of the reactor geometry on the reactor hydrodynamics. Water was utilized as the continuous phase and air in the form of bubbles was applied as the dispersed phase. A two-phase flow model provided by the bubbly flow application mode was employed in this project. In the liquid phase, the turbulence can be described using the - model. Simulated gas holdup and liquid circulation velocity results were compared with experimental data. The predictions of the simulation are in good agreement with the experimental data.

关键词: airlift reactor     gas holdup     liquid circulation velocity     bubbly flow     computational fluid dynamics (CFD)    

Application of different CFD multiphase models to investigate effects of baffles and nanoparticles on

Ali SHAHMOHAMMADI,Arezou JAFARI

《化学科学与工程前沿(英文)》 2014年 第8卷 第3期   页码 320-329 doi: 10.1007/s11705-014-1437-7

摘要: In this work, the effect of baffles in a pipe on heat transfer enhancement was studied using computational fluid dynamics (CFD) in the presence of Al O nanoparticles which are dispersed into water. Fluid flow through the horizontal tube with uniform heat flux was simulated numerically and three dimensional governing partial differential equations were solved. To find an accurate model for CFD simulations, the results obtained by the single phase were compared with those obtained by three different multiphase models including Eulerian, mixture and volume of fluid (VOF) at Reynolds numbers in range of 600 to 3000, and two different nanoparticle concentrations (1% and 1.6%). It was found that multiphase models could better predict the heat transfer in nanofluids. The effect of baffles on heat transfer of nanofluid flow was also investigated through a baffled geometry. The numerical results show that at Reynolds numbers in the range of 600 to 2100, the heat transfer of nanofluid flowing in the geometry without baffle is greater than that of water flowing through a tube with baffle, whereas the difference between these effects (nanofluid and baffle) decreases with increasing the Reynolds number. At higher Reynolds numbers (2100–3000) the baffle has a greater effect on heat transfer enhancement than the nanofluid.

关键词: CFD simulation     heat transfer     nanofluid     baffle     single phase model     multiphase model    

Simulation of bubble column reactors using CFD coupled with a population balance model

Tiefeng WANG

《化学科学与工程前沿(英文)》 2011年 第5卷 第2期   页码 162-172 doi: 10.1007/s11705-009-0267-5

摘要: Bubble columns are widely used in chemical and biochemical processes due to their excellent mass and heat transfer characteristics and simple construction. However, their fundamental hydrodynamic behaviors, which are essential for reactor scale-up and design, are still not fully understood. To develop design tools for engineering purposes, much research has been carried out in the area of computational fluid dynamics (CFD) modeling and simulation of gas-liquid flows. Due to the importance of the bubble behavior, the bubble size distribution must be considered in the CFD models. The population balance model (PBM) is an effective approach to predict the bubble size distribution, and great efforts have been made in recent years to couple the PBM into CFD simulations. This article gives a selective review of the modeling and simulation of bubble column reactors using CFD coupled with PBM. Bubble breakup and coalescence models due to different mechanisms are discussed. It is shown that the CFD-PBM coupled model with proper bubble breakup and coalescence models and interphase force formulations has the ability of predicting the complex hydrodynamics in different flow regimes and, thus, provides a unified description of both the homogeneous and heterogeneous regimes. Further study is needed to improve the models of bubble coalescence and breakup, turbulence modification in high gas holdup, and interphase forces of bubble swarms.

关键词: bubble column     computational fluid dynamics     bubble breakup and coalescence     population balance model     bubble size distribution    

Computational fluid dynamics simulation of aerosol transport and deposition

Yingjie TANG, Bing GUO

《环境科学与工程前沿(英文)》 2011年 第5卷 第3期   页码 362-377 doi: 10.1007/s11783-011-0365-8

摘要: In this article computational fluid dynamics (CFD) simulation of aerosol transport and deposition, i.e. the transport and deposition of particles in an aerosol, is reviewed. The review gives a brief account of the basics of aerosol mechanics, followed by a description of the general CFD approach for flow field simulation, turbulence modeling, wall treatments and simulation of particle motion and deposition. Then examples from the literature are presented, including CFD simulation of particle deposition in human respiratory tract and particle deposition in aerosol devices. CFD simulation of particle transport and deposition may provide information that is difficult to obtain through physical experiments, and it may help reduce the number of experiments needed for device design. Due to the difficulty of describing turbulent flow and particle-eddy interaction, turbulent dispersion of particles remains one of the greatest challenges for CFD simulation. However, it is possible to take a balanced approach toward quantitative description of aerosol dispersion using CFD simulation in conjunction with empirical relations.

关键词: computational fluid dynamics (CFD)     aerosol     transport     deposition    

CFD Simulation of thermal hydraulic characteristics in a typical upper plenum of RPV

Mingjun WANG, Lianfa WANG, Yingjie WANG, Wenxi TIAN, Jian DENG, Guanghui SU, Suizheng QIU

《能源前沿(英文)》 2021年 第15卷 第4期   页码 930-945 doi: 10.1007/s11708-021-0728-1

摘要: A comparative computational fluid dynamics (CFD) study was conducted on the three different types of pressurized water reactor (PWR) upper plenum, named TYPE 1 (support columns (SCs) and control rod guide tubes (CRGTs) with two large windows), TYPE 2 (SCs and CRGTs without windows), and TYPE 3 (two parallel perforated barrel shells and CRGTs). First, three types of upper plenum geometry information were collected, simplified, and adopted into the BORA facility, which is a 1/5 scale system of the four-loop PWR reactor. Then, the geometry, including the upper half core, upper plenum region, and hot legs, was built using the platform. After that, an unsteady calculation to simulate the reactor balance operation at hot full power scenario was performed. Finally, the differences of flowrate distribution at the core outlet and temperature distribution and transverse velocity inside the hot legs with different upper plenum internals were compared. The results suggest that TYPE 1 upper plenum internals cause the largest flowrate difference at the core outlet while TYPE 3 leads to the most even distributed flowrate. The distribution and evolution pattern of the tangential velocity inside hot legs is highly dependent on the upper plenum internals. Two counter-rotating swirls exist inside the TYPE 1 hot leg and only one swirl revolving around the hog leg axis exist inside the TYPE 2 hot leg. For TYPE 3, two swirls like that of TYPE 1 rotating around the hot leg axis significantly increase the temperature homogenization speed. This research provides meaningful guidelines for the future optimization and design of advanced PWR upper plenum internal structures.

关键词: pressurized water reactor (PWR)     upper plenum     internal structures     temperature distribution     computational fluid dynamics (CFD)    

Numerical simulation of biodiesel fuel combustion and emission characteristics in a direct injection

Yi REN, Ehab ABU-RAMADAN, Xianguo LI,

《能源前沿(英文)》 2010年 第4卷 第2期   页码 252-261 doi: 10.1007/s11708-010-0036-7

摘要: The effect of the physical and chemical properties of biodiesel fuels on the combustion process and pollutants formation in Direct Injection (DI) engine are investigated numerically by using multi-dimensional Computational Fluid Dynamics (CFD) simulation. In the current study, methyl butanoate (MB) and -heptane are used as the surrogates for the biodiesel fuel and the conventional diesel fuel. Detailed kinetic chemical mechanisms for MB and -heptane are implemented to simulate the combustion process. It is shown that the differences in the chemical properties between the biodiesel fuel and the diesel fuel affect the whole combustion process more significantly than the differences in the physical properties. While the variations of both the chemical and the physical properties between the biodiesel and diesel fuel influence the soot formation at the equivalent level, the variations in the chemical properties play a crucial role in the NO emissions formation.

关键词: biodiesel     diesel engine     CFD simulation     combustion     pollutant formation    

基于DEM的资料短缺地区设计洪水推求

张婷,冯平

《中国工程科学》 2011年 第13卷 第12期   页码 68-73

摘要:

以缺少径流资料的福州市北部山区流域为例,通过数字高程模型(DEM)技术与新安江三水源模型相结合的方法,探讨了资料短缺地区设计洪水的计算方法在汇流计算中,通过DEM推求等流时线,避免了在地图上勾绘等流时线的繁琐工作。随着全国各地数字高程模型的建立,将其运用到水文计算当中有重要的现实意义。

关键词: 资料短缺地区     设计洪水     数字高程模型(DEM    等流时线    

标题 作者 时间 类型 操作

Numerical simulation of two-dimensional spouted bed with draft plates by discrete element method

ZHAO Yongzhi, JIANG Maoqiang, CHENG Yi, JIN Yong

期刊论文

Multiscale mechanical modeling of hydrated cement paste under tensile load using the combined DEM-MD

Yue HOU, Linbing WANG

期刊论文

CFD simulation on membrane distillation of NaCl solution

Zhaoguang XU, Yanqiu PAN, Yalan YU

期刊论文

Computational simulation methods for fiber reinforced composites

Vladimír KOMPI, Zuzana MURINKOV, Sergey RJASANOW, Richards GRZIBOVSKIS, Qinghua QIN,

期刊论文

Experimental study on bubble behavior and CFD simulation of large-scale slurry bubble column reactor

Haoyi SUN, Tao LI, Weiyong YING, Dingye FANG

期刊论文

Combustion mechanism development and CFD simulation for the prediction of soot emission during flaring

Anan Wang,Helen H. Lou,Daniel Chen,Anfeng Yu,Wenyi Dang,Xianchang Li,Christopher Martin,Vijaya Damodara,Ajit Patki

期刊论文

Vortex-induced vibration of stay cable under profile velocity using CFD numerical simulation method

Wenli CHEN, Hui LI,

期刊论文

CFD simulation on shell-and-tube heat exchangers with small-angle helical baffles

Minhua ZHANG,Fang MENG,Zhongfeng GENG

期刊论文

CFD simulation of the hydrodynamics in an internal air-lift reactor with two different configurations

Mona EBRAHIMIFAKHAR, Elmira MOHSENZADEH, Sadegh MORADI, Mostafa MORAVEJI, Mahmoud SALIMI

期刊论文

Application of different CFD multiphase models to investigate effects of baffles and nanoparticles on

Ali SHAHMOHAMMADI,Arezou JAFARI

期刊论文

Simulation of bubble column reactors using CFD coupled with a population balance model

Tiefeng WANG

期刊论文

Computational fluid dynamics simulation of aerosol transport and deposition

Yingjie TANG, Bing GUO

期刊论文

CFD Simulation of thermal hydraulic characteristics in a typical upper plenum of RPV

Mingjun WANG, Lianfa WANG, Yingjie WANG, Wenxi TIAN, Jian DENG, Guanghui SU, Suizheng QIU

期刊论文

Numerical simulation of biodiesel fuel combustion and emission characteristics in a direct injection

Yi REN, Ehab ABU-RAMADAN, Xianguo LI,

期刊论文

基于DEM的资料短缺地区设计洪水推求

张婷,冯平

期刊论文