Records with Subject: Modelling and Simulations
Showing records 1 to 25 of 361. [First] Page: 1 2 3 4 5 Last
Numerical Assessment of the Influences of Gas Pressure on Coal Burst Liability
Haochen Zhao, Rennie B. Kaunda
January 23, 2020 (v1)
Keywords: bursting energy index, coal bump, gas pressure, rockburst, seismicity
When coal mines exploit deep seams with high-gas content, risks are encountered due to the additional high likelihood of rock bursting potential problems. The bursts of coal pillars usually lead to severe fatalities, injuries, and destruction of property, including impeding access to active mine workings underground. The danger exists given that conditions in the already highly brittle coal material can be exacerbated by high stress and high gas pressure conditions. It is thus critical to develop methods that improve current understanding about bursting liability, and techniques to forecast or prevent coal bursting in underground coal mines. This study uses field data from a deep coal mine, and numerical modeling to investigate the effects of gas pressure and mechanical compressive stresses on coal bursting liability in high gas content coal seams. The bursting energy index is adopted to determine the coal bursting liability under high gas pressure conditions. The adopted methodology u... [more]
Dynamic Simulation of an Absorption Cooling System with Different Working Mixtures
Jesús Cerezo, Rosenberg J. Romero, Jonathan Ibarra, Antonio Rodríguez, Gisela Montero, Alexis Acuña
January 23, 2020 (v1)
Keywords: crystallization, dynamic condition, evacuated tube solar collector, solar absorption cooling
High consumption of electricity represents an economic and social problem in warm places, caused by the massive use of cooling machines. Absorption systems are a sustainable method for air conditioning applications. However, environmental conditions should be analyzed to avoid crystallization problems of the working mixture. This article presents a thermal analysis of a solar absorption cooling system in dynamic conditions using NH₃-H₂O, H₂O-LiBr, NH₃-NaSCN, NH₃-LiNO₃, and H₂O-LiCl working mixtures using Equation Engineering Solver (EES) and TRaNsient SYstem Simulation (TRNSYS) software. A solar collector area of 42.5 m² was selected to carry out the thermal analysis. The results showed that H₂O-LiCl obtained the maximum solar (0.67) and minimum heating (0.33) fraction. However, it obtained the maximum lost heat fraction (0.12), in spite of obtaining the best coefficient of performance (COP) among the other working mixtures, due mainly to a crystallization problem. The gain fraction (G... [more]
Numerical Study of Periodic Magnetic Field Effect on 3D Natural Convection of MWCNT-Water/Nanofluid with Consideration of Aggregation
Lioua Kolsi, Hakan F. Oztop, Kaouther Ghachem, Mohammed A. Almeshaal, Hussein A. Mohammed, Houman Babazadeh, Nidal Abu-Hamdeh
January 19, 2020 (v1)
Keywords: 3D natural convection, aggregation, MWCNT-nanofluid, periodic magnetic field
In this paper, a numerical study is performed to investigate the effect of a periodic magnetic field on three-dimensional free convection of MWCNT (Mutli-Walled Carbone Nanotubes)-water/nanofluid. Time-dependent governing equations are solved using the finite volume method under unsteady magnetic field oriented in the x-direction for various Hartmann numbers, oscillation periods, and nanoparticle volume fractions. The aggregation effect is considered in the evaluation of the MWCNT-water/nanofluid thermophysical properties. It is found that oscillation period, the magnitude of the magnetic field, and adding nanoparticles have an important effect on heat transfer, temperature field, and flow structure.
Research on the Dynamic Behaviors of the Jet System of Adaptive Fire-Fighting Monitors
Xiaoming Yuan, Xuan Zhu, Chu Wang, Lijie Zhang, Yong Zhu
January 19, 2020 (v1)
Keywords: adaptive control, duffing equation, dynamics, fire-fighting monitor, flow control, jet system
Based on the principles of nonlinear dynamics, a dynamic model of the jet system for adaptive fire-fighting monitors was established. The influence of nonlinear fluid spring force on the dynamic model was described by the Duffing equation. Results of numerical calculation indicate that the nonlinear action of the fluid spring force leads to the nonlinear dynamic behavior of the jet system and fluid gas content, fluid pressure, excitation frequency, and excitation amplitude are the key factors affecting the dynamics of the jet system. When the excitation frequency is close to the natural frequency of the corresponding linear dynamic system, a sudden change in vibration amplitude occurs. The designed adaptive fire-fighting monitor had no multi-cycle, bifurcation, or chaos in the range of design parameters, which was consistent with the stroboscopic sampling results in the dynamic experiment of jet system. This research can provide a basis for the dynamic design and optimization of the ad... [more]
Numerical and Experimental Investigation of External Characteristics and Pressure Fluctuation of a Submersible Tubular Pumping System
Yan Jin, Xiaoke He, Ye Zhang, Shanshan Zhou, Hongcheng Chen, Chao Liu
January 19, 2020 (v1)
Keywords: external characteristics, measurement, numerical simulation, pressure fluctuation, submersible tubular pumping system
This paper presents an investigation of external flow characteristics and pressure fluctuation of a submersible tubular pumping system by using a combination of numerical simulation and experimental methods. The steady numerical simulation is used to predicted the hydraulic performance of the pumping system, and the unsteady calculation is adopted to simulate the pressure fluctuation in different components of a submersible tubular pumping system. A test bench for a model test and pressure pulsation measurement is built to validate the numerical simulation. The results show that the performance curves of the calculation and experiment are in agreement with each other, especially in the high efficiency area, and the deviation is minor under small discharge and large discharge conditions. The pressure pulsation distributions of different flow components, such as the impeller outlet, middle of the guide vane, and guide vane outlet and bulb unit, are basically the same as the measurement d... [more]
Diffusion in Binary Aqueous Solutions of Alcohols by Molecular Simulation
Alexander Klinov, Ivan Anashkin
January 19, 2020 (v1)
Keywords: alcohols, diffusion coefficient, intermolecular interaction, molecular dynamics, Water
Based on the molecular dynamics method, the calculations for diffusion coefficients were carried out in binary aqueous solutions of three alcohols: ethanol, isopropanol, and tert-butanol. The intermolecular potential TIP4P/2005 was used for water; and five force fields were analyzed for the alcohols. The force fields providing the best accuracy of calculation were identified based on a comparison of the calculated self-diffusion coefficients of pure alcohols with the experimental data for internal (Einstein) diffusion coefficients of alcohols in solutions. The temperature and concentration dependences of the interdiffusion coefficients were determined using Darken’s Equation. Transport (Fickian) diffusion coefficients were calculated using a thermodynamic factor determined by the non-random two-liquid (NRTL) and Willson models. It was demonstrated that for adequate reproduction of the experimental data when calculating the transport diffusion coefficients, the thermodynamic factor has... [more]
Numerical Simulation of a Wall-Flow Particulate Filter Made of Biomorphic Silicon Carbide Able to Fit Different Fuel/Biofuel Inputs
M. Pilar Orihuela, Onoufrios Haralampous, Ricardo Chacartegui, Miguel Torres García, Julián Martínez-Fernández
January 19, 2020 (v1)
Keywords: biodiesel, biomorphic silicon carbide, diesel particulate filter, internal combustion engine, particulate matter emissions, vegetal waste
To meet the increasingly strict emission limits imposed by regulations, internal combustion engines for transport applications require the urgent development of novel emission abatement systems. The introduction of biodiesel or other biofuels in the engine operation is considered to reduce greenhouse gas emissions. However, these alternative fuels can affect the performance of the post-combustion systems due to the variability they introduce in the exhaust particle distribution and their particular physical properties. Bioceramic materials made from vegetal waste are characterized by having an orthotropic hierarchical microstructure, which can be tailored in some way to optimize the filtration mechanisms as a function of the particle distribution of the combustion gases. Consequently, they can be good candidates to cope with the variability that new biofuel blends introduce in the engine operation. The objective of this work is to predict the filtration performance of a wall-flow parti... [more]
Heat Transfer Enhancement by Coupling of Carbon Nanotubes and SiO2 Nanofluids: A Numerical Approach
Fitnat Saba, Saima Noor, Naveed Ahmed, Umar Khan, Syed Tauseef Mohyud-Din, Zarqa Bano, El-Sayed M. Sherif, Ilyas Khan
January 19, 2020 (v1)
Keywords: (CNT-SiO2/H2O) hybrid nanofluid, heat transfer, Hermite polynomials, numerical results, permeable wall, viscous dissipation, wavelets
This article comprises the study of three-dimensional squeezing flow of (CNT-SiO2/H2O) hybrid nanofluid. The flow is confined inside a rotating channel whose lower wall is stretchable as well as permeable. Heat transfer with viscous dissipation is a main subject of interest. We have analyzed mathematically the benefits of hybridizing SiO 2 -based nanofluid with carbon nanotubes ( CNTs ) nanoparticles. To describe the effective thermal conductivity of the CNTs -based nanofluid, a renovated Hamilton−Crosser model (RHCM) has been employed. This model is an extension of Hamilton and Crosser’s model because it also incorporates the effect of the interfacial layer. For the present flow scenario, the governing equations (after the implementation of similarity transformations) results in a set of ordinary differential equations (ODEs). We have solved that system of ODEs, coupled with suitable boundary conditions (BCs), by implementing a newly proposed modified Hermite... [more]
CFD Study of Gas Holdup and Frictional Pressure Drop of Vertical Riser Inside IC Reactor
Sheng Wang, He Dong, Zhongfeng Geng, Xiuqin Dong
January 19, 2020 (v1)
Keywords: flow pattern, frictional pressure drop, gas holdup, multiple flow regimes model, vertical riser
The internal circulation system in Internal Circulation (IC) reactor plays an important role in increasing volumetric loading rate and promoting the mixing between sludge and wastewater. In order to design the internal circulation system, the flow behaviors of gas-liquid inside vertical riser should be studied in detail. In the present study, the Multiple Flow Regimes model is adopted to capture the phase interface for different flow conditions. The flow patterns, internal circulation flow rate, gas holdup, and frictional pressure drop of vertical riser are investigated. The results show that the bubble flow inside a vertical riser is in a stable flow condition. There exists a maximum value for internal circulation flow rate with the increasing superficial gas velocity. The parameters of Martinelli models for gas holdup and frictional pressure drop are improved based on Computational Fluid Dynamics (CFD) results. The deviations between the calculated gas holdup and frictional pressure... [more]
Experimental and Numerical Investigation on the Tip Leakage Vortex Cavitation in an Axial Flow Pump with Different Tip Clearances
Bin Xu, Xi Shen, Desheng Zhang, Weibin Zhang
January 19, 2020 (v1)
Keywords: axial flow pump, cavitation, tip clearance, tip leakage vortex
The tip gap existing between the blade tip and casing can give rise to tip leakage flow and interfere with the main flow, which causes unstable flow characteristics and intricate vortex in the passage. Investigation on the tip clearance effect is of great important due to its extensive applications in the rotating component of pumps. In this study, a scaling axial flow pump used in a south-north water diversion project with different sizes of tip clearances was employed to study the tip clearance effect on tip leakage vortex (TLV) characteristics. This analysis is based on a modified turbulence model. Validations were carried out using a high-speed photography technique. The tip clearance effect on the generation and evolution of TLV was investigated through the mean velocity, pressure, and vorticity fields. Results show that there are two kinds of TLV structures in the tip region. Accompanied by tip clearance increasing, the viscous loss in the tip area of the axial flow pump increase... [more]
Experimental and Numerical Study on Gas-Liquid Two-Phase Flow Behavior and Flow Induced Noise Characteristics of Radial Blade Pumps
Qiaorui Si, Chunhao Shen, Asad Ali, Rui Cao, Jianping Yuan, Chuan Wang
January 7, 2020 (v1)
Keywords: gas-liquid two-phase flow, miniature drainage pump, pressure, radiate noise
Miniature drainage pumps with a radial blade are widely used in situations with critical constant head and low noise requests, but the stable operation state is often broken up by the entraining gas. In order to explore the internal flow characteristics under gas−liquid two phase flow, pump performance and emitted noise measurements were processed under different working conditions. Three-dimensional numerical calculations based on the Euler inhomogeneous model and obtained experimental boundaries were carried out under different inlet air void fractions (IAVFs). A hybrid numerical method was proposed to obtain the flow-induced emitted noise characteristics. The results show there is little influence on pump characteristics when the IAVF is less than 1%. The pump head slope degradation was found to increase with air content. The bubbles adhere to the impeller hub on the blade’s suction side and spread to the periphery with a big IAVF, leading to unstable operation. It is obvious that v... [more]
Numerical Investigation of Design and Operating Parameters of Thermal Gradient Continuous-Flow PCR Microreactor Using One Heater
Usama Perwez, Imran Aziz, Faisal Ahmed, Mohsin Raza Khan
January 7, 2020 (v1)
Keywords: continuous-flow microreactor, Lab on Chip (LOC), point-of-care, one heater, PCR kinetics, polymerase chain reaction (PCR)
To respond to the dire need for miniaturization and process simplification of continuous-flow PCR (CF-PCR) device, this paper represents design and operation guide of a novel metal alloy assisted hybrid microdevice (polydimethylsiloxane (PDMS) and glass) for CF-PCR employing one heater. In this research, the specific objectives are to determine whether one heater chip design will be flexible enough when the size of DNA base pair is varied and to investigate whether one heater CF-PCR device will be able to resolve the longstanding problem of thermal crosstalk. Furthermore, the parametric study is performed to determine which of the fourteen parameters have the greatest impact on the performance of one heater CF-PCR device. The main objective of this parametric study is to distinguish between the parameters that are either critical to the chip performance or can be freely specified. It is found that substrate thickness, flow rate, channel spacing, aspect ratio, channel pass length and ex... [more]
Activation Energy and Second Order Slip in Bioconvection of Oldroyd-B Nanofluid over a Stretching Cylinder: A Proposed Mathematical Model
Iskander Tlili, H. Waqas, Abulmajeed Almaneea, Sami Ullah Khan, M. Imran
January 7, 2020 (v1)
Keywords: activation energy, motile microorganisms, Oldroyd-B nanofluid, shooting technique, stretching cylinder
The thermal performances based on the interaction of nanoparticles are the topic of great interest in recent years. In the current continuation, we have utilized the activation energy and thermal radiation consequences in the bioconvection flow of magnetized Oldroyd-B nanoparticles over a stretching cylinder. As a novelty, the second order slip features (Wu’s slip) and convective Nield boundary assumptions are also introduced for the flow situation. The heat performances of nanofluids are captured with an evaluation of the famous Buongiorno’s model which enables us to determine the attractive features of Brownian motion and thermophoretic diffusion. The suggested thermal system is based on the flow velocity, nanoparticles temperature, nanoparticles volume fraction and motile microorganisms. The governing flow equations for the flow problem are constituted with relevant references for which numerically solution is developed via shooting algorithm. A detailed graphically analysis for the... [more]
Numerical Simulation on Hydraulic Characteristics of Nozzle in Waterjet Propulsion System
Chuan Wang, Xiaoke He, Li Cheng, Can Luo, Jing Xu, Kun Chen, Weixuan Jiao
January 7, 2020 (v1)
Keywords: efficiency, energy loss, hydraulic performance, nozzle, numerical simulation, waterjet propulsion
As an important over-current component of the waterjet propulsion system, the main function of a nozzle is to transform the mechanical energy of the propulsion pump into the kinetic energy of the water and eject the water flow to obtain thrust. In this study, the nozzle with different geometry and parameters was simulated based on computational fluid dynamics simulation and experiment. Numerical results show a good agreement with experimental results. The results show that the nozzle with a circular shape outlet shrinks evenly. Under the designed flow rate condition, the velocity uniformity of the circular nozzle is 0.26% and 0.34% higher than that of the elliptical nozzle and the rounded rectangle nozzle, respectively. The pump efficiency of the circular nozzle is 0.31% and 0.14% higher than that of the others. The pressure recovery and hydraulic loss of the circular nozzle are superior. The hydraulic characteristics of the propulsion pump and waterjet propulsion system are optimal wh... [more]
Unsteady Flow Process in Mixed Waterjet Propulsion Pumps with Nozzle Based on Computational Fluid Dynamics
Can Luo, Hao Liu, Li Cheng, Chuan Wang, Weixuan Jiao, Di Zhang
January 7, 2020 (v1)
Keywords: Computational Fluid Dynamics, test, unsteady flow process, waterjet propulsion pump
The unsteady flow process of waterjet pumps is related to the comprehensive performance and phenomenon of rotating stall and cavitation. To analyze the unsteady flow process on the unsteady condition, a computational domain containing nozzle, impeller, outlet guide vane (OGV), and shaft is established. The surface vortex of the blade is unstable at the valley point of the hydraulic unstable zone. The vortex core and morphological characteristics of the vortex will change in a small range with time. The flow of the best efficiency point and the start point of the hydraulic unstable zone on each turbo surface is relatively stable. At the valley point of the hydraulic unstable zone, the flow and pressure fields are unstable, which causes the flow on each turbo surface to change with time. The hydraulic performance parameters are measured by establishing the double cycle test loop of a waterjet propulsion device compared with numerical simulated data. The verification results show that the... [more]
Effect of Orientation and Aspect Ratio of an Internal Flat Plate on Natural Convection in a Circular Enclosure
Anjie Wang, Cunlie Ying, Yingdong Wang, Lijun Yang, Yunjian Ying, Lulu Zhai, Wei Zhang
January 7, 2020 (v1)
Keywords: aspect ratio, flat plate, horizontal, natural convection, orientation, vertical
This work presents a numerical investigation on natural convection in a circular enclosure with an internal flat plate at Ra = 106. The cross-section area of the plate was fixed at three values, H·W/D2 = 0.01, 0.04, and 0.09, in which H and W are the height and width of the plate and D is the diameter of the enclosure while the aspect ratio changes, which makes the plate vertically placed (H > W) or horizontally placed (H < W). The objective of this work was to explore the effects of the orientation and aspect ratio of the plate on the characteristics of natural convection in various aspects. The numerical results reveal that the overall heat transfer rate is higher for the vertically placed plate and increases with the cross-section area, while the width of the plate has almost no effect for the horizontally placed plate, especially for the plate with a relatively large cross-section area. Depending on the orientation and aspect ratio, there can be one primary vortex, one primary a... [more]
Thermo-Fluidic Characteristics of Two-Phase Ice Slurry Flows Based on Comparative Numerical Methods
Shehnaz Akhtar, Haider Ali, Cheol Woo Park
January 7, 2020 (v1)
Keywords: heat transfer coefficient, ice slurry, mass fraction, two-phase flow
Ice slurry is a potential secondary refrigerant for commercial refrigeration systems because of its remarkable thermal properties. It is necessary to optimize the heat transfer process of ice slurry to reduce the energy consumption of the refrigeration system. Thus, this study investigates the heat transfer performance of single-phase (aqueous solution) and two-phase (ice slurry) refrigerants in a straight horizontal tube. The numerical simulations for ice slurry were performed with ice mass fraction ranging from 5% to 20%. The effects of flow velocity and ice concentration on the heat transfer coefficient were examined. The results showed that heat transfer coefficient of ice slurry is considerably higher than those of single-phase flow, particularly at high flow velocity and ice content, where increase in heat transfer with a factor of two was observed. The present results confirmed that ice slurry heat transfer ability is considerably affected by flow velocity and ice concentration... [more]
Model Study on Burden Distribution in COREX Melter Gasifier
Haifeng Li, Zongshu Zou, Zhiguo Luo, Lei Shao, Wenhui Liu
January 6, 2020 (v1)
Keywords: burden layer structure, burden pile width, COREX melter gasifier, mixed charging
COREX is one of the commercialized smelting reduction ironmaking processes. It mainly includes two reactors, i.e., a (reduction) shaft furnace (SF) and a melter gasifier (MG). In comparison with the conventional blast furnace (BF), the COREX MG is not only equipped with a more complicated top charging system consisting of one gimbal distributor for coal and eight flap distributors for direct reduction iron (DRI), but also the growth mechanism of its burden pile is in a developing phase, rather than that in a fully-developed phase in a BF. Since the distribution of charged burden plays a crucial role in determining the gas flow and thus in achieving a stable operation, it is of considerable importance to investigate the burden distribution influenced by the charging system of COREX MG. In the present work, a mathematical model is developed for predicting the burden distribution in terms of burden layer structure and radial ore/coal ratio within the COREX MG. Based on the burden pile wid... [more]
Systematic Study of Pressure Fluctuation in the Riser of a Dual Inter-Connected Circulating Fluidized Bed: Using Single and Binary Particle Species
Yusif A. Alghamdi, Zhengbiao Peng, Caimao Luo, Zeyad Almutairi, Behdad Moghtaderi, Elham Doroodchi
January 6, 2020 (v1)
Keywords: chemical looping combustion, circulating fluidized bed, cold flow model, fast fourier transform, power spectrum density, pressure fluctuation, riser
This study systematically investigates the pressure fluctuation in the riser of a dual interconnected circulating fluidized bed (CFB) representing a 10 kWth cold-flow model (CFM) of a chemical-looping combustion (CLC) system. Specifically, a single-species system (SSS) and a binary-mixtures system (BMS) of particles with different sizes and densities were utilized. The pressure fluctuation was analyzed using the fast Fourier transform (FFT) method. The effect of introducing a second particle, changing the inventory, composition (i.e., 5, 10 to 20 wt.%), particle size ratio, and fluidization velocity were investigated. For typical SSS experiments, the results were similar to those scarcely reported in the literature, where the pressure fluctuation intensity was influenced by varying the initial operating conditions. The pressure fluctuations of BMS were investigated in detail and compared with those obtained from SSS experiments. BMS exhibited different behaviour; it had intense pressur... [more]
Removal of an Ethoxylated Alkylphenol by Adsorption on Zeolites and Photocatalysis with TiO2/Ag
Claudia Aguilar Ucán, Mohamed Abatal, Carlos Montalvo Romero, Francisco Anguebes Franseschi, Miguel Angel Ramirez Elias, Denis Cantú Lozano
January 2, 2020 (v1)
Keywords: ethoxylated alkylphenol, heterogeneous photocatalysis, water pollution, zeolite adsorption
Two advanced removal methods (adsorption and photocatalysis) were compared for the elimination of an ethoxylated alkylphenol (nonylphenol polyethylene glycol, NPEG). For the adsorption process, zeolites were used in their natural state, and the process was characterized by DRX (X-ray diffraction) and SEM−EDS (Scanning electron microscopy). The analysis of the results of the adsorption kinetics was carried out using different isotherms to interpret the removal capacity of zeolites. The Temkin kinetic model better predicted the experimental data and was satisfactorily adjusted to models of pseudo-second order (PSO). On the other hand, for photocatalysis, nano-particles of Ag (silver) were deposited on titanium oxide (TiO2) Degussa-P25 by photo-deposition, and the catalyst was characterized by diffuse reflectance and SEM−EDS. The data obtained using the two removal techniques were analyzed by UV−Vis (ultraviolet-visible spectrophotometry) and total organic carbon (TOC). The kinetic data w... [more]
Transport and Deposition of Large Aspect Ratio Prolate and Oblate Spheroidal Nanoparticles in Cross Flow
Hans O. Åkerstedt
January 2, 2020 (v1)
Keywords: boundary layers, composite manufacturing, cross flow, deposition, non-spherical particles, Stokes flow, transport
The objective of this paper was to study the transport and deposition of non-spherical oblate and prolate shaped particles for the flow in a tube with a radial suction velocity field, with an application to experiments related to composite manufacturing. The transport of the non- spherical particles is governed by a convective diffusion equation for the probability density function, also called the Fokker−Planck equation, which is a function of the position and orientation angles. The flow is governed by the Stokes equation with an additional radial flow field. The concentration of particles is assumed to be dilute. In the solution of the Fokker−Planck equation, an expansion for small rotational Peclet numbers and large translational Peclet numbers is considered. The solution can be divided into an outer region and two boundary layer regions. The outer boundary layer region is governed by an angle-averaged convective-diffusion equation. The solution in the innermost boundary layer regi... [more]
A Numerical Study on Influent Flow Rate Variations in a Secondary Settling Tank
Junwei Su, Le Wang, Yumin Zhang, Zhaolin Gu
January 2, 2020 (v1)
Keywords: Computational Fluid Dynamics, numerical simulation, secondary settling tank, solid–liquid two-phase flow
The secondary settling tank is an essential unit for the biochemical treatment of domestic sewage, and its operational effect influences the quality of effluent. Under the influence of the confluence of rainwater and sewage, wastewater use habits, etc., the inflow of the secondary sedimentation tank changes over time. In this paper, OpenFOAM, an open-source computational fluid dynamics package, was used to study the dynamic behaviors of solid−liquid two-phase flow in the tank under influent flow rate variations. A coupled method including a mixture model, drift equation and a dynamic boundary method is proposed. Numerical investigations were carried out for a 2D axisymmetric sedimentation tank using 12 cases. With increasing influent flow rate, sludge accumulates continuously in the bottom left side of the tank, sludge hopper, and inlet; the sludge blanket thickness near the right end of the tank increases continuously; and the sludge concentration in the tank approximately linearly in... [more]
CFD Applications in Energy Engineering Research and Simulation: An Introduction to Published Reviews
Alfredo Iranzo
January 2, 2020 (v1)
Keywords: combustion, Computational Fluid Dynamics, energy engineering, heat transfer, Modelling, Renewable and Sustainable Energy, Simulation, thermal radiation, turbulence
Computational Fluid Dynamics (CFD) has been firmly established as a fundamental discipline to advancing research on energy engineering. The major progresses achieved during the last two decades both on software modelling capabilities and hardware computing power have resulted in considerable and widespread CFD interest among scientist and engineers. Numerical modelling and simulation developments are increasingly contributing to the current state of the art in many energy engineering aspects, such as power generation, combustion, wind energy, concentrated solar power, hydro power, gas and steam turbines, fuel cells, and many others. This review intends to provide an overview of the CFD applications in energy and thermal engineering, as a presentation and background for the Special Issue “CFD Applications in Energy Engineering Research and Simulation” published by Processes in 2020. A brief introduction to the most significant reviews that have been published on the particular topics is... [more]
CFD Simulation on Hydrodynamic Behaviors of Anaerobic Granule Swarms
Xiuqin Dong, Sheng Wang, Zhongfeng Geng
January 2, 2020 (v1)
Keywords: anaerobic granule swarm, Computational Fluid Dynamics, drag force coefficient, Reynolds number, voidage
An internal circulation (IC) anaerobic reactor is widely used in the treatment of municipal and industrial wastewater with high volumetric loading rates. The performance of an IC reactor is closely related with hydrodynamic behaviors of anaerobic granules. Typically, anaerobic granules work in swarms and the settling behavior of a granule is disturbed by other granules. However, the research on anaerobic granule swarms is insufficient. In this work, Computational Fluid Dynamics (CFD) method was employed to study the hydrodynamic behaviors of anaerobic granule swarms with various voidages. The simulated results showed that the average velocity inside granules increased significantly as the voidage of granule swarm decreased and as the Reynolds number increased. The maximum shear stress on the granule’s surface increased with decreasing voidage and increasing Reynolds number. Based on the hydrodynamic behaviors of anaerobic granule swarms, an improved model of drag force coefficient for... [more]
Lattice Boltzmann Simulation on Droplet Flow through 3D Metal Foam
Jian Zhang, Xinhai Yu, Shan-Tung Tu
January 2, 2020 (v1)
Keywords: droplet break, lattice Boltzmann method, metal foam, multiphase flow
The hydrodynamics of droplets passing through metal foam is investigated using the lattice Boltzmann method (LBM). The accurate 3D porous structure for the simulation is generated by X-ray micro-computed tomography. The simulated results are in good agreement with the experimental ones using high-speed video. The simulated results show that for droplets passing metal foam, there is a critical capillary number, Cac (around 0.061), above which the droplet continues to deform until it breaks up. The simulated results show that the capillary number, droplet size, pores diameter, and thickness of metal foam have the significant effect of droplets deforming and breaking up when the droplets pass through the metal foam. To avoid the calescence of two droplets at the inlet zone of the metal foam, the distance between droplets should be larger than three times the diameter of the droplet.
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