Experimental studies and CFD simulations of conical spouted bed hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Wang, Z.
2008-07-01
This thesis involved both experimental research and mathematical modelling of the hydrodynamics of conical spouted beds. Although conical spouted beds are commonly used for drying suspensions, solutions and pasty materials, they can also be used for catalytic partial oxidation of methane to synthesis gas, coal gasification and liquefaction, and pyrolysis of sawdust. Pressure transducers and static pressure probes were used in the experimental studies to investigate the evolution of the internal spout and the local static pressure distribution. Optical fibre probes were used to measure axial particle velocity profiles and voidage profiles. The gas mixing behaviour inside a conical spouted bed was examined using a step trace injection technique in which helium was used as the tracer and thermal conductivity cells were used as the detectors. For the mathematical modelling, a stream-tube model based on the bed structure inside a conical spouted bed was proposed to simulate partial spouting states. An adjustable parameter was introduced into the model to enable total pressure drop prediction under different operating conditions, and to estimate axial superficial gas velocity profiles and gauge pressure profiles. A mathematical model based on characteristics of conical spouted beds and FLUENT software was also developed and validated using measured experimental data. The proposed CFD model can simulate both stable spouting and partial spouting states, with an adjustable solids-phase source term. The effect of all possible factors on simulation results were investigated, including the fluid inlet profile, solid bulk viscosity, frictional viscosity, restitution coefficient, exchange coefficient, and solid phase source term. In addition to simulating the gas mixing behaviours inside a conical spouted bed, the new CFD model simulated cylindrical packed beds and cylindrical fluidized beds in one code package.
Directory of Open Access Journals (Sweden)
Hoffmann Alex C.
2013-05-01
Full Text Available Particle tracks in a hydrocyclone generated both experimentally by positron emission particle tracking (PEPT and numerically with Eulerian-Lagranian CFD have been studied and compared. A hydrocyclone with a cylinder-on-cone design was used in this study, the geometries used in the CFD simulations and in the experiments being identical. It is shown that it is possible to track a fast-moving particle in a hydrocyclone using PEPT with high temporal and spatial resolutions. The numerical 3-D particle trajectories were generated using the Large Eddy Simulation (LES turbulence model for the fluid and Lagrangian particle tracking for the particles. The behaviors of the particles were analyzed in detail and were found to be consistent between experiments and CFD simulations. The tracks of the particles are discussed and related to the fluid flow field visualized in the CFD simulations using the cross-sectional static pressure distribution.
Combining CFD simulation with experimental RTD function for hydrocyclone separator studies
International Nuclear Information System (INIS)
The first part of this report presents radiotracer experimental Residence Time Distribution (RTD) functions for hydrocyclone separators, their analysis and macro modelling. The second part of the report presents the Computational Fluid Dynamics (CFD) simulation for the hydrocyclone. Combining the experimental data and the CFD simulation results allows understanding the fundamental principles of the flow and solids' separation in hydrocyclone. The experimental data help choosing the proper parameters for CFD simulation and from the other side the CFD results allow better analysis and macro modelling of the experimental data. Radiotracer methods have been used for industrial experiments. For CFD simulation the FLUENT software has been applied. (author)
CFD Simulations of Soap Separation; CFD-simulering av avsaapning
Energy Technology Data Exchange (ETDEWEB)
Birkestad, Per
2010-07-01
A part of Vaermeforsk, the 'Skogsindustriella programmet', has identified the possibility to increase the production of tall oil, and hence the competitiveness, in Swedish pulp mills through an increase in the efficiency of the soap separation tanks. Currently, soap is extracted from the black liquor through a sedimentation process where the less dense soap rise to the top of the liquor tank where it is removed through a over-flow ducting at the top of the tank. Vaermeforsk seeks a better understanding of the detailed flow and the separation mechanisms within the liquor tanks and has initiated a study of computational fluid dynamics (CFD) of the tanks. The aim of the study has been threefold; To develop CFD-methods for use in the study of soap separation processes, to investigate the detailed flow within two Swedish liquor tanks and one North American soap skimmer and lastly to develop new design rules for use in future designs of soap separation tanks. The project shows that CFD is a useful tool for the investigation of black liquor and soap flow within a soap separation tank. The CFD simulations of three existing liquor tanks show that the previously used design-rules based on surface loads are inadequate as the actual flow velocities within the tanks are two orders of magnitude larger than those previously used as reference (the surface load). The CFD simulations also show that the black liquor flow, and hence the soap separation, is very sensitive to density variations on the black liquor inlet and temperature variations as small as 1 deg C can significantly affect the liquor flow.
Thermal hydraulic simulations, error estimation and parameter sensitivity studies in Drekar::CFD
Energy Technology Data Exchange (ETDEWEB)
Smith, Thomas Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Shadid, John N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pawlowski, Roger P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Cyr, Eric C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wildey, Timothy Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2014-01-01
This report describes work directed towards completion of the Thermal Hydraulics Methods (THM) CFD Level 3 Milestone THM.CFD.P7.05 for the Consortium for Advanced Simulation of Light Water Reactors (CASL) Nuclear Hub effort. The focus of this milestone was to demonstrate the thermal hydraulics and adjoint based error estimation and parameter sensitivity capabilities in the CFD code called Drekar::CFD. This milestone builds upon the capabilities demonstrated in three earlier milestones; THM.CFD.P4.02 [12], completed March, 31, 2012, THM.CFD.P5.01 [15] completed June 30, 2012 and THM.CFD.P5.01 [11] completed on October 31, 2012.
CFD simulations to study the effects of wall protrusions on microfluidic mixing
International Nuclear Information System (INIS)
In this study the effects of different types of wall protrusions on microfluidic mixing are studied using computational fluid dynamics (CFD) simulations. Two new protrusions, single first bracket protrusions and double opposite first bracket protrusions (DOFBPs), are conceptualized, evaluated through CFD simulations and compared to protrusions having standard geometrical shapes, e.g. rectangular protrusions, triangular protrusions and semicircular protrusions. In the range of Reynolds numbers covered in this study, the microchannel having an opposed T-junction and DOFBPs is found to provide good mixing. A hybrid approach relying on the modification of microfluidic junctions as well as wall protrusions for enhancing microfluidic mixing is also evaluated. The microchannel based on the hybrid approach of an OA 10°–20°–165° WY-junction and DOFBPs is also found to provide very good mixing for a wide range of Reynolds numbers. (paper)
CFD simulations to study the effects of wall protrusions on microfluidic mixing
Sarkar, Sourav; Singh, K. K.; Shankar, V.; Shenoy, K. T.
2015-08-01
In this study the effects of different types of wall protrusions on microfluidic mixing are studied using computational fluid dynamics (CFD) simulations. Two new protrusions, single first bracket protrusions and double opposite first bracket protrusions (DOFBPs), are conceptualized, evaluated through CFD simulations and compared to protrusions having standard geometrical shapes, e.g. rectangular protrusions, triangular protrusions and semicircular protrusions. In the range of Reynolds numbers covered in this study, the microchannel having an opposed T-junction and DOFBPs is found to provide good mixing. A hybrid approach relying on the modification of microfluidic junctions as well as wall protrusions for enhancing microfluidic mixing is also evaluated. The microchannel based on the hybrid approach of an OA 10°-20°-165° WY-junction and DOFBPs is also found to provide very good mixing for a wide range of Reynolds numbers.
International Nuclear Information System (INIS)
Particle tracks in a hydro-cyclone generated both experimentally by positron emission particle tracking (PEPT) and numerically with Eulerian-Lagrangian CFD have been studied and compared. A hydro-cyclone with a cylinder-on-cone design was used in this study, the geometries used in the CFD simulations and in the experiments being identical. It is shown that it is possible to track a fast-moving particle in a hydro-cyclone using PEPT with high temporal and spatial resolutions. The numerical 3-D particle trajectories were generated using the Large Eddy Simulation (LES) turbulence model for the fluid and Lagrangian particle tracking for the particles. The behaviors of the particles were analyzed in detail and were found to be consistent between experiments and CFD simulations. The tracks of the particles are discussed and related to the fluid flow field visualized in the CFD simulations using the cross-sectional static pressure distribution. (authors)
Directory of Open Access Journals (Sweden)
Tholudin Mat Lazim
2004-01-01
Full Text Available The main objective of the present work is to study the effect of an external store to a subsonic fighter aircraft. Generally most modern fighter aircraft is designed with an external store installation. In this project a subsonic fighter aircraft model has been manufactured using a computer numerical control machine for the purpose of studying the effect of the external store aerodynamic interference on the flow around the aircraft wing. A computational fluid dynamic (CFD and wind tunnel testing experiments have been carried out to ensure the aerodynamic characteristic of the model then certified the aircraft will not facing any difficulties in stability and controllability. In the CFD experiment, commercial CFD code is used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model together with an external store was tested in a low speed wind tunnel with test section sized 0.45 m×0.45 m. Result in the two-dimensional pressure distribution obtained by both experiments are comparable. There is only 12% deviation in pressure distribution found in wind tunnel testing compared to the result predicted by the CFD. The result shows that the effect of the external storage is only significant at the lower surface of the wing and almost negligible at the upper surface of the wing. Aerodynamic interference is due to the external storage were mostly evidence on a lower surface of the wing and almost negligible on the upper surface at low angle of attack. In addition, the area of influence on the wing surface by store interference increased as the airspeed increase.
There is a need to properly develop the application of Computational Fluid Dynamics (CFD) methods in support of air quality studies involving pollution sources near buildings at industrial sites. CFD models are emerging as a promising technology for such assessments, in part due ...
Experimental study and CFD simulation of rotational eccentric cylinder in a magnetorheological fluid
Energy Technology Data Exchange (ETDEWEB)
Omidbeygi, F. [Computational Fluid Dynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, 16846 Tehran (Iran, Islamic Republic of); Hashemabadi, S.H., E-mail: hashemabadi@iust.ac.ir [Computational Fluid Dynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, 16846 Tehran (Iran, Islamic Republic of)
2012-07-15
In this study, a magnetorheological (MR) fluid is prepared using carbonyl iron filings and low viscosity lubricating oil. The effects of magnetic field and weight percentage of particles on the viscosity of the MR fluid have been measured using a rotational viscometer. The yield stress under an applied magnetic field was also obtained experimentally. In the absence of an applied magnetic field, the MR fluid behaves as a Newtonian fluid. When the magnetic field is applied, the MR fluid behaves like Bingham plastics with a magnetic field dependent yield stress. Afterward, the results compared with those of CFD simulation of two eccentric cylinders in the MR fluid. Results show that the influences of MR effects, caused by the applied magnetic field, on the model characteristics are significant and not negligible. The viscosity is enhanced by increasing of the magnetic field, eccentricity ratio and weight percentage of suspensions. The MR effects and increasing of weight percentage and eccentricity ratio also provide an enhancement in the yield stresses and required total torque for rotation of inner cylinder. Also the simulation results indicate a good representation of the experiment by the model. - Highlights: Black-Right-Pointing-Pointer Preparation of a magnetorheological fluid with carbonyl iron particles in lubricating oil. Black-Right-Pointing-Pointer Rheological measurement for influence of solid content and magnetic field intensity. Black-Right-Pointing-Pointer Simulation of eccentric rotating cylinder in prepared MR fluid with CFD techniques.
Integrating CFD and building simulation
DEFF Research Database (Denmark)
Bartak, M.; Beausoleil-Morrison, I.; Clarke, J.A.;
2002-01-01
To provide practitioners with the means to tackle problems related to poor indoor environments, building simulation and computational 3uid dynamics can usefully be integrated within a single computational framework. This paper describes the outcomes from a research project sponsored by the European...... Commission, which furthered the CFD modelling aspects of the ESP-r system. The paper summarises the form of the CFD model, describes the method used to integrate the thermal and 3ow domains and reports the outcome from an empirical validation exercise. © 2002 Published by Elsevier Science Ltd....
Efficient Turbulence Modeling for CFD Wake Simulations
DEFF Research Database (Denmark)
van der Laan, Paul
Wind turbine wakes can cause 10-20% annual energy losses in wind farms, and wake turbulence can decrease the lifetime of wind turbine blades. One way of estimating these effects is the use of computational fluid dynamics (CFD) to simulate wind turbines wakes in the atmospheric boundary layer. Since...... wind farm, the simulated results cannot be compared directly with wind farm measurements that have a high uncertainty in the measured reference wind direction. When this uncertainty is used to post-process the CFD results, a fairer comparison with measurements is achieved....... this flow is in the high Reynolds number regime, it is mainly dictated by turbulence. As a result, the turbulence modeling in CFD dominates the wake characteristics, especially in Reynolds-averaged Navier-Stokes (RANS). The present work is dedicated to study and develop RANS-based turbulence models...
Li, Kun; Yu, Zhuang
2008-01-01
Urban heat islands are one of the most critical urban environment heat problems. Landsat ETM+ satellite data were used to investigate the land surface temperature and underlying surface indices such as NDVI and NDBI. A comparative study of the urban heat environment at different scales, times and locations was done to verify the heat island characteristics. Since remote sensing technology has limitations for dynamic flow analysis in the study of urban spaces, a CFD simulation was used to validate the improvement of the heat environment in a city by means of wind. CFD technology has its own shortcomings in parameter setting and verification, while RS technology is helpful to remedy this. The city of Wuhan and its climatological condition of being hot in summer and cold in winter were chosen to verify the comparative and combinative application of RS with CFD in studying the urban heat island.
Directory of Open Access Journals (Sweden)
Zhuang Yu
2008-10-01
Full Text Available Urban heat islands are one of the most critical urban environment heat problems. Landsat ETM+ satellite data were used to investigate the land surface temperature and underlying surface indices such as NDVI and NDBI. A comparative study of the urban heat environment at different scales, times and locations was done to verify the heat island characteristics. Since remote sensing technology has limitations for dynamic flow analysis in the study of urban spaces, a CFD simulation was used to validate the improvement of the heat environment in a city by means of wind. CFD technology has its own shortcomings in parameter setting and verification, while RS technology is helpful to remedy this. The city of Wuhan and its climatological condition of being hot in summer and cold in winter were chosen to verify the comparative and combinative application of RS with CFD in studying the urban heat island.
Recent Efforts for Credible CFD Simulations in China
Directory of Open Access Journals (Sweden)
Li Li
2011-01-01
Full Text Available In this paper some recent efforts for credible computational fluid dynamics (CFD simulations in China are reviewed. The most important effort is that, following similar activities in the West such as ECARP and AIAA Drag Prediction Workshops, a series of workshops on credible CFD simulations had been initiated. These workshops were with ambitions to assess the status of CFD in China. Another major effort is an ongoing project to establish a software platform for studying the credibility of CFD solvers and performing credible CFD simulations. The platform, named WiseCFD, was designed to implement a seamless CFD process and to circumvent tedious repeating manual operations. It had also been a powerful job manager for CFD with capabilities to support plug and play (PnP solver integration as well as distributed or parallel computations. Some future work on WiseCFD was proposed, and also envisioned was how WiseCFD and the European QNET-CFD Knowledge Base can benefit mutually.
Directory of Open Access Journals (Sweden)
Tholudin Mat Lazim
2003-01-01
Full Text Available The main objective of the present work is to study the effect of an external store on a subsonic fighter aircraft. Generally most modern fighter aircrafts are designed with an external store installation. In this study, a subsonic fighter aircraft model has been manufactured using a computer numerical control machine for the purpose of studying the effect of the aerodynamic interference of the external store on the flow around the aircraft wing. A computational fluid dynamic (CFD simulation was also carried out on the same configuration. Both the CFD and the wind tunnel testing were carried out at a Reynolds number 1.86×105 to ensure that the aerodynamic characteristic can certify that the aircraft will not be face any difficulties in its stability and controllability. Both the experiments and the simulation were carried out at the same Reynolds number in order to verify each other. In the CFD simulation, a commercial CFD code was used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model together with an external store was tested in a low speed wind tunnel with a test section sized 0.45 m×0.45 m. Measured and computed results for the two-dimensional pressure distribution were satisfactorily comparable. There is only a 19% deviation between pressure distribution measured in wind tunnel testing and the result predicted by the CFD. The result shows that the effect of the external storage is only significant on the lower surface of the wing and almost negligible on the upper surface of the wing. Aerodynamic interference due to the external store was most evident on the lower surface of the wing and almost negligible on the upper surface at a low angle of attack. In addition, the area of influence on the wing surface by the store interference increased as the airspeed increased.
Recent Efforts for Credible CFD Simulations in China
Bai Wen; Li Li; Liang Yihua
2011-01-01
In this paper some recent efforts for credible computational fluid dynamics (CFD) simulations in China are reviewed. The most important effort is that, following similar activities in the West such as ECARP and AIAA Drag Prediction Workshops, a series of workshops on credible CFD simulations had been initiated. These workshops were with ambitions to assess the status of CFD in China. Another major effort is an ongoing project to establish a software platform for studying the credibility of CF...
Energy Technology Data Exchange (ETDEWEB)
Morghi, Youssef; Mesquita, Amir Zacarias; Santos, Andre Augusto Campagnole dos; Vasconcelos, Victor, E-mail: ymo@cdtn.br, E-mail: amir@cdtn.br, E-mail: aacs@cdtn.br, E-mail: vitors@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)
2015-07-01
For the experimental study on the air/water countercurrent flow limitation in Nuclear Reactors, were built at CDTN an acrylic test sections with the same geometric shape of 'hot leg' of a Pressurized Water Reactor (PWR). The hydraulic circuit is designed to be used with air and water at pressures near to atmospheric and ambient temperature. Due to the complexity of the CCFL experimental, the numerical simulation has been used. The aim of the numerical simulations is the validation of experimental data. It is a global trend, the use of computational fluid dynamics (CFD) modeling and prediction of physical phenomena related to heat transfer in nuclear reactors. The most used CFD codes are: FLUENT®, STAR- CD®, Open Foam® and CFX®. In CFD, closure models are required that must be validated, especially if they are to be applied to nuclear reactor safety. The Thermal- Hydraulics Laboratory of CDTN offers computing infrastructure and license to use commercial code CFX®. This article describes a review about CCFL and the use of CFD for numerical simulation of this phenomenal for Nuclear Rector. (author)
International Nuclear Information System (INIS)
For the experimental study on the air/water countercurrent flow limitation in Nuclear Reactors, were built at CDTN an acrylic test sections with the same geometric shape of 'hot leg' of a Pressurized Water Reactor (PWR). The hydraulic circuit is designed to be used with air and water at pressures near to atmospheric and ambient temperature. Due to the complexity of the CCFL experimental, the numerical simulation has been used. The aim of the numerical simulations is the validation of experimental data. It is a global trend, the use of computational fluid dynamics (CFD) modeling and prediction of physical phenomena related to heat transfer in nuclear reactors. The most used CFD codes are: FLUENT®, STAR- CD®, Open Foam® and CFX®. In CFD, closure models are required that must be validated, especially if they are to be applied to nuclear reactor safety. The Thermal- Hydraulics Laboratory of CDTN offers computing infrastructure and license to use commercial code CFX®. This article describes a review about CCFL and the use of CFD for numerical simulation of this phenomenal for Nuclear Rector. (author)
CFD Simulation of Annular Centrifugal Extractors
Directory of Open Access Journals (Sweden)
S. Vedantam
2012-01-01
Full Text Available Annular centrifugal extractors (ACE, also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of centrifugal field. For the development of rational and reliable design procedures, it is important to understand the flow patterns in the mixer and settler zones. Computational Fluid Dynamics (CFD has played a major role in the constant evolution and improvements of this device. During the past thirty years, a large number of investigators have undertaken CFD simulations. All these publications have been carefully and critically analyzed and a coherent picture of the present status has been presented in this review paper. Initially, review of the single phase studies in the annular region has been presented, followed by the separator region. In continuation, the two-phase CFD simulations involving liquid-liquid and gas-liquid flow in the annular as well as separator regions have been reviewed. Suggestions have been made for the future work for bridging the existing knowledge gaps. In particular, emphasis has been given to the application of CFD simulations for the design of this equipment.
Experimental Measurements and CFD Simulations
Directory of Open Access Journals (Sweden)
Arijit A. Ganguli
2012-01-01
Full Text Available Bubble dynamics of a single condensing vapor bubble in a subcooled pool boiling system with a centrally heated cylindrical tank has been studied in the Rayleigh number range 7.9×1012
Zhuang Yu; Kun Li
2008-01-01
Urban heat islands are one of the most critical urban environment heat problems. Landsat ETM+ satellite data were used to investigate the land surface temperature and underlying surface indices such as NDVI and NDBI. A comparative study of the urban heat environment at different scales, times and locations was done to verify the heat island characteristics. Since remote sensing technology has limitations for dynamic flow analysis in the study of urban spaces, a CFD simulation was used to vali...
CFD simulation of coaxial injectors
Landrum, D. Brian
1993-01-01
The development of improved performance models for the Space Shuttle Main Engine (SSME) is an important, ongoing program at NASA MSFC. These models allow prediction of overall system performance, as well as analysis of run-time anomalies which might adversely affect engine performance or safety. Due to the complexity of the flow fields associated with the SSME, NASA has increasingly turned to Computational Fluid Dynamics (CFD) techniques as modeling tools. An important component of the SSME system is the fuel preburner, which consists of a cylindrical chamber with a plate containing 264 coaxial injector elements at one end. A fuel rich mixture of gaseous hydrogen and liquid oxygen is injected and combusted in the chamber. This process preheats the hydrogen fuel before it enters the main combustion chamber, powers the hydrogen turbo-pump, and provides a heat dump for nozzle cooling. Issues of interest include the temperature and pressure fields at the turbine inlet and the thermal compatibility between the preburner chamber and injector plate. Performance anomalies can occur due to incomplete combustion, blocked injector ports, etc. The performance model should include the capability to simulate the effects of these anomalies. The current approach to the numerical simulation of the SSME fuel preburner flow field is to use a global model based on the MSFC sponsored FNDS code. This code does not have the capabilities of modeling several aspects of the problem such as detailed modeling of the coaxial injectors. Therefore, an effort has been initiated to develop a detailed simulation of the preburner coaxial injectors and provide gas phase boundary conditions just downstream of the injector face as input to the FDNS code. This simulation should include three-dimensional geometric effects such as proximity of injectors to baffles and chamber walls and interaction between injectors. This report describes an investigation into the numerical simulation of GH2/LOX coaxial
Directory of Open Access Journals (Sweden)
Yan Zhenghua
2013-11-01
Full Text Available Large scale fire tests of building external wall insulation system were conducted. In the experiment, thermal-couples were mounted to measure the insulation system surface temperature and the gas temperature inside rooms at the second and third floors. Photos were also taken during the fire tests. The measurement provides information of the ignition and fire spread of the external insulation system which consists of surface protection layer, glass fibre net, bonding thin layer, anchor and the load bearing wall. Comprehensive simulations of the fire tests were carried out using an advanced CFD fire simulation software Simtec (Simulation of Thermal Engineering Complex [1, 2], which is now released by Simtec Soft Sweden, with the turbulent flow, turbulent combustion, thermal radiation, soot formation, convective heat transfer, the fully coupled three dimensional heat transfer inside solid materials, the ‘burn-out' of the surface protection layer and the pyrolysis of the insulation layer, etc, all computed. The simulation is compared with experimental measurement for validation. The simulation well captured the burning and fire spread of the external insulation wall.
CFD simulation of neutral ABL flows
DEFF Research Database (Denmark)
Zhang, Xiaodong
This work is to evaluate the CFD prediction of Atmospheric Boundary Layer flow field over different terrains employing Fluent 6.3 software. How accurate the simulation could achieve depend on following aspects: viscous model, wall functions, agreement of CFD model with inlet wind velocity profile...... and top boundary condition. Fluent employ wall function roughness modifications based on data from experiments with sand grain roughened pipes and channels, describe wall adjacent zone with Roughness Height (Ks) instead of Roughness Length (z0). In a CFD simulation of ABL flow, the mean wind velocity...... ABL and the measurements are best documented until now. Comparison with measured data shows that the CFD model can well predict the velocity field and relative turbulence kinetic energy field. Furthermore, a series of artificial complex terrains are designed, and some of the main simulation results...
CFD simulation of nuclear graphite oxidation / P. Sukdeo.
Sukdeo, Preeyanand
2010-01-01
This study investigates the development of a strategy to simulate nuclear graphite oxidation with Computational Fluid Dynamics (CFD) to determine an estimate of graphite lost. The task was achieved by comparing the results of the CFD approach with a number of different experiments. For molecular diffusion, simulated results were compared to analytical solutions. Mass flow rates under conditions of natural convection were sourced from the 2002 NACOK experiment. Experimental data...
CFD simulation of nanofiber-enhanced air filter media
Tronville, Paolo Maria
2015-01-01
The first step in a CFD analysis of filter media flow is to create a computational domain geometry which imitates the simulated media as closely as is practical. The media in the present study combined a relatively flat web of nanofibers with a cellulosic fiber support media. A CFD grid suited to calculating the flow patterns through the cellulosic media structure would be far too coarse to simulate flow around the nanofiber web elements. This scale difference forces some assumption about the...
Ratkovich, N; Chan, C C V; Bentzen, T R; Rasmussen, M R
2012-01-01
Membrane bioreactors (MBRs) have been used successfully in biological wastewater treatment for effective solids-liquid separation. However, a common problem encountered with MBR systems is fouling of the membrane resulting in frequent membrane cleaning and replacement which makes the system less appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be improved by understanding the shear stress over the membrane surface. Modern tools such as computational fluid dynamics (CFD) can be used to diagnose and understand the shear stress in an MBR. Nevertheless, proper experimental validation is required to validate CFD simulation. In this work experimental measurements of shear stress induced by impellers at a membrane surface were made with an electrochemical approach and the results were used to validate CFD simulations. As good results were obtained with the CFD model (<9% error), it was extrapolated to include the non-Newtonian behaviour of activated sludge. PMID:22592479
International Nuclear Information System (INIS)
Chemical Looping Combustion is an energy efficient combustion technology for the inherent separation of carbon dioxide for both gaseous and solid fuels. For scale up and further development of this process multi-phase CFD-based simulations have a strong potential which rely on kinetic models for the solid/gaseous reactions. Reaction models are usually simple in structure in order to keep the computational cost low. They are commonly derived from thermogravimetric experiments. With only few CFD-based simulations performed on chemical looping combustion, there is a lack in understanding of the role and of the sensitivity of the applied chemical reaction model on the outcome of a simulation. The aim of this investigation is therefore the study of three different carrier materials CaSO4, Mn3O4 and NiO with the gaseous fuels H2 and CH4 in a batch type reaction vessel. Four reaction models namely the linear shrinking core, the spherical shrinking core, the Avrami-Erofeev and a recently proposed multi parameter model are applied and compared on a case by case basis. (authors)
CFD Simulation and Experimental Study of Winglets at Low Subsonic Flow
Directory of Open Access Journals (Sweden)
Sanjay Kumar Sardiwal
2014-05-01
Full Text Available A winglet is a device attached at the wingtip, used to improve aircraft efficiency by lowering the induced drag caused by wingtip vortices. It is a vertical or angled extension at the tips of each wing. Winglets work by increasing the effective aspect ratio of a wing without adding greatly to the structural stress and hence necessary weight of the wing structure. This paper describes a CFD 3-dimensional winglets analysis that was performed on a rectangular wing of NACA653218 cross sectional airfoil. The wing is of 660 mm span and 121 mm chord and was analyzed for two shape configurations, semicircle and elliptical. The objectives of the analysis were to compare the aerodynamic characteristics of the two winglet configurations and to investigate the performance of the two winglets shape simulated at selected cant angle of 0, 45 and 60 degrees. The computational simulation was carried out by FLUENT 6.2 solver using Finite Volume Approach. The simulation was done at low subsonic flow and at various angles of attack using Spalart-Allmaras couple implicit solver. A comparison of aerodynamics characteristics of lift coefficient CL , drag coefficient CD and lift to drag ratio, L/D was made and it was found that the addition of the elliptical and semi circular winglet gave a larger lift curve slope and higher Lift-to-Drag Ratio in comparison to the baseline wing alone. Elliptical winglet with 45 degree cant angle was the best overall design giving about 8 percent increase in lift curve slope and the best Lift-to-Drag Ratio.
CFD simulation of neutral ABL flows
Zhang, Xiaodong
2009-01-01
This work is to evaluate the CFD prediction of Atmospheric Boundary Layer flow field over different terrains employing Fluent 6.3 software. How accurate the simulation could achieve depend on following aspects: viscous model, wall functions, agreement of CFD model with inlet wind velocity profile and top boundary condition. Fluent employ wall function roughness modifications based on data from experiments with sand grain roughened pipes and channels, describe wall adjacent zone with Roughness...
CFD Technology for Rotorcraft Gearbox Windage Aerodynamics Simulation
Handschuh, Robert; Hill, Matthew; Kunz, Robert; Long, Lyle; Morris, Philip; Noack, Ralph
2009-01-01
A computational fluid dynamics (CFD) method is adapted, validated and applied to spinning gear systems with emphasis on predicting windage losses. Several spur gears and a disc are studied. The CFD simulations return good agreement with measured windage power loss. Turbulence modeling choices, the relative importance of viscous and pressure torques with gear speed and the physics of the complex 3-D unsteady flow field in the vicinity of the gear teeth are studied.
Comparative Study for Modeling Reactor Internal Geometry in CFD Simulation of PHWR Internal Flow
Energy Technology Data Exchange (ETDEWEB)
Lee, Gong Hee; Woo, Sweng Woong; Cheong, Ae Ju [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)
2013-10-15
The main objective of the present study is to compare the results predicted by using either the real geometry of tubes or porous medium assumption and to assess the prediction performance of both methods. Estimating the local subcooling of the moderator in a CANDU calandria under transient conditions is one of the major concerns in the CANDU safety analysis. Therefore extensive CFD analyses have been performed for predicting the moderator temperature in a CANDU calandria or its similar shape. However most of previous studies used a porous medium assumption instead of considering the real geometry of calandria tube. A porous medium assumption has some possible weaknesses; The increased production of turbulence due to vortex shedding in the wake of the individual tubes is not considered in the turbulence model. It is difficult to identify the true effects of the outer ring of calandria tubes on the generation of the highly non-uniform flows in the reflector region. It is not clear how well the pressure loss models quantitatively represent the three-dimensional effects of the turbulent flows through the calandria tubes.
Application perspectives of simulation techniques CFD in nuclear power plants
International Nuclear Information System (INIS)
The scenarios simulation in nuclear power plants is usually carried out with system codes that are based on concentrated parameters networks. However situations exist in some components where the flow is predominantly 3-D, as they are the natural circulation, mixed and stratification phenomena. The simulation techniques of computational fluid dynamics (CFD) have the potential to simulate these flows numerically. The use of CFD simulations embraces many branches of the engineering and continues growing, however, in relation to its application with respect to the problems related with the safety in nuclear power plants, has a smaller development, although is accelerating quickly and is expected that in the future they play a more emphasized paper in the analyses. A main obstacle to be able to achieve a general acceptance of the CFD is that the simulations should have very complete validation studies, sometimes not available. In this article a general panorama of the state of the methods application CFD in nuclear power plants is presented and the problem associated to its routine application and acceptance, including the view point of the regulatory authorities. Application examples are revised in those that the CFD offers real benefits and are also presented two illustrative study cases of the application of CFD techniques. The case of a water recipient with a heat source in its interior, similar to spent fuel pool of a nuclear power plant is presented firstly; and later the case of the Boron dilution of a water volume that enters to a nuclear reactor is presented. We can conclude that the CFD technology represents a very important opportunity to improve the phenomena understanding with a strong component 3-D and to contribute in the uncertainty reduction. (Author)
CFD simulation of pulse combustion's performance
Rahmatika, Annie Mufyda; Widiyastuti, W.; Winardi, Sugeng; Nurtono, Tantular; Machmudah, Siti; Kusdianto, Joni, I. Made
2016-02-01
This study aims to show changes in the performance of combustion using pulse combustion at specified intervals using simulation. Simulations is performed using Computational Fluid Dynamics analysis (CFD) software Ansys Fluent 15.0. Analysis used 2D illustration axisymmetric with k-ɛ turbulence models. Propane was selected as fuel at a flow rate of 15 L/min. Air with flow rate of 375 L/min is used as oxidizer. To investigate the advantages of using pulse combustion, the simulated pulse combustion is compared to normal combustion without a pulse. This is done by displaying descriptions of the phenomenon, mechanisms and results output gas combustor. From the analysis of simulation results showed that in 1 minute burning time, burning fuel without requiring pulse as much as 15 L while the pulse combustion requires half of the fuel which is 12.5 L. However, the higher average of temperature was generated by pulse combustion and the amounts of unburned fuel that comes out of the combustor less than without the use of pulse combustion. So, it can be concluded that the pulse combustion is more efficient than combustion without a pulse.
Validation of Francis Water Turbine CFD Simulations
Čarija, Zoran; Mrša, Zoran; Fućak, Sanjin
2008-01-01
This paper compares data from calculated and measured results covering the whole operating range for a 20 MW Francis turbine in order to validate the CFD simulation. Computed hydraulic characteristics are determined for each analyzed operating point by running numerical simulations of turbulent fluid flow through a complete Francis Turbine model using the commercial fluid flow solver Fluent. The measured hydraulic characteristics were defined by on-site measurements according to the IEC41 int...
Roles of Ⅴ/Ⅲ ratio and mixture degree in GaN growth: CFD and MD simulation study
Institute of Scientific and Technical Information of China (English)
Zhou An; Xiu Xiang-Qian; Zhang Rong; Xie Zi-Li; Hua Xue-Mei; Liu Bin; Han Ping
2013-01-01
To understand the mechanism of Gallium nitride (GaN) film growth is of great importance for their potential applications.In this paper,we investigate the growth behavior of the GaN film by combining computational fluid dynamics (CFD) and molecular dynamics (MD) simulations.Both of the simulations show that Ⅴ/Ⅲ mixture degree can have important impacts on the deposition behavior,and it is found that the more uniform the mixture is,the better the growth is.Besides,by using MD simulations,we illustrate the whole process of the GaN growth.Furthermore,we also find that the Ⅴ/Ⅲ ratio can affect the final roughness of the GaN film.When the Ⅴ/Ⅲ ratio is high,the surface of final GaN film is smooth.The present study provides insights into GaN growth from the macroscopic and microscopic views,which may provide some suggestions on better experimental GaN preparation.
Directory of Open Access Journals (Sweden)
Amol S. Kinkar
2015-02-01
Full Text Available Abstract Heavy industrialization amp modernization of society demands in increasing of power cause to research amp develop new technology amp efficient utilization of existing power units. Variety of sources are available for power generation such as conventional sources like thermal hydro nuclear and renewable sources like wind tidal biomass geothermal amp solar. Out of these most common amp economical way for producing the power is by thermal power stations. Various industrial boilers plays an important role to complete the power generation cycle such as CFBC Circulating Fluidized Bed Combustion FBC Fluidized Bed Combustion AFBC Atmospheric Fluidized Bed Combustion Boiler CO Boiler RG amp WHR Boiler Waster heat recovery Boiler. This paper is intended to comprehensively give an account of knowledge related to refractory amp its failure in CFBC boiler with due effect of flue gas flow during operation on refractory by using latest technology of CAD Computer aided Design amp CAE Computer aided Engineering. By conceptual application of these technology the full scale model is able to analyze in regards the flow of flue gas amp bed material flow inside the CFBC loop via CFD Computational Fluid Dynamics software. The results obtained are helpful to understand the impact of gas amp particles on refractory in different areas amp also helped to choose suitable refractory material in different regions.
Development and application of computational fluid dynamics (CFD) simulations are being advanced through case studies for simulating air pollutant concentrations from sources within open fields and within complex urban building environments. CFD applications have been under deve...
Numerical study and simulation of nano-bubble formation with CFD
Hamid Reza Ghorbani; Vahid Ghorbani
2014-01-01
In recent years, microbubble and nanobubble technologies have drawn great attention due to their wide applications in many fields of science and technology, such as water treatment, biomedical engineering, and nanomaterials. In this work, we numerically studied nano-bubble formation process by entering air into a submerged orifice in a cylindrical vessel. The simulations were carried out using SOLA-VOF method. In this code, complete form of Navier-stocks equations was predicted two dimensions...
Numerical study and simulation of nano-bubble formation with CFD
Directory of Open Access Journals (Sweden)
Hamid Reza Ghorbani
2014-09-01
Full Text Available In recent years, microbubble and nanobubble technologies have drawn great attention due to their wide applications in many fields of science and technology, such as water treatment, biomedical engineering, and nanomaterials. In this work, we numerically studied nano-bubble formation process by entering air into a submerged orifice in a cylindrical vessel. The simulations were carried out using SOLA-VOF method. In this code, complete form of Navier-stocks equations was predicted two dimensions and using finite difference method. In addition, the effect of air flow rate on the nano-bubble size and its formation time at very low rates was studied.
CFD simulation of an industrial hydrocyclone with Eulerian-Eulerian approach:A case study
Institute of Scientific and Technical Information of China (English)
Safa Raziyeh; Soltani Goharrizi Ataallah⇑
2014-01-01
In the present study, a three-dimensional computational fluid dynamics simulation together with exper-imental field measurements was applied to optimize the performance of an industrial hydrocyclone at Sarcheshmeh copper complex. In the simulation, the Eulerian-Eulerian approach was used for solid and liquid phases, the latter being water. In this approach, nine continuous phases were considered for the solid particles with different sizes and one continuous phase for water. The continuity and momen-tum equations with inclusion of buoyancy and drag forces were solved by the finite volume method. The k-e RNG turbulence model was used for modeling of turbulency. There was a good agreement between the simulation results and the experimental data. After validation of the model accuracy, the effect of inlet solid percentage, pulp inlet velocity, rod inserting in the middle of the hydrocyclone and apex diam-eter on hydrocyclone performance was investigated. The results showed that by decreasing the inlet solid percentage and increasing the pulp inlet velocity, the efficiency of hydrocyclone increased. Decreasing the apex diameter caused an increase in the hydrocyclone efficiency.
Operations based optimisation using simulation and CFD
Doherty, JJ; Clifton, DP; Gillan, MA; Ciampoli, F
2007-01-01
An initial investigation of an optimisation based approach for design across a continuous range of operating conditions is presented. The objective for this 'operations based optimisation' approach is to avoid the need to choose critical design point conditions and associated weighting factors by tackling the overall operational performance instead. The approach integrates numerical optimisation, response surface modelling, CFD and operational simulation. An optimisation test bed involving th...
Takahashi, M.; Kawabata, Y.; Washitani, T.; Tanaka, S.; Maeda, S.; Mimotogi, S.
2014-03-01
In progress of lithography technologies, the importance of Mask3D analysis has been emphasized because the influence of mask topography effects is not avoidable to be increased explosively. An electromagnetic filed simulation method, such as FDTD, RCWA and FEM, is applied to analyze those complicated phenomena. We have investigated Constrained Interpolation Profile (CIP) method, which is one of the Method of Characteristics (MoC), for Mask3D analysis in optical lithography. CIP method can reproduce the phase of propagating waves with less numerical error by using high order polynomial function. The restrictions of grid distance are relaxed with spatial grid. Therefore this method reduces the number of grid points in complex structure. In this paper, we study the feasibility of CIP scheme applying a non-uniform and spatial-interpolated grid to practical mask patterns. The number of grid points might be increased in complex layout and topological structure since these structures require a dense grid to remain the fidelity of each design. We propose a spatial interpolation method based on CIP method same as time-domain interpolation to reduce the number of grid points to be computed. The simulation results of two meshing methods with spatial interpolation are shown.
METC CFD simulations of hot gas filtration
Energy Technology Data Exchange (ETDEWEB)
O`Brien, T.J.
1995-06-01
Computational Fluid Dynamic (CFD) simulations of the fluid/particle flow in several hot gas filtration vessels will be presented. These simulations have been useful in designing filtration vessels and in diagnosing problems with filter operation. The simulations were performed using the commercial code FLUENT and the METC-developed code MFIX. Simulations of the initial configuration of the Karhula facility indicated that the dirty gas flow over the filter assemblage was very non-uniform. The force of the dirty gas inlet flow was inducing a large circulation pattern that caused flow around the candles to be in opposite directions on opposite sides of the vessel. By introducing a system of baffles, a more uniform flow pattern was developed. This modification may have contributed to the success of the project. Several simulations of configurations proposed by Industrial Filter and Pump were performed, varying the position of the inlet. A detailed resolution of the geometry of the candles allowed determination of the flow between the individual candles. Recent simulations in support of the METC/CeraMem Cooperative Research and Development Agreement have analyzed the flow in the vessel during the cleaning back-pulse. Visualization of experiments at the CeraMem cold-flow facility provided confidence in the use of CFD. Extensive simulations were then performed to assist in the design of the hot test facility being built by Ahlstrom/Pyropower. These tests are intended to demonstrate the CeraMem technology.
CFD simulation of bubble column
Energy Technology Data Exchange (ETDEWEB)
Ekambara, K., E-mail: ekambara@ualberta.c [Department of Chemical and Materials Engineering, University of Alberta, 536 CME Building, Edmonton, AB, T6G 2G6 (Canada); Dhotre, M.T. [Thermal-Hydraulics Laboratory, Nuclear Energy and Safety Department, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)
2010-05-15
Three-dimensional simulations of gas-liquid flow in the bubble column using the Euler-Euler approach is presented. The attempt is made to assess the performance and applicability of different turbulence models namely, k-epsilon, k-epsilon RNG, k-omega, Reynolds stress model (RSM) and large eddy simulation (LES) using a commercial code (ANSYS-CFX). For this purpose, the predictions are compared against the experimental data of . Performance of the turbulence models is assessed on basis of comparison of axial liquid velocity, fractional gas hold-up, turbulent kinetic energy and turbulent eddy dissipation rate. All the non-drag (turbulent dispersion, virtual mass and lift force) and drag force were incorporated in the model. The low-Reynolds number treatment of the k-omega yields a better qualitative prediction than the k-epsilon model. The RSM predictions are comparable with LES results and seemed to give better prediction near the sparger, where the flow is more anisotropic and gives a clue why RANS approaches fails to predict the flow in this region. However, the large eddy simulations showed good agreement with the experimental data, but requires higher computational time than RSM.
CFD Simulation on Ethylene Furnace Reactor Tubes
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics (CFD) technique was presented. This approach took the flow, heat transfer, mass transfer and thermal cracking reactions in the reactor tubes into consideration. The coupled reactor model was solved with the SIMPLE algorithm. Some detailed information about the flow field, temperature field and concentration distribution in the reactor tubes was obtained, revealing the basic characteristics of the hydrodynamic phenomena and reaction behavior in the reactor tubes. The CFD approach provides the necessary information for conclusive decisions regarding the production optimization, the design and improvement of reactor tubes, and the new techniques implementation.
Recommendations for CFD Simulation of Reactor Internal Flow
Energy Technology Data Exchange (ETDEWEB)
Lee, Gong Hee; Bang, Young Seok; Woo, Sweng Woong; Cheong, Ae Ju [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)
2013-10-15
The inlet nozzle-to-outlet nozzle pressure losses inside reactor model were used for the verification of the magnitudes calculated by pressure loss methods. Although the competitiveness of CFD is continuously growing due to the rapid developments in computer hardware technology, computer capacity is still a limiting factor for CFD calculations to produce completely accurate results in the prediction of reactor internal flow. Therefore simplified geometries and turbulence models have to be used, and the computer capacity puts restrictions on the resolution in space and time. This leads to modeling errors and numerical errors that give more or less inaccurate results. In this paper a summary of the recommendations drawn from the analysis of the scale-down APR+ (Advanced Power Reactor Plus) internal flow are explained in the regulatory viewpoint. In this paper a summary of the recommendations for CFD simulation of reactor internal flow were explained in the regulatory viewpoint. Among them, an exact representation of the internal structures, especially located in the upstream of reactor core, may be the most important item for the accurate reactor internal flow simulation. To enhance the completeness of this study an additional CFD simulation to consider real geometry of reactor internal structures is on-going and the simulation results will be explained in the separate papers.
CFD Simulation of Air Velocity Distribution in Occupied Livestock Buildings
DEFF Research Database (Denmark)
Svidt, Kjeld; Zhang, G.; Bjerg, B.
In modem livestock buildings the design of the ventilation systems is important in order to obtain good air distribution. The use of Computational Fluid Dynamics for predicting the air flow and air quality makes it possible to include the effect of room geometry, equipment and occupants in the de...... this study laboratory measurements in a ventilated test room with "pig simulators" are compared with CFD-simulations....
CFD simulation on performance of new type umbrella plate scrubber
Institute of Scientific and Technical Information of China (English)
LI Shan-hong; LI Cai-ting; ZENG Guang-ming; LI Si-min; WANG Fei; WANG Da-yong
2008-01-01
A new type of umbrella plate scrubber was developed to address the pollution due to the dust, dioxide sulfur and other harmful gases, which were emitted from coal-burning boilers. The performance of the new device was studied through computational fluid dynamics(CFD) simulation and experiment methods. Initial work included experimental measurement of inlet-velocity, and gas phase simulation using Reynolds stress model(RSM). After gas phase was converged, particles were injected from the inlet of the new device. Discrete phase model(DPM) was used for particle trajectories determination. The pressure drop and the collection efficiency of the new device were predicted through simulation. The simulation results show that the pressure drop of the new devices is 230-250 Pa and the efficiency is 84%-86%, with the inlet velocity equal to 10.6 m/s and the dust concentration ranging from 2 to 22 g/m3. The CFD simulation results of the new device show good agreement with experimental data. The relative error of the pressure drop and the efficiency is approximately 4% and 10% respectively. The results obtained both from the numerical simulation and from the experiment demonstrate that CFD simulation is an effective method for this type of study.
FASTEF Heat exchanger tube rupture CFD simulation
Energy Technology Data Exchange (ETDEWEB)
Moreau, V., E-mail: moreau@crs4.it [CRS4, Centre for Advanced Studies, Research and Development in Sardinia, Polaris, Edificio 1, 09010 Pula, CA (Italy)
2012-11-15
The aim of this technical note is to present CFD simulations of a tube rupture incidental scenario in a Primary Heat eXchanger (PHX)/Primary Pump (PP) assembly for two design variants of the FAst-Spectrum Transmutation Experimental Facility FASTEF ongoing design, in the framework of the FP7 Central Design Team (CDT) European project. The simulation domain reproduces with some simplification the entire primary coolant loop. The objective is to understand whether it is necessary take some counter-measures to avoid the ingress of steam in the cold plenum. The simulation has been performed on two successive updates of the design and of the nominal operation. The simulations show a good resistance to steam ingress, under the condition that provision is made to avoid an excessive accumulation of steam at the top of the PHX/PP assembly casing.
CFD Simulation of Laboratory Scale Airlift Reactor
Czech Academy of Sciences Publication Activity Database
Šimčík, Miroslav; Havlica, Jaromír; Růžička, Marek; Drahoš, Jiří
Bratislava: Slovak Society of Chemical Engineering, 2008 - (Markoš, J.), s. 310 ISBN 978-80-227-2903-1. [35th International Conference of Slovak Society of Chemical Engineering. Tatranské Matliare (SK), 26.05.2008-30.05.2008] R&D Projects: GA ČR GA104/07/1110; GA ČR GA104/06/1418 Institutional research plan: CEZ:AV0Z40720504 Keywords : cfd simulation * airlift reactor Subject RIV: CI - Industrial Chemistry, Chemical Engineering
CFD simulation of highly transient flows
Denton, G. S.
2009-01-01
This thesis describes the fundamental extension and extensive testing of a robust CFD model for predicting outflow following the failure of pressurised hydrocarbon pipelines. The main thrust of the study involves the extension of the basic outflow model to account for complex pipeline systems, improvements of the theoretical basis and numerical stability. The basic model, based on the numerical solution of conservation equations using the method of characteristics, incorporates a suitabl...
CFD simulation of a solar tower
Energy Technology Data Exchange (ETDEWEB)
Koten, Hasan; Yukselenturk, Yalcyn; Yilmaz, Mustafa [Marmara University Mechanical Engineering Department (Turkey)], E-mail: hasan.koten@marmara.edu.tr
2011-07-01
With the depletion of fossil fuels and the rising concerns about their impacts on the environment, the use of alternative energy sources has become necessary. Among the alternatives, solar energy, with its unlimited resources and its low impact on the environment, is the most promising. The aim of this paper is to present a numerical model of a regular solar tower. A CFD analysis of the solar tower was performed with a commercial CFD code and velocity fields, temperature measurements and flow characteristics were determined and compared to experimental results available in the literature. It was found that the numerical model is capable of assessing the buoyant air flow in chimneys. In addition results showed that increasing the solar chimney height, solar collector area, or solar irradiance increases power generation capacity while ambient temperature does not significantly affect this capacity. This study provided a numerical model which is proficient in modeling solar towers.
CFD simulation of solids suspension in stirred tanks: Review
Directory of Open Access Journals (Sweden)
Ochieng Aoyi
2010-01-01
Full Text Available Many chemical reactions are carried out using stirred tanks, and the efficiency of such systems depends on the quality of mixing, which has been a subject of research for many years. For solid-liquid mixing, traditionally the research efforts were geared towards determining mixing features such as off-bottom solid suspension using experimental techniques. In a few studies that focused on the determination of solids concentration distribution, some methods that have been used have not been accurate enough to account for some small scale flow mal-distribution such as the existence of dead zones. The present review shows that computational fluid dynamic (CFD techniques can be used to simulate mixing features such as solids off-bottom suspension, solids concentration and particle size distribution and cloud height. Information on the effects of particle size and particle size distribution on the solids concentration distribution is still scarce. Advancement of the CFD modeling is towards coupling the physical and kinetic data to capture mixing and reaction at meso- and micro-scales. Solids residence time distribution is important for the design; however, the current CFD models do not predict this parameter. Some advances have been made in recent years to apply CFD simulation to systems that involve fermentation and anaerobic processes. In these systems, complex interaction between the biochemical process and the hydrodynamics is still not well understood. This is one of the areas that still need more attention.
CFD Simulation of Liquid Rocket Engine Injectors
Farmer, Richard; Cheng, Gary; Chen, Yen-Sen; Garcia, Roberto (Technical Monitor)
2001-01-01
Detailed design issues associated with liquid rocket engine injectors and combustion chamber operation require CFD methodology which simulates highly three-dimensional, turbulent, vaporizing, and combusting flows. The primary utility of such simulations involves predicting multi-dimensional effects caused by specific injector configurations. SECA, Inc. and Engineering Sciences, Inc. have been developing appropriate computational methodology for NASA/MSFC for the past decade. CFD tools and computers have improved dramatically during this time period; however, the physical submodels used in these analyses must still remain relatively simple in order to produce useful results. Simulations of clustered coaxial and impinger injector elements for hydrogen and hydrocarbon fuels, which account for real fluid properties, is the immediate goal of this research. The spray combustion codes are based on the FDNS CFD code' and are structured to represent homogeneous and heterogeneous spray combustion. The homogeneous spray model treats the flow as a continuum of multi-phase, multicomponent fluids which move without thermal or velocity lags between the phases. Two heterogeneous models were developed: (1) a volume-of-fluid (VOF) model which represents the liquid core of coaxial or impinger jets and their atomization and vaporization, and (2) a Blob model which represents the injected streams as a cloud of droplets the size of the injector orifice which subsequently exhibit particle interaction, vaporization, and combustion. All of these spray models are computationally intensive, but this is unavoidable to accurately account for the complex physics and combustion which is to be predicted, Work is currently in progress to parallelize these codes to improve their computational efficiency. These spray combustion codes were used to simulate the three test cases which are the subject of the 2nd International Workshop on-Rocket Combustion Modeling. Such test cases are considered by
CFD studies of mass transfer performance in pulsed column
International Nuclear Information System (INIS)
A tracer injection technique was used to study the mass transfer characteristics of aqueous phase in the Φ 38 mm pulsed sieve extraction column. A computational fluid dynamics (CFD) model has been developed to simulation the mass transfer process of the tracer. The residence time distribution of the tracer which get from CFD simulation were used to fitting the aqueous phase axial dispersion coefficient. The experiment results were in consistence with the simulation results; The simulation results show that the concentration of tracer change with pulsed velocity; The axial dispersion co efficient fitting by CFD model was Similar with published data. The presented CFD predictions and validation with experimental data will provide a possible ways to eliminate experiments and will contribute to better understanding of the hydrodynamics in extraction columns. (authors)
Validation of CFD Simulations of Cerebral Aneurysms With Implication of Geometric Variations
Hoi, Yiemeng; Woodward, Scott H.; Kim, Minsuok; Taulbee, Dale B.; Meng, Hui
2006-01-01
Computational fluid dynamics (CFD) simulations using medical-image-based anatomical vascular geometry are now gaining clinical relevance. This study aimed at validating the CFD methodology for studying cerebral aneurysms by using particle image velocimetry (PIV) measurements, with a focus on the effects of small geometric variations in aneurysm models on the flow dynamics obtained with CFD. Method of Approach. An experimental phantom was fabricated out of silicone elastomer to best mimic a sp...
Indoor Airflow Simulation inside Lecture Room: A CFD Approach
Lin, S.; Tee, B. T.; Tan, C. F.
2015-09-01
Indoor air flow distribution is important as it will affect the productivity of the occupants. Poor air flow distribution not only cause discomfort to the occupants but also influence their ability to conduct their activities. The main purpose of this study is to investigate the indoor air flow inside lecture rooms through CFD simulation approach. Two types of air-conditioning configuration system in lecture rooms have been selected for this study which includes the split unit and centralized system. The air flow distribution between these two systems are analyzed and compared. Physical measurement is conducted using a velocity meter for validation purpose. CFD simulation is developed by using ANSYS Fluent software. The results specifically the air velocity and temperature data are compared and validated. Based on the findings, design recommendation is proposed with the aim to improve on the current air flow distribution in the lecture rooms.
The Role of CFD Simulation in Rocket Propulsion Support Activities
West, Jeff
2011-01-01
Outline of the presentation: CFD at NASA/MSFC (1) Flight Projects are the Customer -- No Science Experiments (2) Customer Support (3) Guiding Philosophy and Resource Allocation (4) Where is CFD at NASA/MSFC? Examples of the expanding Role of CFD at NASA/MSFC (1) Liquid Rocket Engine Applications : Evolution from Symmetric and Steady to 3D Unsteady (2)Launch Pad Debris Transport-> Launch Pad Induced Environments (a) STS and Launch Pad Geometry-steady (b) Moving Body Shuttle Launch Simulations (c) IOP and Acoustics Simulations (3)General Purpose CFD Applications (4) Turbomachinery Applications
CFD Simulation of Nanosufur Crystallization Incorporating Population Balance Modeling
Fatemeh Golkhou; Mahmod Tajee Hamed Mosavian
2013-01-01
A physical vapor condensation process for synthesizing nanosized sulfur powder as a precursor for various industries was simulated by the use of computational ?uid dynamic (CFD) modeling. The phase change, swirl flow and heat transfer taking place inside the cyclone are analyzed along with particle formation via gas condensation method. The population balance model is a mathematical framework for the modeling of crystal size distribution (CSD) and the study of gas-phase changes leading to nuc...
CFD simulation of mixing in anaerobic digesters.
Terashima, Mitsuharu; Goel, Rajeev; Komatsu, Kazuya; Yasui, Hidenari; Takahashi, Hiroshi; Li, Y Y; Noike, Tatsuya
2009-04-01
A three-dimensional CFD model incorporating the rheological properties of sludge was developed and applied to quantify mixing in a full-scale anaerobic digester. The results of the model were found to be in good agreement with experimental tracer response curve. In order to predict the dynamics of mixing, a new parameter, UI (uniformity index) was defined. The visual patterns of tracer mixing in simulation were well reflected in the dynamic variation in the value of UI. The developed model and methods were applied to determine the required time for complete mixing in a full-scale digester at different solid concentrations. This information on mixing time is considered to be useful in optimizing the feeding cycles for better digester performance. PMID:19081247
Feasibility of patient specific aortic blood flow CFD simulation.
Svensson, Johan; Gårdhagen, Roland; Heiberg, Einar; Ebbers, Tino; Loyd, Dan; Länne, Toste; Karlsson, Matts
2006-01-01
Patient specific modelling of the blood flow through the human aorta is performed using computational fluid dynamics (CFD) and magnetic resonance imaging (MRI). Velocity patterns are compared between computer simulations and measurements. The workflow includes several steps: MRI measurement to obtain both geometry and velocity, an automatic levelset segmentation followed by meshing of the geometrical model and CFD setup to perform the simulations follwed by the actual simulations. The computational results agree well with the measured data. PMID:17354898
Study of indoor radon distribution using measurements and CFD modeling
International Nuclear Information System (INIS)
Measurement and/or prediction of indoor radon (222Rn) concentration are important due to the impact of radon on indoor air quality and consequent inhalation hazard. In recent times, computational fluid dynamics (CFD) based modeling has become the cost effective replacement of experimental methods for the prediction and visualization of indoor pollutant distribution. The aim of this study is to implement CFD based modeling for studying indoor radon gas distribution. This study focuses on comparison of experimentally measured and CFD modeling predicted spatial distribution of radon concentration for a model test room. The key inputs for simulation viz. radon exhalation rate and ventilation rate were measured as a part of this study. Validation experiments were performed by measuring radon concentration at different locations of test room using active (continuous radon monitor) and passive (pin-hole dosimeters) techniques. Modeling predictions have been found to be reasonably matching with the measurement results. The validated model can be used to understand and study factors affecting indoor radon distribution for more realistic indoor environment. - Highlights: • Indoor radon distribution has been studied using active and passive measurements and CFD simulation. • At low ventilation, non-uniformity of radon concentration was observed. • Measured wall radon flux and ventilation rate has been used in simulations. • CFD simulation results were found to be close to measurements
Survey of CFD studies on automotive buffeting
International Nuclear Information System (INIS)
In the current automobile market buffeting is one of the customer frequent complaints on luxury cars and SUVs. Buffeting is a low frequency but high level wind noise and makes people inside the vehicle uncomfortable if it lasts for a long period of time. The physical mechanism of buffeting is a complicated phenomenon of aeroacoustic resonance. The aeroacoustic characteristics of buffeting depend on vehicle features and operating conditions. In this paper, a survey of CFD studies on the automotive buffeting is presented. Firstly, several buffeting related concepts, such as Helmholtz resonator, flow over a cavity, shear layer instability and vortex shedding, are reviewed and relevant references are listed. Then, a historic survey of the buffeting investigation is made with emphasis on computational studies. As an example, the buffeting studies at DaimlerChrysler are selected to demonstrate the procedure of CFD simulation for automotive buffeting. The procedure is then validated by the correlation with wind tunnel testing. After that the validated procedure is applied to find solutions for buffeting reduction. Finally, some comments on buffeting studies are addressed. (author)
Application of CFD Code PHOENICS for simulating CYCLONE SEPARATORS
International Nuclear Information System (INIS)
The work presents a computational fluid dynamics (CFD) calculation to investigate the flow field in a tangential inlet cyclone which is mainly used for the separation of the moisture from an air stream. Three-dimensional, steady state Eulerian simulations of the turbulent gas - droplet flow in a cyclone separator have been performed. Numerical simulation was carried out using CFD code PHOENICS for the given geometry of separators available in literature
CFD Simulation of the NREL Phase VI Rotor
Song, Yang
2014-01-01
The simulation of the turbulent and potentially separating flow around a rotating, twisted, and tapered airfoil is a challenging task for CFD simulations. This paper describes CFD simulations of the NREL Phase VI turbine that was experimentally characterized in the 24.4m x 36.6m NREL/NASA Ames wind tunnel (Hand et al., 2001). All computations in this article are performed on the experimental base configuration of 0o yaw angle, 3o tip pitch angle, and a rotation rate of 72 rpm. The significance of specific mesh resolution regions to the accuracy of the CFD prediction is discussed. The ability of CFD to capture bulk quantities, such as the shaft torque, and the detailed flow characteristics, such as the surface pressure distributions, are explored for different inlet wind speeds. Finally, the significant three-dimensionality of the boundary layer flow is demonstrated.
Simulation and Scale-up of Barium Sulphate Precipitation Process Using CFD Modeling
Institute of Scientific and Technical Information of China (English)
龚俊波; 卫宏远; 王静康; JohnGarsideb
2005-01-01
Some empirical mixing models were used to describe the imperfect mixing in precipitation process.However, the models can not, in general, reflect the details of interactions between mixing and crystallization in a vessel. In this study, CFD (computational fluid dynamics) technique were developed by simulating the precipitation of barium sulphate in stirred tanks by integration of population balance equations with a CFD solver. Two typical impellers, Rushton and pitched blade turbines, were employed for agitation. The influence of feed concentration and position on crystal product properties was investigated by CFD simulation. The scale-up of these precipitators was systematically studied. Significant effect on the crystal properties was found for the scale-up under some conditions.Keywords simulation, scale up, precipitation, CFD(computational fluid dynamics)
CFD simulations of the MEXICO rotor
DEFF Research Database (Denmark)
Bechmann, Andreas; Sørensen, Niels N.; Zahle, Frederik
2011-01-01
The wake behind a wind turbine model is investigated using Computational Fluid Dynamics (CFD), and results are compared with measurements. The turbine investigated is the three‐bladed test rotor (D = 4.5 m) used in the Model Experiments in Controlled Conditions (MEXICO) wind tunnel experiment....... During the MEXICO experiment, particle image velocimetry measurements of the induction upstream and downstream of the rotor were performed for different operating conditions, giving a unique dataset to verify theoretical models and CFD models. The present paper first describes the efforts in reproducing...
COMPARISON OF AXIAL FAN ROTOR EXPERIMENTAL DATA WITH CFD SIMULATION
Aleš Prachař
2016-01-01
Data obtained from an experimental simulation on a new test rig for axial fans are compared to a CFD simulation. The Edge solver is used and the development needed for the simulation (boundary conditions, free stream consistency) is described. Adequate agreement between the measured and calculated data is observed.
COMPARISON OF AXIAL FAN ROTOR EXPERIMENTAL DATA WITH CFD SIMULATION
Directory of Open Access Journals (Sweden)
Aleš Prachař
2016-02-01
Full Text Available Data obtained from an experimental simulation on a new test rig for axial fans are compared to a CFD simulation. The Edge solver is used and the development needed for the simulation (boundary conditions, free stream consistency is described. Adequate agreement between the measured and calculated data is observed.
Supercritical water: On a road from CFD to NPP simulations
International Nuclear Information System (INIS)
The Fission and Radiation Physics Group at the Aalto University is contributing to the Finnish SCWR activities within the GEN4FIN-network. Our research involves reactor core thermal hydraulics, and in particular, heat transfer phenomena in supercritical water including both theoretical studies and simulations with APROS and OpenFOAM. APROS is a software applicable to full-scale power plant simulations and OpenFOAM an open source CFD code. The complicated heat transfer in the supercritical region is a very challenging problem for the design of SCWRs and their safety assessment. The steam tables of APROS have been extended to the supercritical region and their functionality has been tested with, e.g. blowdown simulations where the transient is rapid, hence mainly challenging for numerical stability whereas heat transfer has negligible effects. Numerous different heat correlations for supercritical water have been suggested , but simulations of benchmark experiments have shown that for instance fuel clad temperatures generally cannot be described sufficiently accurately. This discrepancy has been encountered in several process simulation codes. The largest errors occur near the pseudo critical line, during the heat transfer deterioration. It turns out that the physics in supercritical water is clearly more intricate than in ordinary boiling heat transfer where rather satisfactory heat transfer correlations are available. Full 3D CFD calculations allow a better description of various aspects of heat transfer in the supercritical region, i.e., effects arising from turbulence , buoyancy , varying material properties etc. On the other hand, CFD calculations are not feasible for plant-scale simulations. We have selected some simplified geometries and parameter ranges to study SCW heat transfer in a reactor. Old experiments have been calculated with satisfactory results with OpenFOAM to check its validity. A steady state case of heat transfer in a circular pipe with upward
CFD Simulation of the NREL Phase VI Rotor
Song, Yang; Perot, J. Blair
2014-01-01
The simulation of the turbulent and potentially separating flow around a rotating, twisted, and tapered airfoil is a challenging task for CFD simulations. This paper describes CFD simulations of the NREL Phase VI turbine that was experimentally characterized in the 24.4m x 36.6m NREL/NASA Ames wind tunnel (Hand et al., 2001). All computations in this article are performed on the experimental base configuration of 0o yaw angle, 3o tip pitch angle, and a rotation rate of 72 rpm. The significanc...
Fuel assembly simulations using LRGR-CFD and CGCFD
International Nuclear Information System (INIS)
In addition to the traditional fuel assembly simulation approaches using system codes, subchannel codes or porous medium approaches, as well as detailed CFD simulations to analyze single sub channels, a Low Resolution Geometry Resolving (LRGR) CFD approach and a Coarse-Grid-CFD (CGCFD) approach is taken. Both methods are based on a low resolution mesh that allows the capture of large and medium scale flow features such as recirculation zones, which cannot be reproduced by the system codes, subchannel codes and porous media approaches. The LRGR approach allows for instance fine-tuning the porous parameters which are important input for a porous medium approach. However, it should be noted that the prediction of detailed flow features such as secondary flows is not feasible. Using this approach, the consequences of flow blockages for detection possibilities and cladding temperatures can be discussed. Within the Coarse-Grid CFD approach a subgrid model (SGM) accounts for sub grid volumetric forces which are derived from validated CFD simulations. The volumetric forces take account of the non resolved physics due to the coarse mesh. The CGCFD approach with SGM can be applied to simulate complete fuel assemblies or even complete cores capturing the unique features of the complex flow induced by the fuel assembly geometry and its spacers. In such a case, grids with a very low grid resolution are employed. The current paper discusses and presents both, the CGCFD and the LRGR approaches. (author)
CFD Simulations of Tiltrotor Configurations in Hover
Potsdam, Mark a.; Strawn, Roger C.
2002-01-01
Navier-Stokes computational fluid dynamics calculations are presented for isolated, half-span, and full-span V-22 tiltrotor hover configurations. These computational results extend the validity of CFD hover methodology beyond conventional rotorcraft applications to tiltrotor configurations. Computed steady-state, isolated rotor performance agrees well with experimental measurements, showing little sensitivity to grid resolution. However, blade-vortex interaction flowfield details are sensitive to numerical dissipation and are more difficult to model accurately. Time-dependent, dynamic, half- and full-span installed configurations show sensitivities in performance to the tiltrotor fountain flow. As such, the full-span configuration exhibits higher rotor performance and lower airframe download than the half-span configuration. Half-span rotor installation trends match available half-span data, and airframe downloads are reasonably well predicted. Overall, the CFD solutions provide a wealth of flowfield details that can be used to analyze and improve tiltrotor aerodynamic performance.
CFD Simulation of Personal Exposure to Contaminant Sources in Ventilated Rooms
DEFF Research Database (Denmark)
Brohus, Henrik
In this study Computational Fluid Dynamics (CFD) is used to predict the personal exposure to contaminant sources in a ventilated room. A CFD model of a person is located in a displacement ventilated room as well as in a mixing ventilated room. The personal exposure to different contaminant sources...... is simulated, taking both the concentration gradients and the local influence of the person into account....
CFD Simulation of Personal Exposure to Contaminant Sources in Ventilated Rooms
Brohus, Henrik
1997-01-01
In this study Computational Fluid Dynamics (CFD) is used to predict the personal exposure to contaminant sources in a ventilated room. A CFD model of a person is located in a displacement ventilated room as well as in a mixing ventilated room. The personal exposure to different contaminant sources is simulated, taking both the concentration gradients and the local influence of the person into account.
Static load balancing for CFD distributed simulations
Energy Technology Data Exchange (ETDEWEB)
Chronopoulos, A T; Grosu, D; Wissink, A; Benche, M
2001-01-26
The cost/performance ratio of networks of workstations has been constantly improving. This trend is expected to continue in the near future. The aggregate peak rate of such systems often matches or exceeds the peak rate offered by the fastest parallel computers. This has motivated research towards using a network of computers, interconnected via a fast network (cluster system) or a simple Local Area Network (LAN) (distributed system), for high performance concurrent computations. Some of the important research issues arise such as (1) Optimal problem partitioning and virtual interconnection topology mapping; (2) Optimal execution scheduling and load balancing. CFD codes have been efficiently implemented on homogeneous parallel systems in the past. In particular, the helicopter aerodynamics CFD code TURNS has been implemented with MPI on the IBM SP with parallel relaxation and Krylov iterative methods used in place of more traditional recursive algorithms to enhance performance. In this implementation the space domain is divided into equal subdomain which are mapped to the processors. We consider the implementation of TURNS on a LAN of heterogeneous workstations. In order to deal with the problem of load balancing due to the different processor speeds we propose a suboptimal algorithm of dividing the space domain into unequal subdomains and assign them to the different computers. The algorithm can apply to other CFD applications. We used our algorithm to schedule TURNS on a network of workstations and obtained significantly better results.
Simulation and Aerodynamic Analysis of the Flow Around the Sailplane Using CFD Techniques
Directory of Open Access Journals (Sweden)
Sebastian Marian ZAHARIA
2015-12-01
Full Text Available In this paper, it was described the analysis and simulation process using the CFD technique and the phenomena that shows up in the engineering aero-spatial practice, directing the studies of simulation for the air flows around sailplane. The analysis and aerodynamic simulations using Computational Fluid Dynamics techniques (CFD are well set as instruments in the development process of an aeronautical product. The simulation techniques of fluid flow helps engineers to understand the physical phenomena that take place in the product design since its prototype faze and in the same time allows for the optimization of aeronautical products’ performance concerning certain design criteria.
Analysis of a waste-heat boiler by CFD simulation
Energy Technology Data Exchange (ETDEWEB)
Yang, Yongziang; Jokilaakso, A. [Helsinki Univ. of Technology, Otaniemi (Finland)
1996-12-31
Waste-heat boilers play important roles in the continuous operation of a smelter and in the conservation of energy. However, the fluid flow and heat transfer behaviour has not been well studied, concerning the boiler performance and design. This presentation describes simulated gas flow and heat transfer of a waste-heat boiler in the Outokumpu copper flash smelting process. The governing transport equations for the conservation of mass, momentum and enthalpy were solved with a commercial CFD-code PHOENICS. The standard k-{epsilon} turbulence model and a composite-flux radiation model were used in the computations. The computational results show that the flow is strongly recirculating and distinctly three-dimensional in most part of the boiler, particularly in the radiation section. The predicted flow pattern and temperature distribution were in a good agreement with laboratory models and industrial measurements. The results provide detailed information of flow pattern, the temperature distribution and gas cooling efficiency. The CFD proved to be a useful tool in analysing the boiler operation. (author)
Boiling flow simulation in Neptune-CFD and Fluent codes
International Nuclear Information System (INIS)
This paper presents simulations of the convective boiling flow performed with NEPTUNE-CFD and FLUENT codes. The DEBORA experiments carried out at CEA Grenoble were used as an experimental data set. In these experiments, freon R12 flows upwards inside a vertical pipe. Radial profiles of the flow variables are measured at the end of the heated section. Seven DEBORA cases were selected for simulation. NEPTUNE-CFD code was used without modifications because it contains all necessary models. In FLUENT, an important part of the models has been implemented by programming in User Defined Functions. The comparison of the radial profiles of void fraction, liquid temperature, gas velocity and mean bubble diameter at the end of the heated section shows that both codes can provide reasonable results in boiling conditions. The presented work was carried out within the 6. Framework EC NURESIM project. NEPTUNE-CFD code is implemented in the NURESIM platform. (authors)
CFD simulation of flow through heart: a perspective review.
Khalafvand, S S; Ng, E Y K; Zhong, L
2011-01-01
The heart is an organ which pumps blood around the body by contraction of muscular wall. There is a coupled system in the heart containing the motion of wall and the motion of blood fluid; both motions must be computed simultaneously, which make biological computational fluid dynamics (CFD) difficult. The wall of the heart is not rigid and hence proper boundary conditions are essential for CFD modelling. Fluid-wall interaction is very important for real CFD modelling. There are many assumptions for CFD simulation of the heart that make it far from a real model. A realistic fluid-structure interaction modelling the structure by the finite element method and the fluid flow by CFD use more realistic coupling algorithms. This type of method is very powerful to solve the complex properties of the cardiac structure and the sensitive interaction of fluid and structure. The final goal of heart modelling is to simulate the total heart function by integrating cardiac anatomy, electrical activation, mechanics, metabolism and fluid mechanics together, as in the computational framework. PMID:21271418
Simulation of unprotected LOFA in MTR reactors using a mix CFD and one-d computation tool
International Nuclear Information System (INIS)
Highlights: • No CFD study of LOFA without SCRAM in MTR reactor has been found in the literature. • A chart that provides safety limits during the unprotected LOFA sequences is provided. • The CFD model developed can be adapted for simulating reactivity insertion accident. - Abstract: CFD is expected to feature more frequently in reactor thermal hydraulics. The reason for the increased use of multidimensional CFD methods is not only the increased availability of capable computer systems but also the ongoing drive to improve and reduce uncertainty in our predictions of important phenomena. In this work, a CFD model coupled with the reactor point kinetics equations is developed using the CFD code, Fluent to simulate loss of flow accident (LOFA) without SCRAM in a typical material testing reactor (MTR). The CFD model is used to simulate the core behavior during transient up to the onset of nucleate boiling (ONB) point. PARET code is used not only to validate the CFD model but also to complete simulation during the sub-cooled boiling regime. The focus is on establishing a new CFD approach in the reactor safety analysis and determining the two-phase flow stability boundaries as function of initial reactor conditions. Both ONB and onset of flow instability (OFI) is predicted. Besides a useful chart is provided, which describes the stability region in terms of initial reactor power, core inlet temperature, and power peaking factor
CFD-DEM simulations of current-induced dune formation and morphological evolution
Sun, Rui; Xiao, Heng
2016-06-01
Understanding the fundamental mechanisms of sediment transport, particularly those during the formation and evolution of bedforms, is of critical scientific importance and has engineering relevance. Traditional approaches of sediment transport simulations heavily rely on empirical models, which are not able to capture the physics-rich, regime-dependent behaviors of the process. With the increase of available computational resources in the past decade, CFD-DEM (computational fluid dynamics-discrete element method) has emerged as a viable high-fidelity method for the study of sediment transport. However, a comprehensive, quantitative study of the generation and migration of different sediment bed patterns using CFD-DEM is still lacking. In this work, current-induced sediment transport problems in a wide range of regimes are simulated, including 'flat bed in motion', 'small dune', 'vortex dune' and suspended transport. Simulations are performed by using SediFoam, an open-source, massively parallel CFD-DEM solver developed by the authors. This is a general-purpose solver for particle-laden flows tailed for particle transport problems. Validation tests are performed to demonstrate the capability of CFD-DEM in the full range of sediment transport regimes. Comparison of simulation results with experimental and numerical benchmark data demonstrates the merits of CFD-DEM approach. In addition, the improvements of the present simulations over existing studies using CFD-DEM are presented. The present solver gives more accurate prediction of sediment transport rate by properly accounting for the influence of particle volume fraction on the fluid flow. In summary, this work demonstrates that CFD-DEM is a promising particle-resolving approach for probing the physics of current-induced sediment transport.
CFD Simulation of Nanosufur Crystallization Incorporating Population Balance Modeling
Directory of Open Access Journals (Sweden)
Fatemeh Golkhou
2013-01-01
Full Text Available A physical vapor condensation process for synthesizing nanosized sulfur powder as a precursor for various industries was simulated by the use of computational ?uid dynamic (CFD modeling. The phase change, swirl flow and heat transfer taking place inside the cyclone are analyzed along with particle formation via gas condensation method. The population balance model is a mathematical framework for the modeling of crystal size distribution (CSD and the study of gas-phase changes leading to nucleation of the first solid particles. In this paper the Direct Quadrature Method of Moments is used for solving the transport equations of the moments of the size distribution. The temperature, velocity and particle size distribution ranges inside the cyclone were computed. The results show the formation of nanosulfur particles in 1-7 nm range.
Heat transfer measurements and CFD simulations of an impinging jet
Petera, Karel; Dostál, Martin
2016-03-01
Heat transport in impinging jets makes a part of many experimental and numerical studies because some similarities can be identified between a pure impingement jet and industrial processes like, for example, the heat transfer at the bottom of an agitated vessel. In this paper, experimental results based on measuring the response to heat flux oscillations applied to the heat transfer surface are compared with CFD simulations. The computational cost of a LES-based approach is usually too high therefore a comparison with less computationally expensive RANS-based turbulence models is made in this paper and a possible improvement of implementing an anisotropic explicit algebraic model for the turbulent heat flux model is evaluated.
International Nuclear Information System (INIS)
Drastic urbanization and manhattanization are causing various problems in wind environment. This study suggests a CFD simulation method to evaluate wind environment in the early design stage of high-rise buildings. The CFD simulation of this study is not a traditional in-depth simulation, but a method to immediately evaluate wind environment for each design alternative and provide guidelines for design modification. Thus, the CFD simulation of this study to evaluate wind environments uses BIM-based CFD tools to utilize building models in the design stage. This study examined previous criteria to evaluate wind environment for pedestrians around buildings and selected evaluation criteria applicable to the CFD simulation method of this study. Furthermore, proper mesh generation method and CPU time were reviewed to find a meaningful CFD simulation result for determining optimal design alternative from the perspective of wind environment in the design stage. In addition, this study is to suggest a wind environment evaluation method through a BIM-based CFD simulation.
CFD Vision 2030 Study: A Path to Revolutionary Computational Aerosciences
Slotnick, Jeffrey; Khodadoust, Abdollah; Alonso, Juan; Darmofal, David; Gropp, William; Lurie, Elizabeth; Mavriplis, Dimitri
2014-01-01
This report documents the results of a study to address the long range, strategic planning required by NASA's Revolutionary Computational Aerosciences (RCA) program in the area of computational fluid dynamics (CFD), including future software and hardware requirements for High Performance Computing (HPC). Specifically, the "Vision 2030" CFD study is to provide a knowledge-based forecast of the future computational capabilities required for turbulent, transitional, and reacting flow simulations across a broad Mach number regime, and to lay the foundation for the development of a future framework and/or environment where physics-based, accurate predictions of complex turbulent flows, including flow separation, can be accomplished routinely and efficiently in cooperation with other physics-based simulations to enable multi-physics analysis and design. Specific technical requirements from the aerospace industrial and scientific communities were obtained to determine critical capability gaps, anticipated technical challenges, and impediments to achieving the target CFD capability in 2030. A preliminary development plan and roadmap were created to help focus investments in technology development to help achieve the CFD vision in 2030.
Westerwalbesloh, Christoph; Grünberger, Alexander; Stute, Birgit; Weber, Sophie; Wiechert, Wolfgang; Kohlheyer, Dietrich; von Lieres, Eric
2015-11-01
A microfluidic device for microbial single-cell cultivation of bacteria was modeled and simulated using COMSOL Multiphysics. The liquid velocity field and the mass transfer within the supply channels and cultivation chambers were calculated to gain insight in the distribution of supplied nutrients and metabolic products secreted by the cultivated bacteria. The goal was to identify potential substrate limitations or product accumulations within the cultivation device. The metabolic uptake and production rates, colony size, and growth medium composition were varied covering a wide range of operating conditions. Simulations with glucose as substrate did not show limitations within the typically used concentration range, but for alternative substrates limitations could not be ruled out. This lays the foundation for further studies and the optimization of existing picoliter bioreactor systems. PMID:26345659
Introducing CFD in the optical simulation of linear Fresnel collectors
Moghimi, M. A.; Rungasamy, A.; Craig, K. J.; Meyer, J. P.
2016-05-01
This paper seeks to determine whether the Finite Volume method within a commercially available Computational Fluid Dynamics (CFD) solver (ANSYS Fluent) can model radiation with comparable accuracy to a Monte Carlo ray-tracing software package (SolTrace). A detailed investigation was performed into modeling techniques that can be used to significantly reduce the optical errors traditionally associated with CFD modeling of radiation false scattering and ray effect using a simple optical test case. The strategies formulated in the first part of this paper were used to model a variety of Linear Fresnel Collector Concentrating Solar Power Plants. This paper shows that commercial CFD packages yield accurate results for line focusing concentrating solar applications and simple geometries, validating its use in an integrated environment where both optical and thermal performance of these plants can be simulated and optimized.
CFD-DEM Simulations of Current-Induced Dune Formation and Morphological Evolution
Sun, Rui
2015-01-01
Understanding the fundamental mechanisms of sediment transport, particularly those during the formation and evolution of bedforms, is of critical scientific importance and has engineering relevance. Traditional approaches of sediment transport simulations heavily rely on empirical models, which are not able to capture the physics-rich, regime-dependent behaviors of the process. With the increase of available computational resources in the past decade, CFD-DEM (computational fluid dynamics-discrete element method) has emerged as a viable high-fidelity method for the study of sediment transport. However, a comprehensive, quantitative study of the generation and migration of different sediment bed patterns using CFD-DEM is still lacking. In this work, current-induced sediment transport problems in a wide range of regimes are simulated, including 'flat bed in motion', `small dune', `vortex dune' and suspended transport. Simulations are performed by using SediFoam, an open-source, massively parallel CFD-DEM solver...
Validation of CFD Simulation for Ammonia Emissions from an Equeous Solution
DEFF Research Database (Denmark)
Rong, Li; Elhadidib, Basman; Khalifa, Ezzat;
2011-01-01
as boundary condition for CFD prediction of ammonia emission. The accuracy of CFD simulation depends on many factors. In this study, the effects of appropriate geometry model, inlet turbulent parameters and three turbulence models (low-Reynolds number k–ε model, renormalization group k–ε model and...... current HLC models generally over-predict the ammonia emissions from aqueous solution in this study whereas VLE gives better agreement between simulated and measured results. A linear relation is observed between ammonia mass transfer coefficient obtained from the VLE relation and those from HLC models....
CFD Simulation of a Natural Circulation Helium Loop
Knížat Branislav; Hlbočan Peter; Mlkvik Marek
2015-01-01
The paper deals with a flow in a closed helium loop serving for cooling of a fast reactor. The flow in pipeline branches of the system is simulated by methods of CFD. The purpose is to find exact values of pressure losses, so that heat exchangers could be successfully designed and so that the power available for a loop drive could be optimally utilized. General approach to the simulation is presented, as well as the calculation procedure and achieved results.
CFD Simulation of a Natural Circulation Helium Loop
Directory of Open Access Journals (Sweden)
Knížat Branislav
2015-12-01
Full Text Available The paper deals with a flow in a closed helium loop serving for cooling of a fast reactor. The flow in pipeline branches of the system is simulated by methods of CFD. The purpose is to find exact values of pressure losses, so that heat exchangers could be successfully designed and so that the power available for a loop drive could be optimally utilized. General approach to the simulation is presented, as well as the calculation procedure and achieved results.
Dynamic Analysis and CFD Numerical Simulation on Backpressure Filling System
Jing Qian; Lu, J. P.; Hui, S L; Ma, Y J; D. Y. Li
2015-01-01
A backpressure filling system is a kind of air type filling system which could be applied to power type, fine or coarse grain, or mixtures with fine and coarse components. The working principle of backpressure filling system was discussed based on fundamental hydromechanics. The research limit values of backpressure were achieved via mechanical analysis. Comparing with the exit velocity of material by theoretical analysis and numerical simulation, the CFD simulation model was confirmed and it...
Energy Technology Data Exchange (ETDEWEB)
Noh, Kwang-Chul [Department of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea); Kim, Hyuk-Soon; Oh, Myung-Do [Department of Mechanical and Information Engineering, University of Seoul, Seoul 130-743 (Korea)
2010-04-15
A study was carried out to look for the source of contamination and examine the route of contaminant transfer in the minienvironment applied in LCD process clean room of Korea. As the minienvironment model, one of the clean room with much large space and low particle concentration was selected to investigate. Firstly, the particle concentrations were measured without any information on the source and the route of contaminants transfer. Through considering the results of particle measurements and CFD simulations simultaneously, however, it was revealed that the critical contamination source was the stocker and the contaminants were transferred by the airflow pattern in this study. As an improvement action, reducing the airflow rate of exhaust fans and installing additional fan filter units (FFUs) were carried out. As a result, the velocity distribution was improved and the particle concentration was reduced in the target minievironment. Also, the defect rate related to this minienvironment decreased. With the help of the experimental and the numerical tools, the effective method for contamination control was developed. Furthermore, this article provides recommendation for future work to improve the yield and save the energy consumption simultaneously. (author)
CFD Simulation of Liquid-solid Multiphase Flow in Mud Mixer
Directory of Open Access Journals (Sweden)
T.Y. Kim
2016-08-01
Full Text Available In the present study, a computational fluid dynamics (CFD simulation was performed to analyze the mixing phenomena associated with multi-phase flow in a mud mixing system. For the validation of CFD simulation, firstly a liquid-solid multiphase flow inside horizontal pipe was simulated and compared with the experiments and other numerical simulations. And then, the multiphase flow simulation was carried out for the mud mixer in the drilling handling system in order to understand mixing phenomena and predict the mixing efficiency. For the modeling and simulation, a commercial software, STAR-CCM+, based on a finite-volume method (FVM was adopted. The simulation results for liquid-solid flow inside the pipe shows a good agreement with the experimental data. With the same multiphase model, the simulation for mud mixer is performed under the generalized boundary condition and then pressure drop through the mud mixer will be discussed.
DPM dissipation experiment at MST's experimental mine and comparison with CFD simulation
Institute of Scientific and Technical Information of China (English)
ZHENG Yi; LAN Hai; THIRUVENGADAM Magesh; TIEN Jerry C
2011-01-01
Diesel Particulate Matter (DPM) is regulated in the U.S.for both underground coal and metal/nonmetal mines.Today,many underground mines still face difficulty in compliance with DPM regulations.The DPM research carried out in Missouri University of Science and Technology (MST) is to use computational fluid dynamics (CFD) to study the DPM distribution in commonly used face areas.The result is expected to be used for selection of DPM reduction strategies and better working practices,which can help the underground mines to meet regulation limits and improve the working environment for the miners.An experiment was conducted at MST's Experimental Mine to validate CFD simulation.DPM was collected at four locations downstream of a stationary diesel engine.The experiment data were then compared with the CFD simulation results.The comparison shows that CFD simulation can forecast the location of DPM concentration with practical accuracy (less than 0.15 m).CFD can be used to further study DPM distribution in commonly used working faces and give guidance to DPM reduction.
Dynamic Analysis and CFD Numerical Simulation on Backpressure Filling System
Directory of Open Access Journals (Sweden)
Jing Qian
2015-01-01
Full Text Available A backpressure filling system is a kind of air type filling system which could be applied to power type, fine or coarse grain, or mixtures with fine and coarse components. The working principle of backpressure filling system was discussed based on fundamental hydromechanics. The research limit values of backpressure were achieved via mechanical analysis. Comparing with the exit velocity of material by theoretical analysis and numerical simulation, the CFD simulation model was confirmed and its related parameters were determined. The CFD numerical simulation shows the relationship between production capacity of packaging machine and backpressure, and the results matched actual operation of the equipment well. Combining with the demand of device capacity, the range of backpressure could be controlled at 8 kPa~11 kPa.
Energy Technology Data Exchange (ETDEWEB)
Galindo G, I. F., E-mail: igalindo@iie.org.mx [Instituto de Investigaciones Electricas, Reforma No. 113, Col. Palmira, 62490 Cuernavaca, Morelos (Mexico)
2013-10-15
The scenarios simulation in nuclear power plants is usually carried out with system codes that are based on concentrated parameters networks. However situations exist in some components where the flow is predominantly 3-D, as they are the natural circulation, mixed and stratification phenomena. The simulation techniques of computational fluid dynamics (CFD) have the potential to simulate these flows numerically. The use of CFD simulations embraces many branches of the engineering and continues growing, however, in relation to its application with respect to the problems related with the safety in nuclear power plants, has a smaller development, although is accelerating quickly and is expected that in the future they play a more emphasized paper in the analyses. A main obstacle to be able to achieve a general acceptance of the CFD is that the simulations should have very complete validation studies, sometimes not available. In this article a general panorama of the state of the methods application CFD in nuclear power plants is presented and the problem associated to its routine application and acceptance, including the view point of the regulatory authorities. Application examples are revised in those that the CFD offers real benefits and are also presented two illustrative study cases of the application of CFD techniques. The case of a water recipient with a heat source in its interior, similar to spent fuel pool of a nuclear power plant is presented firstly; and later the case of the Boron dilution of a water volume that enters to a nuclear reactor is presented. We can conclude that the CFD technology represents a very important opportunity to improve the phenomena understanding with a strong component 3-D and to contribute in the uncertainty reduction. (Author)
Visualization Co-Processing of a CFD Simulation
Vaziri, Arsi
1999-01-01
OVERFLOW, a widely used CFD simulation code, is combined with a visualization system, pV3, to experiment with an environment for simulation/visualization co-processing on a SGI Origin 2000 computer(O2K) system. The shared memory version of the solver is used with the O2K 'pfa' preprocessor invoked to automatically discover parallelism in the source code. No other explicit parallelism is enabled. In order to study the scaling and performance of the visualization co-processing system, sample runs are made with different processor groups in the range of 1 to 254 processors. The data exchange between the visualization system and the simulation system is rapid enough for user interactivity when the problem size is small. This shared memory version of OVERFLOW, with minimal parallelization, does not scale well to an increasing number of available processors. The visualization task takes about 18 to 30% of the total processing time and does not appear to be a major contributor to the poor scaling. Improper load balancing and inter-processor communication overhead are contributors to this poor performance. Work is in progress which is aimed at obtaining improved parallel performance of the solver and removing the limitations of serial data transfer to pV3 by examining various parallelization/communication strategies, including the use of the explicit message passing.
International Nuclear Information System (INIS)
The study consists in simulating the emptying of the tank when the water level is near the level of the suction nozzle. The objective pursued is to detect the harmful phenomena that may occur in aspiration, ranging from the appearance of vortices and bubble formation to excessive fluid accelerations. (Author)
Development of a compartment model based on CFD simulations for description of mixing in bioreactors
Directory of Open Access Journals (Sweden)
Crine, M.
2010-01-01
Full Text Available Understanding and modeling the complex interactions between biological reaction and hydrodynamics are a key problem when dealing with bioprocesses. It is fundamental to be able to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. CFD can provide detailed modeling about hydrodynamics and mixing. However, it is computationally intensive, especially when reactions are taken into account. Another way to predict hydrodynamics is the use of "Compartment" or "Multi-zone" models which are much less demanding in computation time than CFD. However, compartments and fluxes between them are often defined by considering global quantities not representative of the flow. To overcome the limitations of these two methods, a solution is to combine compartment modeling and CFD simulations. Therefore, the aim of this study is to develop a methodology in order to propose a compartment model based on CFD simulations of a bioreactor. The flow rate between two compartments can be easily computed from the velocity fields obtained by CFD. The difficulty lies in the definition of the zones in such a way they can be considered as perfectly mixed. The creation of the model compartments from CFD cells can be achieved manually or automatically. The manual zoning consists in aggregating CFD cells according to the user's wish. The automatic zoning defines compartments as regions within which the value of one or several properties are uniform with respect to a given tolerance. Both manual and automatic zoning methods have been developed and compared by simulating the mixing of an inert scalar. For the automatic zoning, several algorithms and different flow properties have been tested as criteria for the compartment creation.
Simplistic Approach to Characterize Sloshing Phenomena using CFD Simulation
Mahmud, Md; Khan, Rafiqul; Xu, Qiang
2015-03-01
Liquid sloshing in vessels caused by forced acceleration has been the subject of intense investigations for last several decades both by experiments and numerical simulations. Many studies are done to minimize the sloshing induced forces on the vessel internals and some studies focused on different ways to describe the sloshing patterns. Most of the sloshing characterization methods are done using complex mathematical manipulation and more simplified method may be useful for better practical understanding. In this study, simple/easily understandable methods are explored to describe sloshing phenomenon through Computation Fluid Dynamics (CFD) simulation. Several parameters were varied including liquid level/tank length ratio, wave induced vessel motions, motion frequency, amplitudes in various sea state conditions. Parameters such as hydrodynamic force, pressure, moments, turbulent kinetic energy, height of the free surface, vorticity are used to quantify the sloshing intensity. In addition, visual inspections of sloshing motion are done through gas-liquid/oil-water interface fluctuation, streamlines, vector profiles. An equation connecting independent variables to resultant quantities will be established that will make it easier to describe the sloshing.
CFD simulations of a spouted bed equipment for particle coating
Energy Technology Data Exchange (ETDEWEB)
Wolff Filho, Germano Klaus; Cabral, Paulo Alexandre de Moraes [Centro Tecnologico do Exercito (CTEx-RJ), Rio de Janeiro, RJ (Brazil)]. E-mails: klauswolff@ctex.eb.br; paulo@ctex.eb.br
2007-07-01
Due to their solids circulation characteristics and excellent gas-particle contact, spouted beds have been used in several engineering applications, including nuclear fuel particles coatings. A laboratory scale equipment was mounted, aiming particles coating for use in nuclear fuel research. The line operates with a spouted bed reactor filled with particles on whose surface the deposition process happens. Some computational simulations, using the CFD commercial code PHOENICS{sup R} , were made in order to show some of the equipment possibilities and limitations. It's important to exhaust theoretical investigations about this kind of system, because experimental conditions seem to be dangerous, beyond associated difficulties in process control and operation. In this work, CFD simulations are used to obtain patterns of solids and gas flows. (author)
Simulation of natural circulation in a rectangular loop using CFD code PHOENICS
Energy Technology Data Exchange (ETDEWEB)
Kumar, M.; Borghain, A.; Maheshwari, N.K.; Vijayan, P.K. [Bhabha Atomic Reseach Centre, Trombay, Mumbai (India). Reactor Engineering Div.
2011-05-15
Single phase natural circulation in a rectangular loop is simulated using the PHOENICS code, a general purpose Computational Fluid Dynamics (CFD) code. The rectangular loop, having different operating power levels, has been modeled with the help of the Multiple Block Fine Grid Embedment (MBFGE) technique. The Co-located Co-variant Method (CCM) is used to simulate this loop in PHOENICS. Extensive experimental and CFD studies have been conducted on single phase natural circulation in a rectangular loop. The paper presents the results of three-dimensional CFD analysis for the prediction of steady state behavior in a rectangular loop and its comparison with experimental data. The results of code prediction and readily available experimental data show good agreement. (orig.)
CFD simulation of air discharge tests in the PPOOLEX facility
International Nuclear Information System (INIS)
This report summarizes the CFD simulation results of two air discharge tests of the characterizing test program in 2007 with the scaled down PPOOLEX facility. Air was blown to the dry well compartment and from there through a DN200 blowdown pipe into the condensation pool (wet well). The selected tests were modeled with Fluent CFD code. Test CHAR-09-1 was simulated to 28.92 seconds of real time and test CHAR-09-3 to 17.01 seconds. The VOF model was used as a multiphase model and the standard k ε-model as a turbulence model. Occasional convergence problems, usually at the beginning of bubble formation, required the use of relatively short time stepping. The simulation time costs threatened to become unbearable since weeks or months of wall-clock time with 1-2 processors were needed. Therefore, the simulated time periods were limited from the real duration of the experiments. The results obtained from the CFD simulations are in a relatively good agreement with the experimental results. Simulated pressures correspond well to the measured ones and, in addition, fluctuations due to bubble formations and breakups are also captured. Most of the differences in temperature values and in their behavior seem to depend on the locations of the measurements. In the vicinity of regions occupied by water in the experiments, thermocouples getting wet and drying slowly may have had an effect on the measured temperature values. Generally speaking, most temperatures were simulated satisfyingly and the largest discrepancies could be explained by wetted thermocouples. However, differences in the dry well and blowdown pipe top measurements could not be explained by thermocouples getting wet. Heat losses and dry well / wet well heat transfer due to conduction have neither been estimated in the experiments nor modeled in the simulations. Estimation of heat conduction and heat losses should be carried out in future experiments and they should be modeled in future simulations, too. (au)
CFD Simulation of Hydrodynamics of Rectangular External Loop Airlift Reactor
Czech Academy of Sciences Publication Activity Database
Šimčík, Miroslav; Růžička, Marek; Havlica, Jaromír; Drahoš, Jiří; Teixeira, J.
Praha: Process Engineering Publisher, 2008, s. 862. ISBN 978-80-02-02050-9. [18th International Congress of Chemical and Process Engineering CHISA 2008. Praha (CZ), 24.08.2008-28.08.2008] R&D Projects: GA ČR GA104/07/1110; GA ČR GA104/06/1418 Institutional research plan: CEZ:AV0Z40720504 Keywords : cfd simulation * loop airlift reactor * gas-liquid systems Subject RIV: CI - Industrial Chemistry, Chemical Engineering
CFD simulation of vented explosion and turbulent flame propagation
Directory of Open Access Journals (Sweden)
Tulach Aleš
2015-01-01
Full Text Available Very rapid physical and chemical processes during the explosion require both quality and quantity of detection devices. CFD numerical simulations are suitable instruments for more detailed determination of explosion parameters. The paper deals with mathematical modelling of vented explosion and turbulent flame spread with use of ANSYS Fluent software. The paper is focused on verification of preciseness of calculations comparing calculated data with the results obtained in realised experiments in the explosion chamber.
CFD simulation of vented explosion and turbulent flame propagation
Tulach Aleš; Mynarz Miroslav; Kozubková Milada
2015-01-01
Very rapid physical and chemical processes during the explosion require both quality and quantity of detection devices. CFD numerical simulations are suitable instruments for more detailed determination of explosion parameters. The paper deals with mathematical modelling of vented explosion and turbulent flame spread with use of ANSYS Fluent software. The paper is focused on verification of preciseness of calculations comparing calculated data with the results obtained in realised experiments...
CFD simulation of the discharge flow from standard Rushton impeller
Bohuš Kysela; Jiří Konfršt; Ivan Fořt; Zdeněk Chára
2014-01-01
The radial discharge jet from the standard Rushton turbine was investigated by the CFD calculations and compared with results from the Laser Doppler Anemometry (LDA) measurements. The Large Eddy Simulation (LES) approach was employed with Sliding Mesh (SM) model of the impeller motion. The obtained velocity profiles of the mean ensemble-averaged velocity and r.m.s. values of the fluctuating velocity were compared in several distances from the impeller blades. The calculated values of mean ens...
CFD simulation of vented explosion and turbulent flame propagation
Tulach, Aleš; Mynarz, Miroslav; Kozubková, Milada
2015-05-01
Very rapid physical and chemical processes during the explosion require both quality and quantity of detection devices. CFD numerical simulations are suitable instruments for more detailed determination of explosion parameters. The paper deals with mathematical modelling of vented explosion and turbulent flame spread with use of ANSYS Fluent software. The paper is focused on verification of preciseness of calculations comparing calculated data with the results obtained in realised experiments in the explosion chamber.
CFD simulation of Kelvin-Helmholtz instability
International Nuclear Information System (INIS)
Kelvin-Helmholtz instability appears in stratified two-fluid flow at surface. When the relative velocity is higher than the critical relative velocity, the growth of waves occurs. The experiment of Thorpe [1] used as a benchmark in the present paper, is made in a rectangular glass tube filled with two immiscible fluids of various densities. We simulated the growth of instability with CFX-5.7 code and compared simulation with analytical solution. It was found that surface tension force, which stabilizes growth of waves, actually has a destabilizing effect in simulation, unless very small timestep and residual is used. In CFX code system of nonlinear Navier-Stokes equations is linearised and solved iterative in each timestep, until prescribed residual is achieved. On the other hand, simulation without surface tension force is more stable than analytical result predicts. (author)
Imposing resolved turbulence in CFD simulations
DEFF Research Database (Denmark)
Gilling, L.; Sørensen, Niels N.
2011-01-01
In large‐eddy simulations, the inflow velocity field should contain resolved turbulence. This paper describes and analyzes two methods for imposing resolved turbulence in the interior of the domain in Computational Fluid Dynamics simulations. The intended application of the methods is to impose...... resolved turbulence immediately upstream of the region or structure of interest. Comparing to the alternative of imposing the turbulence at the inlet, there is a large potential to reduce the computational cost of the simulation by reducing the total number of cells. The reduction comes from a lower demand...... modifying the source terms. None of the two methods can impose synthetic turbulence with good results, but it is shown that by running the turbulence field through a short precursor simulation, very good results are obtained. Copyright © 2011 John Wiley & Sons, Ltd....
CFD simulation of the magnetophoretic separation in a microchannel
International Nuclear Information System (INIS)
The CFD simulation of the separation of labeled biospecies from a native fluid flowing through a planar microchannel, mediated by a magnetic field is presented in this study. The fluid flow, coupled with Eulerian advection-convection concentration equation, is utilized to model the transport of the magnetic biospecies. A moderate-gradient magnetic field caused accumulation of the magnetic labeled species in the vicinity of the higher magnetic field region. The re-distribution of the magnetically labeled species in the region close to the highest magnetic field zone presents a scheme for the focusing or collection of these species from the heterogeneous samples under the simulation conditions. The magnetic-fluidic interactions and interplay between the magnetophoretic mass transfer and molecular diffusion for different throughputs are analyzed. The study found out that the axial magnetic forces, created from a dipole-like magnetic field, is playing a major role in the vortex formation, and this complements the downward vertical force in confining the particles to a small region near the point with the highest magnetic strength. Also, the study predicts that the generated viscous shear stress levels in the interior region of the channel provide a safe transport mechanism for the biological cells in the solution. - Highlights: → Transport of magnetic microparticles through a planar microchannel is modeled and simulated. → Full Eulerian approach is used to solve the flow and concentration fields. → Simulations show a practical scheme for the collection of magnetically labeled biospecies. → Vortex formation as related to the magnetic force and flow fields is analyzed.
CFD simulation of the magnetophoretic separation in a microchannel
Energy Technology Data Exchange (ETDEWEB)
Khashan, Saud A., E-mail: skhashan@uaeu.ac.ae [Department of Mechanical Engineering, College of Engineering, UAE University, P.O. Box 17555, Al-Ain (United Arab Emirates); Elnajjar, Emad, E-mail: eelnajjar@uaeu.ac.ae [Department of Mechanical Engineering, College of Engineering, UAE University, P.O. Box 17555, Al-Ain (United Arab Emirates); Haik, Yousef, E-mail: yhaik@uaeu.ac.ae [Department of Mechanical Engineering, College of Engineering, UAE University, P.O. Box 17555, Al-Ain (United Arab Emirates)
2011-12-15
The CFD simulation of the separation of labeled biospecies from a native fluid flowing through a planar microchannel, mediated by a magnetic field is presented in this study. The fluid flow, coupled with Eulerian advection-convection concentration equation, is utilized to model the transport of the magnetic biospecies. A moderate-gradient magnetic field caused accumulation of the magnetic labeled species in the vicinity of the higher magnetic field region. The re-distribution of the magnetically labeled species in the region close to the highest magnetic field zone presents a scheme for the focusing or collection of these species from the heterogeneous samples under the simulation conditions. The magnetic-fluidic interactions and interplay between the magnetophoretic mass transfer and molecular diffusion for different throughputs are analyzed. The study found out that the axial magnetic forces, created from a dipole-like magnetic field, is playing a major role in the vortex formation, and this complements the downward vertical force in confining the particles to a small region near the point with the highest magnetic strength. Also, the study predicts that the generated viscous shear stress levels in the interior region of the channel provide a safe transport mechanism for the biological cells in the solution. - Highlights: > Transport of magnetic microparticles through a planar microchannel is modeled and simulated. > Full Eulerian approach is used to solve the flow and concentration fields. > Simulations show a practical scheme for the collection of magnetically labeled biospecies. > Vortex formation as related to the magnetic force and flow fields is analyzed.
CFD Simulations on Interference Effects between Offshore Wind Turbines
Weihing, P.; Meister, K.; Schulz, C.; Lutz, Th; Krämer, E.
2014-06-01
This paper presents results of detailed 3D CFD simulations of two 5MW wind turbines sited in the German wind farm Alpha Ventus which are located behind each other at half-wake conditions. The focus of interest in this study is put on wake - turbine interaction, in order to derive the main shadow effects and their influence on blade loads and power response of the downstream turbine. For this purpose, Detached Eddy Simulations (DES) were performed using the flow solver FLOWer from DLR (German Aerospace Center). To consider all relevant aerodynamic effects, the main turbine components are represented as direct model with resolved boundary layers. Measurement-based turbulent inflow conditions are prescribed to realistically account for the atmospheric boundary layer. In order to analyze the flow conditions in front of the downstream turbine, wake propagation and velocity spectra are evaluated and compared with the undisturbed atmospheric boundary layer. Their impact on loads and power production and their corresponding fluctuations is discussed by comparing these with the upstream turbine. It was found, that fatigue loads occurring at half-wake conditions are significantly higher for the downstream turbine, since blade load fluctuations are highly amplified by the unsteady wake of the upstream turbine.
CFD Simulations on Interference Effects between Offshore Wind Turbines
International Nuclear Information System (INIS)
This paper presents results of detailed 3D CFD simulations of two 5MW wind turbines sited in the German wind farm Alpha Ventus which are located behind each other at half-wake conditions. The focus of interest in this study is put on wake – turbine interaction, in order to derive the main shadow effects and their influence on blade loads and power response of the downstream turbine. For this purpose, Detached Eddy Simulations (DES) were performed using the flow solver FLOWer from DLR (German Aerospace Center). To consider all relevant aerodynamic effects, the main turbine components are represented as direct model with resolved boundary layers. Measurement-based turbulent inflow conditions are prescribed to realistically account for the atmospheric boundary layer. In order to analyze the flow conditions in front of the downstream turbine, wake propagation and velocity spectra are evaluated and compared with the undisturbed atmospheric boundary layer. Their impact on loads and power production and their corresponding fluctuations is discussed by comparing these with the upstream turbine. It was found, that fatigue loads occurring at half-wake conditions are significantly higher for the downstream turbine, since blade load fluctuations are highly amplified by the unsteady wake of the upstream turbine
Energy Technology Data Exchange (ETDEWEB)
Zeng, J.; Kato, S.; Murakami, S. [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science
1998-01-01
Described herein is coupled simulation of CFD, radiation and moisture transport, as part of the program for development of computational thermal manikin, to investigate total heat radiation characteristics from a human body. The transport phenomena are investigated for a single human body model, approximately 1.65m high, in an indoor space of 15.4m{sup 3} in volume, where the Fanger model and Gagge`s 2 node model are used to simulate heat radiation from a model. The results include heat balances on the walls, and temperature distributions, heat transport characteristics by convection and radiation, latent heat transport characteristics and wet fraction distributions over the manikin surfaces under given conditions of wind velocity, temperature and temperature distribution. It is found that both models give proper estimates for average characteristics of total heat radiation from a human body, and that the Gagge model gives slightly better results for local distributions of latent heat transfer over the body surface. 16 refs., 27 figs., 1 tab.
Sensitivity analysis and application guides for integrated building energy and CFD simulation
Energy Technology Data Exchange (ETDEWEB)
Zhiqiang John Zhai [Colorado Univ., Boulder, CO (United States). Dept. of Civil, Environmental, and Architectural Engineering; Qingyan Yan Chen [Purdue Univ., West Lafayette, IN (United States). School of Mechanical Engineering
2006-09-15
Building energy simulation (ES) and computational fluid dynamics (CFD) programs provide complementary information essential to evaluating building thermal performance. Integration of the two programs eliminates many model assumptions in separate applications and thus improves the quality of simulation results. This paper discusses the potential building and environmental characteristics that may affect the necessity and effectiveness of applying an ES-CFD coupling simulation. These characteristics and the solution accuracy requirement determine whether a coupled simulation is needed for a specific building and which coupling method can provide the best solution with the compromise of both accuracy and efficiency. The study conducts a sensitivity analysis of the coupling simulation to the potential influential factors, based on which general suggestions on appropriate usage of the coupling simulation are provided. (author)
Sensitivity analysis and application guides for integrated building energy and CFD simulation
Energy Technology Data Exchange (ETDEWEB)
Zhai, Z.J. [Department of Civil, Environmental and Architectural Engineering, University of Colorado at Boulder, Boulder, CO (United States); Chen, Q.Y. [School of Mechanical Engineering, Purdue University, West Lafayette, IN (United States)
2006-07-01
Building energy simulation (ES) and computational fluid dynamics (CFD) programs provide complementary information essential to evaluating building thermal performance. Integration of the two programs eliminates many model assumptions in separate applications and thus improves the quality of simulation results. This paper discusses the potential building and environmental characteristics that may affect the necessity and effectiveness of applying an ES-CFD coupling simulation. These characteristics and the solution accuracy requirement determine whether a coupled simulation is needed for a specific building and which coupling method can provide the best solution with the compromise of both accuracy and efficiency. The study conducts a sensitivity analysis of the coupling simulation to the potential influential factors, based on which general suggestions on appropriate usage of the coupling simulation are provided. (author)
Energy Technology Data Exchange (ETDEWEB)
Ruiz, S. [Idiada Automotive Technology SA (Spain)
2003-09-01
Lateral wind gusts affect the driving characteristics of a vehicle in a complex way. This is why a sophisticated test procedure is employed, i.e. integrated multibody and CFD simulation. For an exact virtual analysis of the dynamic response of a motor car to complex aerodynamic excitations, Idiada Automotive Technology SA, Spain, used the MKS program MSC.Adams by MSC. Software in combination with the CFD program STAR-CD. (orig.) [German] Seitenwindboeen verursachen aerodynamische Seitenkraefte, Gier- und Wankmomente, die das Fahrverhalten und die Querstabilitaet beeinflussen. Die komplexen Fahrverhaeltnisse in Seitenwindtests erfordern deshalb einen anspruchsvollen Ansatz fuer dieses Phaenomen: die Integration von Mehrkoerper- und CFD-Simulation. Fuer eine exakte virtuelle Analyse der Fahrzeugdynamik bei komplexen aerodynamischen Anregungen verwendete Idiada Automotive Technology SA, Spanien, das MKS-Programm MSC.Adams von MSC.Software in Verbindung mit dem CFD-Programm STAR-CD. (orig.)
CFD simulation research on residential indoor air quality.
Yang, Li; Ye, Miao; He, Bao-Jie
2014-02-15
Nowadays people are excessively depending on air conditioning to create a comfortable indoor environment, but it could cause some health problems in a long run. In this paper, wind velocity field, temperature field and air age field in a bedroom with wall-hanging air conditioning running in summer are analyzed by CFD numerical simulation technology. The results show that wall-hanging air conditioning system can undertake indoor heat load and conduct good indoor thermal comfort. In terms of wind velocity, air speed in activity area where people sit and stand is moderate, most of which cannot feel wind flow and meet the summer indoor wind comfort requirement. However, for air quality, there are local areas without ventilation and toxic gases not discharged in time. Therefore it is necessary to take effective measures to improve air quality. Compared with the traditional measurement method, CFD software has many advantages in simulating indoor environment, so it is hopeful for humans to create a more comfortable, healthy living environment by CFD in the future. PMID:24365517
CFD simulation of mixing for high-solids anaerobic digestion.
Wu, Binxin
2012-08-01
A computational fluid dynamics (CFD) model that simulates mechanical mixing for high-solids anaerobic digestion was developed. Numerical simulations of mixing manure slurry which exhibits non-Newtonian pseudo-plastic fluid behavior were performed for six designs: (i) one helical ribbon impeller; (ii) one anchor impeller; (iii) one curtain-type impeller; (iv) three counterflow (CF-2) impellers; (v) two modified high solidity (MHS 3/39°) impellers; and (vi) two pitched blade turbine impellers. The CFD model was validated against measurements for mixing a Herschel-Bulkley fluid by ribbon and anchor impellers. Based on mixing time with respect to mixing energy level, three impeller types (ribbon, CF-2, and MHS 3/39°) stand out when agitating highly viscous fluids, of these mixing with two MHS 3/39° impellers requires the lowest power input to homogenize the manure slurry. A comparison of digestion material demonstrates that the mixing energy varies with manure type and total solids concentration to obtain a given mixing time. Moreover, an in-depth discussion about the CFD strategy, the influences of flow regime and impeller type on mixing characteristics, and the intrinsic relation between mixing and flow field is included. PMID:22422446
CFD simulation of air–steam flow with condensation
Energy Technology Data Exchange (ETDEWEB)
Vyskocil, Ladislav, E-mail: Ladislav.Vyskocil@ujv.cz; Schmid, Josef; Macek, Jiri
2014-11-15
Highlights: • Condensation model for CFD code Fluent. • Suitable for flow of air–steam mixture with additional non-condensable gases. • Suitable for both compressible and incompressible flow. • Successfully tested on the CONAN experiments and PANDA Test 9bis experiment. - Abstract: This article presents a custom condensation model for commercial CFD code Fluent. The condensation model was developed for the species transport model in Fluent code and it is suitable for both compressible and incompressible flow of air–steam mixture with additional non-condensable gases. The condensation model consists of two parts: condensation in volume and condensation on the wall. Condensation in volume is modeled by “return to saturation in constant time scale” method. Condensation on the wall is calculated from diffusion of steam through a layer of non-condensable gases near the wall. The performance of the condensation model was tested on the CONAN experiments. In these experiments, air–steam mixture flows downwards through a vertical channel with square cross section. One vertical wall of the channel is cooled and the steam condenses on it. The same model was then applied in simulation of PANDA Test 9bis experiment with condensation. In this test, two vessels connected with a pipe were filled with air; and steam was released into the first vessel. As the steam concentration increased in the vessels, the steam started condensing on the walls. The results of CFD simulations of both CONAN and PANDA experiments compared well with the measured data.
CFD simulation of air–steam flow with condensation
International Nuclear Information System (INIS)
Highlights: • Condensation model for CFD code Fluent. • Suitable for flow of air–steam mixture with additional non-condensable gases. • Suitable for both compressible and incompressible flow. • Successfully tested on the CONAN experiments and PANDA Test 9bis experiment. - Abstract: This article presents a custom condensation model for commercial CFD code Fluent. The condensation model was developed for the species transport model in Fluent code and it is suitable for both compressible and incompressible flow of air–steam mixture with additional non-condensable gases. The condensation model consists of two parts: condensation in volume and condensation on the wall. Condensation in volume is modeled by “return to saturation in constant time scale” method. Condensation on the wall is calculated from diffusion of steam through a layer of non-condensable gases near the wall. The performance of the condensation model was tested on the CONAN experiments. In these experiments, air–steam mixture flows downwards through a vertical channel with square cross section. One vertical wall of the channel is cooled and the steam condenses on it. The same model was then applied in simulation of PANDA Test 9bis experiment with condensation. In this test, two vessels connected with a pipe were filled with air; and steam was released into the first vessel. As the steam concentration increased in the vessels, the steam started condensing on the walls. The results of CFD simulations of both CONAN and PANDA experiments compared well with the measured data
Energy Technology Data Exchange (ETDEWEB)
Wanninger, Andreas; Ceuca, Sabin Cristian; Macian-Juan, Rafael [Technische Univ. Muenchen, Garching (Germany). Dept. of Nuclear Engineering
2013-07-01
Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)
International Nuclear Information System (INIS)
Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Bueno, B.; Cejudo, J.; Carrillo, A.
2008-07-01
Computational fluid dynamics (CFD) application to building energy simulation (STE) allows better modelling of indoor air performance and therefore it can be used to optimize the design of natural ventilation systems. In this paper, a natural ventilation system based on thermal chimney applied to a residential building is analyzed. Energy Plus simulations are applied to an apartment and results are coupled to CFD simulations to determine ventilation rates and study convection in the space. CFD simulations are also applied to evaluate indoor air distribution and study how ventilation rate is affected by the pressure drop at ventilation grilles. (Author)
A Multiscale/Multifidelity CFD Framework for Robust Simulations
Lee, Seungjoon; Kevrekidis, Yannis; Karniadakis, George
2015-11-01
We develop a general CFD framework based on multifidelity simulations to target multiscale problems but also resilience in exascale simulations, where faulty processors may lead to gappy simulated fields. We combine approximation theory and domain decomposition together with machine learning techniques, e.g. co-Kriging, to estimate boundary conditions and minimize communications by performing independent parallel runs. To demonstrate this new simulation approach, we consider two benchmark problems. First, we solve the heat equation with different patches of the domain simulated by finite differences at fine resolution or very low resolution but also with Monte Carlo, hence fusing multifidelity and heterogeneous models to obtain the final answer. Second, we simulate the flow in a driven cavity by fusing finite difference solutions with solutions obtained by dissipative particle dynamics - a coarse-grained molecular dynamics method. In addition to its robustness and resilience, the new framework generalizes previous multiscale approaches (e.g. continuum-atomistic) in a unified parallel computational framework.
CFD simulation of DEBORA boiling experiments
Rzehak, Roland; Krepper, Eckhard
2012-08-01
In this work we investigate the present capabilities of computational fluid dynamics for wall boiling. The computational model used combines the Euler/Euler two-phase flow description with heat flux partitioning. This kind of modeling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, bubble size and liquid temperature as well as axial profiles of wall temperature. After reviewing the theoretical and experimental basis of correlations used in the ANSYS CFX model used for the calculations, we give a careful assessment of the necessary recalibrations to describe the DEBORA tests. The basic CFX model is validated by a detailed comparison to the experimental data for two selected test cases. Simulations with a single set of calibrated parameters are found to give reasonable quantitative agreement with the data for several tests within a certain range of conditions and reproduce the observed tendencies correctly. Several model refinements are then presented each of which is designed to improve one of the remaining deviations between simulation and measurements. Specifically we consider a homogeneous MUSIG model for the bubble size, modified bubble forces, a wall function for turbulent boiling flow and a partial slip boundary condition for the liquid phase. Finally, needs for further model developments are identified and promising directions discussed.
CFD Simulation of Infiltration Heat Recovery
Energy Technology Data Exchange (ETDEWEB)
Buchanan, C.R.; Sherman, M.H.
1998-07-01
Infiltration has traditionally been assumed to affect the energy load of a building by an amount equal to the product of the infiltration flow rate and the sensible enthalpy difference between inside and outside. Results from detailed computational fluid dynamics simulations of five wall geometries over a range of infiltration rates show that heat transfer between the infiltrating air and walls can be substantial, reducing the impact of infiltration. Factors affecting the heat recovery are leakage path length, infiltration flow rate, and wall construction. The classical method for determination of the infiltration energy load was found to over-predict the amount by as much as 95 percent and by at least 10 percent. However, the air flow paths typical of building envelopes give over-predictions at the low end of this range.
CFD development for macro particle simulations
Zhao, Xiang; Glenn, Chance; Xiao, Zhigang; Zhang, Sijun
2014-05-01
Numerous industrial operations involve fluid-particle systems, in which both phases display very complex behaviour. Some examples include fluidisation technology in catalytic reactors, pneumatic transportation of grain or powder materials, carbon nanotube alignment in the nano-devices and circuit integration and so on. In this paper, a macro particle method is developed to model the fluid-particle flows. The macro particle is formed by a collection of micro-sized particles so that the number of macro particles to be tracked is much less than the number of smaller particles. Unlike the calculations of instantaneous point variables of fluid phase with moving discrete boundaries of the smaller particles with direct numerical simulation, the boundary of each macro particle is just dealt with the blocked-off approach. On the other hand, the flow fields based on the present method is solved by original Navier-Stokes, rather than the modified ones based on the locally averaged theorem. The flow fields are solved on the length scale of computational cells, while the resolutions of solid particles are the size of macro particle, which is determined as needed in specific applications. The macro particle method is validated by several selected cases, which demonstrate that the macro particle method could accurately resolve fluid-particle systems in an efficient, robust and flexible fashion.
Efficient parallel CFD-DEM simulations using OpenMP
Amritkar, Amit; Deb, Surya; Tafti, Danesh
2014-01-01
The paper describes parallelization strategies for the Discrete Element Method (DEM) used for simulating dense particulate systems coupled to Computational Fluid Dynamics (CFD). While the field equations of CFD are best parallelized by spatial domain decomposition techniques, the N-body particulate phase is best parallelized over the number of particles. When the two are coupled together, both modes are needed for efficient parallelization. It is shown that under these requirements, OpenMP thread based parallelization has advantages over MPI processes. Two representative examples, fairly typical of dense fluid-particulate systems are investigated, including the validation of the DEM-CFD and thermal-DEM implementation with experiments. Fluidized bed calculations are performed on beds with uniform particle loading, parallelized with MPI and OpenMP. It is shown that as the number of processing cores and the number of particles increase, the communication overhead of building ghost particle lists at processor boundaries dominates time to solution, and OpenMP which does not require this step is about twice as fast as MPI. In rotary kiln heat transfer calculations, which are characterized by spatially non-uniform particle distributions, the low overhead of switching the parallelization mode in OpenMP eliminates the load imbalances, but introduces increased overheads in fetching non-local data. In spite of this, it is shown that OpenMP is between 50-90% faster than MPI.
CFD simulation of smooth and T-abrupt exits in circulating fluidized bed risers
Institute of Scientific and Technical Information of China (English)
Xuezhi Wu; Fan Jiang; Xiang Xu; Yunhan Xiao
2010-01-01
Gas-solid flow in circulating fluidized bed(CFB)risers depends not only on operating conditions but also on exit configurations.Few studies investigated the effects of exit configurations on flow structure using computational fluid dynamics(CFD).This paper provides a 2D two-fluid model to simulate a cold bench-scale square cross-section riser with smooth and T-abrupt exits.The drag force between the gas and solid phases plays an important role in CFD.Since the drag force model based on homogeneous twophase flow,such as the Wen-Yu correlation,could not capture the heterogeneous structures in gas-solid flow,the structure-dependent energy-minimization multi-scale(EMMS)drag force model(Wang.Ge,&Li,2008),applicable for Geldart B particles(sand),was integrated into the two-fluid model.The calculated axial solids hold-up profiles were respectively exponential curve for smooth exit and C-shaped curve for T-abrupt exit,both consistent with experimental data.This study once again proves the key role of drag force in CFD simulation and also shows the validity of CFD simulation(two-fluid model)to describe exit effects on gas-solid flow in CFB risers.
Directory of Open Access Journals (Sweden)
Kruggel-Emden H.
2011-03-01
Full Text Available Chemical Looping Combustion is an energy efficient combustion technology for the inherent separation of carbon dioxide for both gaseous and solid fuels. For scale up and further development of this process multi-phase CFD-based simulations have a strong potential which rely on kinetic models for the solid/gaseous reactions. Reaction models are usually simple in structure in order to keep the computational cost low. They are commonly derived from thermogravimetric experiments. With only few CFD-based simulations performed on chemical looping combustion, there is a lack in understanding of the role and of the sensitivity of the applied chemical reaction model on the outcome of a simulation. The aim of this investigation is therefore the study of three different carrier materials CaSO4, Mn3O4 and NiO with the gaseous fuels H2 and CH4 in a batch type reaction vessel. Four reaction models namely the linear shrinking core, the spherical shrinking core, the Avrami-Erofeev and a recently proposed multi parameter model are applied and compared on a case by case basis. La combustion en boucle chimique (Chemical Looping Combustion est une technologie de combustion efficace permettant le captage in situ du CO2 pour des charges gazeuses ou solides. Dans l’optique du développement et de l’extrapolation du procédé, la CFD est un outil de simulation à fort potentiel qui s’appuie notamment sur des modèles cinétiques pour décrire les réactions gaz-solide. Ces modèles décrivant les réactions sont généralement assez simples pour limiter les temps de simulation et sont obtenus à partir d’expérimentations en thermobalance. Il y a encore peu de travaux de modélisation CFD du procédé CLC et il est difficile d’estimer l’importance du modèle décrivant les réactions chimiques sur les résultats des simulations. Le but de ce travail est donc d’étudier la combustion de charges gazeuses H2 et CH4 dans des réacteurs en batch en consid
3D CFD Simulations of MOCVD Synthesis System of Titanium Dioxide Nanoparticles
Siti Hajar Othman; Suraya Abdul Rashid; Tinia Idaty Mohd Ghazi; Norhafizah Abdullah
2013-01-01
This paper presents the 3-dimensional (3D) computational fluid dynamics (CFD) simulation study of metal organic chemical vapor deposition (MOCVD) producing photocatalytic titanium dioxide (TiO2) nanoparticles. It aims to provide better understanding of the MOCVD synthesis system especially of deposition process of TiO2 nanoparticles as well as fluid dynamics inside the reactor. The simulated model predicts temperature, velocity, gas streamline, mass fraction of reactants and products, kinetic...
CFD simulation of centrifugal cells washers.
Kellet, Beth E; Binbing, Han; Dandy, David S; Wickramasinghe, S Ranil
2004-01-01
The feasibility of using computational fluid dynamics to guide the design of better centrifuges for processing shed blood is explored here. The velocity field and the rate of protein removal from the shed blood have been studied. The results indicate that computational fluid dynamics could help screen preliminary centrifuge bowl designs thus reducing the number of initial experimental tests required when developing new centrifuge bowls. Though the focus of this work is on washing shed blood the methods developed here are applicable to the design of centrifuge bowls for other blood processing applications. PMID:15133962
An integrated CFD simulation tool in naval architecture and offshore (NAO) engineering
Jaswar, Maimun, A.; Priyanto, A.; Wahid, Mazlan Abdul; Zamani, Saman, Pauzi
2012-06-01
Integrated Computational Fluid Dynamic as a simulation tool for optimization of ship and offshore designs have been developed with higher reliability and accuracy by many institutions. The Department of Marine Technology at the Faculty of Mechanical Engineering, University Teknologi Malaysia has recently developed an integrated CFD simulation tool using potential theory, which intends to upgrade student's level understanding the application of fluid dynamic to ship and offshore structure designs. This paper discusses the application of integrated Naval Architecture and Offshore (NAO) CFD simulation tool for hull performance analysis in term of wave resistance. Detailed discussion on pressure distribution around the hull and generated wave profile by the hull are also presented. As a case study, hull performance of VLCC tanker is simulated using the tool.
CFD simulation of hydrodynamic characteristics on pulse combustor
Rahmatika, Annie Mufyda; Salihat, Efaning; Tikasari, Rachma; Widiyastuti, W.; Winardi, Sugeng
2016-02-01
The purpose of this research is to study the simulation of the combustion characteristics and performances in pulse combustor using different excess air composition and different pulse combustor geometry using CFD (Computational Fluid Dynamics) software Ansys FLUENT 15.0. The distribution of temperature, pressure, and fluid velocity using 2D axisymmetric with k-ɛ turbulence models. Two kind geometries of pulse combustors were selected and compared their performance. The first combustor, called geometry A has expanded tail-pipe with diameter 10 mm expanded to 20 mm with length 86 mm. The second combustor, called geometry B has cylinder tailpipe which 10 mm in diameter and 200 mm in length. Air and propane were selected as oxidizer and fuel, respectively, at temperature 27°C and pressure 1 atm with varied excess air of 0%, 23%, 200%, and 500%. The simulation result shows that the average temperature of outflow gas combustion decreased with increasing the excess air. On the other hand, the pressure amplitude increased with increasing the excess air. Amplitude of presure for excess air of 0%, 23%, 200% and 500% were 14,976.03 Pa; 26,100.19 Pa; 41,529.02 Pa; and 85,019.01 Pa, respectively. The geometry of pulse combustor affected the performance of gas combustion produced. Geometry A showed that the energy produced in the combustion cycle amounts to 538,639 to 958,639 J/kg. On the other hand, geometry B showed that the generated energy was in the range 864,502 to 1,280,814 J/kg. Combustor with geometry B provided more effective combustion performance rather than B caused by its larger heat transfer area sectional area.
CFD-DEM and Experimental Study of Bubbling in a Fluidized Bed
Khawaja, Hassan Abbas
2015-01-01
In this study, phenomenon of bubbling is investigated using CFD-DEM and experiments. A CFD-DEM simulation is setup to model the fluidized beds of different sizes. Geldart D particles of 1.2 mm diameter and 1000 Kg/m3 density are modelled. Study revealed different types of fluidization regimes as stated in the literature. An experimental setup is built to obtain the results for the comparison. Comparison revealed that results obtained from both methodologies; CFD-DEM and experiments are ...
CFD Simulations Of Sonic Booms In Near And Mid Fields
Cheung, Samson H.; Edwards, Thomas A.; Lawrence, Scott L.
1992-01-01
Report discusses computational fluid dynamics (CFD) to simulate generation and propagation of sonic booms in near- and mid-field regions of supersonic flows about simplified bodies representative of advanced airplanes. Parabolized Navier-Stokes equations integrated by implicit, approximate-factorization, finite-volume algorithm in which crossflow inviscid fluxes evaluated by Roe's flux-difference-splitting scheme. Near-field solutions obtained by applying algorithm to flows immediately surrounding bodies. Solutions transferred to computer codes based on Whitham"s F-function theory for extrapolation to far-field.
Active-passive measurements and CFD based modelling for indoor radon dispersion study
International Nuclear Information System (INIS)
Computational fluid dynamics (CFD) play a significant role in indoor pollutant dispersion study. Radon is an indoor pollutant which is radioactive and inert gas in nature. The concentration level and spatial distribution of radon may be affected by the dwelling's ventilation conditions. Present work focus at the study of indoor radon gas distribution via measurement and CFD modeling in naturally ventilated living room. The need of the study is the prediction of activity level and to study the effect of natural ventilation on indoor radon. Two measurement techniques (Passive measurement using pin-hole dosimeters and active measurement using continuous radon monitor (SRM)) were used for the validation purpose of CFD results. The CFD simulation results were compared with the measurement results at 15 points, 3 XY planes at different heights along with the volumetric average concentration. The simulation results found to be comparable with the measurement results. The future scope of these CFD codes is to study the effect of varying inflow rate of air on the radon concentration level and dispersion pattern. - Highlights: • The distribution of radon gas in indoor environment was simulated using CFD modelling. • The distribution of radon was found to be more homogenous in open room condition. • The radon concentration level in open room was low as compare to closed room due to enhanced ventilation rate. • Simulation results are in agreement with active and passive measurements results
CFD simulation of gas and particles combustion in biomass furnaces
Energy Technology Data Exchange (ETDEWEB)
Griselin, Nicolas
2000-11-01
In this thesis, gas and particle combustion in biomass furnaces is investigated numerically. The aim of this thesis is to use Computational Fluid Dynamics (CFD) technology as an effective computer based simulation tool to study and develop the combustion processes in biomass furnaces. A detailed model for the numerical simulation of biomass combustion in a furnace, including fixed-bed modeling, gas-phase calculation (species distribution, temperature field, flow field) and gas-solid two-phase interaction for flying burning particles is presented. This model is used to understand the mechanisms of combustion and pollutant emissions under different conditions in small scale and large scale furnaces. The code used in the computations was developed at the Division of Fluid Mechanics, LTH. The flow field in the combustion enclosure is calculated by solving the Favre-averaged Navier-Stokes equations, with standard {kappa} - {epsilon} turbulence closure, together with the energy conservation equation and species transport equations. Discrete transfer method is used for calculating the radiation source term in the energy conservation equation. Finite difference is used to solve the general form of the equation yielding solutions for gas-phase temperatures, velocities, turbulence intensities and species concentrations. The code has been extended through this work in order to include two-phase flow simulation of particles and gas combustion. The Favre-averaged gas equations are solved in a Eulerian framework while the submodels for particle motion and combustion are used in the framework of a Lagrangian approach. Numerical simulations and measurement data of unburned hydrocarbons (UHC), CO, H{sub 2}, O{sub 2} and temperature on the top of the fixed bed are used to model the amount of tar and char formed during pyrolysis and combustion of biomass fuel in the bed. Different operating conditions are examined. Numerical calculations are compared with the measured data. It is
A CFD Simulation for a Design of Core Flow Simulator for SMART
Energy Technology Data Exchange (ETDEWEB)
Ko, Yung Joo; Bae, Hwang; Euh, Dong Jin; Kwon, Tae Soon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2010-05-15
The conceptual design of the SMART reactor has been developed at KAERI since 1997, for the generation of electric power and also for seawater desalination. In order to verify the performance of the SMART design in respect to flow and pressure distribution, an experimental test facility named SCOP has been developed. The core flow distribution will be measured by using a simulator preserving the flow characteristics of the prototype, which will be utilized for the evaluation of the core thermal margin. The present study is to develop and verify design parameters applied to the core flow simulator by using proven CFD software. A CFX version 11 has been used to evaluate the flow characteristics of the core simulator using a 1/5 length scale of SMART core assembly. To conserve flow similarity, the Euler number which is expressed as the ratio of a differential pressure to a dynamic pressure should be similar under a sufficient turbulent flow condition
A CFD Simulation Process for Fast Reactor Fuel Assemblies
Energy Technology Data Exchange (ETDEWEB)
Kurt D. Hamman; Ray A. Berry
2010-09-01
A CFD modeling and simulation process for large-scale problems using an arbitrary fast reactor fuel assembly design was evaluated. Three-dimensional flow distributions of sodium for several fast reactor fuel assembly pin spacing configurations were simulated on high performance computers using commercial CFD software. This research focused on 19-pin fuel assembly “benchmark” geometry, similar in design to the Advanced Burner Test Reactor, where each pin is separated by helical wire-wrap spacers. Several two-equation turbulence models including the k–e and SST (Menter) k–? were evaluated. Considerable effort was taken to resolve the momentum boundary layer, so as to eliminate the need for wall functions and reduce computational uncertainty. High performance computers were required to generate the hybrid meshes needed to predict secondary flows created by the wire-wrap spacers; computational meshes ranging from 65 to 85 million elements were common. A general validation methodology was followed, including mesh refinement and comparison of numerical results with empirical correlations. Predictions for velocity, temperature, and pressure distribution are shown. The uncertainty of numerical models, importance of high fidelity experimental data, and the challenges associated with simulating and validating large production-type problems are presented.
A CFD simulation process for fast reactor fuel assemblies
Energy Technology Data Exchange (ETDEWEB)
Hamman, Kurt D., E-mail: Kurt.Hamman@inl.go [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Berry, Ray A. [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States)
2010-09-15
A CFD modeling and simulation process for large-scale problems using an arbitrary fast reactor fuel assembly design was evaluated. Three-dimensional flow distributions of sodium for several fast reactor fuel assembly pin spacing configurations were simulated on high performance computers using commercial CFD software. This research focused on 19-pin fuel assembly 'benchmark' geometry, similar in design to the Advanced Burner Test Reactor, where each pin is separated by helical wire-wrap spacers. Several two-equation turbulence models including the k-{epsilon} and SST (Menter) k-{omega} were evaluated. Considerable effort was taken to resolve the momentum boundary layer, so as to eliminate the need for wall functions and reduce computational uncertainty. High performance computers were required to generate the hybrid meshes needed to predict secondary flows created by the wire-wrap spacers; computational meshes ranging from 65 to 85 million elements were common. A general validation methodology was followed, including mesh refinement and comparison of numerical results with empirical correlations. Predictions for velocity, temperature, and pressure distribution are shown. The uncertainty of numerical models, importance of high fidelity experimental data, and the challenges associated with simulating and validating large production-type problems are presented.
Design and Analysis of Missile Systems through CFD Simulations
Chakraborty, Debasis
2010-10-01
Development of indigenous CFD codes and their applications for complex aerodynamic and propulsive flow problems pertaining to DRDO missiles are presented. Grid generators, 3D Euler and Navier Stokes solvers are developed in-house using state of art numerical techniques and physical models. These softwares are used extensively for aerodynamic characterization of missiles over a wide range of Mach number, angle of attack, control surface deflection and store separation studies. Significant contributions are made in the design of high speed propulsion systems of various ongoing and future missiles through CFD analysis internal flow field. Important design modifications were suggested and the propulsion system performances were optimized. Capabilities have been developed for many advanced topics including computational aeroelasticity, coupled Euler Boltzmann solver, etc.
Lime Kiln Modeling. CFD and One-dimensional simulations
Energy Technology Data Exchange (ETDEWEB)
Svedin, Kristoffer; Ivarsson, Christofer; Lundborg, Rickard
2009-03-15
The incentives for burning alternative fuels in lime kilns are growing. An increasing demand on thorough investigations of alternative fuel impact on lime kiln performance have been recognized, and the purpose of this project has been to develop a lime kiln CFD model with the possibility to fire fuel oil and lignin. The second part of the project consists of three technical studies. Simulated data from a one-dimensional steady state program has been used to support theories on the impact of biofuels and lime mud dryness. The CFD simulations was carried out in the commercial code FLUENT. Due to difficulties with the convergence of the model the calcination reaction is not included. The model shows essential differences between the two fuels. Lignin gives a different flame shape and a longer flame length compared to fuel oil. Mainly this depends on how the fuel is fed into the combustion chamber and how much combustion air that is added as primary and secondary air. In the case of lignin combustion the required amount of air is more than in the fuel oil case. This generates more combustion gas and a different flow pattern is created. Based on the values from turbulent reaction rate for the different fuels an estimated flame length can be obtained. For fuel oil the combustion is very intense with a sharp peak in the beginning and a rapid decrease. For lignin the combustion starts not as intense as for the fuel oil case and has a smoother shape. The flame length appears to be approximately 2-3 meter longer for lignin than for fuel oil based on turbulent reaction rate in the computational simulations. The first technical study showed that there are many benefits of increasing dry solids content in the lime mud going into a kiln such as increased energy efficiency, reduced TRS, and reduced sodium in the kiln. However, data from operating kilns indicates that these benefits can be offset by increasing exit gas temperature that can limit kiln production capacity. Simulated
Engineering-Based Thermal CFD Simulations on Massive Parallel Systems
Frisch, Jérôme
2015-05-22
The development of parallel Computational Fluid Dynamics (CFD) codes is a challenging task that entails efficient parallelization concepts and strategies in order to achieve good scalability values when running those codes on modern supercomputers with several thousands to millions of cores. In this paper, we present a hierarchical data structure for massive parallel computations that supports the coupling of a Navier–Stokes-based fluid flow code with the Boussinesq approximation in order to address complex thermal scenarios for energy-related assessments. The newly designed data structure is specifically designed with the idea of interactive data exploration and visualization during runtime of the simulation code; a major shortcoming of traditional high-performance computing (HPC) simulation codes. We further show and discuss speed-up values obtained on one of Germany’s top-ranked supercomputers with up to 140,000 processes and present simulation results for different engineering-based thermal problems.
Engineering-Based Thermal CFD Simulations on Massive Parallel Systems
Directory of Open Access Journals (Sweden)
Jérôme Frisch
2015-05-01
Full Text Available The development of parallel Computational Fluid Dynamics (CFD codes is a challenging task that entails efficient parallelization concepts and strategies in order to achieve good scalability values when running those codes on modern supercomputers with several thousands to millions of cores. In this paper, we present a hierarchical data structure for massive parallel computations that supports the coupling of a Navier–Stokes-based fluid flow code with the Boussinesq approximation in order to address complex thermal scenarios for energy-related assessments. The newly designed data structure is specifically designed with the idea of interactive data exploration and visualization during runtime of the simulation code; a major shortcoming of traditional high-performance computing (HPC simulation codes. We further show and discuss speed-up values obtained on one of Germany’s top-ranked supercomputers with up to 140,000 processes and present simulation results for different engineering-based thermal problems.
CFD Simulation Of Air-Flow Over A „Quarter-Circular” Object Valided By Experimental Measurement
Králik Juraj; Hubová Oľga; Konečná Lenka
2015-01-01
A Computer-Fluid-Dynamic (CFD) simulation of air-flow around quarter-circular object using commercial software ANSYS Fluent was used to study iteration of building to air-flow. Several, well know transient turbulence models were used and results were compared to experimental measurement of this object in Boundary Layer Wind Tunnel (BLWT) of Slovak University of Technology (SUT) in Bratislava. Main focus of this article is to compare pressure values from CFD in three different elevations, whic...
Proposition of an outflow boundary approach for carotid artery stenosis CFD simulation.
Zhang, Yu; Furusawa, Toyoki; Sia, Sheau Fung; Umezu, Mitsuo; Qian, Yi
2013-01-01
The purpose of this study was to propose an innovative approach of setting outlet boundary conditions for the computational fluid dynamics (CFD) simulation of human common carotid arteries (CCAs) bifurcation based on the concept of energy loss minimisation at flow bifurcation. Comparisons between this new approach and previously reported boundary conditions were also made. The results showed that CFD simulation based on the proposed boundary conditions gave an accurate prediction of the critical stenosis ratio of carotid arteries (at around 65%). Other boundary conditions, such as the constant external pressure (P = 0) and constant outflow ratio, either overestimated or underestimated the critical stenosis ratio of carotid arteries. The patient-specific simulation results furthermore indicated that the calculated internal carotid artery flow ratio at CCA bifurcation (61%) coincided with the result obtained by clinical measurements through the use of Colour Doppler ultrasound. PMID:22288780
CFD Simulation of Spent Fuel in a Dry Storage System
International Nuclear Information System (INIS)
The spent fuel pool is expected to be full in few years. It is a serious problem one should not ignore. The dry storage type is considered as the interim storage system in Korea. The system stores spent fuel in a storage canister filled with an inert gas and the canister is cooled by a natural convection system using air or helium, radiation, and conduction. The spent fuel is heated by decay heat. The spent fuel is allowed to cool under a limiting temperature to avoid a fuel failure. Recently, the thermal hydraulic characteristics for a single bundle of the spent fuel were investigated through a CFD simulation. It would be of great interest to investigate the maximum fuel temperature in a dry storage system. The present paper deals with the thermal hydraulic characteristics of spent fuel for a dry storage system using the CFD method. A 3-D thermal flow simulation was carried out to predict the temperature of spent fuel. A dry storage system composed of 32 fuel bundles was modeled. The inlet temperature of the outer bundle is higher and that of inner bundle, however, is higher at the outlet. In a single fuel assembly, a center temperature of the fuel assembly was higher than elsewhere
CFD Simulation of Spent Fuel in a Dry Storage System
Energy Technology Data Exchange (ETDEWEB)
Kwack, Young Kyun; In, Wang Kee; Shin, Chang Hwan; Chun, Tae Hyun; Kook, Dong Hak [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-10-15
The spent fuel pool is expected to be full in few years. It is a serious problem one should not ignore. The dry storage type is considered as the interim storage system in Korea. The system stores spent fuel in a storage canister filled with an inert gas and the canister is cooled by a natural convection system using air or helium, radiation, and conduction. The spent fuel is heated by decay heat. The spent fuel is allowed to cool under a limiting temperature to avoid a fuel failure. Recently, the thermal hydraulic characteristics for a single bundle of the spent fuel were investigated through a CFD simulation. It would be of great interest to investigate the maximum fuel temperature in a dry storage system. The present paper deals with the thermal hydraulic characteristics of spent fuel for a dry storage system using the CFD method. A 3-D thermal flow simulation was carried out to predict the temperature of spent fuel. A dry storage system composed of 32 fuel bundles was modeled. The inlet temperature of the outer bundle is higher and that of inner bundle, however, is higher at the outlet. In a single fuel assembly, a center temperature of the fuel assembly was higher than elsewhere.
CFD simulation on membrane distillation of NaCl solution
Institute of Scientific and Technical Information of China (English)
Zhaoguang XU; Yanqiu PAN; Yalan YU
2009-01-01
A computational fluid dynamics (CFD) simu-lation 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.
Simulation and analysis of void drift using sub-channel analysis code and CFD code
Energy Technology Data Exchange (ETDEWEB)
Pang, Bo; Cheng, Xu; Otic, Ivan [Karlsruhe Institute of Technology (KIT) (Germany). Inst. of Fusion and Reactor Technology (IFRT)
2012-11-01
Prediction accuracy of a sub-channel analysis depends strongly on the modeling of the interchannel transverse exchange effect. Disregarding the forced mixing effects caused by extra constructive elements the natural inter-channel transverse exchange effect can be decomposed into [1] [2] [3]: turbulent mixing (TM) due to the natural eddy diffusion, diversion cross flow (DC) induced by radial pressure gradient and void drift (VD) specially under two-phase flow conditions. Among the three components, the physical mechanism of void drift is not well clarified. Previous to the time and cost demanding experimental research a systematic numerical simulation of the inter-channel exchange effect with CFD code can provide supplemental information about the physical mechanism behind the not well clarified void drift phenomena. Compared to sub-channel analysis code, CFD code solves the flow dynamic problem with a much finer mesh and in a more physical way. The inter-channel exchange terms are solved in the conservation equations rather than modeled with closure equations. Furthermore, the inter-phase exchange terms are also taken into account. A better understanding of the void drift phenomenon and a modification of the void drift models in a sub-channel analysis code basing on the CFD analysis can be achieved. In present study, both sub-channel and CFD analysis are carried out for studying the void drift in a rod bundle geometry. A model is proposed to determine the sub-channel scale void drift mass flux based on the CFD simulation results. (orig.)
CFD simulations of a hydrocyclone in absence of an air core
Directory of Open Access Journals (Sweden)
Delgadillo J.A.
2012-01-01
Full Text Available Computational Fluid Dynamics (CFD is a versatile means to predict the characteristics of flow in fluid mechanics problems under a wide range of design and operating conditions . Applying the CFD in many engineering fields alleviates the problem of the usual engineering design. Recent advance in computational methods and computer technology make CFD an efficient means to study the dynamics of many physical systems. CFD simulations use three dimensional grid and the Reynolds Stress Model (RSM to investigate the flow without air core in a 6˝ hydrocyclone have been conducted using FLUENT. The numerical results are compared with the experimental data related to the Laser Doppler Anemometry (LDA measurements of velocity. In the experimental study, a new procedure is developed to reorient the laser beams that permit one to measure two velocity components at a single point using LDA. The conclusion developed from these experiments enables one to use the LDA directly in the hydrocyclone wall without recourse to auxiliary attachments such as an enclosing box that usually used to minimize the refraction effects of laser beams which are caused by the curved solid wall of the hydrocyclone and the refractive index of the test medium.
Simulation of dilute pneumatic conveying with different types of bends by CFD-DEM
International Nuclear Information System (INIS)
Bends are one of the most commonly used facilities to change flow direction in pneumatic conveying. It is important to understand the effect of the bend to the gas-solid flow structures in a pneumatic conveying system. CFD-DEM is one of powerful methods to study the fundamentals of gas-solid flow, as it takes the particle-particle and particle-wall collisions into account. But the time consumption is one of major limitations for its application. In this paper, a three-dimensional CFD-DEM model which ignores the effect of void fraction to the gas phase is used to simulate the dilute gas-solid flow. Gas-solid flows in different types of bends including horizontal-vertical, vertical-horizontal and horizontal-horizontal 90° bends are studied. The present CFD-DEM model is verified by compared the rope structure with the result for traditional CFD-DEM model in horizontal-vertical case. Compared the particle rope dispersion in different types of bends, the rope disperses more quickly in the vertical-horizontal case than others, and the solid flow structure is the most complicated in the horizontal- horizontal case. As their various solid flow structures, the collision data of three cases also seem different
CFD model simulation of LPG dispersion in urban areas
Pontiggia, Marco; Landucci, Gabriele; Busini, Valentina; Derudi, Marco; Alba, Mario; Scaioni, Marco; Bonvicini, Sarah; Cozzani, Valerio; Rota, Renato
2011-08-01
There is an increasing concern related to the releases of industrial hazardous materials (either toxic or flammable) due to terrorist attacks or accidental events in congested industrial or urban areas. In particular, a reliable estimation of the hazardous cloud footprint as a function of time is required to assist emergency response decision and planning as a primary element of any Decision Support System. Among the various hazardous materials, the hazard due to the road and rail transportation of liquefied petroleum gas (LPG) is well known since large quantities of LPG are commercialized and the rail or road transportation patterns are often close to downtown areas. Since it is well known that the widely-used dispersion models do not account for the effects of any obstacle like buildings, tanks, railcars, or trees, in this paper a CFD model has been applied to simulate the reported consequences of a recent major accident involving an LPG railcar rupture in a congested urban area (Viareggio town, in Italy), showing both the large influence of the obstacles on LPG dispersion as well as the potentials of CFD models to foresee such an influence.
CFD simulation of blood flow inside the corkscrew collaterals of the Buerger’s disease
Sharifi, Alireza; Charjouei Moghadam, Mohammad
2016-01-01
Introduction: Buerger’s disease is an occlusive arterial disease that occurs mainly in medium and small vessels. This disease is associated with Tobacco usage. The existence of corkscrew collateral is one of the established characteristics of the Buerger’s disease. Methods: In this study, the computational fluid dynamics (CFD) simulation of blood flow within the corkscrew artery of the Buerger’s disease is conducted. The geometry of the artery is constructed based on the actual corkscrew arte...
Two-Phase Flow Simulations for PTS Investigation by Means of Neptune_CFD Code
Fabio Moretti; Maria Cristina Galassi; Pierre Coste; Christophe Morel
2009-01-01
Two-dimensional axisymmetric simulations of pressurized thermal shock (PTS) phenomena through Neptune_CFD module are presented aiming at two-phase models validation against experimental data. Because of PTS complexity, only some thermal-hydraulic aspects were considered. Two different flow configurations were studied, occurring when emergency core cooling (ECC) water is injected in an uncovered cold leg of a pressurized water reactor (PWR)Ã¢Â€Â”a plunging water jet entering a free surface, an...
CFD numerical simulation of air natural convection over a heated cylindrical surface
Flori, M.; Vîlceanu, L.
2015-06-01
In this study a CFD numerical simulation is used to describe the fluid flow and heat transfer in air surrounding a heated horizontal cylinder. The model is created in 2D space dimension involving a finite element solver of Navier-Stokes equations. As natural convection phenomenon is induced by a variable fluid density field with temperature rising, the Boussinesq approximation was coupled to the model.
CFD simulation of flow patterns in unbaffled stirred tank with CD-6 impeller
Devi Tamphasana Thiyam; Kumar Bimlesh
2012-01-01
Understanding the flow in stirred vessels can be useful for a wide number of industrial applications. There is a wealth of numerical simulations of stirring vessels with standard impeller such as Rushton turbine and pitch blade turbine. Here, a CFD study has been performed to observe the spatial variations (angular, axial and radial) of hydrodynamics (velocity and turbulence field) in unbaffled stirred tank with Concave-bladed Disc turbine (CD-6) impeller. Three speeds (N=296, 638 &...
CFD Studies on Biomass Thermochemical Conversion
Directory of Open Access Journals (Sweden)
Lifeng Yan
2008-06-01
Full Text Available Thermochemical conversion of biomass offers an efficient and economically process to provide gaseous, liquid and solid fuels and prepare chemicals derived from biomass. Computational fluid dynamic (CFD modeling applications on biomass thermochemical processes help to optimize the design and operation of thermochemical reactors. Recent progression in numerical techniques and computing efficacy has advanced CFD as a widely used approach to provide efficient design solutions in industry. This paper introduces the fundamentals involved in developing a CFD solution. Mathematical equations governing the fluid flow, heat and mass transfer and chemical reactions in thermochemical systems are described and sub-models for individual processes are presented. It provides a review of various applications of CFD in the biomass thermochemical process field.
CFD simulation and analysis of emulsion droplet formation from straight-through microchannels.
Kobayashi, Isao; Mukataka, Sukekuni; Nakajima, Mitsutoshi
2004-10-26
We recently proposed a technique for preparing monodisperse emulsions with a coefficient of variation below 5% from a silicon array of micrometer-sized channels perpendicular to the plate surface, named a straight-through microchannel (MC). This study involved three-dimensional computational fluid dynamics (CFD) simulations to calculate the formation of an oil-in-water (O/W) emulsion droplet from straight-through MCs with circular and elliptic cross sections. The CFD results demonstrated that the oil phase that passed through the elliptic MCs exceeding a threshold aspect ratio between 3 and 3.5 was cut off spontaneously into a small droplet with a diameter of approximately 40 microm. Sufficient space for water at the channel exit had to be maintained for successful droplet formation. The formation and shrinkage of a neck inside the channel caused an increased pressure difference inside the channel and an increased velocity value near the neck. The pressure and velocity values at the neck drastically changed, and the neck was cut off instantaneously just before the completion of droplet formation. This process was triggered by a gradually increased pressure difference between the circular neck and inflating oil phase. The findings obtained in this paper provide useful numerical and visual information about the droplet formation phenomena from the straight-through MCs. The CFD results were verified by the experimental results, showing that the CFD approach can help design a suitable channel structure. PMID:15491227
CFD Simulation of Polydispersed Bubbly Two-Phase Flow around an Obstacle
Directory of Open Access Journals (Sweden)
E. Krepper
2009-01-01
Full Text Available This paper concerns the model of a polydispersed bubble population in the frame of an ensemble averaged two-phase flow formulation. The ability of the moment density approach to represent bubble population size distribution within a multi-dimensional CFD code based on the two-fluid model is studied. Two different methods describing the polydispersion are presented: (i a moment density method, developed at IRSN, to model the bubble size distribution function and (ii a population balance method considering several different velocity fields of the gaseous phase. The first method is implemented in the Neptune_CFD code, whereas the second method is implemented in the CFD code ANSYS/CFX. Both methods consider coalescence and breakup phenomena and momentum interphase transfers related to drag and lift forces. Air-water bubbly flows in a vertical pipe with obstacle of the TOPFLOW experiments series performed at FZD are then used as simulations test cases. The numerical results, obtained with Neptune_CFD and with ANSYS/CFX, allow attesting the validity of the approaches. Perspectives concerning the improvement of the models, their validation, as well as the extension of their applicability range are discussed.
Study of Swirl and Tumble Motion using CFD
Directory of Open Access Journals (Sweden)
Abhilash M Bharadwaj
2013-06-01
Full Text Available The call for environmentally compatible and economical vehicles, still satisfying demands for high performance, necessitates immense efforts to develop innovative engine concepts. In an Internal Combustion Engine the performance, efficiency and emission formation depends on the formation of air-fuel mixture inside the engine cylinder. The fluid flow dynamics plays an important role for air-fuel mixture preparation to obtain the better engine combustion, performance and efficiency. Due to the extreme conditions inside a typical IC-engine (high combustion temperatures and pressures, precipitation of soot and other combustion products, etc. experimental techniques are sometimes limited in approaching the above mentioned problem. Alternatively, computer simulations (Computational Fluid Dynamics, CFD offer the opportunity to carry out repetitive parameter studies with clearly defined boundary conditions in order to investigate various configurations. We investigate two important, common fluid flow patterns from computational fluid dynamics (CFD simulations, namely, swirl and tumble motion typical of automotive engines. These two parameters represents the fluid flow behaviors occurred inside combustion chamber which influences the air streams to the cylinder during intake stroke and enhances greatly the mixing of air and fuel to give better mixing during compression stoke. In this study we are concerned on the swirl motion of inducted air during the suction stroke and during compression stroke. The results obtain from the numerical analysis can be employed to examine the homogeneity of air-fuel mixture structure for better combustion process and engine performance.
Study of Swirl and Tumble Motion using CFD
Directory of Open Access Journals (Sweden)
Aravind T
2012-08-01
Full Text Available The call for environmentally compatible and economical vehicles, still satisfying demands for high performance, necessitates immense efforts to develop innovative engine concepts. In an Internal Combustion Engine the performance, efficiency and emission formation depends on the formation of air-fuel mixture inside the engine cylinder. The fluid flow dynamics plays an important role for air-fuel mixture preparation to obtain the better engine combustion, performance and efficiency. Due to the extreme conditions inside a typical IC-engine (high combustion temperatures and pressures, precipitation of soot and other combustion products, etc. experimental techniques are sometimes limited in approaching the above mentioned problem. Alternatively, computer simulations (Computational Fluid Dynamics, CFD offer the opportunity to carry out repetitive parameter studies with clearly defined boundary conditions in order to investigate various configurations. We investigate two important, common fluid flow patterns from computational fluid dynamics (CFD simulations, namely, swirl and tumble motion typical of automotive engines. These two parameters represents the fluid flow behaviors occurred inside combustion chamber which influences the air streams to the cylinder during intake stroke and enhances greatly the mixing of air and fuel to give better mixing during compression stoke. In this study we are concerned on the swirl motion of inducted air during the suction stroke and during compression stroke. The results obtain from the numerical analysis can be employed to examine the homogeneity of air-fuel mixture structure for better combustion process and engine performance.
Comparative Study of Commercial CFD Software Performance for Prediction of Reactor Internal Flow
International Nuclear Information System (INIS)
Even if some CFD software developers and its users think that a state-of-the-art CFD software can be used to reasonably solve at least single-phase nuclear reactor safety problems, there remain limitations and uncertainties in the calculation result. From a regulatory perspective, the Korea Institute of Nuclear Safety (KINS) is presently conducting the performance assessment of commercial CFD software for nuclear reactor safety problems. In this study, to examine the prediction performance of commercial CFD software with the porous model in the analysis of the scale-down APR (Advanced Power Reactor Plus) internal flow, a simulation was conducted with the on-board numerical models in ANSYS CFX R.14 and FLUENT R.14. It was concluded that depending on the CFD software, the internal flow distribution of the scale-down APR was locally somewhat different. Although there was a limitation in estimating the prediction performance of the commercial CFD software owing to the limited amount of measured data, CFX R.14 showed more reasonable prediction results in comparison with FLUENT R.14. Meanwhile, owing to the difference in discretization methodology, FLUENT R.14 required more computational memory than CFX R.14 for the same grid system. Therefore, the CFD software suitable to the available computational resource should be selected for massively parallel computations
Validation process of the ISIS CFD software for fire simulation
International Nuclear Information System (INIS)
Fire codes are more and more used for safety analysis of nuclear power plants. In several OECD member countries, the accuracy of the calculated simulation with CFD code has to be demonstrated; this is the aim of the Verification and Validation process (V and V). In this context the French 'Institut de Radioprotection et de Surete Nucleaire' (IRSN) develops a computational software, named ISIS, dedicated to the simulation of buoyant fire in compartment mechanically ventilated. ISIS is based on the scientific computing development platform PELICANS and benefits of the practicalities for implementing methods. The code ISIS is a freeware, available at https://gforge.irsn.fr/gf/project/isis. The physical modelling used in ISIS is classic for industrial application in large compartments. The turbulence approach is based on the Reynolds-Averaged-Navier-Stokes equations, supplemented by a two-equation closure and the eddy viscosity model. The turbulent production term is adapted to cope with buoyancy effects. Combustion modelling relies on a single reaction equation. The classical eddy dissipation approach is used for the mean chemical reaction rate which means that it is controlled solely by the turbulent mixture. The Finite Volume method is employed to treat radiation exchanges. Both incompressible and low Mach number flows are dealt with. The originality of the ISIS code is its capacity to take into account the effect of ventilation on the pressure. The thermodynamic pressure and the mass flow rate for ventilation vents are related by the mass balances in the compartment and in the ventilation branch where an aeraulic resistance is taken into account. For numerical solution, a fractional step algorithm has been developed. The spatial discretization combines mixed finite element for the Navier-Stokes equation and finite volumes scheme for transport (advection-diffusion-reaction) equation in order to ensure the velocity stability and the conservation in physical range of
CFD Parametric Study of Consortium Impeller
Cheng, Gary C.; Chen, Y. S.; Garcia, Roberto; Williams, Robert W.
1993-01-01
Current design of high performance turbopumps for rocket engines requires effective and robust analytical tools to provide design impact in a productive manner. The main goal of this study is to develop a robust and effective computational fluid dynamics (CFD) pump model for general turbopump design and analysis applications. A Finite Difference Navier-Stokes flow solver, FDNS, which includes the extended k-epsilon turbulence model and appropriate moving interface boundary conditions, was developed to analyze turbulent flows in turbomachinery devices. A second-order central difference scheme plus adaptive dissipation terms was employed in the FDNS code, along with a predictor plus multi-corrector pressure-based solution procedure. The multi-zone, multi-block capability allows the FDNS code to efficiently solve flow fields with complicated geometry. The FDNS code has been benchmarked by analyzing the pump consortium inducer, and it provided satisfactory results. In the present study, a CFD parametric study of the pump consortium impeller was conducted using the FDNS code. The pump consortium impeller, with partial blades, is a new design concept of the advanced rocket engines. The parametric study was to analyze the baseline design of the consortium impeller and its modification which utilizes TANDEM blades. In the present study, the TANDEM blade configuration of the consortium impeller considers cut full blades for about one quarter chord length from the leading edge and clocks the leading edge portion with an angle of 7.5 or 22.5 degrees. The purpose of the present study is to investigate the effect and trend of the TANDEM blade modification and provide the result as a design guideline. A 3-D flow analysis, with a 103 x 23 x 30 mesh grid system and with the inlet flow conditions measured by Rocketdyne, was performed for the baseline consortium impeller. The numerical result shows that the mass flow rate splits through various blade passages are relatively uniform
DEFF Research Database (Denmark)
Tajsoleiman, Tannaz; J. Abdekhodaie, Mohammad; Gernaey, Krist;
2016-01-01
the main bottlenecks in this type of processes. In this regard, mathematical modelling and computational fluid dynamics simulation (CFD) are powerful tools to identify an efficient and optimized design by providing reliable insights of the process. This study presents a mathematical model and CFD...... simulation of cartilage cell culture under a perfusion flow, which allows not only to characterize the supply of nutrients and metabolic products inside a fibrous scaffold, but also to assess the overall culture condition and predict the cell growth rate. Afterwards, the simulation results supported finding...
Validation process of ISIS CFD software for fire simulation
Energy Technology Data Exchange (ETDEWEB)
Lapuerta, C., E-mail: celine.lapuerta@irsn.fr [Institut de Radioprotection et de Surete Nucleaire (IRSN), BP3, 13115 Saint Paul-lez-Durance (France); ETIC Laboratory, IRSN-CNRS-UAM (I,II), 5 rue Enrico Fermi, 13453 Marseille Cedex 13 (France); Suard, S., E-mail: sylvain.suard@irsn.fr [Institut de Radioprotection et de Surete Nucleaire (IRSN), BP3, 13115 Saint Paul-lez-Durance (France); ETIC Laboratory, IRSN-CNRS-UAM (I,II), 5 rue Enrico Fermi, 13453 Marseille Cedex 13 (France); Babik, F., E-mail: fabrice.babik@irsn.fr [Institut de Radioprotection et de Surete Nucleaire (IRSN), BP3, 13115 Saint Paul-lez-Durance (France); Rigollet, L., E-mail: laurence.rigollet@irsn.fr [Institut de Radioprotection et de Surete Nucleaire (IRSN), BP3, 13115 Saint Paul-lez-Durance (France); ETIC Laboratory, IRSN-CNRS-UAM (I,II), 5 rue Enrico Fermi, 13453 Marseille Cedex 13 (France)
2012-12-15
Fire propagation constitutes a major safety concern in nuclear facilities. In this context, IRSN is developing a CFD code, named ISIS, dedicated to fire simulations. This software is based on a coherent set of models that can be used to describe a fire in large, mechanically ventilated compartments. The system of balance equations obtained by combining these models is discretized in time using fractional step methods, including a pressure correction technique for solving hydrodynamic equations. Discretization in space combines two techniques, each proven in the relevant context: mixed finite elements for hydrodynamic equations and finite volumes for transport equations. ISIS is currently in an advanced stage of verification and validation. The results obtained for a full-scale fire test performed at IRSN are presented.
Evaluation for External Reactor Vessel Cooling System using CFD Simulation
Energy Technology Data Exchange (ETDEWEB)
Seo, Seok Bin; Park, Seong Dae; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)
2012-05-15
To ensure the safety of the nuclear plants, there are lots of safety systems in the nuclear plant. One of them is External Reactor Vessel Cooling system (ERVC) which is operated when a molten corium is relocated in a lower head of a reactor vessel. As ERVC system runs, coolant flows down into a reactor cavity to remove a decay heat from the molten corium. This work simulated the ERVC system which is applied to APR1400 with CFD. To estimate the efficiency of the ERVC system, we designed the reactor cavity of the ERVC system of APR1400 in a full scale. From the designed model, we measured temperature distribution of the reactor vessel outer wall. Two kinds of coolant were used in this computational approach. One is present flooding matter which is water. The other is liquid metal gallium. With varying the area of the inlet and outlet of reactor cavity, we evaluated the importance of each variable
CFD simulation of mixing in egg-shaped anaerobic digesters.
Wu, Binxin
2010-03-01
A computational fluid dynamics (CFD) model that characterizes mechanical draft tube mixing in egg-shaped anaerobic digesters was developed. Simulation of flow patterns were carried out with a propeller rotating from 400 to 750rpm, assuming liquid manure to be Newtonian (water) and non-Newtonian fluids depending on the total solids (TS) concentration. Power number and flow number of the propeller in water mixing were validated against lab specifications and experimental data from a field test. The rotational direction and placement of the propeller were examined to identify the primary pumping mode and the optimum position of the propeller fixed inside the tube. Quantitative comparisons of two mixing methods and two digester shapes indicated that mechanical draft tube mixing is more efficient than external pumped recirculation, and that the egg shape provides for more efficient mixing than the cylindrical shape. Furthermore, scale-up rules for mixing in egg-shaped digesters were investigated. PMID:19913870
CFD Simulation of the Discharge Flow from Standard Rushton Impeller
Directory of Open Access Journals (Sweden)
Bohuš Kysela
2014-01-01
Full Text Available The radial discharge jet from the standard Rushton turbine was investigated by the CFD calculations and compared with results from the Laser Doppler Anemometry (LDA measurements. The Large Eddy Simulation (LES approach was employed with Sliding Mesh (SM model of the impeller motion. The obtained velocity profiles of the mean ensemble-averaged velocity and r.m.s. values of the fluctuating velocity were compared in several distances from the impeller blades. The calculated values of mean ensemble-averaged velocities are rather in good agreement with the measured ones as well as the derived power number from calculations. However, the values of fluctuating velocities are obviously lower from LES calculations than from LDA measurements.
Scaling studies and conceptual experiment designs for NGNP CFD assessment
Energy Technology Data Exchange (ETDEWEB)
D. M. McEligot; G. E. McCreery
2004-11-01
The objective of this report is to document scaling studies and conceptual designs for flow and heat transfer experiments intended to assess CFD codes and their turbulence models proposed for application to prismatic NGNP concepts. The general approach of the project is to develop new benchmark experiments for assessment in parallel with CFD and coupled CFD/systems code calculations for the same geometry. Two aspects of the complex flow in an NGNP are being addressed: (1) flow and thermal mixing in the lower plenum ("hot streaking" issue) and (2) turbulence and resulting temperature distributions in reactor cooling channels ("hot channel" issue). Current prismatic NGNP concepts are being examined to identify their proposed flow conditions and geometries over the range from normal operation to decay heat removal in a pressurized cooldown. Approximate analyses have been applied to determine key non-dimensional parameters and their magnitudes over this operating range. For normal operation, the flow in the coolant channels can be considered to be dominant turbulent forced convection with slight transverse property variation. In a pressurized cooldown (LOFA) simulation, the flow quickly becomes laminar with some possible buoyancy influences. The flow in the lower plenum can locally be considered to be a situation of multiple hot jets into a confined crossflow -- with obstructions. Flow is expected to be turbulent with momentumdominated turbulent jets entering; buoyancy influences are estimated to be negligible in normal full power operation. Experiments are needed for the combined features of the lower plenum flows. Missing from the typical jet experiments available are interactions with nearby circular posts and with vertical posts in the vicinity of vertical walls - with near stagnant surroundings at one extreme and significant crossflow at the other. Two types of heat transfer experiments are being considered. One addresses the "hot channel" problem, if necessary
Coupled CFD - system-code simulation of a gas cooled reactor
Energy Technology Data Exchange (ETDEWEB)
Yan, Yizhou; Rizwan-uddin, E-mail: yizhou.yan@shawgrp.com, E-mail: rizwan@illinois.edu [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL(United States)
2011-07-01
A generic coupled CFD - system-code thermal hydraulic simulation approach was developed based on FLUENT and RELAP-3D, and applied to LWRs. The flexibility of the coupling methodology enables its application to advanced nuclear energy systems. Gas Turbine - Modular Helium Reactor (GT-MHR) is a Gen IV reactor design which can benefit from this innovative coupled simulation approach. Mixing in the lower plenum of the GT-MHR is investigated here using the CFD - system-code coupled simulation tool. Results of coupled simulations are presented and discussed. The potential of the coupled CFD - system-code approach for next generation of nuclear power plants is demonstrated. (author)
Study on combustible gas leakageage and diffusion by CFD simulation%可燃气泄漏扩散的CFD研究
Institute of Scientific and Technical Information of China (English)
刘欣
2012-01-01
is instructive to accident prevention and control, platform emergency and evacuation mechanism, etc. In this paper, on the basis of prophase investigation and in-depth analysis, according to the actual operation status of equipment, the main leakageage points on the platform were selected. Using computational fluid dynamics simulation, building the reasonable physical model, selecting the appropriate diffusion equation and the boundary condition, CFD simulate of gas leakageage on the platforms was carried out. It is shown from the calculated results that the contact tower and the testing separator of the platform are most inclined to leakageage gas, so it is recommended to enhance the daily maintenance of the pipelines, valves and flanges in the above units to prevent and control accidents. The contact tower, production separator and gas pigging launcher of the center platform, gas well Christmas tree, testing manifold and testing separator of the wellhead platform have higher operation pressure with more serious consequences and larger range of influence after the leakageage and diffusion, so it is recommended to do inspection on the above key equipments based on risk analysis. The firewall, control room and other rooms will, to a certain extent, affect the ventilation in the deck space, and there will be a larger range of influence after the gas leakageage when the wind is on the windward side of the above barriers. At this point, it is recommended to strictly control the ignition sources over the whole region of influence. The danger zone and fire zone of the platforms can be effectively divided with the help of the calculated CFD results, which provide reference for the refinement of the emergency program, the post-accident emergency command and the selection of correct escape routes.
CFD simulation of contaminant decay for high reynolds flow in a controlled environment.
Lambert, Andrew R; Lin, Ching-Long; Mardorf, Eunice; O'Shaughnessy, Patrick
2010-01-01
This study examines the usage of computational fluid dynamics (CFDs) for estimating the time-elapsed decay of contaminants within a chamber experiencing high Reynolds flow. CFD results were compared with measurements taken at a controlled facility. In addition, parameters of the CFD simulation were examined; namely the effects of turbulence and inertial transport at high Reynolds number ventilating flows, as well as inlet duct configuration and its effect on the inlet velocity profile. The agreement between the computational and experimental clearance times was quite good, with percent errors as low as -5.32% at high flow rate and -11.8% at the lower flow rate. This study determined that for high Reynolds flow, diffusive transport effects may be ignored as the majority of mass is transported via the bulk stream, i.e. momentum transport. In addition, resolving the inlet velocity profile was of prime importance for accurate simulation of ventilating flows and prediction of contaminant washout. This was done by including the inlet duct geometry in the computational domain. In addition, it was found that despite different flow rates, the predicted contaminant washout took approximately 12-13% longer than predicted assuming instantaneous mixing. Furthermore, percent error between computational and experimental data as low as -5.32% shows that CFD is a useful tool for studying ventilation phenomena. PMID:19671796
Challenges in assessing the grid sensitivity of hydro-turbine CFD simulations
International Nuclear Information System (INIS)
Despite the great progress made over the last 20 years, making reliable predictions with CFD is still a challenge. In fact the hydraulic machinery community rarely relies entirely on numerical simulations to provide final designs. The core of the problem lies with the estimation of the solution accuracy. Grid convergence studies are a useful way to check for grid independence and can provide some insight into the actual solution accuracy. However, conducting such studies for complex, detached flows involves many challenges among which: creating progressively refined grids and comparing with measurement results. This paper investigates this problem through the practical example of the BulbT experimental setup for which multiple CFD runs were conducted
Leuva, Dhawal
2011-07-01
Motion of propellant in the liquid propellant tanks due to inertial forces transferred from actions like stage separation and trajectory correction of the launch vehicle is known as propellant slosh. If unchecked, propellant slosh can reach resonance and lead to complete loss of the spacecraft stability, it can change the trajectory of the vehicle or increase consumption of propellant from the calculated requirements, thereby causing starvation of the latter stages of the vehicle. Predicting the magnitude of such slosh events is not trivial. Several passive mechanisms with limited operating range are currently used to mitigate the effects of slosh. An active damping mechanism concept developed here can operate over a large range of slosh frequencies and is much more effective than passive damping devices. Spherical and cylindrical tanks modeled using the ANSYS CFX software package considers the free surface of liquid propellant exposed to atmospheric pressure. Hydrazine is a common liquid propellant and since it is toxic, it cannot be used in experiment. But properties of hydrazine are similar to the properties of water; therefore water is substituted as propellant for experimental study. For close comparison of the data, water is substituted as propellant in CFD simulation. The research is done in three phases. The first phase includes modeling free surface slosh using CFD and validation of the model by comparison to previous experimental results. The second phase includes developing an active damping mechanism and simulating the behavior using a CFD model. The third phase includes experimental development of damping mechanism and comparing the CFD simulation to the experimental results. This research provides an excellent tool for low cost analysis of damping mechanisms for propellant slosh as well as proves that the concept of an active damping mechanism developed here, functions as expected.
CFD simulation of a chemical-looping fuel reactor utilizing solid fuel
Energy Technology Data Exchange (ETDEWEB)
Mahalatkar, K.; Kuhlman, J.; Huckaby, E.D.; O' Brien, T. [West Virginia University, Morgantown, WV (United States)
2011-08-15
A computational fluid dynamic (CFD) study has been carried out for the fuel reactor for a new type of combustion technology called chemical-looping combustion (CLC). CLC involves combustion of fuels by heterogeneous chemical reactions with an oxygen carrier, usually a granular metal oxide, exchanged between two reactors. There have been extensive experimental studies on CLC, however CFD simulations of this concept are quite limited. In the present paper we have developed a CFD model for the fuel reactor of a chemical-looping combustor described in the literature, which utilized a Fe-based carrier (ilmenite) and coal. An Eulerian multiphase continuum model was used to describe both the gas and solid phases, with detailed sub-models to account for fluid-particle and particle-particle interaction forces. Global reaction models of fuel and carrier chemistry were utilized. The transient results obtained from the simulations were compared with detailed experimental time-varying outlet species concentrations (Leion et al., 2008) and provided a reasonable match with the reported experimental data.
The numerical simulation based on CFD of hydraulic turbine pump
Duan, X. H.; Kong, F. Y.; Liu, Y. Y.; Zhao, R. J.; Hu, Q. L.
2016-05-01
As the functions of hydraulic turbine pump including self-adjusting and compensation with each other, it is far-reaching to analyze its internal flow by the numerical simulation based on CFD, mainly including the pressure field and the velocity field in hydraulic turbine and pump.The three-dimensional models of hydraulic turbine pump are made by Pro/Engineer software;the internal flow fields in hydraulic turbine and pump are simulated numerically by CFX ANSYS software. According to the results of the numerical simulation in design condition, the pressure field and the velocity field in hydraulic turbine and pump are analyzed respectively .The findings show that the static pressure decreases systematically and the pressure gradient is obvious in flow area of hydraulic turbine; the static pressure increases gradually in pump. The flow trace is regular in suction chamber and flume without spiral trace. However, there are irregular traces in the turbine runner channels which contrary to that in flow area of impeller. Most of traces in the flow area of draft tube are spiral.
CFD simulation of hydrogen deflagration in a vented room
Tolias, I. C.; Venetsanos, A. G.; Markatos, N. C.; Kiranoudis, C. T.
2015-09-01
In the present work, CFD simulations of hydrogen deflagration in a real scale vented room are performed. Two ignition points were simulated: at the wall opposite to the vent (back ignition) and at the center of the chamber (center ignition). The overpressure time series and flame front velocities are compared with the experimental results. The combustion model is based on the turbulent flame speed concept. The turbulent flame speed is calculated based on a modification of Yakhot's equation, in order to account for all the main physical mechanisms which appear in hydrogen deflagrations. Special attention is given to the simulation of Rayleigh-Taylor instability. This instability occurs at the vent area and results in sudden explosion of the mixture that has been pushed outside the chamber at the initial stage of the explosion. The importance of this external explosion to the generated overpressures inside the chamber is highlighted. The agreement between experimental and computational results is satisfactory in both back ignition and center ignition cases.
CFD Simulations and Experimental Verification on Nucleate Pool Boiling of Liquid Nitrogen
Xiaobin, Zhang; Wei, Xiong; Jianye, Chen; Yuchen, Wang; Tang, K.
To explore the mechanism of nucleate pool boiling of cryogenic fluids, an experimental apparatus was built to conduct a visualization study and verify the CFD boiling model. Apart from the general measurements of the super-heat and heat flux, the influences of super-heat on bubble departure diameters were specially analyzed. Based on the observations, the whole nucleate boiling process from bubble formation to departure from the heated wall can be divided into three stages: low heat flux stage; transitional stage; fully developed nucleate boiling (FDNB) stage. CFD simulations with several existing correlations and the attained values from the experiments for the bubble diameter were finally conducted, and the results fitted well with the present experimental data.
Method for CFD Simulation of Propellant Slosh in a Spherical Tank
Benson, David J.; Mason, Paul A.
2011-01-01
Propellant sloshing can impart unwanted disturbances to spacecraft, especially if the spacecraft controller is driving the system at the slosh frequency. This paper describes the work performed by the authors in simulating propellant slosh in a spherical tank using computational fluid dynamics (CFD). ANSYS-CFX is the CFD package used to perform the analysis. A 42 in spherical tank is studied with various fill fractions. Results are provided for the forces on the walls and the frequency of the slosh. Snapshots of slosh animation give a qualitative understanding of the propellant slosh. The results show that maximum slosh forces occur at a tank fill fraction of 0.4 and 0.6 due to the amount of mass participating in the slosh and the room available for sloshing to occur. The slosh frequency increases as the tank fill fraction increases.
International Nuclear Information System (INIS)
Highlights: • Direct CFD method for flow-pressure characteristic of a pressure control valve. • Fitted and interpreted the constants of the spool hydraulic force equation. • Established a flow coefficient function of both valve opening and pressure drop. • Developed an indirect CFD method based on the valve-governing equations. - Abstract: This study aims to elaborate on specific computational fluid dynamics (CFD) simulation methods for fitting the flow-pressure curve of a pressure control valve, which is spring-load valve widely used in the automotive fuel supply system. Given that the couple mechanism exists between the flow field in the valve and the spring system, numerous researchers chose to fit the characteristic curve with experimental approaches but scarcely focused on CFD methods. A direct CFD method is introduced in this study to solve this problem. Two evaluation criteria are used to determine whether the internal flow is physically real. An experiment is conducted to verify the simulation results, and the accuracy of this CFD method is proved. However, it is designed to solve one operating condition with fixed spring parameters and the accuracy depends on the amount of operating conditions. Thus, an indirect CFD method is developed based on the well-elaborated valve-governing equations to improve the efficiency and broaden the application extension. This method aims to simulate the exact value of the equation constants to uncouple the flow by numerical method. It is capable of dealing with changed operating conditions and varied spring parameters, and the results are also verified. The visualization of the internal flow provides a better understanding of the flow fields in the valve. The valve gap directly influences the hydraulic force distribution on the spool and causes most pressure loss. The physical meaning of the function constants are explained based on the flow analysis
Comparison of CFD simulation of night purge ventilation to full-scale building measurements
Chigurupati, Asha; Gorle, Catherine; Iaccarino, Gianluca
2014-11-01
Efforts to improve the understanding of air motion in and around buildings can lead to more efficient natural ventilation systems, thereby significantly reducing a building's heating and cooling demands. CFD simulations enable solving the details of the flow and convective heat transfer in buildings and have the potential to predict the performance of natural ventilation with a high degree of accuracy. Understanding the actual predictive capability of CFD simulations is however complicated by the complexity of the geometry and physics involved, and the uncertainty and variability in the boundary conditions. In the present study we model the night flush process in the Y2E2 building on Stanford University's campus and compare the results to measurements in the full-scale, operational building. We model half of the building, which consists of three floors with office spaces and two atriums. We solve the RANS equations using ANSYS/Fluent and k-e RNG theory turbulence closure model for the duration of one night flush and will present a comparison of the CFD results to measurements of the temperature on each floor in both atriums. Future investigations will focus on the potential of reducing the discrepancy between observed and predicted values by varying uncertain model parameters and boundary conditions.
Comparison of CFD simulations and measurements of flow affected by coanda effect
Directory of Open Access Journals (Sweden)
Jícha Miroslav
2012-04-01
Full Text Available The article deals with experimental research and numerical simulations of specific phenomena in fluid flows called Coanda effect (CE, which has numerous important engineering applications. Although many researchers have concerned with wall jets, the physics of this flow still remains not well understood. This study is focused on analysis of behaviour of jet flow close to the wall and influence of its inclination. The flow has been visualized using smoke and velocity was measured by means of Hot Wire Anemometry (HWA. CFD simulations have been performed on the same geometry and compared with experiments in order to find a tool for correct prediction of the CE.
Comparison of CFD simulations and measurements of flow affected by coanda effect
Fišer, Jan; Jedelský, Jan; Vach, Tomáš; Forman, Matěj; Jícha, Miroslav
2012-04-01
The article deals with experimental research and numerical simulations of specific phenomena in fluid flows called Coanda effect (CE), which has numerous important engineering applications. Although many researchers have concerned with wall jets, the physics of this flow still remains not well understood. This study is focused on analysis of behaviour of jet flow close to the wall and influence of its inclination. The flow has been visualized using smoke and velocity was measured by means of Hot Wire Anemometry (HWA). CFD simulations have been performed on the same geometry and compared with experiments in order to find a tool for correct prediction of the CE.
Energy Technology Data Exchange (ETDEWEB)
Arranz Iglesias, J.; Gavilan Moreno, C.; Sarti Fernandez, F.
2014-07-01
The study consists in simulating the emptying of the tank when the water level is near the level of the suction nozzle. The objective pursued is to detect the harmful phenomena that may occur in aspiration, ranging from the appearance of vortices and bubble formation to excessive fluid accelerations. (Author)
CFD and DNS methodologies development for fuel bundle simulations
International Nuclear Information System (INIS)
Development and application of Computational Fluid Dynamics (CFD) and Direct Numerical Simulation (DNS) approaches to the simulation of coolant flow inside nuclear fuel bundles are presented, focusing on the advantages and limitations of the different methodologies and on their synergetic potential. High Reynolds number flow cases are analyzed with the adoption of an improved anisotropic turbulence modeling, which adopts a non-linear stress strain correlation and an improved near wall treatment. The capability of the model of predicting the coolant flow distribution inside the bundles is shown and discussed on the base of comparison with experimental data for a variety of geometrical and Reynolds number conditions. In particular wall shear stresses, velocity, and secondary flow distributions comparisons are shown. Moreover, DNS computations are performed adopting an algorithm based on the finite difference method, extended to boundary fitted coordinate systems in order to efficiently concentrate grids near the distorted wall boundaries. The validity and significance of the results is discussed underlying the importance of the insights into the turbulence structure. The calculations are further extended to higher Reynolds numbers, which cannot in general be treated with DNS approach, renouncing to the estimation of the higher-order moments, but limited to the evaluation of the averaged velocity profiles, turbulence intensities and Reynolds stresses. (authors)
Flow and particle deposition in the Turbuhaler: a CFD simulation.
Milenkovic, J; Alexopoulos, A H; Kiparissides, C
2013-05-01
In this work the steady-state flow in a commercial dry powder inhaler device, DPI (i.e., Turbuhaler) is described using computational fluid dynamics. The Navier-Stokes equations are solved using commercial CFD software considering different flow models, i.e., laminar, k-ε, k-ε RNG, and k-ω SST as well as large Eddy simulation. Particle motion and deposition are described using a Eulerian-fluid/Lagrangian-particle approach. Particle collisions with the DPI walls are taken to result in deposition when the normal collision velocity is less than a critical capture velocity. Flow and particle deposition, for a range of mouthpiece pressure drops (i.e., 800-8800 Pa), as well as particle sizes corresponding to single particles and aggregates (i.e., 0.5-20 μm), are examined. The total volumetric outflow rate, the overall particle deposition as well as the spatial distribution of deposition sites in the DPI are determined. The transitional k-ω SST model for turbulent flow was found to produce results most similar to a reference solution obtained with LES, as well as experimental results for the pressure drop in the DPI. Overall, the simulation results are found to be in agreement with the available experimental data for local and total particle deposition. PMID:23528279
Propulsion Simulations with the Unstructured-Grid CFD Tool TetrUSS
Deere, Karen A.; Pandya, Mohagna J.
2002-01-01
A computational investigation has been completed to assess the capability of the NASA Tetrahedral Unstructured Software System (TetrUSS) for simulation of exhaust nozzle flows. Three configurations were chosen for this study: (1) a fluidic jet effects model, (2) an isolated nacelle with a supersonic cruise nozzle, and (3) a fluidic pitchthrust- vectoring nozzle. These configurations were chosen because existing data provided a means for measuring the ability of the TetrUSS flow solver USM3D for simulating complex nozzle flows. Fluidic jet effects model simulations were compared with structured-grid CFD (computational fluid dynamics) data at Mach numbers from 0.3 to 1.2 at nozzle pressure ratios up to 7.2. Simulations of an isolated nacelle with a supersonic cruise nozzle were compared with wind tunnel experimental data and structured-grid CFD data at Mach numbers of 0.9 and 1.2, with a nozzle pressure ratio of 5. Fluidic pitch-thrust-vectoring nozzle simulations were compared with static experimental data and structured-grid CFD data at static freestream conditions and nozzle pressure ratios from 3 to 10. A fluidic injection case was computed with the third configuration at a nozzle pressure ratio of 4.6 and a secondary pressure ratio of 0.7. Results indicate that USM3D with the S-A turbulence model provides accurate exhaust nozzle simulations at on-design conditions, but does not predict internal shock location at overexpanded conditions or pressure recovery along a boattail at transonic conditions.
Two-phase Euler-Lagrange CFD simulation of evaporative cooling in a Wind Tower
Energy Technology Data Exchange (ETDEWEB)
Saffari, Hamid; Hosseinnia, S.M. [Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16844 (Iran)
2009-09-15
A new design of Wind Tower is investigated numerically under different structural parameters and environmental conditions. The new design is some wetted columns, consisting of wetted curtains hung in the tower column, which are modeled as surfaces that inject droplets of water with very low speed. The CFD open source package - Open FOAM - is used. The current three-dimensional CFD simulation has adopted both the Eulerian approach for the air phase and the Lagrangian approach for the water phase. The effects of water droplet diameter and water droplet temperature on the thermal performance of the Wind Tower are investigated at specific inlet air velocity and relative humidity and height of wetted columns. Also, the effects of wind velocity, temperature, and relative humidity inlet to Wind Tower are studied. Changing the height of the wetted columns and its effect on the evaporative cooling in other specific parameters is studied. The results obtained from the present CFD study are compared with the analytical data taken from the literature and a good agreement is observed. As a result, the height of 10 m of wetted columns decreases 12 K of the ambient air temperature and increases 22% of its relative humidity. (author)
Sources of error in CEMRA-based CFD simulations of the common carotid artery
Khan, Muhammad Owais; Wasserman, Bruce A.; Steinman, David A.
2013-03-01
Magnetic resonance imaging is often used as a source for reconstructing vascular anatomy for the purpose of computational fluid dynamics (CFD) analysis. We recently observed large discrepancies in such "image-based" CFD models of the normal common carotid artery (CCA) derived from contrast enhanced MR angiography (CEMRA), when compared to phase contrast MR imaging (PCMRI) of the same subjects. A novel quantitative comparison of velocity profile shape of N=20 cases revealed an average 25% overestimation of velocities by CFD, attributed to a corresponding underestimation of lumen area in the CEMRA-derived geometries. We hypothesized that this was due to blurring of edges in the images caused by dilution of contrast agent during the relatively long elliptic centric CEMRA acquisitions, and confirmed this with MRI simulations. Rescaling of CFD models to account for the lumen underestimation improved agreement with the velocity levels seen in the corresponding PCMRI images, but discrepancies in velocity profile shape remained, with CFD tending to over-predict velocity profile skewing. CFD simulations incorporating realistic inlet velocity profiles and non-Newtonian rheology had a negligible effect on velocity profile skewing, suggesting a role for other sources of error or modeling assumptions. In summary, our findings suggest that caution should be exercised when using elliptic-centric CEMRA data as a basis for image-based CFD modeling, and emphasize the importance of comparing image-based CFD models against in vivo data whenever possible.
CFD Simulation of Heat and Fluid Flow for Spent Fuel in a Dry Storage
Energy Technology Data Exchange (ETDEWEB)
In, Wangkee; Kwack, Youngkyun; Kook, Donghak; Koo, Yanghyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2014-05-15
A dry storage system is used for the interim storage of spent fuel prior to permanent depository and/or recycling. The spent fuel is initially stored in a water pool for more than 5 years at least after dispatch from the reactor core and is transported to dry storage. The dry cask contains a multiple number of spent fuel assemblies, which are cooled down in the spent fuel pool. The dry cask is usually filled up with helium gas for increasing the heat transfer to the environment outside the cask. The dry storage system has been used for more than a decade in United States of America (USA) and the European Union (EU). Korea is also developing a dry storage system since its spent fuel pool is anticipated to be full within 10 years. The spent fuel will be stored in a dry cask for more than 40 years. The integrity and safety of spent fuel are important for long-term dry storage. The long-term storage will experience the degradation of spent fuel such as the embrittlement of fuel cladding, thermal creep and hydride reorientation. High burn-up fuel may expedite the material degradation. It is known that the cladding temperature has a strong influence on the material degradation. Hence, it is necessary to accurately predict the local distribution of the cladding temperature using the Computational Fluid Dynamics (CFD) approach. The objective of this study is to apply the CFD method for predicting the three-dimensional distribution of fuel temperature in a dry cask. This CFD study simulated the dry cask for containing the 21 fuel assemblies under development in Korea. This paper presents the fluid velocity and temperature distribution as well as the fuel temperature. A two-step CFD approach was applied to simulate the heat and fluid flow in a dry storage of 21 spent fuel assemblies. The first CFD analysis predicted the helium flow and temperature in a dry cask by a assuming porous body of the spent fuel. The second CFD analysis was to simulate a spent fuel assembly in the
CFD Simulation of Heat and Fluid Flow for Spent Fuel in a Dry Storage
International Nuclear Information System (INIS)
A dry storage system is used for the interim storage of spent fuel prior to permanent depository and/or recycling. The spent fuel is initially stored in a water pool for more than 5 years at least after dispatch from the reactor core and is transported to dry storage. The dry cask contains a multiple number of spent fuel assemblies, which are cooled down in the spent fuel pool. The dry cask is usually filled up with helium gas for increasing the heat transfer to the environment outside the cask. The dry storage system has been used for more than a decade in United States of America (USA) and the European Union (EU). Korea is also developing a dry storage system since its spent fuel pool is anticipated to be full within 10 years. The spent fuel will be stored in a dry cask for more than 40 years. The integrity and safety of spent fuel are important for long-term dry storage. The long-term storage will experience the degradation of spent fuel such as the embrittlement of fuel cladding, thermal creep and hydride reorientation. High burn-up fuel may expedite the material degradation. It is known that the cladding temperature has a strong influence on the material degradation. Hence, it is necessary to accurately predict the local distribution of the cladding temperature using the Computational Fluid Dynamics (CFD) approach. The objective of this study is to apply the CFD method for predicting the three-dimensional distribution of fuel temperature in a dry cask. This CFD study simulated the dry cask for containing the 21 fuel assemblies under development in Korea. This paper presents the fluid velocity and temperature distribution as well as the fuel temperature. A two-step CFD approach was applied to simulate the heat and fluid flow in a dry storage of 21 spent fuel assemblies. The first CFD analysis predicted the helium flow and temperature in a dry cask by a assuming porous body of the spent fuel. The second CFD analysis was to simulate a spent fuel assembly in the
CFD study on inlet flow blockage accidents in rectangular fuel assembly
Energy Technology Data Exchange (ETDEWEB)
Fan, Wenyuan, E-mail: fanwy@mail.ustc.edu.cn; Peng, Changhong, E-mail: pengch@ustc.edu.cn; Guo, Yun, E-mail: guoyun79@ustc.edu.cn
2015-10-15
Highlights: • 3D CFD and Relap5 simulations on inlet flow blockage are performed. • Transient effects are investigated by dynamic mesh technique. • Similar flow and power redistributions are predicted in both methods. • Local effects of the blockage are captured by CFD method and analyzed. - Abstract: Three-dimensional transient CFD simulation of 90% inlet flow blockage accidents in rectangular fuel assembly is performed, using the dynamic mesh technique. One-dimensional steady calculation is done for comparison, using Relap5 code. Similar mass flow rate redistributions and asymmetric power redistributions of the plate in the blocked scenario are obtained. No boiling is predicted in both simulations, however, CFD approach provides more in-depth investigations of flow transients and the thermal-hydraulic interaction. The development of flow blockage transients is so fast that the rapid redistribution of mass flow rates occurs in only 0.015 s after the formation of the blockage. As a sequence of the inlet flow blockage, jet-flows and reversed flows occur in the blocked channel. This leads to complex temperature distributions of coolants and fuel plates, in which, the highest coolant temperature no longer occurs around the channel outlet. The present study shows the advantage and significance of the application of three-dimensional transient CFD technique in investigating flow blockage accidents.
CFD study on inlet flow blockage accidents in rectangular fuel assembly
International Nuclear Information System (INIS)
Highlights: • 3D CFD and Relap5 simulations on inlet flow blockage are performed. • Transient effects are investigated by dynamic mesh technique. • Similar flow and power redistributions are predicted in both methods. • Local effects of the blockage are captured by CFD method and analyzed. - Abstract: Three-dimensional transient CFD simulation of 90% inlet flow blockage accidents in rectangular fuel assembly is performed, using the dynamic mesh technique. One-dimensional steady calculation is done for comparison, using Relap5 code. Similar mass flow rate redistributions and asymmetric power redistributions of the plate in the blocked scenario are obtained. No boiling is predicted in both simulations, however, CFD approach provides more in-depth investigations of flow transients and the thermal-hydraulic interaction. The development of flow blockage transients is so fast that the rapid redistribution of mass flow rates occurs in only 0.015 s after the formation of the blockage. As a sequence of the inlet flow blockage, jet-flows and reversed flows occur in the blocked channel. This leads to complex temperature distributions of coolants and fuel plates, in which, the highest coolant temperature no longer occurs around the channel outlet. The present study shows the advantage and significance of the application of three-dimensional transient CFD technique in investigating flow blockage accidents
Thermal hydraulic investigations and optimization on the EVC system of a PWR by CFD simulation
Energy Technology Data Exchange (ETDEWEB)
Xi, Mengmeng [Department of Nuclear Science and Technology, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, 710049 Xi’an (China); Zhang, Dalin, E-mail: dlzhang@mail.xjtu.edu.cn [Department of Nuclear Science and Technology, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, 710049 Xi’an (China); Tang, Mao [China Nuclear Power Design Engineering Co., Ltd., 518124 Shenzhen (China); Wang, Chenglong; Zheng, Meiyin; Qiu, Suizheng [Department of Nuclear Science and Technology, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, 710049 Xi’an (China)
2015-08-15
Highlights: • This study constructs a full CFD model for the EVC system of a PWR. • The complex fluid and solid coupling is treated in the computation. • Primary characteristics of the velocity, pressure and temperature distributions in the EVC system are investigated. • The optimization of the EVC system with different inlet boundaries are performed. - Abstract: In order to optimize the design of Reactor Pit Ventilation (EVC) system in a Pressurized Water Reactor (PWR), it is necessary to study the characteristics of the velocity, pressure and temperature fields in the EVC system. A full computational fluid dynamics (CFD) model for the EVC system is constructed by a commercial CFD code, where the complex fluid and solid coupling is treated. The Shear Stress Transport (SST) model is adopted to perform the turbulence calculation. This paper numerically investigates the characteristics of the velocity, pressure and temperature distributions in the EVC system. In particular, the effects of inlet air parameters on the thermal hydraulic characteristics and the reactor pit structure are also discussed for the EVC system optimization. Simulations are carried out with different mesh sizes and boundary conditions for sensitivity analysis. The computational results are important references to optimize the design and verify the rationality of the EVC system.
CFD Simulation and Optimisation of a Low Energy Ventilation and Cooling System
Directory of Open Access Journals (Sweden)
John Kaiser Calautit
2015-04-01
Full Text Available Mechanical Heating Ventilation and Air-Conditioning (HVAC systems account for 60% of the total energy consumption of buildings. As a sector, buildings contributes about 40% of the total global energy demand. By using passive technology coupled with natural ventilation from wind towers, significant amounts of energy can be saved, reducing the emissions of greenhouse gases. In this study, the development of Computational Fluid Dynamics (CFD analysis in aiding the development of wind towers was explored. Initial concepts of simple wind tower mechanics to detailed design of wind towers which integrate modifications specifically to improve the efficiency of wind towers were detailed. From this, using CFD analysis, heat transfer devices were integrated into a wind tower to provide cooling for incoming air, thus negating the reliance on mechanical HVAC systems. A commercial CFD code Fluent was used in this study to simulate the airflow inside the wind tower model with the heat transfer devices. Scaled wind tunnel testing was used to validate the computational model. The airflow supply velocity was measured and compared with the numerical results and good correlation was observed. Additionally, the spacing between the heat transfer devices was varied to optimise the performance. The technology presented here is subject to a patent application (PCT/GB2014/052263.
Thermal hydraulic investigations and optimization on the EVC system of a PWR by CFD simulation
International Nuclear Information System (INIS)
Highlights: • This study constructs a full CFD model for the EVC system of a PWR. • The complex fluid and solid coupling is treated in the computation. • Primary characteristics of the velocity, pressure and temperature distributions in the EVC system are investigated. • The optimization of the EVC system with different inlet boundaries are performed. - Abstract: In order to optimize the design of Reactor Pit Ventilation (EVC) system in a Pressurized Water Reactor (PWR), it is necessary to study the characteristics of the velocity, pressure and temperature fields in the EVC system. A full computational fluid dynamics (CFD) model for the EVC system is constructed by a commercial CFD code, where the complex fluid and solid coupling is treated. The Shear Stress Transport (SST) model is adopted to perform the turbulence calculation. This paper numerically investigates the characteristics of the velocity, pressure and temperature distributions in the EVC system. In particular, the effects of inlet air parameters on the thermal hydraulic characteristics and the reactor pit structure are also discussed for the EVC system optimization. Simulations are carried out with different mesh sizes and boundary conditions for sensitivity analysis. The computational results are important references to optimize the design and verify the rationality of the EVC system
CFD simulation of critical heat flux in a rod bundle
International Nuclear Information System (INIS)
The critical heat flux (CHF) condition is characterized by a sharp reduction of the local heat transfer coefficient which results from the replacement of liquid by vapour adjacent to the heat transfer surface. If the surface heat flux is the independent variable, the condition manifests itself as a sharp increase in surface temperature as the critical heat flux value is reached. The critical heat flux forms an important boundary for the performance of the heat exchange equipment. Determination of the critical heat flux is one of the key issues in nuclear reactor safety. This paper presents numerical simulations of boiling flow in a rod bundle with Departure from Nucleate Boiling (DNB) condition at the end of the middle rod. Large Water Loop CHF tests were used as a data set for our simulations. The Large Water Loop (LWL) is non-active pressurised-water equipment with technological and thermal parameters corresponding to those of PWR. The CHF experimental facility (a part of the Large Water Loop) has been designed for research into CHF in water flow through a bundle of electrically heated vertical rods. The critical conditions were determined under constant pressure, inlet water temperature and mass flux and for quasi steady-state - by gradually increasing the heat input. The rods are modelled by hollow tubes with direct heating of the wall. NEPTUNE-CFD code was used for numerical simulations. The computational domain covered a 30 deg. quasi-symmetric section of the actual channel. Simplified grid spacers were included in the domain. Calculations were performed with two-fluid approach with models for drag, lift, added mass and turbulent dispersion forces as well as for interfacial heat and mass transfer. Turbulent dispersion coefficient was based on void fraction gradient and on drag and mass forces. K-epsilon model was used for the prediction of the liquid turbulence, the flow of vapour was assumed to be laminar. Generalized wall heat-flux-splitting model was used
CFD simulation of critical heat flux in a tube
International Nuclear Information System (INIS)
equation with Yao's models for coalescence and break-up of the bubbles. Numerical simulations were performed for the four series of data selected from the tables. In every series, one of the following parameters was variable while the remaining three parameters were fixed. The parameters were: local equilibrium quality, mass flux, pressure and the tube diameter. In every data point, numerical simulation was performed to check whether the NEPTUNE-CFD can predict occurrence of the critical heat flux. After that, wall heat flux in simulation was increased or decreased so as to find out the interval of wall heat fluxes at which boiling crisis occurs. Grid independence was tested by calculating the same cases on three grids with different resolution. Results show that presented approach can be used for high mass fluxes and high pressures. On the other hand, in one low-mass-flux case, the CHF in calculation occurred at wall heat flux as low as 80 pc of experimental heat flux. In low pressure cases, it was impossible to obtain stable solution due to numerical oscillations. Presented work was done within 7. FP EURATOM NURISP project. NEPTUNE-CFD code is implemented in the NURESIM platform. (authors)
The presentation summarizes developments of ongoing applications of fine-scale (geometry specific) CFD simulations to urban areas within atmospheric boundary layers. Enabling technology today and challenges for the future are discussed. There is a challenging need to develop a ...
Cfd Simulation to the Flow Field of Venturi Injector
Huang, Xingfa; Li, Guangyong; Wang, Miao
Venturi injector is widely used in fertigation system due to its obvious advantages such as cheap and robust system without mobile pieces, simple structure, convenient to operation, stable performance, needless of external energy for operation etc. At present, the hydraulic parameters such as suction capacity (injection rate) for the most of the Venturi injectors produced domestically are not very desirable. In this paper, CFD (Computational Fluid Dynamics) method was used to simulate the inner flow field of the Venturi injectors, and the relationships among the structure parameters (i.e., throat length L, throat diameter D, slot diameter Da) and suction capacity q, and the optimal structure sizes of the Venturi injector were analyzed. The results show that when the inlet pressure and the slot position are kept unchanged as the sample one, the suction capacity of Venturi injector increases with the decrease of throat diameter D and throat length L, and the increase of slot diameter Da; while keeping the slot diameter Da, throat diameter D and throat length L unchanged, the suction capacity of Venturi injector q increases with the increase of inlet pressure P. The optimal combination of the structural parameters in this size was selected as follows: throat diameter D=8mm, slot diameter Da=18.5mm, and throat length L=14mm. In this case, the suction capacity of the Venturi injector q=1.203m3/h. The results can provide theoretic support for domestic Venturi injector research, design and manufacturing.
CFD simulation of boundary effects on closely spaced jets
Shrivastava, Ishita; Adams, Eric
2015-11-01
In coastal areas characterized by shallow water depth, industrial effluents are often diluted using multiple closely spaced jets. Examples of such effluents include brine from desalination plants, treated wastewater from sewage treatment plants and heated water from thermal power plants. These jets are arranged in various orientations, such as unidirectional diffusers and rosette groups, to maximize mixing with ambient water. Due to effects of dynamic pressure, the jets interact with each other leading to mixing characteristics which are quite different from those of individual jets. The effect of mutual interaction is exaggerated under confinement, when a large number of closely spaced jets discharge into shallow depth. Dilution through an outfall, consisting of multiple jets, depends on various outfall and ambient parameters. Here we observe the effects of shoreline proximity, in relation to diffuser length and water depth, on the performance of unidirectional diffusers discharging to quiescent water. For diffusers located closer to shore, less dilution is observed due to the limited availability of ambient water for dilution. We report on the results of Computational Fluid Dynamics (CFD) simulations and compare the results with experimental observations.
Energy Technology Data Exchange (ETDEWEB)
Pitz, William J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); McNenly, Matt J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Whitesides, Russell [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Mehl, Marco [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Killingsworth, Nick J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Westbrook, Charles K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-12-17
Predictive chemical kinetic models are needed to represent next-generation fuel components and their mixtures with conventional gasoline and diesel fuels. These kinetic models will allow the prediction of the effect of alternative fuel blends in CFD simulations of advanced spark-ignition and compression-ignition engines. Enabled by kinetic models, CFD simulations can be used to optimize fuel formulations for advanced combustion engines so that maximum engine efficiency, fossil fuel displacement goals, and low pollutant emission goals can be achieved.
RAPID CREATION OF CFD-CAPABLE CAD-MODELS FOR CABIN AIR VENTILATION SIMULATION
Fuchte, Jörg; Wick, Andreas; Rajkowski, Sergej
2011-01-01
The objective of this paper is to describe a method for rapid creation of cabin CAD (Computer Aided Design) models for usage in CFD (Computational Fluid Dynamics) simulations of cabin air ventilation. The intention is to automate the process of model creation in order to speed up the process and reduce the workload both in CAD modeling and mesh creation. The described method is part of a larger process intended to facilitate the usage of CFD cabin air ventilation simulations for passenger com...
Modeling and Simulation of Hamburger Cooking Process Using Finite Difference and CFD Methods
Directory of Open Access Journals (Sweden)
J. Sargolzaei
2011-01-01
Full Text Available Unsteady-state heat transfer in hamburger cooking process was modeled using one dimensional finite difference (FD and three dimensional computational fluid dynamic (CFD models. A double-sided cooking system was designed to study the effect of pressure and oven temperature on the cooking process. Three different oven temperatures (114, 152, 204°C and three different pressures (20, 332, 570 pa were selected and 9 experiments were performed. Applying pressure to hamburger increases the contact area of hamburger with heating plate and hence the heat transfer rate to the hamburger was increased and caused the weight loss due to water evaporation and decreasing cooking time, while increasing oven temperature led to increasing weight loss and decreasing cooking time. CFD predicted results were in good agreement with the experimental results than the finite difference (FD ones. But considering the long time needed for CFD model to simulate the cooking process (about 1 hour, using the finite difference model would be more economic.
Landazuri, Andrea C.
This dissertation focuses on aerosol transport modeling in occupational environments and mining sites in Arizona using computational fluid dynamics (CFD). The impacts of human exposure in both environments are explored with the emphasis on turbulence, wind speed, wind direction and particle sizes. Final emissions simulations involved the digitalization process of available elevation contour plots of one of the mining sites to account for realistic topographical features. The digital elevation map (DEM) of one of the sites was imported to COMSOL MULTIPHYSICSRTM for subsequent turbulence and particle simulations. Simulation results that include realistic topography show considerable deviations of wind direction. Inter-element correlation results using metal and metalloid size resolved concentration data using a Micro-Orifice Uniform Deposit Impactor (MOUDI) under given wind speeds and directions provided guidance on groups of metals that coexist throughout mining activities. Groups between Fe-Mg, Cr-Fe, Al-Sc, Sc-Fe, and Mg-Al are strongly correlated for unrestricted wind directions and speeds, suggesting that the source may be of soil origin (e.g. ore and tailings); also, groups of elements where Cu is present, in the coarse fraction range, may come from mechanical action mining activities and saltation phenomenon. Besides, MOUDI data under low wind speeds (potential deleterious effects, but also that the application of CFD represents an important contribution to actual dispersion modeling studies; therefore, Computational Fluid Dynamics can be used as a source apportionment tool to identify areas that have an effect over specific sampling points and susceptible regions under certain meteorological conditions, and these conclusions can be supported with inter-element correlation matrices and lead isotope analysis, especially since there is limited access to the mining sites. Additional results concluded that grid adaption is a powerful tool that allows to refine
CFD simulation of flow patterns in unbaffled stirred tank with CD-6 impeller
Directory of Open Access Journals (Sweden)
Devi Tamphasana Thiyam
2012-01-01
Full Text Available Understanding the flow in stirred vessels can be useful for a wide number of industrial applications. There is a wealth of numerical simulations of stirring vessels with standard impeller such as Rushton turbine and pitch blade turbine. Here, a CFD study has been performed to observe the spatial variations (angular, axial and radial of hydrodynamics (velocity and turbulence field in unbaffled stirred tank with Concave-bladed Disc turbine (CD-6 impeller. Three speeds (N=296, 638 & 844.6 rpm have been considered for this study. The angular variations of hydrodynamics of stirred tank were found very less as compared to axial and radial variations.
DEFF Research Database (Denmark)
Zhang, Chen; Chen, Qingyan; Heiselberg, Per Kvols;
2015-01-01
Diffuse ceiling ventilation uses perforations in the suspended ceiling to deliver air into the occupied zone. Due to the complex geometry of the diffuser, it is not possible to build an exact geometrical model in CFD simulation. Two numerical models are proposed in this study, one is a simplified...
CFD simulation of a TG–DSC furnace during the indium phase change process
International Nuclear Information System (INIS)
Highlights: ► Working behaviour in TGA–DSC is studied. ► A CFD model of the original device is simulated. ► Indium is employed as sample and a melting model is programmed. ► Heat flux to the sample is computed. ► Experimental and simulated results are compared. -- Abstract: A ThermoGravimetric Analyser with Differential Scanning Calorimeter (TGA–DSC) was modelled and simulated to evaluate heat transfer to the sample and the internal operation of the equipment. For this purpose, a mesh was generated based on a CAD design of the real geometry, and several models were applied. Some of these models were built into the CFD commercial software, and some were developed by the authors. Realistic boundary conditions were applied, and a control system based on PID operation was implemented to manage the heat released by an electrical resistance, similar to the real equipment. Finally, simulation results were obtained and contrasted with real data.
Salem, A I; Okoth, G; Thöming, J
2011-05-01
The most important requirements for achieving effective separation conditions in inclined plate settler (IPS) are its hydraulic performance and the equal distribution of suspensions between settler channels, both of which depend on the inlet configuration. In this study, three different inlet structures were used to explore the effect of feeding a bench scale IPS via a nozzle distributor on its hydraulic performance and separation efficiency. Experimental and Computational Fluid Dynamic (CFD) analyses were carried out to evaluate the hydraulic characteristics of the IPS. Comparing the experimental results with the predicted results by CFD simulation implies that the CFD software can play a useful role in studying the hydraulic performance of the IPS by employing residence time distribution (RTD) curves. The results also show that the use of a nozzle distributor can significantly enhance the hydraulic performance of the IPS, which contributes to the improvement of its separation efficiency. PMID:21546049
Assessment of Nucleation Site Density Models for CFD Simulations of Subcooled Flow Boiling
Energy Technology Data Exchange (ETDEWEB)
Hoang, N. H.; Chu, I. C.; Euh, D. J.; Song, C. H. [KAERI, Daejeon (Korea, Republic of)
2015-05-15
of the nucleation site density to the computation of the near wall heat transfer in the subcooled flow boiling, the evaluation of existing correlations of the nucleation site density are interested in this study. This assessment is carried out with published databases available in the literature. A CFD simulation of the DEBORA test using different models of the nucleation site density is then presented. The nucleation site density does not depend simply on only the wall superheat or cavity size. The surface conditions have a significant influence on the formation of the nucleation site density.
Assessment of Nucleation Site Density Models for CFD Simulations of Subcooled Flow Boiling
International Nuclear Information System (INIS)
of the nucleation site density to the computation of the near wall heat transfer in the subcooled flow boiling, the evaluation of existing correlations of the nucleation site density are interested in this study. This assessment is carried out with published databases available in the literature. A CFD simulation of the DEBORA test using different models of the nucleation site density is then presented. The nucleation site density does not depend simply on only the wall superheat or cavity size. The surface conditions have a significant influence on the formation of the nucleation site density
Possibilities for simulating the smoke rollback effect in underground mines using CFD software
Adjiski, Vancho
2014-01-01
The effect of fire generated smoke rollback in underground mines can be dangerous and a potentially fatal threat to all who are endangered by the fire. Three critical stages in the process of smoke rollback are 3D local phenomena that can be analysed by CFD software simulations. With the help of a 3D-CFD analysis we can observe the critical stages of smoke rollback and their reaction to a ventilation network. The CFD provides the opportunity to expand the range of prediction of smoke spread f...
Scaling studies and conceptual experiment designs for NGNP CFD assessment
International Nuclear Information System (INIS)
The objective of this report is to document scaling studies and conceptual designs for flow and heat transfer experiments intended to assess CFD codes and their turbulence models proposed for application to prismatic NGNP concepts. The general approach of the project is to develop new benchmark experiments for assessment in parallel with CFD and coupled CFD/systems code calculations for the same geometry. Two aspects of the complex flow in an NGNP are being addressed: (1) flow and thermal mixing in the lower plenum (''hot streaking'' issue) and (2) turbulence and resulting temperature distributions in reactor cooling channels (''hot channel'' issue). Current prismatic NGNP concepts are being examined to identify their proposed flow conditions and geometries over the range from normal operation to decay heat removal in a pressurized cooldown. Approximate analyses have been applied to determine key non-dimensional parameters and their magnitudes over this operating range. For normal operation, the flow in the coolant channels can be considered to be dominant turbulent forced convection with slight transverse property variation. In a pressurized cooldown (LOFA) simulation, the flow quickly becomes laminar with some possible buoyancy influences. The flow in the lower plenum can locally be considered to be a situation of multiple hot jets into a confined crossflow--with obstructions. Flow is expected to be turbulent with momentum dominated turbulent jets entering; buoyancy influences are estimated to be negligible in normal full power operation. Experiments are needed for the combined features of the lower plenum flows. Missing from the typical jet experiments available are interactions with nearby circular posts and with vertical posts in the vicinity of vertical walls--with near stagnant surroundings at one extreme and significant crossflow at the other. Two types of heat transfer experiments are being considered. One addresses the ''hot channel'' problem, if
CFD simulation of steam jet-induced thermal mixing in subcooled water pool
Energy Technology Data Exchange (ETDEWEB)
Moon, Young-Tae, E-mail: moon@kopec.co.k [Korea Power Engineering Co., Inc., 360-9 Mabuk-Dong, Giheung-Gu, Yonin-Si, Gyeonggi-Do, 446-713 (Korea, Republic of); Lee, Hee-Do [Korea Power Engineering Co., Inc., 360-9 Mabuk-Dong, Giheung-Gu, Yonin-Si, Gyeonggi-Do, 446-713 (Korea, Republic of); Park, Goon-Cherl [Department of Nuclear Engineering, Seoul National University, San 56-1, Sillim-dong, Kwanak-gu, Seoul, 151-744 (Korea, Republic of)
2009-12-15
This study examined the IRWST thermal mixing phenomena induced by a steam jet in a subcooled water pool. Due to the limitation of the current CFD code to simulate condensation, the steam condensation region model was developed to evaluate the thermal mixing phenomena. Within this region, all the steam was condensed into water, and the steam mass and energy inputs were treated as the source. This calculation was treated using single-phase CFD methods. The benchmark calculation for a thermal mixing experiment in the water tank was performed to develop an optimized 3D evaluation methodology of the thermal-hydraulic behavior in APR1400 IRWST. Steam discharge through the sparger and condensation phenomenon was modeled with the choking flow and thermal mixing model in the quenching tank using CFX11. Three types of thermal mixing experiments, local phenomena test, thermal mixing tests in cylindrical water pool and annulus water pool, were designed to provide data representative of the behavior of the prototype for CFD simulations of the thermal-hydraulic behavior in IRWST. A comparison of the calculated and experimentally measured temperature profiles showed some disagreement particularly around the sparger. The main reason for this disagreement was caused by the difference in the test and simulating conditions at the tank wall. However, moving away from the sparger, the trends of the temperature rise became similar to that in the experiment. Despite these problems, this model is the best way of evaluating the thermal mixing phenomena caused by a steam jet in a subcooled water pool.
Simulation of a MW rotor equipped with vortex generators using CFD and an actuator shape model
DEFF Research Database (Denmark)
Troldborg, Niels; Zahle, Frederik; Sørensen, Niels N.
2015-01-01
This article presents a comparison of CFD simulations of the DTU 10 MW reference wind turbine with and without vortex generators installed on the inboard part of the blades. The vortex generators are modelled by introducing body forces determined using a modified version of the so-called BAY model....... The vortex generator model is validated by applying it for modelling an array of VGs on an airfoil section compared to both wind tunnel measurements and fully gridded CFD....
Method for Lumped Parameter simulation of Digital Displacement pumps/motors based on CFD
DEFF Research Database (Denmark)
Rømer, Daniel; Johansen, Per; Pedersen, Henrik C.;
2013-01-01
design and control of digital displacement machines, there is a need for simulation models, preferably models with low computational cost. Therefore, a low computational cost generic lumped parameter model of digital displacement machine is presented, including a method for determining the needed model...... parameters based on steady CFD results, in order to take detailed geometry information into account. The response of the lumped parameter model is compared to a computational expensive transient CFD model for an example geometry....
International Nuclear Information System (INIS)
In the present study, aeroelastic simulations of horizontal-axis wind turbine rotor blades were conducted using a coupled CFD-CSD method. The unsteady blade aerodynamic loads and the dynamic blade response due to yaw misalignment and non-uniform sheared wind were investigated. For this purpose, a CFD code solving the RANS equations on unstructured meshes and a FEM-based CSD beam solver were used. The coupling of the CFD and CSD solvers was made by exchanging the data between the two solvers in a loosely coupled manner. The present coupled CFD-CSD method was applied to the NREL 5MW reference wind turbine rotor, and the results were compared with those of CFD-alone rigid blade calculations. It was found that aeroelastic blade deformation leads to a significant reduction of blade aerodynamic loads, and alters the unsteady load behaviours, mainly due to the torsional deformation. The reduction of blade aerodynamic loads is particularly significant at the advancing rotor blade side for yawed flow conditions, and at the upper half of rotor disk where wind velocity is higher due to wind shear
Yu, D. O.; Kwon, O. J.
2014-06-01
In the present study, aeroelastic simulations of horizontal-axis wind turbine rotor blades were conducted using a coupled CFD-CSD method. The unsteady blade aerodynamic loads and the dynamic blade response due to yaw misalignment and non-uniform sheared wind were investigated. For this purpose, a CFD code solving the RANS equations on unstructured meshes and a FEM-based CSD beam solver were used. The coupling of the CFD and CSD solvers was made by exchanging the data between the two solvers in a loosely coupled manner. The present coupled CFD-CSD method was applied to the NREL 5MW reference wind turbine rotor, and the results were compared with those of CFD-alone rigid blade calculations. It was found that aeroelastic blade deformation leads to a significant reduction of blade aerodynamic loads, and alters the unsteady load behaviours, mainly due to the torsional deformation. The reduction of blade aerodynamic loads is particularly significant at the advancing rotor blade side for yawed flow conditions, and at the upper half of rotor disk where wind velocity is higher due to wind shear.
Study of tip loss corrections using CFD rotor computations
Shen, W. Z.; Zhu, W. J.; Sørensen, J. N.
2014-12-01
Tip loss correction is known to play an important role for engineering prediction of wind turbine performance. There are two different types of tip loss corrections: tip corrections on momentum theory and tip corrections on airfoil data. In this paper, we study the latter using detailed CFD computations for wind turbines with sharp tip. Using the technique of determination of angle of attack and the CFD results for a NordTank 500 kW rotor, airfoil data are extracted and a new tip loss function on airfoil data is derived. To validate, BEM computations with the new tip loss function are carried out and compared with CFD results for the NordTank 500 kW turbine and the NREL 5 MW turbine. Comparisons show that BEM with the new tip loss function can predict correctly the loading near the blade tip.
Study of tip loss corrections using CFD rotor computations
International Nuclear Information System (INIS)
Tip loss correction is known to play an important role for engineering prediction of wind turbine performance. There are two different types of tip loss corrections: tip corrections on momentum theory and tip corrections on airfoil data. In this paper, we study the latter using detailed CFD computations for wind turbines with sharp tip. Using the technique of determination of angle of attack and the CFD results for a NordTank 500 kW rotor, airfoil data are extracted and a new tip loss function on airfoil data is derived. To validate, BEM computations with the new tip loss function are carried out and compared with CFD results for the NordTank 500 kW turbine and the NREL 5 MW turbine. Comparisons show that BEM with the new tip loss function can predict correctly the loading near the blade tip
COMPUTATIONAL FLUID DYNAMICS (CFD) SIMULATIONS OF DRAG REDUCTION WITH PERIODIC MICRO-STRUCTURED WALL
Institute of Scientific and Technical Information of China (English)
LI Gang; ZHOU Ming; WU Bo; YE Xia; CAI Lan
2008-01-01
Computational fluid dynamics(CFD) simulations are adopted to investigate rectangular microchannel flows with various periodic micro-structured wall by introducing velocity slip boundary condition at low Reynolds number. The purpose of the current study is to numerically find out the effects of periodic micro-structured wall on the flow resistance in rectangular microchannel with the different spacings between microridges ranging from 15 to 60 μm. The simulative results indicate that pressure drop with different spacing between microridges increases linearly with flow velocity and decreases monotonically with slip velocity; Pressure drop reduction also increases with the spacing between microridges at the same condition of slip velocity and flow velocity. The results of numerical simulation are compared with theoretical predictions and experimental results in the literatures. It is found that there is qualitative agreement between them.
How fine is fine enough when doing CFD terrain simulations
DEFF Research Database (Denmark)
Sørensen, Niels N.; Bechmann, Andreas; Réthoré, Pierre-Elouan;
2012-01-01
The present work addresses the problemof establishing the necessary grid resolution to obtain a given level of numerical accuracy using a CFD model for prediction of flow over terrain. It is illustrated, that a very high resolution may be needed if the numerical difference between consecutive...
How fine is fine enough when doing CFD terrain simulations
DEFF Research Database (Denmark)
Sørensen, Niels N.; Bechmann, Andreas; Réthoré, Pierre-Elouan;
The present work addresses the problem of establishing the necessary grid resolution to obtain a given level of numerical accuracy using a CFD model for prediction of flow over terrain. It is illustrated, that a very high resolution may be needed if the numerical difference between consecutive...
Validation of Boundary Conditions for CFD Simulations on Ventilated Rooms
DEFF Research Database (Denmark)
Topp, Claus; Jensen, Rasmus Lund; Pedersen, D.N.;
2001-01-01
The application of Computational Fluid Dynamics (CFD) for ventilation research and design of ventilation systems has increased during the recent years. This paper provides an investigation of direct description of boundary conditions for a complex inlet diffuser and a heated surface. A series of ...
CFD Simulations of Contaminant Transport between two Breathing Persons
DEFF Research Database (Denmark)
Bjørn, Erik; Nielsen, Peter V.
Experiments have shown that exhalation from one person is able to penetrate the breathing zone of another person at a distance. Computational Fluid Dynamics (CFD) is used to investigate the dependency of the personal exposure on some physical parameters, namely: Pulmonary ventilation rate...
Hypersonic Intake Starting Characteristics–A CFD Validation Study
Soumyajit Saha; Debasis Chakraborty
2012-01-01
Numerical simulation of hypersonic intake starting characteristics is presented. Three dimensional RANS equations are solved alongwith SST turbulence model using commercial computational fluid dynamics (CFD) software. Wall pressure distribution and intake performance parameters are found to match well with experimental data for different free stream Mach number in the range of 3-8. The unstarting of the intake is traced from the sudden drop of mass capture ratio. Wall condition (adiabatic or ...
Propulsion Simulations Using Advanced Turbulence Models with the Unstructured Grid CFD Tool, TetrUSS
Abdol-Hamid, Khaled S.; Frink, Neal T.; Deere, Karen A.; Pandya, Mohangna J.
2004-01-01
A computational investigation has been completed to assess the capability of TetrUSS for exhaust nozzle flows. Three configurations were chosen for this study (1) an axisymmetric supersonic jet, (2) a transonic axisymmetric boattail with solid sting operated at different Reynolds number and Mach number, and (3) an isolated non-axisymmetric nacelle with a supersonic cruise nozzle. These configurations were chosen because existing experimental data provided a means for measuring the ability of TetrUSS for simulating complex nozzle flows. The main objective of this paper is to validate the implementation of advanced two-equation turbulence models in the unstructured-grid CFD code USM3D for propulsion flow cases. USM3D is the flow solver of the TetrUSS system. Three different turbulence models, namely, Menter Shear Stress Transport (SST), basic k epsilon, and the Spalart-Allmaras (SA) are used in the present study. The results are generally in agreement with other implementations of these models in structured-grid CFD codes. Results indicate that USM3D provides accurate simulations for complex aerodynamic configurations with propulsion integration.
Agarwal, T K; Sahoo, B K; Gaware, J J; Joshi, M; Sapra, B K
2014-10-01
The release of (220)Rn gas (conventionally referred to as thoron) is an issue of concern from the radiological point of view for occupational environments pertaining to the thorium fuel cycle. Studies for understanding its release and developing systems to control it are crucial for exposure control research. A thorough study of the "Delay Volume Technique" for mitigation of (220)Rn has been carried out. Experiments have been carried out with (220)Rn source and associated measurement system in a cubical chamber (delay chamber) of 0.5 m(3) volume. For different flow conditions and inlet-outlet positions, (220)Rn transmission factor has been obtained. Computational Fluid Dynamics (CFD) technique has been employed for these experimental conditions and the simulated transmission factors have been compared. The results show that the flow and the position of the inlet and outlet play an imperative role in the transportation, mixing and subsequent mitigation of thoron inside the chamber. Predictive capability of CFD technique for such delay volume experiments has been validated in this work. A comparison has been made with uniform mixing model and it is found that the results of simulation differ appreciably from that of uniform mixing model at the tested flow regime. PMID:24860913
Simulation of a semi-industrial pilot plant thickener using CFD approach
Institute of Scientific and Technical Information of China (English)
Majid Ebrahimzadeh Gheshlaghi; Ataallah Soltani Goharrizi; Alireza Aghajani Shahrivar
2013-01-01
Thickeners are important units for water recovery in various industries.In this study,a semi-industrial pilot plant thickener similar to the tailing thickener of the Sarcheshmeh Copper Mine was simulated by CFD modeling.The population balance was used to describe the particle aggregation and breakup.In this population balance,15 particle sizes categories were considered.The Eulerian-Eulerian approach with standard k-ε turbulence model was applied to describe two phases of slurry flow in the thickener under steady-state condition.The simulation results have been compared with the experimental measurements to validate the accuracy of the CFD modeling.After checking the numerical results,the effect of important parameters such as,feed flow rate,solid percentage in the feed,and solid particle size on the thickener performance.was studied.The thickener residence time distribution were obtained by the modeling and also compared with the experimental data.Finally,the effects of feedwell feeding on the average diameter of aggregate and turbulent intensity were evaluated.
CFD simulations of buoyancy driven flow mixing experiments performed at the ROCOM facility
International Nuclear Information System (INIS)
Multi-physics approaches are currently developed at Tractebel Engineering (TE) for accurately simulating the complex interaction between neutronics and thermal-hydraulics during asymmetric accidents. One branch of the improvements of the method focuses on the implementation in the coupled codes package of realistic core inlet distributions obtained from CFD results. Two flow mixing tests performed at the ROCOM facility and representative of asymmetric flow conditions are being simulated with the CFD code ANSYS CFX 12.0. The results show that the main mixing phenomena are qualitatively well reproduced, but a quantitative analysis points out an underestimation of the mixing in the simulations. (author)
Methods for Computationally Efficient Structured CFD Simulations of Complex Turbomachinery Flows
Herrick, Gregory P.; Chen, Jen-Ping
2012-01-01
This research presents more efficient computational methods by which to perform multi-block structured Computational Fluid Dynamics (CFD) simulations of turbomachinery, thus facilitating higher-fidelity solutions of complicated geometries and their associated flows. This computational framework offers flexibility in allocating resources to balance process count and wall-clock computation time, while facilitating research interests of simulating axial compressor stall inception with more complete gridding of the flow passages and rotor tip clearance regions than is typically practiced with structured codes. The paradigm presented herein facilitates CFD simulation of previously impractical geometries and flows. These methods are validated and demonstrate improved computational efficiency when applied to complicated geometries and flows.
CFD aided design of the experimental helium loop for VHTR simulation
International Nuclear Information System (INIS)
A medium-scale helium loop for simulating a VHTR (Very High Temperature Reactor) is now under construction in KAERI (Korea Atomic Energy Research Institute). Two electric heaters of the test helium loop heat the helium fluid up to 950°C at a pressure of 1 ~ 9MPa. To optimize the design specifications of the experimental helium loop, conjugate heat transfer in the high-temperature helium heater was analyzed by using CFD (Computational Fluid Dynamics) simulation. The main factors tested in this CFD analysis were the effects of turbulence, radiation, gravity, and geometrical configuration of the heater. From the analysis results, the optimum design configuration was selected confirming that thermal characteristics of the heater well meet the design requirements. In this study, the interrelated effects of buoyancy forces and radiation heat transfer on the geometrical configuration were closely investigated. It was concluded that the buoyancy effects on the helium flows of the heater would be suppressed by the radiation heat transfer inside the heating channel. Various emissivity values of the reflector material emissivity were also tested. Gravity had greater effects on the temperature distribution for the lower emissivity, but the maximum temperature variations due to the emissivity changes from 0.1 to 0.9 were limited to within a few tens of degrees. Finally, more detailed analyses on the HTH of the medium scale helium loop including the spacers were performed and it is confirmed that the thermal-fluidic characteristics of the HTH satisfied the design requirements. (author)
Meng, Chen; Huang, Jianke; Ye, Chunyu; Cheng, Wenchao; Chen, Jianpei; Li, Yuanguang
2015-07-01
In this study, a numerical simulation using computational fluid dynamics (CFD) was used to investigate the hydrodynamic characteristics of circular ponds with three different impellers (hydrofoil, four-pitched-blade turbine, and grid plate). The reliability of the CFD model was validated by particle image velocimetry (PIV). Hydrodynamic analyses were conducted to evaluate the average velocity magnitude along the light direction (Uz), turbulence properties, average shear stress, pressure loss and the volume percentage of dead zone inside circular ponds. The simulation results showed that Uz value of hydrofoil was 58.9, 40.3, and 28.8% higher than those of grid plate with single arm, grid plate with double arms and four-pitched blade turbines in small-scale circular ponds, respectively. In addition, hydrofoil impeller with down-flow operation had outstanding mixing characteristics. Lastly, the results of Chlorella pyrenoidosa cultivation experiments indicated that the biomass concentration of hydrofoil impeller with down-flow operation was 65.2 and 88.8% higher than those of grid plate with double arms and four-pitched-blade turbine, respectively. Therefore, the optimal circular pond mixing system for microalgae cultivation involved a hydrofoil impeller with down-flow operation. PMID:25680396
Simulation of Solid Suspension in a Stirred Tank Using CFD-DEM Coupled Approach
Institute of Scientific and Technical Information of China (English)
邵婷; 胡银玉; 王文坦; 金涌; 程易
2013-01-01
Computational fluid dynamics-discrete element method (CFD-DEM) coupled approach was employed to simulate the solid suspension behavior in a Rushton stirred tank with consideration of transitional and rotational motions of millions of particles with complex interactions with liquid and the rotating impeller. The simulations were satisfactorily validated with experimental data in literature in terms of measured particle velocities in the tank. Influences of operating conditions and physical properties of particles (i.e., particle diameter and density) on the two-phase flow field in the stirred tank involving particle distribution, particle velocity and vortex were studied. The wide distribution of particle angular velocity ranging from 0 to 105 r·min-1 is revealed. The Magnus force is comparable to the drag force during the particle movement in the tank. The strong particle rotation will generate extra shear force on the particles so that the particle morphology may be affected, especially in the bio-/polymer-product related processes. It can be concluded that the CFD-DEM coupled approach provides a theoretical way to under-stand the physics of particle movement in micro-to macro-scales in the solid suspension of a stirred tank.
CFD aided design of the experimental helium loop for VHTR simulation
Energy Technology Data Exchange (ETDEWEB)
Yoon, C.; Hong, S.D.; Noh, J.M.; Kim, Y.W.; Chang, J.H., E-mail: cyoon@kaeri.re.kr, E-mail: sdhong1@kaeri.re.kr, E-mail: jmnoh@kaeri.re.kr, E-mail: ywkim@kaeri.re.kr, E-mail: jhchang@kaeri.re.kr [Korea Atomic Energy Research Inst., Daejeon (Korea, Republic of)
2011-07-01
A medium-scale helium loop for simulating a VHTR (Very High Temperature Reactor) is now under construction in KAERI (Korea Atomic Energy Research Institute). Two electric heaters of the test helium loop heat the helium fluid up to 950°C at a pressure of 1 ~ 9MPa. To optimize the design specifications of the experimental helium loop, conjugate heat transfer in the high-temperature helium heater was analyzed by using CFD (Computational Fluid Dynamics) simulation. The main factors tested in this CFD analysis were the effects of turbulence, radiation, gravity, and geometrical configuration of the heater. From the analysis results, the optimum design configuration was selected confirming that thermal characteristics of the heater well meet the design requirements. In this study, the interrelated effects of buoyancy forces and radiation heat transfer on the geometrical configuration were closely investigated. It was concluded that the buoyancy effects on the helium flows of the heater would be suppressed by the radiation heat transfer inside the heating channel. Various emissivity values of the reflector material emissivity were also tested. Gravity had greater effects on the temperature distribution for the lower emissivity, but the maximum temperature variations due to the emissivity changes from 0.1 to 0.9 were limited to within a few tens of degrees. Finally, more detailed analyses on the HTH of the medium scale helium loop including the spacers were performed and it is confirmed that the thermal-fluidic characteristics of the HTH satisfied the design requirements. (author)
CFD simulations of a turbulent flow in a T-junction
International Nuclear Information System (INIS)
Very careful T-junction tests are being performed at the Vattenfall Alkarleby Laboratory. Data from a recent test were used as the basis of an OECD/NEA blind benchmark exercise. JNES participated in this blind benchmark exercise. The present T-junction CFD simulation was performed as an incompressible fluid flow and buoyant effect was estimated by using the Boussinesq approximation. Four hexahedral grids (0.25M, 1M, 4M and 16M) were generated for grid size sensitivity study. The Large Eddy Simulation (LES) and the Reynolds Averaged Navier Stokes (RANS) turbulent models were used for a model sensitivity study. All calculation results of LES were closer to the experimental data than those of RANS. (author)
Experimental studies and CFD calculations for buoyancy driven mixing phenomena
Energy Technology Data Exchange (ETDEWEB)
Silva, Marco Jose da, E-mail: M.dasilva@fzd.d [Institute of Safety Research, Forschungszentrum Dresden-Rossendorf e.V., Dresden (Germany); Thiele, Sebastian; Hoehne, Thomas; Vaibar, Roman; Hampel, Uwe [Institute of Safety Research, Forschungszentrum Dresden-Rossendorf e.V., Dresden (Germany)
2010-09-15
In nuclear reactor safety the mixing of borated and deborated water is a critical issue that needs investigation, assessment and prediction. Such mixing is buoyancy driven and numerical codes must correctly model momentum transfer between fluids of different density. To assess and develop CFD models for buoyancy driven mixing we set up a simple vertical mixing test facility (VeMix) and equipped it with a newly developed planar electrical imaging sensor. This imaging sensor acquires conductivity images of the liquid at the rear channel wall with a speed of 2,500 frames/s. By adding NaCl tracer to the denser fluid we were able to visualize the mixing process in high spatial and temporal detail. Furthermore, an image processing algorithm based on the optical flow concept was implemented and tested which allows the measurement of flow pattern velocities. Selected experiments at different Richardson numbers were run with two components of different density (pure water and glucose-water mixture) simulating borated and deborated water in a light water reactor scenario. These experiments were compared to CFD calculations using standard turbulence models. Good agreement between experimental data and CFD simulations was found.
Energy Technology Data Exchange (ETDEWEB)
Karl, C. [MAN Nutzfahrzeuge AG, Muenchen (Germany). Abt. TVGF - Technik, Vorentwicklung, Grundlagen, Fahrdynamik-Simulation; Feldhaus, U.
2008-02-15
The field thermal management, the optimization of the heat balance in vehicles, is an essential factor to reduce fuel consumption and emissions. Like many other units in internal combustion engine R and D, computer based simulation systems are used more and more. At MAN Nutzfahrzeuge AG one developed a simulation system called FasiFlow, based on Flowmaster, to create the CFD simulation model of a cooling circuit in a truck diesel engine. By combining different calculation programs like the tool Flowmaster the system enables entire and precise simulation of hydraulic and thermal processes. (orig.)
3D CFD Simulation von Turboladern innerhalb einer Motorumgebung
Boose, Benjamin
2014-01-01
Im Rahmen dieser Forschungsarbeit wird das Verhalten mehrflutiger Abgasturbolader innerhalb einer Motorumgebung mit pulsierenden Randbedingungen in verschiedenen Motorbetriebspunkten mittels eines CFD Ansatzes untersucht. Dazu wird ein vollständiges dreidimensionales Strömungsmodell eines asymmetrischen Zwillingsstromturboladers aufgebaut, beginnend bei den Abgaskrümmern über die Turbinen- und Verdichtergehäuse inklusive der kompletten Laufräder bis hin zum Vorkatalysator. Die Eintrittsran...
Wind energy; CFD simulation of wakes and wind turbine forces
Fredriksen, Tommy
2015-01-01
Wind power is a clean and renewable energy source, which plays an important role in the world’s energy landscape. When developing a wind farm it is beneficial to analyze the flow pattern in order to maximize the total performance of the wind farm, it is also important to predict wake patterns to prevent structural damage on downstream turbines. Traditional fully detailed CFD models will be very computational heavy to utilize for such analysis. In order to perform an analysis with ...
CFD Simulation Evaluation for Flow Distribution of the Closed Chamber
Hong Bin; Wang Hongmei
2016-01-01
Taking a closed chamber flow field as object, this paper establishes the 3D model of the Closed Chamber. With the conclusion of flow distribution and gasoline vapor concentration distribution of the Closed Chamber reached via the CFD software of Fluent and experiment research, this paper analyzes the flow distribution and concentration distribution of gasoline vapor. Several improvement projects are proposed, such as improving the wind circulation system to optimize the indoor gas concentrati...
CFD simulation of coal and straw co-firing
DEFF Research Database (Denmark)
Junker, Helle; Hvid, Søren L.; Larsen, Ejvind;
This paper presents the results of a major R&D program with the objective to develop CFD based tools to assess the impact of biomass co-firing in suspension fired pulverized coal power plants. The models have been developed through a series of Danish research projects with the overall objective...... emissions. Results are presented for a Danish full-scale boiler that is currently co-firing biomass with coal on a commercial basis....
Time Accurate CFD Simulations of the Orion Launch Abort Vehicle in the Transonic Regime
Ruf, Joseph; Rojahn, Josh
2011-01-01
Significant asymmetries in the fluid dynamics were calculated for some cases in the CFD simulations of the Orion Launch Abort Vehicle through its abort trajectories. The CFD simulations were performed steady state with symmetric boundary conditions and geometries. The trajectory points at issue were in the transonic regime, at 0 and 5 angles of attack with the Abort Motors with and without the Attitude Control Motors (ACM) firing. In some of the cases the asymmetric fluid dynamics resulted in aerodynamic side forces that were large enough that would overcome the control authority of the ACMs. MSFC s Fluid Dynamics Group supported the investigation into the cause of the flow asymmetries with time accurate CFD simulations, utilizing a hybrid RANS-LES turbulence model. The results show that the flow over the vehicle and the subsequent interaction with the AB and ACM motor plumes were unsteady. The resulting instantaneous aerodynamic forces were oscillatory with fairly large magnitudes. Time averaged aerodynamic forces were essentially symmetric.
Skřínský, Jan; Vereš, Ján; Peer, Václav; Friedel, Pavel
2016-06-01
The effect of initial concentration on the explosion behavior of a stoichiometric CH4/O2/N2 mixture under air-combustion conditions was studied. Two mathematical models were used with the aim at simulating the gas explosion in the middle scale explosion vessel, and the associated effects of the temperature for different gas/air concentrations. Peak pressure, maximum rate of pressure rise and laminar burning velocity were measured from pressure time records of explosions occurring in a 1 m3 closed cylindrical vessel. The results of the models were validated considering a set of data (pressure time histories and root mean square velocity). The obtained results are relevant to the practice of gas explosion testing and the interpretation of test results and, they should be taken as the input data for CFD simulation to improve the conditions for standard tests.
3D Transient CFD Simulation of Scroll Compressors with the Tip Seal
Gao, Haiyang; Ding, Hui; Jiang, Yu
2015-08-01
A new template simulation tool is developed for scroll compressors/expanders capable of modelling tip seal leakages. This scroll template generates a high quality 3D multiblock structured mesh from user-input stationary and orbiting scroll surfaces. The mesh movement is then automatically calculated to account for every position of the orbiting scroll, maintaining good grid quality and smooth movement throughout the whole revolution. A state- of-the-art efficient CFD solver is used to solve Navier-Stokes equations, capable of simulation with both real gas and ideal gas. A case study is presented for a generic scroll compressor with refrigerant R410A. The case was run with and without the tip seal volumes. Comparisons are made to show the impact of tip seals on the compressor performance.
West, Jeff S.; Richardson, Brian R.; Schmauch, Preston; Kenny, Robert J.
2011-01-01
Marshall Space Flight Center (MSFC) has been heavily involved in developing the J2-X engine. The Center has been testing a Work Horse Gas Generator (WHGG) to supply gas products to J2-X turbine components at realistic flight-like operating conditions. Three-dimensional time accurate CFD simulations and analytical fluid analysis have been performed to support WHGG tests at MSFC. The general purpose CFD program LOCI/Chem was utilized to simulate flow of products from the WHGG through a turbine manifold, a stationary row of turbine vanes, into a Can and orifice assembly used to control the back pressure at the turbine vane row and finally through an aspirator plate and flame bucket. Simulations showed that supersonic swirling flow downstream of the turbine imparted a much higher pressure on the Can wall than expected for a non-swirling flow. This result was verified by developing an analytical model that predicts wall pressure due to swirling flow. The CFD simulations predicted that the higher downstream pressure would cause the pressure drop across the nozzle row to be approximately half the value of the test objective. With CFD support, a redesign of the Can orifice and aspirator plate was performed. WHGG experimental results and observations compared well with pre-test and post-test CFD simulations. CFD simulations for both quasi-static and transient test conditions correctly predicted the pressure environment downstream of the turbine row and the behavior of the gas generator product plume as it exited the WHGG test article, impacted the flame bucket and interacted with the external environment.
Energy Technology Data Exchange (ETDEWEB)
Jardini, Andre L.; Bineli, Aulus R.R.; Viadana, Adriana M.; Maciel, Maria Regina Wolf; Maciel Filho, Rubens [State University of Campinas (UNICAMP), SP (Brazil). School of Chemical Engineering; Medina, Lilian C.; Gomes, Alexandre de O. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES); Barros, Ricardo S. [University Foundation Jose Bonifacio (FUJB), Rio de Janeiro, RJ (Brazil)
2008-07-01
In this paper, the design of microreactor with microfluidics channels has been carried out in Computer Aided Design Software (CAD) and constructed in rapid prototyping system to be used in chemical reaction processing of the heavy oil fractions. The flow pattern properties of microreactor (fluid dynamics, mixing behavior) have been considered through CFD (computational fluid dynamics) simulations. CFD calculations are also used to study the design and specification of new microreactor developments. The potential advantages of using a microreactor include better control of reaction conditions, improved safety and portability. A more detailed crude assay of the raw national oil, whose importance was evidenced by PETROBRAS/CENPES allows establishing the optimum strategies and processing conditions, aiming at a maximum utilization of the heavy oil fractions, towards valuable products. These residues are able to be processed in microreactor, in which conventional process like as hydrotreating, catalytic and thermal cracking may be carried out in a much more intensified fashion. The whole process development involves a prior thermal study to define the possible operating conditions for a particular task, the microreactor design through computational fluid dynamics and construction using rapid prototyping. This gives high flexibility for process development, shorter time, and costumer/task oriented process/product development. (author)
CFD simulation of aerosol deposition in an anatomically based human large-medium airway model.
Ma, Baoshun; Lutchen, Kenneth R
2009-02-01
Quantitative data on aerosol deposition in the human respiratory tract are useful for understanding the causes of certain lung diseases and for designing efficient drug delivery systems via inhalation. In this study, aerosol deposition in a 3D anatomically based human large-medium airway model was simulated using computational fluid dynamics (CFD). The model extended from mouth to generation 10 and included two-thirds of the airways obtained by multi-detector row computed tomography (MDCT) imaging on normal healthy human subjects. Steady oral inhalation (15, 30, and 60 L/min) and aerosol (1-30 micrometer) deposition were computed by CFD using the realizable k-epsilon turbulence model. Based on the mean turbulence flow field, the computed extrathoracic deposition, ratio of left to right lung deposition, and deposition efficiency at each generation compared favorably with existing in vivo and in vitro experiments. The significant deposition in the large-medium airway model showed that the total tracheobronchial deposition is dominated by the large-medium airways for micrometer-sized aerosol particles. These quantitative data and the methods developed in this study provided valuable means toward subject-specific modeling of aerosol deposition in the human lung based on realistic lung geometry. PMID:19082892
Simulation of Rotary-Wing Near-Wake Vortex Structures Using Navier-Stokes CFD Methods
Kenwright, David; Strawn, Roger; Ahmad, Jasim; Duque, Earl; Warmbrodt, William (Technical Monitor)
1997-01-01
This paper will use high-resolution Navier-Stokes computational fluid dynamics (CFD) simulations to model the near-wake vortex roll-up behind rotor blades. The locations and strengths of the trailing vortices will be determined from newly-developed visualization and analysis software tools applied to the CFD solutions. Computational results for rotor nearwake vortices will be used to study the near-wake vortex roll up for highly-twisted tiltrotor blades. These rotor blades typically have combinations of positive and negative spanwise loading and complex vortex wake interactions. Results of the computational studies will be compared to vortex-lattice wake models that are frequently used in rotorcraft comprehensive codes. Information from these comparisons will be used to improve the rotor wake models in the Tilt-Rotor Acoustic Code (TRAC) portion of NASA's Short Haul Civil Transport program (SHCT). Accurate modeling of the rotor wake is an important part of this program and crucial to the successful design of future civil tiltrotor aircraft. The rotor wake system plays an important role in blade-vortex interaction noise, a major problem for all rotorcraft including tiltrotors.
Study of interactions between sediment particles in sheet flow using CFD-DEM
Sun, Rui; Xiao, Heng
2015-11-01
CFD-DEM simulation is a promising approach in the study of sediment transport. However, the study of sediment transport in sheet flow is still lacking. In this work, a parallelized CFD-DEM solver sediFoam, which has been extensively validated, is applied to the study of sediment transport. Numerical simulations of sediment bed of different characteristics under various waves are studied and compared with the results obtained in the literature, including sediment transport flux, solid volume fraction, and movable bed height. The micro-structures (e.g., contact network) and macroscopic solid phase stresses of the sediment bed are analyzed to gain insight into the inter-particle interactions during the transport process. Additionally, the microstructural properties and solid phase stresses in wave-induced sheet flow are compared to those obtained in unidirectional currents, and significant difference is observed.
Directory of Open Access Journals (Sweden)
Mimoun Maurice
2011-03-01
Full Text Available Abstract Background Controlling airborne contamination is of major importance in burn units because of the high susceptibility of burned patients to infections and the unique environmental conditions that can accentuate the infection risk. In particular the required elevated temperatures in the patient room can create thermal convection flows which can transport airborne contaminates throughout the unit. In order to estimate this risk and optimize the design of an intensive care room intended to host severely burned patients, we have relied on a computational fluid dynamic methodology (CFD. Methods The study was carried out in 4 steps: i patient room design, ii CFD simulations of patient room design to model air flows throughout the patient room, adjacent anterooms and the corridor, iii construction of a prototype room and subsequent experimental studies to characterize its performance iv qualitative comparison of the tendencies between CFD prediction and experimental results. The Electricité De France (EDF open-source software Code_Saturne® (http://www.code-saturne.org was used and CFD simulations were conducted with an hexahedral mesh containing about 300 000 computational cells. The computational domain included the treatment room and two anterooms including equipment, staff and patient. Experiments with inert aerosol particles followed by time-resolved particle counting were conducted in the prototype room for comparison with the CFD observations. Results We found that thermal convection can create contaminated zones near the ceiling of the room, which can subsequently lead to contaminate transfer in adjacent rooms. Experimental confirmation of these phenomena agreed well with CFD predictions and showed that particles greater than one micron (i.e. bacterial or fungal spore sizes can be influenced by these thermally induced flows. When the temperature difference between rooms was 7°C, a significant contamination transfer was observed to
Estimation of Chromatographic Columns Performances using Computer Tomography and CFD Simulations
DEFF Research Database (Denmark)
Schmidt, Irma; Lottes, Florian; Minceva, Mirjana;
2011-01-01
show, that spherical particles seem to be more efficient than irregular ones in terms of HETP, which has to be partly a result of the more homogeneous flow profile they induce. The prediction of column performance in dependence of the structure of the packed bed was simulated by CFD (Computational...... Fluid Dynamics), using a model which besides the hydrodynamics parameters attained by CT also includes adsorption isotherms and mass transfer parameters. The results of the CFD simulation shall help to establish rules for selecting the right adsorption material for a given separation task in advance....
Numerical simulation of sloshing in rectangular tanks with OpenFOAM CFD Package
International Nuclear Information System (INIS)
The aim of this paper is to simulate the sloshing phenomenon using OpenFOAM CFD software package. The present paper treats a 2D numerical simulation of a partially filled tank that is located on a LNG carrier. Experiments were done on a rectangular tank excited with different excitation periods and amplitudes and the pressure was measured at certain locations on the tank walls. The goal of this research is to compare the experimental data for the pressure with the pressure results obtained with the CFD software. It is shown that the obtained results match well with the experimental data.
CFD study of turbulent jet impingement on curved surface
Institute of Scientific and Technical Information of China (English)
Javad Taghinia; Md Mizanur Rahman; Timo Siikonen
2016-01-01
The heat transfer and flow characteristics of air jet impingement on a curved surface are investigated with com-putational fluid dynamics (CFD) approach. The first applied model is a one-equation SGS model for large eddy simulation (LES) and the second one is the SST-SAS hybrid RANS-LES. These models are utilized to study the flow physics in impinging process on a curved surface for different jet-to-surface (h/B) distances at two Reynolds numbers namely, 2960 and 4740 based on the jet exit velocity (Ue) and the hydraulic diameter (2B). The predic-tions are compared with the experimental data in the literature and also the results from RANS k-εmodel. Com-parisons show that both models can produce relatively good results. However, one-equation model (OEM) produced more accurate results especial y at impingement region at lower jet-to-surface distances. In terms of heat transfer, the OEM also predicted better at different jet-to-surface spacings. It is also observed that both models show similar performance at higher h/B ratios.
The status of research on CFD-PBM simulation of liquid-liquid two-phase flow in extraction columns
International Nuclear Information System (INIS)
Computational fluid dynamics (CFD) simulation has gained more and more interest in the chemical engineering researchers and is becoming a useful tool for the chemical engineering research. The research on liquid-liquid two-phase flow CFD simulation in extraction columns is now in its initial stage. There is much work to do for the developing of this research field. The purpose of this article is to review the CFD simulation methods for two-phase flow in extraction column. The population balance model (PBM) is detailedly described in this article because it is the main method used in the two-phase flow CFD simulation currently. Then some examples for the two-phase flow simulation in extraction columns are briefly introduced. The strategy for the research on CFD simulation of two-phase flow in extraction columns is suggested at last. (authors)
CFD simulation of a burner for syngas characterization and experimental validation
Energy Technology Data Exchange (ETDEWEB)
Fantozzi, Francesco; Desideri, Umberto [University of Perugia (Italy). Dept. of Industrial Engineering], Emails: fanto@unipg.it, umberto.desideri@unipg.it; D' Amico, Michele [University of Perugia (Italy). Dept. of Energetic Engineering], E-mail: damico@crbnet.it
2009-07-01
Biomass and waste are distributed and renewable energy sources that may contribute effectively to sustainability if used on a small and micro scale. This requires the transformation through efficient technologies (gasification, pyrolysis and anaerobic digestion) into a suitable gaseous fuel to use in small internal combustion engines and gas turbines. The characterization of biomass derived syngas during combustion is therefore a key issue to improve the performance of small scale integrated plants because synthesis gas show significant differences with respect to Natural Gas (mixture of gases, low calorific value, hydrogen content, tar and particulate content) that may turn into ignition problems, combustion instabilities, difficulties in emission control and fouling. To this aim a burner for syngas combustion and LHV measurement through mass and energy balance was realized and connected to the rotary-kiln laboratory scale pyrolyzer at the Department of Industrial Engineering of the University of Perugia. A computational fluid dynamics (CFD) simulation of the burner was carried out considering the combustion of propane to investigate temperature and pressure distribution, heat transmission and distribution of the combustion products and by products. The simulation was carried out using the CFD program Star-CD. Before the simulation a geometrical model of the burner was built and the volume of model was subdivided in cells. A sensibility analysis of cells was carried out to estimate the approximation degree of the model. Experimental data about combustion emission were carried out with the propane combustion in the burner, the comparison between numerical results and experimental data was studied to validate the simulation for future works involved with the combustion of treated or raw (syngas with tar) syngas obtained from pyrolysis process. (author)
Ma, Baoshun; Ruwet, Vincent; Corieri, Patricia; Theunissen, Raf; Riethmuller, Michel; Darquenne, Chantal
2009-05-01
Accurate modeling of air flow and aerosol transport in the alveolated airways is essential for quantitative predictions of pulmonary aerosol deposition. However, experimental validation of such modeling studies has been scarce. The objective of this study is to validate CFD predictions of flow field and particle trajectory with experiments within a scaled-up model of alveolated airways. Steady flow (Re = 0.13) of silicone oil was captured by particle image velocimetry (PIV), and the trajectories of 0.5 mm and 1.2 mm spherical iron beads (representing 0.7 to 14.6 mum aerosol in vivo) were obtained by particle tracking velocimetry (PTV). At twelve selected cross sections, the velocity profiles obtained by CFD matched well with those by PIV (within 1.7% on average). The CFD predicted trajectories also matched well with PTV experiments. These results showed that air flow and aerosol transport in models of human alveolated airways can be simulated by CFD techniques with reasonable accuracy. PMID:20161301
Investigation on the Use of a Multiphase Eulerian CFD solver to simulate breaking waves
DEFF Research Database (Denmark)
Tomaselli, Pietro D.; Christensen, Erik Damgaard
2015-01-01
The main challenge in CFD multiphase simulations of breaking waves is the wide range of interfacial length scales occurring in the flow: from the free surface measurable in meters down to the entrapped air bubbles with size of a fraction of a millimeter. This paper presents a preliminary...... investigation on a CFD model capable of handling this problem. The model is based on a solver, available in the open-source CFD toolkit OpenFOAM, which combines the Eulerian multi-fluid approach for dispersed flows with a numerical interface sharpening method. The solver, enhanced with additional formulations...... for mass and momentum transfer among phases, was satisfactorily tested against an experimental bubble column flow. The model was then used to simulate the propagation of a laboratory solitary breaking wave. The motion of the free surface was successfully reproduced up to the breaking point. Further...
Institute of Scientific and Technical Information of China (English)
Jing YANG; Li WANG; Huazhi LI
2001-01-01
CFD has penetrated into the field of electronic cooling for some time. Both parallel and staggered plate fin heatsinks are widely used in modern computers. This paper presents the ways to make most use of CFD in optimization design of those heatsinks: the flow and heat transfer of staggered and parallel plate fm heatsinks of various geometry were simulated by using Fluent 5.0 commercial CFD code. Based on 60 different simulation solutions, two correlations, concerning Nusselt number and friction factor as the functions of geometrical and operational parameters of the heatsinks were developed. The presentation parameter examination was also performed by comparing the numerical solutions with the analytical solutions of parallel plate arrays, showing that the correct parameters are used in the correlations.
Transient CFD simulation of a Francis turbine startup
Nicolle, J.; Morissette, J. F.; Giroux, A. M.
2012-11-01
To assess the life expectancy of hydraulic turbines, it is essential to obtain the loading on the blades, especially during transient operations known to be the most damaging. This paper presents a simplified CFD setup to model the startup phase of a Francis turbine while it goes from rest to speed no-load condition. The fluid domain included one distributor sector coupled with one runner passage. The guide vane motion and change in the angular velocity were included in a commercial code with user functions. Comparisons between numerical results and measurements acquired on a full-size turbine showed that most of the flow physics occurring during startup were captured.
Development of hydraulic tanks by multi-phase CFD simulation
Vollmer, Thees; Frerichs, Ludger
2016-01-01
Hydraulic tanks have a variety of different tasks. The have to store the volume of oil needed for asymmetric actors in the system as well as to supply the system with preconditioned oil. This includes the deaeration as air contamination is affecting the overall system performance. The separation of the air in the tank is being realized mainly by passive methods, improving the guidance of the air and oil flow. The use of CFD models to improve the design of hydraulic tank is recently often disc...
CFD simulation of an offshore air intake and exhaust system
Sirevaag, Ola
2015-01-01
The main purpose is to investigate whether the exhaust gases from an offshore turbine can be rerouted to heat the air entering the turbine system, thus keeping air humidity concentration above acceptable levels. To ensure this, temperature of the incoming airflow must be above 4,5 degrees Celsius. Currently the exhaust is vented out to the atmosphere and an electrical anti-icing system is used to heat the air intake. The objective of this thesis is therefore to make a CFD model in OpenFOAM to...
AP-IO: Asynchronous Pipeline I/O for Hiding Periodic Output Cost in CFD Simulation
Directory of Open Access Journals (Sweden)
Ren Xiaoguang
2014-01-01
Full Text Available Computational fluid dynamics (CFD simulation often needs to periodically output intermediate results to files in the form of snapshots for visualization or restart, which seriously impacts the performance. In this paper, we present asynchronous pipeline I/O (AP-IO optimization scheme for the periodically snapshot output on the basis of asynchronous I/O and CFD application characteristics. In AP-IO, dedicated background I/O processes or threads are in charge of handling the file write in pipeline mode, therefore the write overhead can be hidden with more calculation than classic asynchronous I/O. We design the framework of AP-IO and implement it in OpenFOAM, providing CFD users with a user-friendly interface. Experimental results on the Tianhe-2 supercomputer demonstrate that AP-IO can achieve a good optimization effect for the periodical snapshot output in CFD application, and the effect is especially better for massively parallel CFD simulations, which can reduce the total execution time up to about 40%.
AP-IO: asynchronous pipeline I/O for hiding periodic output cost in CFD simulation.
Xiaoguang, Ren; Xinhai, Xu
2014-01-01
Computational fluid dynamics (CFD) simulation often needs to periodically output intermediate results to files in the form of snapshots for visualization or restart, which seriously impacts the performance. In this paper, we present asynchronous pipeline I/O (AP-IO) optimization scheme for the periodically snapshot output on the basis of asynchronous I/O and CFD application characteristics. In AP-IO, dedicated background I/O processes or threads are in charge of handling the file write in pipeline mode, therefore the write overhead can be hidden with more calculation than classic asynchronous I/O. We design the framework of AP-IO and implement it in OpenFOAM, providing CFD users with a user-friendly interface. Experimental results on the Tianhe-2 supercomputer demonstrate that AP-IO can achieve a good optimization effect for the periodical snapshot output in CFD application, and the effect is especially better for massively parallel CFD simulations, which can reduce the total execution time up to about 40%. PMID:24955390
Heat transfer capability of a thermosyphon heat transport device with experimental and CFD studies
International Nuclear Information System (INIS)
Advanced nuclear reactor designs envisage use of passive means of heat transfer during normal operation and accidental conditions. Thermosyphon device is a passive device that can be used for heat exchange applications where heat source and heat sink are separated by some distance. Thermosyphon device operates on natural circulation principle in which the flow is driven by thermally generated density gradients without use of pumps. This paper deals with studies on thermal hydraulic behaviour of a thermosyphon device. Experiments are performed in the thermosyphon device using water as working fluid. CFD simulations with FLUENT are also carried out to simulate experimental conditions. The results obtained from CFD studies are compared with experimental data. (author)
System Identification Applied to Dynamic CFD Simulation and Wind Tunnel Data
Murphy, Patrick C.; Klein, Vladislav; Frink, Neal T.; Vicroy, Dan D.
2011-01-01
Demanding aerodynamic modeling requirements for military and civilian aircraft have provided impetus for researchers to improve computational and experimental techniques. Model validation is a key component for these research endeavors so this study is an initial effort to extend conventional time history comparisons by comparing model parameter estimates and their standard errors using system identification methods. An aerodynamic model of an aircraft performing one-degree-of-freedom roll oscillatory motion about its body axes is developed. The model includes linear aerodynamics and deficiency function parameters characterizing an unsteady effect. For estimation of unknown parameters two techniques, harmonic analysis and two-step linear regression, were applied to roll-oscillatory wind tunnel data and to computational fluid dynamics (CFD) simulated data. The model used for this study is a highly swept wing unmanned aerial combat vehicle. Differences in response prediction, parameters estimates, and standard errors are compared and discussed
A CFD Validation of Fire Dynamics Simulator for Corner Fire
Directory of Open Access Journals (Sweden)
Pavan K. Sharma
2010-12-01
Full Text Available A computational study has been carried out for predicting the behaviour of a corner fire source for a reported experiment using a field model based code Fire Dynamics Simulator (FDS. Time dependent temperature is predicted along with the resulting changes in the plume structure. The flux falling on the wall was also observed. The analysis has been carried out with the correct value of the grid size based on earlier experiences and also by performing a grid sensitivity study. The predicted temperatures of the two scenarios at two points by the current analysis are in very good agreement with the earlier reported experimental data and numerical prediction. The studies have extended the utility of field model based tools to model the particular separate effect phenomenon like corner for one such situation and validate against experimental data. The present study have several applications in such as room fires, hydrogen transport in nuclear reactor containment, natural convection in building flows etc. The present approach uses the advanced Large Eddy Simulation (LES based CFD turbulence model. The paper presents brief description of the code FDS, details of the computational model along with the discussions on the results obtained under these studies. The validated CFD based procedure has been used for solving various problems enclosure fire, ventilated fire and open fire from nuclear industry which are however not included in the present paper.
CFD Simulation Of Air-Flow Over A „Quarter-Circular” Object Valided By Experimental Measurement
Directory of Open Access Journals (Sweden)
Králik Juraj
2015-12-01
Full Text Available A Computer-Fluid-Dynamic (CFD simulation of air-flow around quarter-circular object using commercial software ANSYS Fluent was used to study iteration of building to air-flow. Several, well know transient turbulence models were used and results were compared to experimental measurement of this object in Boundary Layer Wind Tunnel (BLWT of Slovak University of Technology (SUT in Bratislava. Main focus of this article is to compare pressure values from CFD in three different elevations, which were obtained from experimental measurement. Polyhedral mesh type was used in the simulation. Best results on the windward face elevations were obtained using LES turbulence model, where the averaged difference was around 7.71 %. On the leeward face elevations it was SAS turbulence model and averaged differences from was 15.91 %. On the circular face it was SAS turbulence model and averaged differences from all elevations was 12.93 %.
Computational Fluid Dynamics (CFD) Simulations of Jet Mixing in Tanks of Different Scales
Breisacher, Kevin; Moder, Jeffrey
2010-01-01
For long-duration in-space storage of cryogenic propellants, an axial jet mixer is one concept for controlling tank pressure and reducing thermal stratification. Extensive ground-test data from the 1960s to the present exist for tank diameters of 10 ft or less. The design of axial jet mixers for tanks on the order of 30 ft diameter, such as those planned for the Ares V Earth Departure Stage (EDS) LH2 tank, will require scaling of available experimental data from much smaller tanks, as well designing for microgravity effects. This study will assess the ability for Computational Fluid Dynamics (CFD) to handle a change of scale of this magnitude by performing simulations of existing ground-based axial jet mixing experiments at two tank sizes differing by a factor of ten. Simulations of several axial jet configurations for an Ares V scale EDS LH2 tank during low Earth orbit (LEO) coast are evaluated and selected results are also presented. Data from jet mixing experiments performed in the 1960s by General Dynamics with water at two tank sizes (1 and 10 ft diameter) are used to evaluate CFD accuracy. Jet nozzle diameters ranged from 0.032 to 0.25 in. for the 1 ft diameter tank experiments and from 0.625 to 0.875 in. for the 10 ft diameter tank experiments. Thermally stratified layers were created in both tanks prior to turning on the jet mixer. Jet mixer efficiency was determined by monitoring the temperatures on thermocouple rakes in the tanks to time when the stratified layer was mixed out. Dye was frequently injected into the stratified tank and its penetration recorded. There were no velocities or turbulence quantities available in the experimental data. A commercially available, time accurate, multi-dimensional CFD code with free surface tracking (FLOW-3D from Flow Science, Inc.) is used for the simulations presented. Comparisons are made between computed temperatures at various axial locations in the tank at different times and those observed experimentally. The
Simulation of flow around bluff bodies and bridge deck sections using CFD
Liaw, Kai
2005-01-01
This thesis focuses on the simulation of flow around bluff bodies and bridge deck sections, in which unsteady nature and vortex shedding of flow are commonly found, using computational fluid dynamics (CFD). Various turbulence models have been tested to develop understanding and proper modelling techniques for the flow around such bodies. Throughout the thesis, the turbulence models employed, mainly large eddy simulation (LES) and detached eddy simulation (DES), have been validated through...
CFD Studies on Multi Lead Rifled [MLR] Boiler Tubes
Dr T C Mohankumar
2013-01-01
This paper reports the merits of multi lead rifled [MLR] tubes in vertical water tube boiler using CFD tool. Heat transfer enhancement of MLR tubes was mainly taken in to consideration. Performance of multi lead rifled tube was studied by varying its influencing geometrical parameter like number of rifling, height of rifling, length of pitch of rifling for a particular length. The heat transfer analysis was done at operating conditions of an actual coal fired water tube boiler situated at Apo...
Groves, Curtis E.; LLie, Marcel; Shallhorn, Paul A.
2012-01-01
There are inherent uncertainties and errors associated with using Computational Fluid Dynamics (CFD) to predict the flow field and there is no standard method for evaluating uncertainty in the CFD community. This paper describes an approach to -validate the . uncertainty in using CFD. The method will use the state of the art uncertainty analysis applying different turbulence niodels and draw conclusions on which models provide the least uncertainty and which models most accurately predict the flow of a backward facing step.
Using CFD as a support tool for the initial study of Hydraulic Turbomachinery
Directory of Open Access Journals (Sweden)
José Luis Vicéns
2014-03-01
Full Text Available The Engineering Education requires that students acquire an appropriate knowledge on a mathematical computational language as well as on a numerical simulation procedure. The computational language of mathematics usually is taught in advanced courses, once that the curriculum mathematical education is mainly completed; in addition, the numerical simulation is usually located late or even in doctoral studies. In this paper, we propose that the Computational Fluid Dynamics (CFD become to be a teaching-learning tool, instead of a strategic resource only. CFD can be regarded as a transversal skill i.e., as a useful educational tool for the Hydraulic Turbomachines learning, which achieves to overcome some epistemological obstacles of students. We develop a teaching-learning method in which the Tutor Facilitator plays an important role.
Kochevsky, A N
2005-01-01
The paper describes capabilities of numerical simulation of liquid flows with solid and/or gas admixtures in centrifugal pumps using modern commercial CFD software packages, with the purpose to predict performance curves of the pumps treating such media. In particular, the approaches and multiphase flow models available in the package CFX-5 are described; their advantages and disadvantages are analyzed.
Directory of Open Access Journals (Sweden)
P.MANOJ KUMAR,
2011-05-01
Full Text Available In direct injection (DI diesel engines the Analysis of fuel spray with various injection orientations has high influence on engine performance as well as exhaust gas emissions. The fuel injector orientation plays very important role in fuel air mixing. A single cylinder four stroke DI diesel engine with fuel injector havingmulti-hole nozzle injector is considered for the analysis and a computational fluid dynamics (CFD code, STAR-CD is used for the simulation. In the present study, various injector orientations are considered for the analysis. In-cylinder fuel spray is discussed through the 3D fuel spray distribution plots 950 ,1000 and 1100orientation are considered for the analysis. It is concluded that there is an optimal spray orientation angle for the fuel spray for multi hole injector.
CFD simulation of mechanical draft tube mixing in anaerobic digester tanks.
Meroney, Robert N; Colorado, P E
2009-03-01
Computational Fluid Dynamics (CFD) was used to simulate the mixing characteristics of four different circular anaerobic digester tanks (diameters of 13.7, 21.3, 30.5, and 33.5m) equipped with single and multiple draft impeller tube mixers. Rates of mixing of step and slug injection of tracers were calculated from which digester volume turnover time (DVTT), mixture diffusion time (MDT), and hydraulic retention time (HRT) could be calculated. Washout characteristics were compared to analytic formulae to estimate any presence of partial mixing, dead volume, short-circuiting, or piston flow. CFD satisfactorily predicted performance of both model and full-scale circular tank configurations. PMID:19135698
CFD-Simulation zur Untersuchung des Strömungsverhaltens in Strukturrohren
Hellwig, Udo; Nikolaus, Hartwig
2004-01-01
Die CFD (Computational Fluid Dynamics)-Simulation hat mittlerweile in alle technischen Bereiche Einzug gehalten, in denen die Vorhersage strömungstechnischer Ereignisse relevant ist. Nach wie vor ist allerdings eine Validierung von Rechenergebnissen mit Messdaten unerlässlich, um zu vertrauenswürdigen Simulationsergebnissen zu kommen. Dies ist u. a. darauf zurückzuführen, dass die am Markt verfügbare CFD-Software darauf ausgerichtet ist, ein möglichst breites Anwendungsspektrum zu bedienen. D...
CFD simulation of liquid-liquid dispersions in a stirred tank bioreactor
Gelves, R.
2013-10-01
In this paper simulations were developed in order to allow the examinations of drop sizes in liquid-liquid dispersions (oil-water) in a stirred tank bioreactor using CFD simulations (Computational Fluid Dynamics). The effects of turbulence, rotating flow, drop breakage were simulated by using the k-e, MRF (Multiple Reference Frame) and PBM (Population Balance Model), respectively. The numerical results from different operational conditions are compared with experimental data obtained from an endoscope technique and good agreement is achieved. Motivated by these simulated and experimental results CFD simulations are qualified as a very promising tool for predicting hydrodynamics and drop sizes especially useful for liquid-liquid applications which are characterized by the challenging problem of emulsion stability due to undesired drop sizes.
Simulation of Wind Farms in Flat & Complex terrain using CFD
DEFF Research Database (Denmark)
Prospathopoulos, John; Cabezon, D.; Politis, E.S.;
2010-01-01
Use of computational fluid dynamic (CFD) methods to predict the power production from wind entire wind farms in flat and complex terrain is presented in this paper. Two full 3D Navier–Stokes solvers for incompressible flow are employed that incorporate the k–ε and k–ω turbulence models respectively...... also tested. This method features the advantage of not utilizing the wind speed at a specific distance from the rotor disk, which is a doubtful approximation when a W/T is located in the wake of another and/or the terrain is complex. To account for the underestimation of the near wake deficit, a....... The wind turbines (W/Ts) are modelled as momentum absorbers by means of their thrust coefficient using the actuator disk approach. The WT thrust is estimated using the wind speed one diameter upstream of the rotor at hub height. An alternative method that employs an induction-factor based concept is...
CFD Simulation Evaluation for Flow Distribution of the Closed Chamber
Directory of Open Access Journals (Sweden)
Hong Bin
2016-01-01
Full Text Available Taking a closed chamber flow field as object, this paper establishes the 3D model of the Closed Chamber. With the conclusion of flow distribution and gasoline vapor concentration distribution of the Closed Chamber reached via the CFD software of Fluent and experiment research, this paper analyzes the flow distribution and concentration distribution of gasoline vapor. Several improvement projects are proposed, such as improving the wind circulation system to optimize the indoor gas concentration. By improving the structure of wind circulation system, it makes flow distribution more reasonable and significantly improves the uniformity of indoor gas concentration. Through implementation of this improvement, the reliability and performance of the containment chamber obviously program to improve.
CFD simulation of shear-induced aggregation and breakage in turbulent Taylor-Couette flow.
Wang, Liguang; Vigil, R Dennis; Fox, Rodney O
2005-05-01
An experimental and computational investigation of the effects of local fluid shear rate on the aggregation and breakage of approximately 10 microm latex spheres suspended in an aqueous solution undergoing turbulent Taylor-Couette flow was carried out. First, computational fluid dynamics (CFD) simulations were performed and the flow field predictions were validated with data from particle image velocimetry experiments. Subsequently, the quadrature method of moments (QMOM) was implemented into the CFD code to obtain predictions for mean particle size that account for the effects of local shear rate on the aggregation and breakage. These predictions were then compared with experimental data for latex sphere aggregates (using an in situ optical imaging method). Excellent agreement between the CFD-QMOM and experimental results was observed for two Reynolds numbers in the turbulent-flow regime. PMID:15797411
Hristov, Y.; Oxley, G.; Žagar, M.
2014-06-01
The Bolund measurement campaign, performed by Danish Technical University (DTU) Wind Energy Department (also known as RISØ), provided significant insight into wind flow modeling over complex terrain. In the blind comparison study several modelling solutions were submitted with the vast majority being steady-state Computational Fluid Dynamics (CFD) approaches with two equation k-epsilon turbulence closure. This approach yielded the most accurate results, and was identified as the state-of-the-art tool for wind turbine generator (WTG) micro-siting. Based on the findings from Bolund, further comparison between CFD and field measurement data has been deemed essential in order to improve simulation accuracy for turbine load and long-term Annual Energy Production (AEP) estimations. Vestas Wind Systems A/S is a major WTG original equipment manufacturer (OEM) with an installed base of over 60GW in over 70 countries accounting for 19% of the global installed base. The Vestas Performance and Diagnostic Centre (VPDC) provides online live data to more than 47GW of these turbines allowing a comprehensive comparison between modelled and real-world energy production data. In previous studies, multiple sites have been simulated with a steady neutral CFD formulation for the atmospheric surface layer (ASL), and wind resource (RSF) files have been generated as a base for long-term AEP predictions showing significant improvement over predictions performed with the industry standard linear WAsP tool. In this study, further improvements to the wind resource file generation with CFD are examined using an unsteady diurnal cycle approach with a full atmospheric boundary layer (ABL) formulation, with the unique stratifications throughout the cycle weighted according to mesoscale simulated sectorwise stability frequencies.
International Nuclear Information System (INIS)
The Bolund measurement campaign, performed by Danish Technical University (DTU) Wind Energy Department (also known as RISØ), provided significant insight into wind flow modeling over complex terrain. In the blind comparison study several modelling solutions were submitted with the vast majority being steady-state Computational Fluid Dynamics (CFD) approaches with two equation k-ε turbulence closure. This approach yielded the most accurate results, and was identified as the state-of-the-art tool for wind turbine generator (WTG) micro-siting. Based on the findings from Bolund, further comparison between CFD and field measurement data has been deemed essential in order to improve simulation accuracy for turbine load and long-term Annual Energy Production (AEP) estimations. Vestas Wind Systems A/S is a major WTG original equipment manufacturer (OEM) with an installed base of over 60GW in over 70 countries accounting for 19% of the global installed base. The Vestas Performance and Diagnostic Centre (VPDC) provides online live data to more than 47GW of these turbines allowing a comprehensive comparison between modelled and real-world energy production data. In previous studies, multiple sites have been simulated with a steady neutral CFD formulation for the atmospheric surface layer (ASL), and wind resource (RSF) files have been generated as a base for long-term AEP predictions showing significant improvement over predictions performed with the industry standard linear WAsP tool. In this study, further improvements to the wind resource file generation with CFD are examined using an unsteady diurnal cycle approach with a full atmospheric boundary layer (ABL) formulation, with the unique stratifications throughout the cycle weighted according to mesoscale simulated sectorwise stability frequencies
Flow mixing inside a control-rod guide tube – Experimental tests and CFD simulations
International Nuclear Information System (INIS)
This paper covers a combined experimental and computational effort carried out at Vattenfall Research and Development AB in order to study the thermal mixing in the annular region between a top tube and a control-rod stem. The low frequency thermal fluctuations in this region can result in problems with thermal fatigue and have caused cracks in the control-rod stems of several nuclear reactors (). The flow in the vertical annular region formed by the top tube and the control-rod stem is characterized by the mixing of hot bypass flow with cold crud-removal flow. The crud-removal flow is flowing upwards along the control-rod stem, and the warmer bypass flow is entering through eight horizontal holes positioned in the lower part of the guide tube and four holes in the upper part of the top tube, forming jets. Two full-scale models of a control rod, including the control-rod stem and the guide tube, were constructed. The first model, designed to work at atmospheric conditions, was made of Plexiglass, in order to be able to visualize the mixing process, whereas the second one was made of steel to allow for a higher temperature difference between the two flows, and the heating of the top tube. CFD simulations of the case at atmospheric conditions were also carried out. Both the experiments and the simulations showed that the mixing region between the cold crud-removal flow and the warm bypass flow is dominated by large flow structures coming from above. The process is characterized by low frequency, high amplitude temperature fluctuations. The process is basically hydrodynamic, caused by the downward transport of flow structures originated at the upper bypass inlets. The damping thermal effects through buoyancy is of secondary importance, as also the scaling analysis shows, however a slight damping of the temperature fluctuations can be seen due to natural convection due to a pre-heating of the cold crud-removal flow. The comparison between numerical and experimental
CFD Simulation of Airflow in the Side-Platform Stations
Directory of Open Access Journals (Sweden)
Adibi Omid
2015-01-01
Full Text Available Design of an appropriate ventilation system is one of the main concerns in the construction of subways. In this paper, thermal comforts of side-platform stations are investigated by numerical methods. For the numerical simulation, grids are generated by structured methods and governing equations are discretized by finite volume methods. In the numerical simulation, second order upwind and second order central difference scheme are used to consider the convection and diffusion terms of momentum and energy equations, respectively. Results of this study show that in term of thermal comfort, region next to the hallway and the middle part of the platform is the worst zones of the station. In these zones, air velocity is very low (less than 0.5m/s and the air temperature reaches to 34°C which is more than its limit (Tmax≤32°C.
Institute of Scientific and Technical Information of China (English)
JIANG Tao; ZHANG Yingzhao; TANG Sulin; ZHANG Daojun; ZUO Qianmei; LIN Weiren; WANG Yahui; SUN Hui; WANG Bo
2014-01-01
Turbidity currents represent a major agent for sediment transport in lakes, seas and oceans. In particu-lar, they formulate the most significant clastic accumulations in the deep sea, which become many of the world’s most important hydrocarbon reservoirs. Several boreholes in the Qiongdongnan Basin, the north-western South China Sea, have recently revealed turbidity current deposits as significant hydrocarbon res-ervoirs. However, there are some arguments for the potential provenances. To solve this problem, it is es-sential to delineate their sedimentary processes as well as to evaluate their qualities as reservoir. Numerical simulations have been developed rapidly over the last several years, offering insights into turbidity current behaviors, as geologically significant turbidity currents are difficult to directly investigate due to their large scale and often destructive nature. Combined with the interpretation of the turbidity system based on high-resolution 3D seismic data, the paleotophography is acquired via a back-stripping seismic profile integrated with a borehole, i.e., Well A, in the western Qiongdongnan Basin; then a numerical model is built on the basis of this back-stripped profile. After defining the various turbidity current initial boundary conditions, includ-ing grain size, velocity and sediment concentration, the structures and behaviors of turbidity currents are investigated via numerical simulation software ANSYS FLUENT. Finally, the simulated turbidity deposits are compared with the interpreted sedimentary bodies based on 3D seismic data and the potential provenances of the revealed turbidites by Well A are discussed in details. The simulation results indicate that a sedimen-tary body develops far away from its source with an average grain size of 0.1 mm, i.e., sand-size sediment. Taking into account the location and orientation of the simulated seismic line, the consistence between normal forward simulation results and the revealed cores
System–CFD coupled simulations of flow instability in steam generator U tubes
International Nuclear Information System (INIS)
Highlights: • System–CFD coupled simulations are performed for flow instability in SG U tubes. • Flow instability with temperature fluctuation in long U tube is simulated well. • Upward flow occurs simultaneously with downward flow in one U tube. - Abstract: The transient behavior of flow instability in SG U tubes is simulated numerically by performing system–CFD coupled simulations. The system analysis code RELAP5 is used to simulate the overall system behavior in the test facility, which consists of the heating loop and the model SG, and the commercial CFD code FLUENT is used to simulate detailed flow phenomena in the model SG. The flow conditions obtained by RELAP5 are used as the boundary conditions for FLUENT, and the calculated results by FLUENT are used for RELAP5. The flow instability with temperature fluctuation observed experimentally in the long U tube is simulated well, and the downward flow is shown to occur simultaneously with the upward flow in one U tube
Gott, Kevin
This research endeavors to better understand the physical vapor deposition (PVD) vapor transport process by determining the most appropriate fluidic model to design PVD coating manufacturing. An initial analysis was completed based on the calculation of Knudsen number from titanium vapor properties. The results show a dense Navier-Stokes solver best describes flow near the evaporative source, but the material properties suggest expansion into the chamber may result in a strong drop in density and a rarefied flow close to the substrate. A hybrid CFD-DSMC solver is constructed in OpenFOAM for rapidly rarefying flow fields such as PVD vapor transport. The models are patched together combined using a new patching methodology designed to take advantage of the one-way motion of vapor from the CFD region to the DSMC region. Particles do not return to the dense CFD region, therefore the temperature and velocity can be solved independently in each domain. This novel technique allows a hybrid method to be applied to rapidly rarefying PVD flow fields in a stable manner. Parameter studies are performed on a CFD, Navier-Stokes continuum based compressible solver, a Direct Simulation Monte Carlo (DSMC) rarefied particle solver, a collisionless free molecular solver and the hybrid CFD-DSMC solver. The radial momentum at the inlet and radial diffusion characteristics in the flow field are shown to be the most important to achieve an accurate deposition profile. The hybrid model also shows sensitivity to the shape of the CFD region and rarefied regions shows sensitivity to the Knudsen number. The models are also compared to each other and appropriate experimental data to determine which model is most likely to accurately describe PVD coating deposition processes. The Navier-Stokes solvers are expected to yield backflow across the majority of realistic inlet conditions, making their physics unrealistic for PVD flow fields. A DSMC with improved collision model may yield an accurate
CFD simulations in the nuclear containment using the DES turbulence models
Energy Technology Data Exchange (ETDEWEB)
Ding, Peng [School of Engineering, Sun Yat-Sen University, Guangzhou (China); Chen, Meilan [China Nuclear Power Technology Research Institute, Shenzhen (China); Li, Wanai, E-mail: liwai@mail.sysu.edu.cn [Sino-French Institute of Nuclear Engineering & Technology, Sun Yat-Sen University, Guangzhou (China); Liu, Yulan [School of Engineering, Sun Yat-Sen University, Guangzhou (China); Wang, Biao [Sino-French Institute of Nuclear Engineering & Technology, Sun Yat-Sen University, Guangzhou (China)
2015-06-15
Highlights: • The k-ε based DES model is used in the nuclear containment simulation. • The comparison of results between different turbulent models is obtained. • The superiority of DES models is analyzed. • The computational efficiency with the DES turbulence models is explained. - Abstract: Different species of gases would be released into the containment and cause unpredicted disasters during the nuclear severe accidents. It is important to accurately predict the transportation and stratification phenomena of these gas mixtures. CFD simulations of these thermal hydraulic issues in nuclear containment are investigated in this paper. The main work is to study the influence of turbulence model on the calculation of gas transportation and heat transfer. The k-ε based DES and other frequently used turbulence models are used in the steam and helium release simulation in THAI series experiment. This paper will show the superiority of the DES turbulence model in terms of computational efficiency and accuracy with the experimental results, and analyze the necessities of DES model to simulate the large-scale containment flows with both laminar and turbulence regions.
Design and CFD Simulation of the Drift Eliminators in Comparison with PIV Results
Stodůlka, Jiří; Vitkovičová, Rut
2015-05-01
Drift eliminators are the essential part of all modern cooling towers preventing significant losses of liquid water escaping to the enviroment. These eliminators need to be effective in terms of water capture but on the other hand causing only minimal pressure loss as well. A new type of such eliminator was designed and numerically simulated using CFD tools. Results of the simulation are compared with PIV visulisation on the prototype model.
Design and CFD Simulation of the Drift Eliminators in Comparison with PIV Results
Directory of Open Access Journals (Sweden)
Stodůlka Jiří
2015-01-01
Full Text Available Drift eliminators are the essential part of all modern cooling towers preventing significant losses of liquid water escaping to the enviroment. These eliminators need to be effective in terms of water capture but on the other hand causing only minimal pressure loss as well. A new type of such eliminator was designed and numerically simulated using CFD tools. Results of the simulation are compared with PIV visulisation on the prototype model.
Scalable Distributed Schur Complement Methods for CFD Simulation on Many-Core Architectures
Basermann, Achim; Kersken, Hans-Peter
2011-01-01
At the German Aerospace Center (DLR), the parallel simulation systems TAU and TRACE have been developed for the aerodynamic design of aircrafts or turbines for jet engines. Large-scale computing resources allow more detailed numerical investigations with bigger numerical configurations. Up to 50 million grid points in a single simulation are becoming a standard configuration in the industrial design. Both CFD solvers, TAU and TRACE, require the parallel solution of large, sparse real or compl...
Possibilities of Simulation of Fluid Flows Using the Modern CFD Software Tools
Kochevsky, A N
2004-01-01
The article reviews fluid flow models implemented in the leading CFD software tools and designed for simulation of multi-component and multi-phase flows, compressible flows, flows with heat transfer, cavitation and other phenomena. The article shows that these software tools (CFX, Fluent, STAR-CD, etc.) allow for adequate simulation of complex physical effects of different nature, even for problems where performing of physical experiment is extremely difficult.
CFD Simulation of an Anaerobic Membrane BioReactor (AnMBR) to Treat Industrial Wastewater
Laura C. Zuluaga; Luz N. Naranjo; Jan Svojitka; Thomas Wintgens; Manuel Rodriguez; Nicolas Ratkovich
2015-01-01
A Computational Fluid Dynamics (CFD) simulation has been developed for an Anaerobic Membrane BioReactor (AnMBR) to treat industrial wastewater. As the process consists of a side-stream MBR, two separate simulations were created: (i) reactor and (ii) membrane. Different cases were conducted for each one, so the surrounding temperature and the total suspended solids (TSS) concentration were checked. For the reactor, the most important aspects to consider were the dead zones and the mixing, wher...
CFD Simulation of Fish-like Body Moving in Viscous Liquid
Institute of Scientific and Technical Information of China (English)
D. Adkins; Y. Y. Yan
2006-01-01
The study of fish-like bodies moving in liquid is an interesting and challenging research subject in the fields of biolocomotion and biomimetics. Typically the effect of tail oscillation on fluid flow around such a body is highly unsteady, generating vortices and requiting detailed analysis of fluid-structure interactions. An understanding of the complexities of such flows is of interest not only to biologists but also to engineers interested in developing vehicles capable of emulating the high performance of fish propulsion and manoeuvring. In the present study, a computational fluid dynamic (CFD) simulation of a three-dimensional biomimetic fish-like body has been developed to investigate the fluid flows around this body when moving in a viscous liquid. A parametric analysis of the variables that affect the flow surrounding the body is presented, along with flow visualisations, in an attempt to quantify and qualify the effect that these variables have on the performance of the body. The analysis provided by the unsteady transient simulation of a fish-like body has allowed the flow surrounding a fish-like body undergoing periodic oscillations to be studied. The simulation produces a motion of the tail in the (x, y) plane, with the tail oscillating as a rigid body in the form of a sinusoidal wave.
Tip studies using CFD and comparison with tip loss models
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Johansen, J.
The flow past a rotating LM8.2 blade equipped with two different tips are computed using CFD. The different tip flows are analysed and a comparison with two different tip loss models is made. Keywords: tip flow, aerodynamics, CFD......The flow past a rotating LM8.2 blade equipped with two different tips are computed using CFD. The different tip flows are analysed and a comparison with two different tip loss models is made. Keywords: tip flow, aerodynamics, CFD...
CFD simulations of a deforming human lung using dynamic and static CT images
Miyawaki, Shinjiro; Hoffman, Eric A.; Lin, Ching-Long
2015-11-01
The authors have developed a CFD model to simulate airflow in deforming lungs using dynamic (4D) CT images. After obtaining the surface mesh for one CT image, we deformed the surface mesh to match other CT images using an image registration technique. During the CFD simulations, we deformed the surface mesh by cubic interpolation as a function of lung volume, and deformed the volume mesh using a computational solid mechanics-based algorithm. To investigate the effect of CT scanning method and relative hysteresis with respect to lung volume on pressure drop along the central airways, we performed CFD simulations using different numbers of 4D and static CT images of one healthy subject. Based on the simulation with 13 4DCT images, we found that air flow fractions in airways remain nearly constant over time. By comparing the simulations with 13, 2, and 1 4DCT images, we found that the overall effect of relative hysteresis of lung structure on pressure drop along each branch at peak inspiration was 12%, and the effect of deformation was 16%. As a result of the comparison between simulations with 2 and 1 of 4D and static CT images, the effect of CT scanning method was 16-39%, depending on the deformation of the lung. NIH grants R01-HL094315, U01-HL114494, R01-HL112986, and S10-RR022421. Computer time provided by XSEDE.
CFD simulation of particle entrapment of steam generator sludge collector/loose parts weir
International Nuclear Information System (INIS)
A computational fluid dynamics (CFD) study was performed to explore the performance and interaction of two components designed for Pressurized Water Reactor (PWR) recirculating steam generators: the sludge collector and the loose parts weir. The sludge collector is a passive device located in the upper internals region of a PWR steam generator. The sludge collector's function is to trap sludge, particulates suspended in the secondary side recirculating flow and minimize its deposition on the tube bundle, where it increases susceptibility to tube degradation. The loose parts weir is a separate passive device placed around the sludge collector, which is expected to act as a barrier to prevent any loose parts in the upper internals region from reaching the tube bundle. Loose parts in the steam generator, if not captured, can reach the tube bundle and cause tube wall damage. The loose parts weir is considered for installation in combination with the sludge collector for both new and existing steam generators. Previously, the configuration of the sludge collector was determined based on testing and analysis. Inclusion of the loose parts weir significantly alters the flow field of the sludge collector and thus its overall performance. The purpose of this investigation is to verify the performance of the sludge collector and loose parts weir. A CFD study was performed to evaluate the interaction between the sludge collector and a loose parts weir within the steam generator, which provides insight into the flow redistribution. Models were developed for the sludge collector with and without the loose parts weir using commercial CFD software. Results including the velocity and pressure profile in the steam generator upper internals, as well as fluid mass flow passing through the sludge collector, are presented and discussed for various configurations of the sludge collector and loose parts weir. Sludge particle collection rates are estimated using an empirical correlation
CFD simulation of anaerobic digester with variable sewage sludge rheology.
Craig, K J; Nieuwoudt, M N; Niemand, L J
2013-09-01
A computational fluid dynamics (CFD) model that evaluates mechanical mixing in a full-scale anaerobic digester was developed to investigate the influence of sewage sludge rheology on the steady-state digester performance. Mechanical mixing is provided through an impeller located in a draft tube. Use is made of the Multiple Reference Frame model to incorporate the rotating impeller. The non-Newtonian sludge is modeled using the Hershel-Bulkley law because of the yield stress present in the fluid. Water is also used as modeling fluid to illustrate the significant non-Newtonian effects of sewage sludge on mixing patterns. The variation of the sewage sludge rheology as a result of the digestion process is considered to determine its influence on both the required impeller torque and digester mixing patterns. It was found that when modeling the fluid with the Hershel-Bulkley law, the high slope of the sewage stress-strain curve at high shear rates causes significant viscous torque on the impeller surface. Although the overall fluid shear stress property is reduced during digestion, this slope is increased with sludge age, causing an increase in impeller torque for digested sludge due to the high strain rates caused by the pumping impeller. Consideration should be given to using the Bingham law to deal with high strain rates. The overall mixing flow patterns of the digested sludge do however improve slightly. PMID:23764598
CFD simulation of fuel cell proton exchange membrane multichannel
International Nuclear Information System (INIS)
Hydrogen has several applications that make the strongest candidate for implementation as an energy carrier in the future sustainable scenario. Current hydrogen production is based on fossil fuels that have a high contribution to air pollution. The imminent depletion of fossil fuels and high emissions of greenhouse gases that cause consumption has brought the world to consider energy scenarios that are more environmentally friendly and yet profitable. The use of hydrogen as an energy carrier generally occurs with good application prospects. Fuel cells have attracted great interest for its application mainly in the transport sector. The fuel cell PEM proton exchange membrane which convert chemical energy stored in hydrogen into electrical energy directly and efficiently, with water as a byproduct, have the ability to reduce emissions and dependence on fossil fuels. A model for multiple cell PEM five channels using the ANSYS software CFD occurs. Performance analysis and optimization of the thermodynamic and geometric parameters of the fuel cell is performed. It was analyzed the overall electrical performance and assessed performance by local current density, flow and temperatures. (full text)
CFD Simulation of Twin Vertical Axis Tidal Turbines System
Directory of Open Access Journals (Sweden)
Syed Shah Khalid
2013-01-01
Full Text Available As concerns about rising fossil-fuel prices, energy security and climate-change increase, renewable energy can play a vital role in producing local, clean and inexhaustible energy to supply world rising demand for electricity. In this study, hydrodynamic analysis of vertical axis tidal turbine operating side-by-side is numerically analyzed. Two-dimensional numerical modeling of the unsteady flow through the blades of the turbine is performed using ANSYS CFX, hereafter CFX; this is based on a Reynolds-Averaged Navier-Stokes (RANS model. The purpose is to find an optimal distance between the turbines where interaction effect is minimal and constructive, where the turbines operate more efficiently than stand alone turbine. A transient simulation is done on Vertical Axis Tidal Turbine (VATT using the Shear Stress Transport Turbulence (SST model. Main hydrodynamic parameters like torque T, coefficients of performance CP and coefficient of torque CT are investigated. The gap spacing between the turbines has an important role in performance improvement and also in vortex shedding suppression for the flows around two counters rotating systems. The simulation results are validated with Ye and Calisal data. The results of this study prove that the total power output of a twin-turbine system with an optimal layout can be about 24% higher than two times that of a stand-alone turbine. We conclude that the optimally configured counter-rotating twin turbines should be a side-by-side arrangement.
CFD Based Study of Heterogeneous Microclimate in a Typical Chinese Greenhouse in Central China
Institute of Scientific and Technical Information of China (English)
WANG Xiao-wei; LUO Jin-yao; LI Xiao-ping
2013-01-01
Indoor microclimate is important for crop production and quality in greenhouse cultivation. This paper focuses on microclimate study based on a computational fluid dynamics (CFD) model of a typical plastic greenhouse (with a sector shape vertical cross-section) popularly used in central China. A radiation model is added into the CFD model so as to simulate coupling of convective transfers and radiative exchanges at the cover and the roof, instead of using the usual coupling approach based on energy balance. In addition, a fractal permeability model is innovatively adopted in the modeling of the crop canopy. Compared the numerical results with measured experimental data, the model simulation is proved with success. This model then is used to explore the microclimate variable distributions in the greenhouse. It shows that the airflow pattern, temperature and humidity profiles are different from those in a sawtooth Mediterranean-type greenhouse. The study suggests that this deliberately developed CFD model can be served as a useful tool in macroclimate research and greenhouse design investigating.
Feigley, Charles E; Do, Thanh H; Khan, Jamil; Lee, Emily; Schnaufer, Nicholas D; Salzberg, Deborah C
2011-05-01
Computational fluid dynamics (CFD) is used increasingly to simulate the distribution of airborne contaminants in enclosed spaces for exposure assessment and control, but the importance of realistic boundary conditions is often not fully appreciated. In a workroom for manufacturing capacitors, full-shift samples for isoamyl acetate (IAA) were collected for 3 days at 16 locations, and velocities were measured at supply grills and at various points near the source. Then, velocity and concentration fields were simulated by 3-dimensional steady-state CFD using 295K tetrahedral cells, the k-ε turbulence model, standard wall function, and convergence criteria of 10(-6) for all scalars. Here, we demonstrate the need to represent boundary conditions accurately, especially emission characteristics at the contaminant source, and to obtain good agreement between observations and CFD results. Emission rates for each day were determined from six concentrations measured in the near field and one upwind using an IAA mass balance. The emission was initially represented as undiluted IAA vapor, but the concentrations estimated using CFD differed greatly from the measured concentrations. A second set of simulations was performed using the same IAA emission rates but a more realistic representation of the source. This yielded good agreement with measured values. Paying particular attention to the region with highest worker exposure potential-within 1.3 m of the source center-the air speed and IAA concentrations estimated by CFD were not significantly different from the measured values (P = 0.92 and P = 0.67, respectively). Thus, careful consideration of source boundary conditions greatly improved agreement with the measured values. PMID:21422277
Rodriguez, G Y; Valverde-Ramírez, M; Mendes, C E; Béttega, R; Badino, A C
2015-11-01
Global variables play a key role in evaluation of the performance of pneumatic bioreactors and provide criteria to assist in system selection and design. The purpose of this work was to use experimental data and computational fluid dynamics (CFD) simulations to determine the global performance parameters gas holdup ([Formula: see text]) and volumetric oxygen transfer coefficient (k L a), and conduct an analysis of liquid circulation velocity, for three different geometries of pneumatic bioreactors: bubble column, concentric-tube airlift, and split tube airlift. All the systems had 5 L working volumes and two Newtonian fluids of different viscosities were used in the experiments: distilled water and 10 cP glycerol solution. Considering the high oxygen demand in certain types of aerobic fermentations, the assays were carried out at high flow rates. In the present study, the performances of three pneumatic bioreactors with different geometries and operating with two different Newtonian fluids were compared. A new CFD modeling procedure was implemented, and the simulation results were compared with the experimental data. The findings indicated that the concentric-tube airlift design was the best choice in terms of both gas holdup and volumetric oxygen transfer coefficient. The CFD results for gas holdup were consistent with the experimental data, and indicated that k L a was strongly influenced by bubble diameter and shape. PMID:26227509
Energy Technology Data Exchange (ETDEWEB)
Wu, C.Y. [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsingchu 30013, 325 Taiwan (China); Ferng, Y.M., E-mail: ymferng@ess.nthu.edu.t [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsingchu 30013, 325 Taiwan (China); Chieng, C.C.; Liu, C.C. [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsingchu 30013, 325 Taiwan (China)
2010-05-15
A pebble bed geometry is usually adopted for high-temperature gas-cooled reactors (HTGRs), which exhibits inherently safe performance, high conversion efficiency, and low power density design. It is important to understand the thermal-hydraulic characteristics of HTGR core for optimum design and safe operation. Therefore, this study investigates the thermal-hydraulic behaviors in a segment of pebbles predicted by the Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) model using porous and realistic approaches for the complicated geometry. The advantages of each approach's methodology for the closely packed pebble geometry can be revealed by comparing the calculated results. In an engineering application, a CFD simulation with the porous approach for the pebble geometry can quickly and reasonably capture the averaged behaviors of the thermal-hydraulic parameters as the gas flows through the core, including the pressure drop and temperature increase. However, it is necessary to utilize the realistic approach for this complicated geometry to obtain the detailed and localized characteristics within the fluid and solid fuel regions. The present simulation results can provide useful information to help CFD researchers to determine an appropriate approach to be used when investigating the thermal-hydraulic characteristics within the reactor core of a closely packed pebble bed.
Scaling of a PWR steam generator simulator with the help of CFD
International Nuclear Information System (INIS)
A project is planned at PSI to experimentally simulate natural circulation mixing in a PWR steam generator during a severe accident whereby superheated steam is generated and secondary water cooling is lost. To assist in the scaling of the mock-up, CFD with the Reynolds Stress Model is used. The methodology is first validated against the Westinghouse 1/7th scale experiments. Thereafter, the flow field is simulated in the PSI mock-up which consists of 270 U-tubes with 0.005 m diameter and 4.9 m length. We show that the scaling assumptions (recirculation ratio, fraction of tubes seeing the hot plume, etc) are globally confirmed by the CFD simulations. (author)
CFD simulation of flow-induced vibration of an elastically supported airfoil
Šidlof, Petr
2016-03-01
Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge) coupled with 2D incompressible airflow is presented. The geometry of the airfoil, mass, moment of inertia, location of the centroid, linear and torsional stiffness was matched to properties of a physical airfoil model used for wind-tunnel measurements. The simulations were run within the OpenFOAM computational package. The results of the CFD simulations were compared with the experimental data.
CFD simulation of flow-induced vibration of an elastically supported airfoil
Directory of Open Access Journals (Sweden)
Šidlof Petr
2016-01-01
Full Text Available Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge coupled with 2D incompressible airflow is presented. The geometry of the airfoil, mass, moment of inertia, location of the centroid, linear and torsional stiffness was matched to properties of a physical airfoil model used for wind-tunnel measurements. The simulations were run within the OpenFOAM computational package. The results of the CFD simulations were compared with the experimental data.
CFD simulation of a screw compressor including leakage flows and rotor heating
Spille-Kohoff, Andreas, Dr.; Hesse, Jan; El Shorbagy, Ahmed
2015-08-01
Computational Fluid Dynamics (CFD) simulations have promising potential to become an important part in the development process of positive displacement (PD) machines. CFD delivers deep insights into the flow and thermodynamic behaviour of PD machines. However, the numerical simulation of such machines is more complex compared to dynamic pumps like turbines or fans. The fluid transport in size-changing chambers with very small clearances between the rotors, and between rotors and casing, demands complex meshes that change with each time step. Additionally, the losses due to leakage flows and the heat transfer to the rotors need high-quality meshes so that automatic remeshing is almost impossible. In this paper, setup steps and results for the simulation of a dry screw compressor are shown. The rotating parts are meshed with TwinMesh, a special hexahedral meshing program for gear pumps, gerotors, lobe pumps and screw compressors. In particular, these meshes include axial and radial clearances between housing and rotors, and beside the fluid volume the rotor solids are also meshed. The CFD simulation accounts for gas flow with compressibility and turbulence effects, heat transfer between gas and rotors, and leakage flows through the clearances. We show time- resolved results for torques, forces, interlobe pressure, mass flow, and heat flow between gas and rotors, as well as time- and space-resolved results for pressure, velocity, temperature etc. for different discharge ports and working points of the screw compressor. These results are also used as thermal loads for deformation simulations of the rotors.
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Clus, O; Muselli, M; Nikolayev, Vadim; Sharan, Girja; Beysens, D
2007-01-01
Harvesting condensed atmospheric vapour as dew water can be an alternative or complementary potable water resource in specific arid or insular areas. Such radiation-cooled condensing devices use already existing flat surfaces (roofs) or innovative structures with more complex shapes to enhance the dew yield. The Computational Fluid Dynamic - CFD - software PHOENICS has been programmed and applied to such radiation cooled condensers. For this purpose, the sky radiation is previously integrated and averaged for each structure. The radiative balance is then included in the CFD simulation tool to compare the efficiency of the different structures under various meteorological parameters, for complex or simple shapes and at various scales. It has been used to precise different structures before construction. (1) a 7.32 m^2 funnel shape was studied; a 30 degree tilted angle (60 degree cone half-angle) was computed to be the best compromise for funnel cooling. Compared to a 1 m^2 flat condenser, the cooling efficienc...
CFD study of thick flatback airfoils using OpenFOAM
Milián Sanz, José María
2010-01-01
New airfoil designs are created in order to improve both the structural and aerodynamic properties of a wind turbine blade, one example of these are flatback airfoils. Furthermore, a new CFD programme exists in order to study the behavior of the flow around an airfoil, OpenFOAM. The flow around these new airfoils using OpenFOAM is studied in the present thesis. It is used the turbulence model k-! SST for fully turbulent boundary layer and free transition at the boundary layer, modeled with th...
CFD Simulation of Fixed and Variable Pitch Vertical Axis Tidal Turbine
Institute of Scientific and Technical Information of China (English)
Qihu Sheng; Syed Shah Khalid; Zhimin Xiong; Ghazala Sahib; Liang Zhang
2013-01-01
In this paper,hydrodynamic analysis of vertical axis tidal turbine (both fixed pitch & variable pitch) is numerically analyzed.Two-dimensional numerical modeling & simulation of the unsteady flow through the blades of the turbine is performed using ANSYS CFX,hereafter CFX,which is based on a Reynolds-Averaged Navier-Stokes (RANS) model.A transient simulation is done for fixed pitch and variable pitch vertical axis tidal turbine using a Shear Stress Transport turbulence (SST) scheme.Main hydrodynamic parameters like torque T,combined moment CM,coefficients of performance CP and coefficient of torque CT,etc.are investigated.The modeling and meshing of turbine rotor is performed in ICEM-CFD.Moreover,the difference in meshing schemes between fixed pitch and variable pitch is also mentioned.Mesh motion option is employed for variable pitch turbine.This article is one part of the ongoing research on turbine design and developments.The numerical simulation results are validated with well reputed analytical results performed by Edinburgh Design Ltd.The article concludes with a parametric study of turbine performance,comparison between fixed and variable pitch operation for a four-bladed turbine.It is found that for variable pitch we get maximum CP and peak power at smaller revolution per minute N and tip sped ratio λ.
CFD simulation of inlet design effect on deoiling hydrocyclone separation efficiency
Energy Technology Data Exchange (ETDEWEB)
Noroozi, S.; Hashemabadi, S.H. [Computational Fluid Dynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)
2009-12-15
An Eulerian-Eulerian three-dimensional CFD model was developed to study the effect of different inlet designs on deoiling hydrocyclone separation efficiency. Reynolds averaged Navier Stokes and continuity equations were applied to solve steady turbulent flow through the cyclone with the Reynolds stress model. In addition, the modified drag correlation for liquid-liquid emulsion with respect to the Reynolds number range and viscosity ratio of two phases was used and the simulation results were compared with those predicted by the Schiller-Naumann correlation. Pressure profile, tangential and axial velocities and separation efficiency of the deoiling hydrocyclone were calculated for four different inlet designs and compared with the standard design. The simulation results for the standard design demonstrate an acceptable agreement with reported experimental data. The results show that all new four inlet designs offer higher efficiencies compared to the standard design. The difference between the efficiency of the LLHC, of the new inlets and the standard design can be improved by increasing the inlet velocity. Furthermore, the simulations show that the separation efficiency can be improved by about 10 % when using a helical form of inlet. (Abstract Copyright [2009], Wiley Periodicals, Inc.)
Modeling and Simulation of Fixed Bed Adsorption Column using Integrated CFD Approach
Directory of Open Access Journals (Sweden)
A.M. Shariff
2010-01-01
Full Text Available The understanding of detailed fluid flow in the fixed bed adsorption column is substantially crucial since the mass and heat transfer in the bed is influenced by the column hydrodynamics. In this study, an integrated CFD model was developed to model and simulate the adsorption dynamics and hydrodynamics of gaseous fluid (CH4 and CO2 mixture in the fixed bed adsorption column. The developed integrated model was used to determine the CO2 concentration factor at the column (which indicating the CO2 adsorption capacity as a function of time, based on different operating conditions. The simulated results were compared with experimental data and found to give a good agreement with error less than 2.5%. The effect of various influencing parameters such as feed velocity, bed porosity and feed concentration were studied to investigate their influences on the CO2 adsorption capacity. Besides, the effect of inlet CO2 concentration on the bed temperature profile was also studied in the present study.
RELIABLE VALIDATION BASED ON OPTICAL FLOW VISUALIZATION FOR CFD SIMULATIONS
Institute of Scientific and Technical Information of China (English)
姜宗林
2003-01-01
A reliable validation based on the optical flow visualization for numerical simulations of complex flowfields is addressed in this paper.Several test cases,including two-dimensional,axisymmetric and three-dimensional flowfields,were presented to demonstrate the effectiveness of the validation and gain credibility of numerical solutions of complex flowfields.In the validation,images of these flowfields were constructed from numerical results based on the principle of the optical flow visualization,and compared directly with experimental interferograms.Because both experimental and numerical results are of identical physical representation,the agreement between them can be evaluated effectively by examining flow structures as well as checking discrepancies in density.The study shows that the reliable validation can be achieved by using the direct comparison between numerical and experiment results without any loss of accuracy in either of them.
CFD Simulations of Oscillating Flow around Solid and Perforated Plates
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Damping plates have been used for truss spars in gulf of Mexico to reduce the heave motions. The plates are usually perforated with holes for the passage of marine risers, but the effects of the perforation have not been examined thoroughly. In the present study, a computational fluid dynamics investigation into the hydrodynamic forces is carried out by using FLUENT, which is on two-dimensional perforated plates with varying degrees of perforation in oscillating flow under small Keulegan-Carpenter (KC) number. The numerical results of the hydrodynamic coefficients are presented. The effects of both the perforation ratio (PR) and KC number on the hydrodynamic coefficients of the plates are discussed. Some results of the simulated flow patterns around the plates were also given and discussed.
Investigation of furnace processes in power steam generators based on CFD simulation tools
Energy Technology Data Exchange (ETDEWEB)
Risto V. Filkoski; Ilija J. Petrovski [University ' Sts. Cyril & Metodius' , Skopje (Macedonia)
2004-07-01
This article presents the overall frame and principal steps in the numerical modelling of combustion chamber of pulverised coal-fired power boiler OB-380, with tangential disposition of the burners. Commercial CFD software is utilised for creation of a three dimensional model of the boiler furnace, including the platen superheater installed in the upper part of the furnace. The methodology used to perform numerical modelling is briefly described. A standard steady semi-empirical {kappa}-{epsilon} model is employed for description of the turbulent flow. The coupling of velocity and pressure is achieved by the SIMPLE method. Coal combustion is modelled by the mixture fraction/PDF approach for the reaction chemistry, with equilibrium assumption applied for description of the system chemistry. Radiation heat transfer is computed by means of the simplified P-N model, based on the expansion of the radiation intensity into an orthogonal series of spherical harmonics. Some distinctive results concerning the examined boiler performance are presented graphically. On a basis of comparison between the simulation predictions and available site measurements on temperature and heat flux in the furnace, a conclusion can be drawn that the model produces realistic insight into the furnace processes. Qualitative agreement indicates reasonability of the calculations and validates the employed sub-models. The described test case and other experiences with CFD stress the advantages over a purely field data study, such as the ability to quickly and cheaply analyse a variety of design options without actually modifying the object and the availability of significantly more data to interpret the results. 22 refs., 9 figs., 5 tabs.
Study on effect of water hammer in space pipe with CFD
International Nuclear Information System (INIS)
The typical water hammer theory is introduced at first, and the shortcoming of typical water hammer to calculate water hammer in the space pipe is analyzed, and then the CFD method to study the effect of water hammer in space pipe is applied. If the coupling effect of the structure and the fluid is not considered, the fluid govern equation in the space pipe can use the basic fluid control equation. The result can be obtained by CFD technology, when the govern equation and the fluid state equation and the initial condition, boundary condition is obtained. The numerical effect numerical dissipation and the frequency dissipation is avoid when the case include wave process. The CFD is applied to simulate the model in related reference, and discuss the effect of the discrete format and the grid. Finally the progress of the water hammer in the pipe is discussed. The method in this paper can be used in more complex pipe system to simulate the water hammer effect. (authors)
CFD heat transfer simulation of the human upper respiratory tract for oronasal breathing condition
Directory of Open Access Journals (Sweden)
Kambiz Farahmand
2012-01-01
Full Text Available Injuries due to inhalation of hot gas are commonly encountered when dealing with fire and combustible material, which is harmful and threatens human life. In the literature, various studies have been conducted to investigate heat and mass transfer characteristics in the human respiratory tract (HRT. This study focuses on assessing the injury taking place in the upper human respiratory tract and identifying acute tissue damage, based on level of exposure. A three-dimensional heat transfer simulation is performed using Computational Fluid Dynamics (CFD software to study the temperature profile through the upper HRT consisting of the nasal cavity, oral cavity, trachea, and the first two generations of bronchi. The model developed is for the simultaneous oronasal breathing during the inspiration phase with a high volumetric flow rate of 90 liters/minute and the inspired air temperature of 100 degrees Celsius. The geometric model depicting the upper HRT is generated based on the data available and literature cited. The results of the simulation give the temperature distribution along the center and the surface tissue of the respiratory tract. This temperature distribution will help to assess the level of damage induced in the upper respiratory tract and appropriate treatment for the damage. A comparison of nasal breathing, oral breathing, and oronasal breathing is performed. Temperature distribution can be utilized in the design of the respirator systems where inlet temperature is regulated favoring the human body conditions.
CFD Studies on Multi Lead Rifled [MLR] Boiler Tubes
Directory of Open Access Journals (Sweden)
Dr T C Mohankumar
2013-09-01
Full Text Available This paper reports the merits of multi lead rifled [MLR] tubes in vertical water tube boiler using CFD tool. Heat transfer enhancement of MLR tubes was mainly taken in to consideration. Performance of multi lead rifled tube was studied by varying its influencing geometrical parameter like number of rifling, height of rifling, length of pitch of rifling for a particular length. The heat transfer analysis was done at operating conditions of an actual coal fired water tube boiler situated at Apollo Tyres LTD, Chalakudy, India for saturated process steam production. The results showed that the heat transfer increased when compared with existing inner plane wall water tubes.
Energy efficient piston configuration for effective air motion – A CFD study
International Nuclear Information System (INIS)
Highlights: ► All piston crown show similar flow pattern for experimental and simulated studies. ► Piston position plays a predominant role in the air pattern inside the cylinder. ► The flat bowl piston shows higher TKE compared to all other piston crown shape. ► The turbulence intensity and length scale are higher for flat bowl piston. ► The quantitative error between the CFD and PIV analysis is about 5%. -- Abstract: Air motion inside the cylinder is very important from the point of view of energy efficiency. In this direction, piston configuration plays a very crucial role. This study is concerned with the CFD analysis of in-cylinder air motion coupled with the comparison of predicted results with the experimental results available in the literature. Four configurations viz., flat, inclined, centre bowl and inclined offset bowl pistons have been studied. For numerical analysis STAR-CD CFD software has been used. Experimental results available in the literature for comparison are obtained by PIV measurements. From this study, it is concluded that a centre bowl on flat piston is found to be the best from the point of view of tumble ratio, turbulent kinetic energy, turbulent intensity and turbulent length scale which play very important role in imparting proper air motion, there by increasing the energy efficiency of the engine.
Review on CFD simulation in heart with dilated cardiomyopathy and myocardial infarction.
Chan, Bee Ting; Lim, Einly; Chee, Kok Han; Abu Osman, Noor Azuan
2013-05-01
The heart is a sophisticated functional organ that plays a crucial role in the blood circulatory system. Hemodynamics within the heart chamber can be indicative of exert cardiac health. Due to the limitations of current cardiac imaging modalities, computational fluid dynamics (CFD) have been widely used for the purposes of cardiac function assessment and heart disease diagnosis, as they provide detailed insights into the cardiac flow field. An understanding of ventricular hemodynamics and pathological severities can be gained through studies that employ the CFD method. In this research the hemodynamics of two common myocardial diseases, dilated cardiomyopathy (DCM) and myocardial infarction (MI) were investigated, during both the filling phase and the whole cardiac cycle, through a prescribed geometry and fluid structure interaction (FSI) approach. The results of the research indicated that early stage disease identification and the improvement of cardiac assisting devices and therapeutic procedures can be facilitated through the use of the CFD method. PMID:23428371
CFD Simulation of Thermal-Hydraulic Benchmark V1000CT-2 Using ANSYS CFX
Directory of Open Access Journals (Sweden)
Thomas Höhne
2009-01-01
Full Text Available Plant measured data from VVER-1000 coolant mixing experiments were used within the OECD/NEA and AER coupled code benchmarks for light water reactors to test and validate computational fluid dynamic (CFD codes. The task is to compare the various calculations with measured data, using specified boundary conditions and core power distributions. The experiments, which are provided for CFD validation, include single loop cooling down or heating-up by disturbing the heat transfer in the steam generator through the steam valves at low reactor power and with all main coolant pumps in operation. CFD calculations have been performed using a numerical grid model of 4.7 million tetrahedral elements. The Best Practice Guidelines in using CFD in nuclear reactor safety applications has been used. Different advanced turbulence models were utilized in the numerical simulation. The results show a clear sector formation of the affected loop at the downcomer, lower plenum and core inlet, which corresponds to the measured values. The maximum local values of the relative temperature rise in the calculation are in the same range of the experiment. Due to this result, it is now possible to improve the mixing models which are usually used in system codes.
Energy Technology Data Exchange (ETDEWEB)
Arastoopour, Hamid [Illinois Inst. of Technology, Chicago, IL (United States); Abbasian, Javad [Illinois Inst. of Technology, Chicago, IL (United States)
2014-07-31
This project describes the work carried out to prepare a highly reactive and mechanically strong MgO based sorbents and to develop a Population Balance Equations (PBE) approach to describe the evolution of the particle porosity distribution that is linked with Computational Fluid Dynamics (CFD) to perform simulations of the CO2 capture and sorbent regeneration. A large number of MgO-based regenerable sorbents were prepared using low cost and abundant dolomite as the base material. Among various preparation parameters investigated the potassium/magnesium (K/Mg) ratio was identified as the key variable affecting the reactivity and CO2 capacity of the sorbent. The optimum K/Mg ratio is about 0.15. The sorbent formulation HD52-P2 was identified as the “best” sorbent formulation and a large batch (one kg) of the sorbent was prepared for the detailed study. The results of parametric study indicate the optimum carbonation and regeneration temperatures are 360° and 500°C, respectively. The results also indicate that steam has a beneficial effect on the rate of carbonation and regeneration of the sorbent and that the reactivity and capacity of the sorbent decreases in the cycling process (sorbent deactivation). The results indicate that to achieve a high CO2 removal efficiency, the bed of sorbent should be operated at a temperature range of 370-410°C which also favors production of hydrogen through the WGS reaction. To describe the carbonation reaction kinetics of the MgO, the Variable Diffusivity shrinking core Model (VDM) was developed in this project, which was shown to accurately fit the experimental data. An important advantage of this model is that the changes in the sorbent conversion with time can be expressed in an explicit manner, which will significantly reduce the CFD computation time. A Computational Fluid Dynamic/Population Balance Equations (CFD/PBE) model was developed that accounts for the particle (sorbent) porosity distribution and a new version of
Gea, L. M.; Vicker, D.
2006-01-01
The primary objective of this paper is to demonstrate the capability of computational fluid dynamics (CFD) to simulate a very complicated flow field encountered during the space shuttle ascent. The flow field features nozzle plumes from booster separation motor (BSM) and reaction control system (RCS) jets with a supersonic incoming cross flow at speed of Mach 4. The overset Navier-Stokes code OVERFLOW, was used to simulate the flow field surrounding the entire space shuttle launch vehicle (SSLV) with high geometric fidelity. The variable gamma option was chosen due to the high temperature nature of nozzle flows and different plume species. CFD predicted Mach contours are in good agreement with the schlieren photos from wind tunnel test. Flow fields are discussed in detail and the results are used to support the debris analysis for the space shuttle Return To Flight (RTF) task.
CFD simulation of hydrogen mixing and mitigation by means of passive auto-catalytic recombiners
Energy Technology Data Exchange (ETDEWEB)
Kelm, S.; Reinecke, E-A.; Jahn, W., E-mail: s.kelm@fz-juelich.de [Forschungszentrum Juelich GmbH, Juelich (Germany); Allelein, H-J. [RWTH Aachen Univ.. Aachen (Germany)
2011-07-01
Modeling of passive auto-catalytic recombiners (PARs) operation in containment geometries involves a large variety of scales; thus, a CFD calculation resolving all these scales would be much too expensive. Therefore, the mechanistic PAR model REKO-DIREKT, developed at Forschungszentrum Juelich, has been coupled with the commercial CFD code ANSYS CFX in order to simulate PAR operation as well as the induced flow and transport phenomena. Based on a short introduction of REKO-DIREKT, its interface to CFX and the explicit coupling scheme is discussed. The paper is finalized by a first demonstration of simulation capabilities on the basis of the ThAI PAR-4 experiment (Becker Technologies GmbH, Eschborn, Germany). (author)
Verification and Validation Studies for the LAVA CFD Solver
Moini-Yekta, Shayan; Barad, Michael F; Sozer, Emre; Brehm, Christoph; Housman, Jeffrey A.; Kiris, Cetin C.
2013-01-01
The verification and validation of the Launch Ascent and Vehicle Aerodynamics (LAVA) computational fluid dynamics (CFD) solver is presented. A modern strategy for verification and validation is described incorporating verification tests, validation benchmarks, continuous integration and version control methods for automated testing in a collaborative development environment. The purpose of the approach is to integrate the verification and validation process into the development of the solver and improve productivity. This paper uses the Method of Manufactured Solutions (MMS) for the verification of 2D Euler equations, 3D Navier-Stokes equations as well as turbulence models. A method for systematic refinement of unstructured grids is also presented. Verification using inviscid vortex propagation and flow over a flat plate is highlighted. Simulation results using laminar and turbulent flow past a NACA 0012 airfoil and ONERA M6 wing are validated against experimental and numerical data.
Hypersonic Intake Starting Characteristics–A CFD Validation Study
Directory of Open Access Journals (Sweden)
Soumyajit Saha
2012-05-01
Full Text Available Numerical simulation of hypersonic intake starting characteristics is presented. Three dimensional RANS equations are solved alongwith SST turbulence model using commercial computational fluid dynamics (CFD software. Wall pressure distribution and intake performance parameters are found to match well with experimental data for different free stream Mach number in the range of 3-8. The unstarting of the intake is traced from the sudden drop of mass capture ratio. Wall condition (adiabatic or isothermal is seen to have pronounced effect in estimating the performance parameters in the intake. The computed unstarting Mach number is seen to be higher for adiabatic condition compared to isothermal condition. For unstarting case, large separation bubble is seen near the entrance of the intake, which is responsible for expulsion of the shock system out of the intake.Defence Science Journal, 2012, 62(1, pp.147-152, DOI:http://dx.doi.org/10.14429/dsj.62.1340
Cfd Studies of Two Stroke Petrol Engine Scavenging
Directory of Open Access Journals (Sweden)
S Gavudhama Karunanidhi,
2014-07-01
Full Text Available This project deals with the numerical analysis of 2 stroke engine scavenging in two cases. One with an existing condition (Flat headed pistons and another with a new design (Dome headed piston .The numerical analysis is done with help of CFD software ANSYS FLUENT 14.5. Here, the modeling of engine piston with flat headed type and with dome headed types was done in workbench. In ANSYS FLUENT after the geometrical design, for the dynamic motion meshing is used and set up species transport model also. At first the scavenging effect of flat headed piston is analyzed. Later the simulation of piston with dome headed type was also checked. Analyzing the variations from each and selected the best method for scavenging. Finally the scavenging efficiency is calculated for both type arrangements.
CFD Simulation and Validation of Phase Particle Entrapment
Yoosef Peymani, F.; Liu, Yucheng; Hayatdavoudi, Asadollah
2014-09-01
A cost-effective and efficient technology was developed to remove particulate and fibrous matter from a container while avoiding dispersing the particles in the environment. This paper presents the whole process of computationally developing a conceptual system which can efficiently remove particles in the size range of 5-1000 μm from the container. The present work offers the unique virtue that prototyping can be easily followed and it shows an efficient, safe, low-cost method in the early product design stage. In the presented system, a viscous medium was designed to capture and flocculate the particulate matter. One of the factors which will lower the operating costs is that the viscous medium can be easily recycled and the flocculated particles with minimal volume can be disposed of safely. The ANSYS FLUENT package was used to simulate our proposed design. The effects of various particle size, specific gravity, and pressure-velocity boundary conditions on separation efficiency of the design have been studied by using different multiphase models along with viscous and discreet phase models.
Comparison of Engineering Wake Models with CFD Simulations
DEFF Research Database (Denmark)
Andersen, Søren Juhl; Sørensen, Jens Nørkær; Ivanell, S.;
2014-01-01
The engineering wake models by Jensen [1] and Frandsen et al. [2] are assessed for different scenarios simulated using Large Eddy Simulation and the Actuator Line method implemented in the Navier-Stokes equations. The scenarios include the far wake behind a single wind turbine, a long row of...... turbines in an atmospheric boundary layer, idealised cases of an infinitely long row of wind turbines and infinite wind farms with three different spacings. Both models include a wake expansion factor, which is calibrated to fit the simulated wake velocities. The analysis highlights physical deficiencies...
International Nuclear Information System (INIS)
A prototype mixing vessel has been developed by Industrial Technology Division and installed at a multiphase testing facility in MINT Tech Park. A task to investigate the mixing vessel performance using Computational Fluid Dynamics (CFD) has been undertaken using the available FLUENT software in Malaysian Nuclear Agency. This paper discusses the modeling and simulation done in obtaining the Residence Time Distribution (RTD) for the mixing vessel using FLUENT. (author)
CFD simulation of flow-induced vibration of an elastically supported airfoil
Šidlof Petr
2016-01-01
Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge) coupled with 2D incompress...
Guo, Yuan; Deng, Baoqing; Ge, Daqiang; Shen, Xiuzhong
2015-08-01
CFD simulations of gas-solid fluidized beds have been performed in Euler-Euler framework. Green-Gauss Cell Based gradient approximation can predict the solid velocity well among gradient approximations. The dispersed choice in the turbulence model can reproduce the solid velocity correctly while the mixture and per phase choices cannot. The standard k-ɛ model, RNG k-ɛ model and SST k-ω model with the dispersed choice can predict the solid velocity well.
Application of CFD code for simulation of an inclined snow chute flow
Aggarwal, R K; Amod Kumar
2013-01-01
In this paper, 2-D simulation of a 61 m long inclined snow chute flow and its interaction with a catch dam type obstacle has been carried out at Dhundhi field research station near Manali, Himachal Pradesh (India) using a commercially available computational fluid dynamics (CFD) code ANSYS Fluent. Eulerian non-granular multiphase model was chosen to model the snow flow in the surrounding atmospheric air domain. Both air and snow were assumed as laminar and incompressible fluids. User defined ...
CFD simulation of production of NOx in coal-fired furnaces
ASKAROVA ALIYA; BOLEGENOVA SALTANAT; MAXIMOV VALERY; OSPANOVA SHYNAR; BOLEGENOVA SYMBAT
2016-01-01
Computational fluid dynamics (CFD) has been accepted as a powerful and effective tool for control and analysis of coal-fired utility boilers. Since coal burning in a utility boilers is a very complex process that comprises high-temperature reacting turbulent flow, particles transport and radiative heat transfer a reliable numerical simulation models of coal combustion requires high accuracy and careful interpretation of its numerical results.
A Simplified CFD Model for Simulation of the Suction Process Of Reciprocating Compressors
Pereira, Evandro L. L.; Santos, Claudio J.; Deschamps, Cesar J.; Kremer, Rodrigo
2012-01-01
The suction process in reciprocating compressors is strongly affected by the valve dynamics and the pulsating flow throughout the suction muffler. This paper describes a simplified computational fluid dynamics (CFD) model to simulate the flow through the muffler, suction valve and a small region inside the cylinder. The proposed method is applied to predict the suction process of a small reciprocating compressor and its adequacy is compared with a more time elaborate model in terms of accurac...
New Block Distributed Schur Complement Preconditioners for CFD Simulation on Many-Core Architectures
Basermann, Achim; Zöllner, Melven
2012-01-01
At the German Aerospace Center, the parallel simulation systems TAU and TRACE have been developed for the aerodynamic design of aircrafts or turbines for jet engines. For the parallel iterative solution of large, sparse real or complex systems of linear equations, required for both CFD solvers, block-local preconditioners are compared with reformulated global block Distributed Schur Complement (DSC) preconditioning methods. Numerical, performance and scalability results of b...
Disintegration regime of industrial fan-spray atomizers through CFD simulations
Altimira, Mireia; Rivas, Alejandro; RAMOS, JUAN CARLOS; Anton, Raul
2011-01-01
Among all the literature devoted to the investigation of sprays, very few works deal with the influence of the nozzle’s geometry on the characteristics of the spray produced, even though it has been proved to play a crucial role in certain operating regimes. The present paper presents criteria for the determination of the dominant disintegration regime in industrial fan-spray atomizers through CFD simulations accounting for the atomizer’s geometry. QC 20120214
NUMERICAL PREDICTION OF SUBMARINE HYDRODYNAMIC COEFFICIENTS USING CFD SIMULATION
Institute of Scientific and Technical Information of China (English)
PAN Yu-cun; ZHANG Huai-xin; ZHOU Qi-dou
2012-01-01
The submarine Hydrodynamic coefficients are predicted by numerical simulations.Steady and unsteady Reynolds Averaged Navier-Stokes (RANS) simulations are carried out to numerically simulate the oblique towing experiment and the Planar Motion Mechanism (PMM) experiment performed on the SUBOFF submarine model.The dynamic mesh method is adopted to simulate the maneuvering motions of pure heaving,pure swaying,pure pitching and pure yawing.The hydrodynamic forces and moments acting on the maneuvering submarine are obtained.Consequently,by analyzing these results,the hydrodynamic coefficients of the submarine maneuvering motions can be determined.The computational results are verified by comparison with experimental data,which show that this method can be used to estimate the hydrodynamic derivatives of a fully appended submarine.
CFD SIMULATION OF A STIRRED DISHED BOTTOM VESSEL
Petr Vlček; Jan Skočilas; Tomáš Jirout
2013-01-01
This paper deals with simulation of the fluid flow in a stirred curved-bottom vessel equipped with three curved blade impellers. The power number and the impeller flow rate number are dimensionless characteristics of the system determined from simulation results and compared with relevant experimental data or data from the literature. The model of the system was created in the conventional Gambit and Fluent program. The system is solved for two designs — for an unbaffled vessel, and for a baf...
Gekoppelte Simulation hydraulischer Gesamtsysteme unter Einbeziehung von CFD
Habr, Klaus
2002-01-01
Die Modelle der konzentrierten/verteilten Parameter sind die am weitesten verbreiteten Modelle zur Simulation von hydraulischen Gesamtsystemen. Zur Zeit liegt in der Ölhydraulik ein deutlicher Schwerpunkt bei der Verwendung von Modellen mit konzentrierten Parameter vor. In dieser Arbeit konnte gezeigt werden, dass es praxisrelevante Anlagenkonfigurationen gibt, in welchen eine Simulation mit den oben genannten Modellen keine verwertbaren Ergebnisse liefert. Dieser Fall tritt ein, wenn die Wec...
CFD Simulation of Airflow in the Side-Platform Stations
Adibi Omid; Farhanieh Bijan; Afshin Hossein
2015-01-01
Design of an appropriate ventilation system is one of the main concerns in the construction of subways. In this paper, thermal comforts of side-platform stations are investigated by numerical methods. For the numerical simulation, grids are generated by structured methods and governing equations are discretized by finite volume methods. In the numerical simulation, second order upwind and second order central difference scheme are used to consider the convection and diffusion terms of momentu...
CFD Simulation of Vortex Induced Vibration of a Cylindrical Structure
Asyikin, Muhammad Tedy
2012-01-01
This thesis presents the investigation of the flow characteristic and vortex induced vibration (VIV) of a cylindrical structure due to the incompressible laminar and turbulent flow at Reynolds number 40, 100, 200 and 1000. The simulations were performed by solving the steady and transient (unsteady) 2D Navier-Stokes equation. For Reynolds number 40, the simulations were set as a steady and laminar flow and the SIMPLE and QUICK were used as the pressure-velocity coupling scheme and momentum sp...
Determination of pressure drop coefficient by CFD simulation
Skočilasová, Blanka; Skočilas, Jan
2014-08-01
The article deals with method applied to the verification of the turbulence models. The turbulence models were used in the simulation of the Newtonian fluid turbulent flow in the circular tube. The principle of the method is in the comparison of the pressure drop obtained by the simulation and the analytic solution. The parameters of the fluid flow were varied with the specified Reynolds number range. The pressure drop of inserted element in the pipe is evaluated.
Real-Time Visualization of an HPF-based CFD Simulation
Kremenetsky, Mark; Vaziri, Arsi; Haimes, Robert; Chancellor, Marisa K. (Technical Monitor)
1996-01-01
Current time-dependent CFD simulations produce very large multi-dimensional data sets at each time step. The visual analysis of computational results are traditionally performed by post processing the static data on graphics workstations. We present results from an alternate approach in which we analyze the simulation data in situ on each processing node at the time of simulation. The locally analyzed results, usually more economical and in a reduced form, are then combined and sent back for visualization on a graphics workstation.
An Approach to Improved Credibility of CFD Simulations for Rocket Injector Design
Tucker, Paul K.; Menon, Suresh; Merkle, Charles L.; Oefelein, Joseph C.; Yang, Vigor
2007-01-01
Computational fluid dynamics (CFD) has the potential to improve the historical rocket injector design process by simulating the sensitivity of performance and injector-driven thermal environments to. the details of the injector geometry and key operational parameters. Methodical verification and validation efforts on a range of coaxial injector elements have shown the current production CFD capability must be improved in order to quantitatively impact the injector design process.. This paper documents the status of an effort to understand and compare the predictive capabilities and resource requirements of a range of CFD methodologies on a set of model problem injectors. Preliminary results from a steady Reynolds-Average Navier-Stokes (RANS), an unsteady Reynolds-Average Navier Stokes (URANS) and three different Large Eddy Simulation (LES) techniques used to model a single element coaxial injector using gaseous oxygen and gaseous hydrogen propellants are presented. Initial observations are made comparing instantaneous results, corresponding time-averaged and steady-state solutions in the near -injector flow field. Significant differences in the flow fields exist, as expected, and are discussed. An important preliminary result is the identification of a fundamental mixing mechanism, accounted for by URANS and LES, but missing in the steady BANS methodology. Since propellant mixing is the core injector function, this mixing process may prove to have a profound effect on the ability to more correctly simulate injector performance and resulting thermal environments. Issues important to unifying the basis for future comparison such as solution initialization, required run time and grid resolution are addressed.
Giannuzzi, M.
2014-07-01
In electronic systems the presence of bluff bodies, sharp corners and bends are the cause of flow separation and large recirculation bubbles. Since the recirculation vortices develop they encapsulate the heat from an electronic component becoming one of the major contributors of malfunction. Going in depth in this, some numerical simulations of conjugate heat transfer for a heat wall-mounted cube have been performed using the commercial CFD code scSTREAM V11 by Software Cradle Co, Ltd. It is well known that the reliability of CFD analysis depends heavily on the turbulent model employed together with the wall functions implemented. The three low- Reynolds k - epsilon turbulent models developed by Abe-Nagano-Kondoh have been validated against experimental data consisting mainly of velocity profiles and surface temperature distributions provided in literature. The performed validation shows a satisfactory agreement between the measured and simulated data. The turbulent model chosen is then used for the CFD simulation of a complex electronic system.
International Nuclear Information System (INIS)
In electronic systems the presence of bluff bodies, sharp corners and bends are the cause of flow separation and large recirculation bubbles. Since the recirculation vortices develop they encapsulate the heat from an electronic component becoming one of the major contributors of malfunction. Going in depth in this, some numerical simulations of conjugate heat transfer for a heat wall-mounted cube have been performed using the commercial CFD code scSTREAM V11 by Software Cradle Co, Ltd. It is well known that the reliability of CFD analysis depends heavily on the turbulent model employed together with the wall functions implemented. The three low- Reynolds k – ε turbulent models developed by Abe-Nagano-Kondoh have been validated against experimental data consisting mainly of velocity profiles and surface temperature distributions provided in literature. The performed validation shows a satisfactory agreement between the measured and simulated data. The turbulent model chosen is then used for the CFD simulation of a complex electronic system.
CFD SIMULATION OF THE HYDRODYNAMICS AND MIXING TIME IN A STIRRED TANK
Directory of Open Access Journals (Sweden)
AOYI OCHIENG
2010-12-01
Full Text Available Hydrodynamics and mixing efficiency in stirred tanks influence power draw and are therefore important for the design of many industrial processes. In the present study, both experimental and simulation methods were employed to determine the flow fields in different mixing tank configurations in a single phase system. Laser Doppler velocimetry (LDV and computational fluid dynamics (CFD techniques were used to determine the flow fields in systems with and without a draft tube. There was reasonable agreement between the simulation and experimental results. It was shown that the use of a draft tube with a Rushton turbine and hydrofoil impeller resulted in a reduction in the homogenization energy by 19.2 and 17.7%, respectively. This indicates that a reduction in the operating cost can be achieved with the use of a draft tube in a stirred tank and there would be a greater cost reduction in a system stirred by the Rushton turbine compared to that stirred by a propeller.
Shin, Sangmin; Lee, Seungjae; Lee, Sangeun; Yum, Kyungtaek; Park, Heekyung
2012-01-01
This study aims to improve the design factors of air diffuser systems that have been analyzed in laboratory experiments, with consideration of the field conditions of dam reservoirs. In this study, the destratification number (D(N)), destratification radius, and efficiency are considered as design factors. The computational fluid dynamics (CFD) simulation experiment is performed in diverse field conditions in order to analyze these factors. The results illustrate the wider range of D(N) values in field conditions and the relationship of the destratification radius and efficiency to D(N). The results can lead to better performance of air diffuser systems and water quality management in dam reservoir sites. PMID:22678200
Directory of Open Access Journals (Sweden)
John White
2016-02-01
Full Text Available The chief objective of this study is the proposal design and CFD simulation of a new compacted copper wire woven fin heat exchanger and silica gel adsorbent bed used as part of an adsorption refrigeration system. This type of heat exchanger design has a large surface area because of the wire woven fin design. It is estimated that this will help improve the coefficient of performance (COP of the adsorption phase and increase the heat transfer in this system arrangement. To study the heat transfer between the fins and porous adsorbent reactor bed, two experiments were carried out and matched to computational fluid dynamics (CFD results.
Comparison of Engineering Wake Models with CFD Simulations
Andersen, S. J.; Sørensen, J. N.; Ivanell, S.; Mikkelsen, R. F.
2014-06-01
The engineering wake models by Jensen [1] and Frandsen et al. [2] are assessed for different scenarios simulated using Large Eddy Simulation and the Actuator Line method implemented in the Navier-Stokes equations. The scenarios include the far wake behind a single wind turbine, a long row of turbines in an atmospheric boundary layer, idealised cases of an infinitely long row of wind turbines and infinite wind farms with three different spacings. Both models include a wake expansion factor, which is calibrated to fit the simulated wake velocities. The analysis highlights physical deficiencies in the ability of the models to universally predict the wake velocities, as the expansion factor can be fitted for a given case, but with not apparent transition between the cases.
CFD simulation of micro-scale pollutant dispersion in the built environment
Blocken, Bert; Tominaga, Y; Stathopoulos, T
2013-01-01
Outdoor air quality is one of the major environmental problems today. Micro-scale pollutant dispersion covers the building scale and the meteorological micro-scale. Computational Fluid Dynamics (CFD) is increasingly used for micro-scale dispersion studies. Virtual Special Issue groups papers published previously on this topic in Building & Environment. Some trends and directions for future research are outlined.
CFD Simulation of X-Ads Downcomer Thermal Stratification
Anissimov, V.; Alemberti, A.
2006-01-01
This work presents a numerical simulation using CFX 4.4 of the Energy Amplifier Experimental Facility (X-ADS) downcomer channel. The simulation is focused on the Steady-State Analysis. The Intermediate Heat exchangers (IHX) of the X-ADS reference configuration are immersed in the lead-bismuth eutectic of the downcomer. Due to the absence of a physical separation between the primary coolant hot and cold collectors, two different flow paths are available in the downcomer region: inside the IHX ...
CFD simulation analysis and validation for CPR1000 pressurized water reactor
International Nuclear Information System (INIS)
Background: With the rapid growth in the non-nuclear area for industrial use of Computational fluid dynamics (CFD) which has been accompanied by dramatically enhanced computing power, the application of CFD methods to problems relating to Nuclear Reactor Safety (NRS) is rapidly accelerating. Existing research data have shown that CFD methods could predict accurately the pressure field and the flow repartition in reactor lower plenum. But simulations for the full domain of the reactor have not been reported so far. Purpose: The aim is to determine the capabilities of the codes to model accurately the physical phenomena which occur in the full reactor vessel. Methods: The flow field of the CPR1000 reactor which is associated with a typical pressurized water reactor (PWR) is simulated by using ANSYS CFX. The pressure loss in reactor pressure vessel, the hydraulic loads of guide tubes and support columns, and the bypass flow of head dome were obtained by calculations for the full domain of the reactor. The results were validated by comparing with the determined reference value of the operating nuclear plant (LingAo nuclear plant), and the transient simulation was conducted in order to better understand the flow in reactor pressure vessel. Results: It was shown that the predicted pressure loss with CFD code was slightly different with the determined value (10% relative deviation for the total pressure loss), the hydraulic loads were less than the determined value with maximum relative deviation 50%, and bypass flow of head dome was approximately the same with determined value. Conclusion: This analysis practice predicts accurately the physical phenomena which occur in the full reactor vessel, and can be taken as a guidance for the nuclear plant design development and improve our understanding of reactor flow phenomena. (authors)
Application of CFD simulation to predicting upper-room UVGI effectiveness.
Gilkeson, Carl A; Noakes, Catherine
2013-01-01
This study outlines the potential for Computational Fluid Dynamics (CFD) simulation to be used to predict upper-room ultraviolet germicidal irradiation (UVGI) effectiveness to aid system design and the development of future guidance. A numerical study of two wall-mounted UVGI lamps in a mechanically ventilated test chamber is used to assess the influence of modeling parameters on prediction of dose distribution and microorganism inactivation. Irradiance fields for both UVGI fixtures are obtained via radiometry and implemented in the model. A series of sensitivity studies consider the importance of UVGI field accuracy and computational grid and turbulence model selection. Results show that 2D irradiance fields are sufficient for calculating dose and in-activation, whereas a 1D field is inadequate for modeling purposes. Further parametric studies consider the effects of ventilation parameters, UVGI lamp configuration and microorganism susceptibility. These demonstrate the feasibility of modeling the interaction of the airflow and UV field in a room to quantify the dose distribution. Microorganism in-activation can also be accomplished by employing passive scalars and species transport models, however, further validation data are necessary before this can be used to make reliable quantitative predictions. PMID:23106610
CFD Study of an Annular-Ducted Fan Lift System for VTOL Aircraft
Yun Jiang; Bo Zhang; Tao Huang
2015-01-01
The present study aimed at assessing a novel annular-ducted fan lift system for VTOL aircraft through computational fluid dynamics (CFD) simulations. The power and lift efficiency of the lift fan system in hover mode, the lift and drag in transition mode, the drag and flight speed of the aircraft in cruise mode and the pneumatic coupling of the tip turbine and jet exhaust were studied. The results show that the annular-ducted fan lift system can have higher lift efficiency compared to the ro...
CFD SIMULATION OF FLUID CATALYTIC CRACKING IN DOWNER REACTORS
Institute of Scientific and Technical Information of China (English)
Fei; Liu; Fei; Wei; Yu; Zheng; Yong; Jin
2006-01-01
A mathematical model has been developed for the simulation of gas-particle flow and fluid catalytic cracking in downer reactors. The model takes into account both cracking reaction and flow behavior through a four-lump reaction kinetics coupled with two-phase turbulent flow. The prediction results show that the relatively large change of gas velocity affects directly the axial distribution of solids velocity and void fraction, which significantly interact with the chemical reaction. Furthermore, model simulations are carried out to determine the effects of such parameters on product yields, as bed diameter, reaction temperature and the ratio of catalyst to oil, which are helpful for optimizing the yields of desired products. The model equations are coded and solved on CFX4.4.
Aerodynamic degradation of iced airfoils – experiments and CFD simulations
Czech Academy of Sciences Publication Activity Database
Chára, Zdeněk; Horák, V.; Rozehnal, D.
Ashland: ASME, 2009, FEDSM2009-78451. ISBN 978-0-7918-3855-6. [ASME 2009 Fluids Engineering Division Summer Meeting: FEDSM2009. Vail (US), 02.08.2009-06.08.2009] R&D Projects: GA ČR GA103/07/0136; GA MPO FT-TA4/044 Institutional research plan: CEZ:AV0Z20600510 Keywords : ice accretion * numerical simulation * CFX 11 Subject RIV: BK - Fluid Dynamics
Fluid-structure interaction computations for geometrically resolved rotor simulations using CFD
DEFF Research Database (Denmark)
Heinz, Joachim Christian; Sørensen, Niels N.; Zahle, Frederik
2016-01-01
newly developed coupling between HAWC2 and EllipSys3D (HAWC2CFD) is utilized to compute the aero-elastic response of the NREL 5-MW reference wind turbine (RWT) under normal operational conditions. A comparison with the low-fidelity but state-of-the-art aero-elastic solver HAWC2 reveals a very good...... agreement between the two approaches. In a second test case, the response of the NREL 5-MW RWT is computed during a yawed and thus asymmetric inflow. The continuous good agreement confirms the qualities of HAWC2CFD but also illustrates the strengths of a computationally cheaper blade element momentum theory...... (BEM) based solver, as long as the solver is applied within the boundaries of the employed engineering models. Two further test cases encompass flow situations, which are expected to exceed the limits of the BEM model. However, the simulation of the NREL 5-MW RWT during an emergency shut down situation...
Recurrence CFD - a novel approach to simulate multiphase flows with strongly separated time scales
Lichtenegger, Thomas
2016-01-01
Classical Computational Fluid Dynamics (CFD) of long-time processes with strongly separated time scales is computationally extremely demanding if not impossible. Consequently, the state-of-the-art description of such systems is not capable of real-time simulations or online process monitoring. In order to bridge this gap, we propose a new method suitable to decouple slow from fast degrees of freedom in many cases. Based on the recurrence statistics of unsteady flow fields, we deduce a recurrence process which enables the generic representation of pseudo-periodic motion at high spatial and temporal resolution. Based on these fields, passive scalars can be traced by recurrence CFD. While a first, Eulerian Model A solves a passive transport equation in a classical implicit finite-volume environment, a second, Lagrangian Model B propagates fluid particles obeying a stochastic differential equation explicitly. Finally, this new concept is tested by two multiphase processes - a lab scale oscillating bubble column a...
A workflow for patient-individualized virtual angiogram generation based on CFD simulation.
Endres, Jürgen; Kowarschik, Markus; Redel, Thomas; Sharma, Puneet; Mihalef, Viorel; Hornegger, Joachim; Dörfler, Arnd
2012-01-01
Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases. PMID:23193428
A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation
Directory of Open Access Journals (Sweden)
Jürgen Endres
2012-01-01
Full Text Available Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.
Validation of High-Fidelity CFD Simulations for Rocket Injector Design
Tucker, P. Kevin; Menon, Suresh; Merkle, Charles L.; Oefelein, Joseph C.; Yang, Vigor
2008-01-01
Computational fluid dynamics (CFD) has the potential to improve the historical rocket injector design process by evaluating the sensitivity of performance and injector-driven thermal environments to the details of the injector geometry and key operational parameters. Methodical verification and validation efforts on a range of coaxial injector elements have shown the current production CFD capability must be improved in order to quantitatively impact the injector design process. This paper documents the status of a focused effort to compare and understand the predictive capabilities and computational requirements of a range of CFD methodologies on a set of single element injector model problems. The steady Reynolds-Average Navier-Stokes (RANS), unsteady Reynolds-Average Navier-Stokes (URANS) and three different approaches using the Large Eddy Simulation (LES) technique were used to simulate the initial model problem, a single element coaxial injector using gaseous oxygen and gaseous hydrogen propellants. While one high-fidelity LES result matches the experimental combustion chamber wall heat flux very well, there is no monotonic convergence to the data with increasing computational tool fidelity. Systematic evaluation of key flow field regions such as the flame zone, the head end recirculation zone and the downstream near wall zone has shed significant, though as of yet incomplete, light on the complex, underlying causes for the performance level of each technique. 1 Aerospace Engineer and Combustion CFD Team Leader, MS ER42, NASA MSFC, AL 35812, Senior Member, AIAA. 2 Professor and Director, Computational Combustion Laboratory, School of Aerospace Engineering, 270 Ferst Dr., Atlanta, GA 30332, Associate Fellow, AIAA. 3 Reilly Professor of Engineering, School of Mechanical Engineering, 585 Purdue Mall, West Lafayette, IN 47907, Fellow, AIAA. 4 Principal Member of Technical Staff, Combustion Research Facility, 7011 East Avenue, MS9051, Livermore, CA 94550, Associate
CFD Simulation of the Flow Field Inside Screw Powder Feeder
Institute of Scientific and Technical Information of China (English)
SHI Yang-he; SHAO Zong-heng
2011-01-01
A screw powder feeder is an important device for industrial applications. There are many parameters which affect the performance of the screw powder feeder, such as the shapes of the helical screw impeller, the number of screw pitches, etc. This paper presents an analysis of a gas-solid two-phase through screw powder feeder by using a commercial Computational Fluid Dynamics（CFD） code, Fluent. The K-ε model is used to simulate gas flow. Particle trajectory is obtained by the use of a discrete phase model. The results show the effects of gas velocity and panicle size on the transportation performance.
Trimmed CFD Simulation of a Complete Helicopter Configuration
Khier, Walid; Dietz, Markus; Schwarz, Thorsten; Wagner, Siegfried
2007-01-01
An investigation was carried out using the flight mechanics tool HOST weakly coupled to the RANS solver FLOWer to simulate the flow around helicopter configuration under different flight conditions. The configuration considered was a wind tunnel model with powered 4.2 meter four-bladed main rotor, and 0.73 meter two bladed tail rotor. Two forward flight conditions at Mach number equal to 0.059 and 0.204 were considered at 5o and -2o angle of attack, respectively. The objective was to asses th...
CFD Simulation and Optimize of a 10K VM Refrigerator
Pan, Changzhao; Chen, Liubiao; Zhou, Yuan; Wang, Junjie
The VM refrigerator with power being supplied by liquid nitrogen shows great potential for application below 10K. The 2D axisymmetric model refers to actual geometry under oscillating flow conditions is carried out using FLUENT software. The lowest temperature, the pressure in three cavities, the temperature profile along the regenerator is presented. The simulation results show good agreement with available data. Then the regenerator between cold and middle cavity is optimized to obtain the lowest temperature, it is filled with stainless steel screens and lead shot. It is found that there exists an optimal ratio of stainless steel screens and lead in the same length regenerator.
Effect of Particle Orientation during Thermal Processing of Canned Peach Halves: A CFD Simulation
Directory of Open Access Journals (Sweden)
Adreas Dimou
2014-05-01
Full Text Available The objective of this work was to apply Computational Fluid Dynamics (CFD to study the effect of particle orientation on fluid flow, temperature evolution, as well as microbial destruction, during thermal processing of still cans filled with peach halves in sugar syrup. A still metal can with four peach halves in 20% sugar syrup was heated at 100 °C for 20 min and thereafter cooled at 20 °C. Infinite heat transfer coefficient between heating medium and external can wall was considered. Peach halves were orderly placed inside the can with the empty space originally occupied by the kernel facing, in all peaches, either towards the top or the bottom of the can. In a third situation, the can was placed horizontally. Simulations revealed differences on particle temperature profiles, as well as process F values and critical point location, based on their orientation. At their critical points, peach halves with the kernel space facing towards the top of the can heated considerably slower and cooled faster than the peaches having their kernel space facing towards the bottom of the can. The horizontal can case exhibited intermediate cooling but the fastest heating rates and the highest F process values among the three cases examined. The results of this study could be used in designing of thermal processes with optimal product quality.
CFD simulation on flow induced vibrations in high pressure control and emergency stop turbine valve
International Nuclear Information System (INIS)
During the refuelling outage at Unit 2 of Forsmark NPP in 2009, the high pressure turbine valves were replaced. Three month after recommissioning, an oil pipe connected to one of the actuators was broken. Measurements showed high-frequency vibration levels. The pipe break was suspected to be an effect of highly increased vibrations caused by the new valve. In order to establish the origin of the vibrations, investigations by means of CFD-simulations were made. The simulations showed that the increased vibrations most likely stems from the open cavity that the valves centre consists of. (author)
Heat transfer simulation of motorcycle fins under varying velocity using CFD method
Shahril, K.; Mohd Kasim, Nurhayati Binti; Sabri, M.
2013-12-01
Motorcycle engine releases heat to the atmosphere through the mode of force convection. To solve this, fins are provided on the outer of the cylinder. The heat transfer rate is defined depending on the velocity of vehicle, fin geometry and the ambient temperature. Increasing the temperature difference between the object and the environment, increasing the convection heat transfer coefficient, or increasing the surface area of the object increases the heat transfer. Many experimental methods are available in literature to analyze the effect of these factors on the heat transfer rate. However, CFD analysis will be use to simulate the heat transfer of the engine block. ANSYS software is selected to run the simulation.
CFD simulation on flow induced vibrations in high pressure control and emergency stop turbine valve
Energy Technology Data Exchange (ETDEWEB)
Lindqvist, H. [Forsmark Kraftverk AB, Osthammar (Sweden)
2011-07-01
During the refuelling outage at Unit 2 of Forsmark NPP in 2009, the high pressure turbine valves were replaced. Three month after recommissioning, an oil pipe connected to one of the actuators was broken. Measurements showed high-frequency vibration levels. The pipe break was suspected to be an effect of highly increased vibrations caused by the new valve. In order to establish the origin of the vibrations, investigations by means of CFD-simulations were made. The simulations showed that the increased vibrations most likely stems from the open cavity that the valves centre consists of. (author)
2-DIMENSIONAL CFD SIMULATION OF THE AIR FLOW INSIDE A LEMANG OVEN
SUHAILA HUSSAIN; ROSHALIZA HAMIDON
2011-01-01
This paper presents the results obtained from a computational fluid dynamics simulation of the cooking process of a Malay delicacy called lemang inside a specially made oven. The normal way of cooking lemang is by putting it in open fire for more or less 2 hours. By using the lemang oven, the cooking time was reduced to about 1 hour and 20 minutes. A 2-dimesional CFD simulation was done to look at the hot air distribution inside the oven and how it affects the conditions inside the oven and t...
1D engine simulation of a turbocharged SI engine with CFD computation on components
Renberg, Ulrica
2008-01-01
Techniques that can increase the SI- engine efficiency while keeping the emissions very low is to reduce the engine displacement volume combined with a charging system. Advanced systems are needed for an effective boosting of the engine and today 1D engine simulation tools are often used for their optimization. This thesis concerns 1D engine simulation of a turbocharged SI engine and the introduction of CFD computations on components as a way to assess inaccuracies in the 1D model. 1D engine ...
CFD Simulation of X-Ads Downcomer Thermal Stratification
Anissimov, V
2006-01-01
This work presents a numerical simulation using CFX 4.4 of the Energy Amplifier Experimental Facility (X-ADS) downcomer channel. The simulation is focused on the Steady-State Analysis. The Intermediate Heat exchangers (IHX) of the X-ADS reference configuration are immersed in the lead-bismuth eutectic of the downcomer. Due to the absence of a physical separation between the primary coolant hot and cold collectors, two different flow paths are available in the downcomer region: inside the IHX and outside it (IHX by-pass flow). The amount of IHX by-pass flow is determined by the balance between the driving force due to buoyancy (originated by the weight difference between the cooled fluid inside the IHX and the hot outside downcomer fluid) and the IHX pressure losses. At the IHX exit the two flow paths are mixed before the core inlet. This fact provides a potential for a downcomer thermal stratification, which is influenced by the actual value of coolant flow rate outside the IHX. The amount and extension of th...
CFD SIMULATION OF A STIRRED DISHED BOTTOM VESSEL
Directory of Open Access Journals (Sweden)
Petr Vlček
2013-12-01
Full Text Available This paper deals with simulation of the fluid flow in a stirred curved-bottom vessel equipped with three curved blade impellers. The power number and the impeller flow rate number are dimensionless characteristics of the system determined from simulation results and compared with relevant experimental data or data from the literature. The model of the system was created in the conventional Gambit and Fluent program. The system is solved for two designs — for an unbaffled vessel, and for a baffled vessel.The vessel is filled with water and the impeller speed is 100 min−1. Three turbulent models were used for the solution: k-ε, k-ω and RSM. The results were compared with experimental data or data from the literature. The k-ε model had the smallest demands on processor time, and the results compared satisfactorily with the experimental data. The model provides comprehensive information about the characteristics of the system.
CFD simulation of particle suspension in a stirred tank
Institute of Scientific and Technical Information of China (English)
Nana Qi; Hu Zhang; Kai Zhang; Gang Xu; Yongping Yang
2013-01-01
Particle suspension characteristics are predicted computationally in a stirred tank driven by a Smith turbine.In order to verify the hydrodynamic model and numerical method,the predicted power number and flow pattern are compared with designed values and simulated results from the literature,respectively.The effects of particle density,particle diameter,liquid viscosity and initial solid loading on particle suspension behavior are investigated by using the Eulerian-Eulerian two-fluid model and the standard k-ε turbulence model.The results indicate that solid concentration distribution depends on the flow field in the stirred tank.Higher particle density or larger particle size results in less homogenous distribution of solid particles in the tank.Increasing initial solid loading has an adverse impact on the homogeneous suspension of solid particles in a low-viscosity liquid,whilst more uniform particle distribution is found in a high-viscositv liauid.
CFD numerical simulation of Archimedes spiral inlet hydrocyclone
International Nuclear Information System (INIS)
For traditional linear type inlet, hydrocyclone has an unstable inner field, high turbulence intensity and low separation efficiency, this paper proposes an inlet mode that uses an Archimedes spiral hydrocyclone. A Mixture liquid-solid multiphase flow model combined with the kinetic theory of granular flow was used to simulate the high concentration water-sand-air three-phase flow in a hydrocyclone. We analyzed the pressure field, velocity field and turbulent kinetic energy and compared with traditional linear type inlet hydrocyclone inner field. The results show that Archimedes spiral inlet hydrocyclone's pressure field is evenly distributed. The Archimedes spiral inlet hydrocyclone can guide and accelerate the mixture flow and produce small forced vortex and less short circuit flow. The particles easily go to the outer vortex and are separated. The Archimedes spiral inlet hydrocyclone has effectively improved the stability of inner flow field and separation efficiency
PORE-SCALE SIMULATION OF FLUID FLOW IN PACKED-BED REACTORS VIA RIGID-BODY SIMULATIONS AND CFD
Icardi, Matteo; Marchisio, Daniele,; Boccardo, Gianluca
2014-01-01
The problem of fluid flow in porous media is of paramount importance in the process, oil and metallurgical industries, since it is involved in the extraction of minerals and oil, in aquifer dynamics, as well as chemical reactions carried out in fixed bed catalytic reactors. Its CFD simulation is particularly interesting, as it offers the possibility of reducing the extent of costly experimental investigations, but presents a number of technical challenges. One of the main issues is the genera...
CFD simulation and experimental analysis of erosion in a slurry tank test rig
Directory of Open Access Journals (Sweden)
Bart Hans-Jörg
2013-04-01
Full Text Available Erosion occurring in equipment dealing with liquid-solid mixtures such as pipeline parts, slurry pumps, liquid-solid stirred reactors and slurry mixers in various industrial applications results in operational failure and economic costs. A slurry erosion tank test rig is designed and was built to investigate the erosion rates of materials and the influencing parameters such as flow velocity and turbulence, flow angle, solid particle concentration, particles size distribution, hardness and target material properties on the material loss and erosion profiles. In the present study, a computational fluid dynamics (CFD tool is used to simulate the erosion rate of sample plates in the liquid-solid slurry mixture in a cylindrical tank. The predictions were made in a steady state and also transient manner, applying the flow at the room temperature and using water and sand as liquid and solid phases, respectively. The multiple reference frame method (MRF is applied to simulate the flow behavior and liquid-solid interactions in the slurry tank test rig. The MRF method is used since it is less demanding than sliding mesh method (SM and gives satisfactory results. The computational domain is divided into three regions: a rotational or MRF zone containing the mixer, a rotational zone (MRF containing the erosion plates and a static zone (outer liquid zone. It is observed that changing the MRF zone diameter and height causes a very low impact on the results. The simulated results were obtained for two kinds of hard metals namely stainless steel and ST-50 under some various operating conditions and are found in good agreement with the experimental results.
Simulation of hydrogen mitigation in catalytic recombiner. Part-II: Formulation of a CFD model
Energy Technology Data Exchange (ETDEWEB)
Prabhudharwadkar, Deoras M. [Department of Mechanical Engineering, Indian Institute of Technology-Bombay, Powai, Mumbai 400076 (India); Iyer, Kannan N., E-mail: kiyer@me.iitb.ac.i [Department of Mechanical Engineering, Indian Institute of Technology-Bombay, Powai, Mumbai 400076 (India)
2011-05-15
Research highlights: Hydrogen transport in containment with recombiners is a multi-scale problem. A novel methodology worked out to lump the recombiner characteristics. Results obtained using commercial code FLUENT are cast in the form of correlations. Hence, coarse grids can obtain accurate distribution of H{sub 2} in containment. Satisfactory working of the methodology is clearly demonstrated. - Abstract: This paper aims at formulation of a model compatible with CFD code to simulate hydrogen distribution and mitigation using a Passive Catalytic Recombiner in the Nuclear power plant containments. The catalytic recombiner is much smaller in size compared to the containment compartments. In order to fully resolve the recombination processes during the containment simulations, it requires the geometric details of the recombiner to be modelled and a very fine mesh size inside the recombiner channels. This component when integrated with containment mixing calculations would result in a large number of mesh elements which may take large computational times to solve the problem. This paper describes a method to resolve this simulation difficulty. In this exercise, the catalytic recombiner alone was first modelled in detail using the best suited option to describe the reaction rate. A detailed parametric study was conducted, from which correlations for the heat of reaction (hence the rate of reaction) and the heat transfer coefficient were obtained. These correlations were then used to model the recombiner channels as single computational cells providing necessary volumetric sources/sinks to the energy and species transport equations. This avoids full resolution of these channels, thereby allowing larger mesh size in the recombiners. The above mentioned method was successfully validated using both steady state and transient test problems and the results indicate very satisfactory modelling of the component.
Modeling and simulation of PEM fuel cell's flow channels using CFD techniques
Energy Technology Data Exchange (ETDEWEB)
Cunha, Edgar F.; Andrade, Alexandre B.; Robalinho, Eric; Bejarano, Martha L.M.; Linardi, Marcelo [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mails: efcunha@ipen.br; abodart@ipen.br; eric@ipen.br; mmora@ipen.br; mlinardi@ipen.br; Cekinski, Efraim [Instituto de Pesquisas Tecnologicas (IPT-SP), Sao Paulo, SP (Brazil)]. E-mail: cekinski@ipt.br
2007-07-01
Fuel cells are one of the most important devices to obtain electrical energy from hydrogen. The Proton Exchange Membrane Fuel Cell (PEMFC) consists of two important parts: the Membrane Electrode Assembly (MEA), where the reactions occur, and the flow field plates. The plates have many functions in a fuel cell: distribute reactant gases (hydrogen and air or oxygen), conduct electrical current, remove heat and water from the electrodes and make the cell robust. The cost of the bipolar plates corresponds up to 45% of the total stack costs. The Computational Fluid Dynamic (CFD) is a very useful tool to simulate hydrogen and oxygen gases flow channels, to reduce the costs of bipolar plates production and to optimize mass transport. Two types of flow channels were studied. The first type was a commercial plate by ELECTROCELL and the other was entirely projected at Programa de Celula a Combustivel (IPEN/CNEN-SP) and the experimental data were compared with modelling results. Optimum values for each set of variables were obtained and the models verification was carried out in order to show the feasibility of this technique to improve fuel cell efficiency. (author)
International Nuclear Information System (INIS)
In order to comprehensively study the hydrodynamic characteristics of diffuser for marine current turbine with a postpositive bulb, a geometric model of the turbine was established. Three-dimensional CFD simulation of turbulent flow was performed based on the incompressible continuity equation, the Navier-Stokes equations and the Spalart-Allmaras turbulence model. The influence of diffuser was calculated and analyzed by numerical results, which were also compared with model test results. Results showed that the numerical results agree fairly well with model test and the maximum error of impeller efficiency and power is 1.5% and 1.8% in the rated water velocity condition, which are less than 5.8% and 5.5% under other cases respectively. The new type marine current turbine with a bulb for erecting motor which is different from regular, and the diffuser can aggregate water flow, raise inlet water velocity more than 3% and efficiency of impeller effectively increased. After diffuser was added, the power coefficient curve rose over the full range, so the high power area became widely, and then remarkably prolonged power time as well as increased generated energy, it is also significant for efficient utilization of marine current energy and environmental pollution remission
CFD Simulation of Propane Cracking Tube Using Detailed Radical Kinetic Mechanism
Institute of Scientific and Technical Information of China (English)
张楠; 邱彤; 陈丙珍
2013-01-01
In the radiant section of cracking furnace, the thermal cracking process is highly coupled with turbulent flow, heat transfer and mass transfer. In this paper, a three-dimensional simulation of propane pyrolysis reactor tube is performed based on a detailed kinetic radical cracking scheme, combined with a comprehensive rigorous compu-tational fluid dynamics (CFD) model. The eddy-dissipation-concept (EDC) model is introduced to deal with turbu-lence-chemistry interaction of cracking gas, especially for the multi-step radical kinetics. Considering the high as-pect ratio and severe gradient phenomenon, numerical strategies such as grid resolution and refinement, stepping method and relaxation technique at different levels are employed to accelerate convergence. Large scale of radial nonuniformity in the vicinity of the tube wall is investigated. Spatial distributions of each radical reaction rate are first studied, and made it possible to identify the dominant elementary reactions. Additionally, a series of operating conditions including the feedstock feed rate, wall temperature profile and heat flux profile towards the reactor tubes are investigated. The obtained results can be used as scientific guide for further technical retrofit and operation op-timization aiming at high conversion and selectivity of pyrolysis process.
CFD Simulation of Oriifce Flow in Oriifce-type Liquid Distributor
Institute of Scientific and Technical Information of China (English)
Yu Hongfeng; Li Xingang; Sui Hong; Li Hong
2013-01-01
In this study, a suitable CFD (computational lfuid dynamics) model has been developed to investigate the inlfu-ence of liquid height on the discharge coefifcient of the oriifce-type liquid distributors. The oriifce lfow in different diam-eters and liquid heights has been realized using the shear stress transport (SST) turbulence model and the Gamma Theta transition (GTT) model. In the ANSYS CFX software, two models are used in conjunction with an automatic wall treatment which allows for a smooth shift from a wall function (WF) to a low turbulent-Re near wall formulation (LTRW). The results of the models coupled with LTRW are closer to the experimental results compared with the models with WF, indicating that LTRW is more appropriate for the prediction of boundary layer characteristics of oriifce lfow. Simulation results show that the lfow conditions of oriifces change with the variation of liquid height. With respect to the turbulence in oriifce, the SST model coupled with LTRW is recommended. However, with respect to the transition to turbulence in oriifce with an increase in liquid height, the predictions of GTT model coupled with LTRW are superior to those obtained using other models.
CFD simulation of bubbling and collapsing characteristics in a gas-solid fluidized bed
Institute of Scientific and Technical Information of China (English)
Pei Pei; Zhang Kai; Lu Erwei; Wen Dongsheng
2009-01-01
Computational Fluid Dynamics (CFD) has become an alternative method to experiments for understanding the fluid dynamics of multiphase flow. A two-fluid model, which contains additional terms in both the gas- and solid-phase momentum equations, is used to investigate the fluidization quality in a fluidized bed. A case study for quartz sand with a density of 2,660 kg/m3 and a diameter of 500 μm,whose physical property is similar to a new kind of catalyst for producing clean fuels through the residue fluid catalytic cracking process, is simulated in a two-dimensional fluidized bed with 0.57 m width and 1.00 m height. Transient bubbling and collapsing characteristics are numerically investigated in the platform of CFX 4.4 by integrating user-defined Fortran subroutines. The results show that the fluidization and collapse process is in fair agreement with the classical theory of Geldart B classification, but the collapse time is affected by bubbles at the interface between the dense phase and freeboard.
CFD simulations of the effect of inlet conditions on Taylor flow formation
International Nuclear Information System (INIS)
The mechanism of Taylor bubble formation and the resulting bubble size in capillaries at low superficial gas velocity (UGS < 0.04 m/s) were investigated using Computational Fluid Dynamics (CFD). A co-flow inlet configuration in a 1 mm ID capillary with two gas nozzle sizes of 0.11 mm and 0.34 mm ID, respectively, was studied. Air and three liquids - water, octane and 'semi-octane' - were used as test fluids. Bubble formation followed a multi-stage mechanism while the bubble shape during formation deviated from the spherical one assumed in the literature. The three-phase contact line was also found to move along the top wall of the nozzle for the small size nozzle, which had an effect on the bubble size formed. Simulated bubble sizes compared favourably with experimental data in a similar system. Bubble sizes were found to increase with increasing gas and decreasing liquid velocities and increasing nozzle size and nozzle wall thickness. From the fluid properties, surface tension was found to have a strong effect on bubble size but not density or viscosity. An increase in contact angle also increased bubble size. From the available literature correlations those that included phase fraction or ratios of superficial phase velocities were found to predict better the observed bubble sizes
CFD Simulation of Flow Features and Vorticity Structures in Tuna-Like Swimming
Institute of Scientific and Technical Information of China (English)
YANG Liang; SU Yu-min
2011-01-01
The theoretical research on the propulsive principle of aquatic animal becomes more important and attracted more researchers to make efforts on it.In the present study,a computational fluid dynamic(CFD)simulation of a three-dimensional traveling-wave undulations body of tuna has been developed to investigate the fluid flow features and vorticity structures around this body when moving in a straight line.The undulation only takes place in the posterior half of the fish,and the tuna-tail is considered as a lunate fin oscillating with the mode combined swaying with yawing.A Reynolds-averaged Navier-Stokes(BANS)equation is developed,employing a control-volume method and a k-omega SST turbulent model;meanwhile an unstructured tetrahedral grid,which is generated for the three-dimensional geometry,is used based on the deformation of the hind parts of the body and corresponding movement of the tail.We calculated the hydrodynamic performance of tuna-like body when a tuna swims in a uniform velocity,and compared the input power coefficient,output power coefficient and propulsive efficiency of the oscillating tuna-tail with or without body vortex shedding.Additionally,the load distribution on the body,flow features and vorticity structures around the body were demonstrated.The effect of interaction between the body-generated vortices and the tail-generated vorticity on the hydrodynamic performance can be obtained.
CFD simulation of flow features and vorticity structures in tuna-like swimming
Yang, Liang; Su, Yu-Min
2011-03-01
The theoretical research on the propulsive principle of aquatic animal becomes more important and attracted more researchers to make efforts on it. In the present study, a computational fluid dynamic (CFD) simulation of a three-dimensional traveling-wave undulations body of tuna has been developed to investigate the fluid flow features and vorticity structures around this body when moving in a straight line. The undulation only takes place in the posterior half of the fish, and the tuna-tail is considered as a lunate fin oscillating with the mode combined swaying with yawing. A Reynolds-averaged Navier-Stokes (RANS) equation is developed, employing a control-volume method and a k-omega SST turbulent model; meanwhile an unstructured tetrahedral grid, which is generated for the three-dimensional geometry, is used based on the deformation of the hind parts of the body and corresponding movement of the tail. We calculated the hydrodynamic performance of tuna-like body when a tuna swims in a uniform velocity, and compared the input power coefficient, output power coefficient and propulsive efficiency of the oscillating tuna-tail with or without body vortex shedding. Additionally, the load distribution on the body, flow features and vorticity structures around the body were demonstrated. The effect of interaction between the body-generated vortices and the tail-generated vorticity on the hydrodynamic performance can be obtained.
Modeling and simulation of PEM fuel cell's flow channels using CFD techniques
International Nuclear Information System (INIS)
Fuel cells are one of the most important devices to obtain electrical energy from hydrogen. The Proton Exchange Membrane Fuel Cell (PEMFC) consists of two important parts: the Membrane Electrode Assembly (MEA), where the reactions occur, and the flow field plates. The plates have many functions in a fuel cell: distribute reactant gases (hydrogen and air or oxygen), conduct electrical current, remove heat and water from the electrodes and make the cell robust. The cost of the bipolar plates corresponds up to 45% of the total stack costs. The Computational Fluid Dynamic (CFD) is a very useful tool to simulate hydrogen and oxygen gases flow channels, to reduce the costs of bipolar plates production and to optimize mass transport. Two types of flow channels were studied. The first type was a commercial plate by ELECTROCELL and the other was entirely projected at Programa de Celula a Combustivel (IPEN/CNEN-SP) and the experimental data were compared with modelling results. Optimum values for each set of variables were obtained and the models verification was carried out in order to show the feasibility of this technique to improve fuel cell efficiency. (author)
Hajati, Omid; Zarrabi, Khalil; Karimi, Reza; Hajati, Azadeh
2012-01-01
There is still controversy over the differences in the patency rates of the sequential and individual coronary artery bypass grafting (CABG) techniques. The purpose of this paper was to non-invasively evaluate hemodynamic parameters using complete 3D computational fluid dynamics (CFD) simulations of the sequential and the individual methods based on the patient-specific data extracted from computed tomography (CT) angiography. For CFD analysis, the geometric model of coronary arteries was reconstructed using an ECG-gated 64-detector row CT. Modeling the sequential and individual bypass grafting, this study simulates the flow from the aorta to the occluded posterior descending artery (PDA) and the posterior left ventricle (PLV) vessel with six coronary branches based on the physiologically measured inlet flow as the boundary condition. The maximum calculated wall shear stress (WSS) in the sequential and the individual models were estimated to be 35.1 N/m(2) and 36.5 N/m(2), respectively. Compared to the individual bypass method, the sequential graft has shown a higher velocity at the proximal segment and lower spatial wall shear stress gradient (SWSSG) due to the flow splitting caused by the side-to-side anastomosis. Simulated results combined with its surgical benefits including the requirement of shorter vein length and fewer anastomoses advocate the sequential method as a more favorable CABG method. PMID:23365974
CFD simulation of aggregation and breakage processes in laminar Taylor-Couette flow.
Wang, L; Marchisio, D L; Vigil, R D; Fox, R O
2005-02-15
An experimental and computational investigation of the effects of local fluid shear rate on the aggregation and breakage of approximately 10 microm latex spheres suspended in an aqueous solution undergoing laminar Taylor-Couette flow was carried out according to the following program. First, computational fluid dynamics (CFD) simulations were performed and the flow field predictions were validated with data from particle image velocimetry experiments. Subsequently, the quadrature method of moments (QMOM) was implemented into the CFD code to obtain predictions for mean particle size that account for the effects of local shear rate on the aggregation and breakage. These predictions were then compared with experimental data for latex sphere aggregates (using an in situ optical imaging method) and with predictions using spatial average shear rates. The mean particle size evolution predicted by CFD and QMOM using appropriate kinetic expressions that incorporate information concerning the particle morphology (fractal dimension) and the local fluid viscous effects on aggregation collision efficiency match well with the experimental data. PMID:15589543
Energy Technology Data Exchange (ETDEWEB)
Richard W. Johnson; Hugh M. McIlroy
2010-08-01
The U. S. Department of Energy (DOE) is supporting the development of a next generation nuclear plant (NGNP), which will be based on a very high temperature reactor (VHTR) design. The VHTR is a single-phase helium-cooled reactor wherein the helium will be heated initially to 750 °C and later to temperatures approaching 1000 °C. The high temperatures are desired to increase reactor efficiency and to provide a heat source for the manufacture of hydrogen and other applications. While computational fluid dynamics (CFD) has not been used in the past to design or license nuclear reactors in the U. S., it is expected that CFD will be used in the design and safety analysis of forthcoming designs. This is partly because of the maturity of CFD and partly because detailed information is desired of the flow and heat transfer inside the reactor to avoid hot spots and other conditions that might compromise reactor safety. Numerical computations of turbulent flow should be validated against experimental data for flow conditions that contain some or all of the physics expected in the thermal fluid machinery of interest. To this end, a scaled model of a narrow slice of the lower plenum of the prismatic VHTR was constructed and installed in the Idaho National Laboratory’s (INL) matched index of refraction (MIR) test facility and data were taken. The data were then studied and compared to CFD calculations to help determine their suitability for validation data. One of the main findings was that the inlet data, which were measured and controlled by calibrated mass flow rotameters and were also measured using detailed stereo particle image velocimetry (PIV) showed considerable discrepancies in mass flow rate between the two methods. The other finding was that a randomly unstable recirculation zone occurs in the flow. This instability has a very significant effect on the flow field in the vicinity of the inlet jets. Because its time scale is long and because it is apparently a
Validation of impinging jet models to be used in CANDU calandria vessel CFD simulations
International Nuclear Information System (INIS)
The knowledge of the external wall temperature distributions on calandria tubes is of major concern in nuclear safety analysis. One of the models used by the Canadian industry consists in replacing the calandria by an equivalent porous media with appropriate anisotropic hydraulic resistances. This technique has the advantage to treat a non-connected domain as an equivalent quasi-continuous media; however, it cannot provide information about local velocity variations. Within the framework of the present study, a full-scale modeling of the moderator using a Computational Fluid Dynamic code (FLUENT) is underway. The use of a 2D model have shown that the geometry of calandria nozzles have a strong effect on the flow distribution. Some authors suggest to model the flow at the entrance of the calandria as successive flow circulation through a portion of a straight pipe, a curved pipe, and a circular nozzle placed in front of an impinging plate, and to use the results as input data in full-scale calculations. Obtaining these data requires large computational resources before performing complete flow simulations, while they do necessarily represent neither the real geometry nor the actual flow conditions. Therefore, the present study is aimed to find appropriate water-jet modeling approaches that can help in improving moderator circulation simulations. In particular, the principal interest consists in finding a semi-analytical nozzle model that can be used as a constitutive relationship in a CFD code. This approach will contribute both to increase the number of meshes in the calandria vessel as well as to decrease the computational time. (author)
CFD Simulation of Pilot HDS Trickle-Bed Reactor
Tukač, V.
2012-01-01
The goal of this study is to compare experimental measurement obtained by RTD method with result of computational model. The goal of this work is to evaluate influence of dilution extent on operation of pilot test reactor and to forecast interaction between intrinsic reaction kinetic, hydrodynamics and mass transfer.
CFD simulation of solids suspension in stirred tanks: Review
Ochieng Aoyi; Onyango Mrice S.
2010-01-01
Many chemical reactions are carried out using stirred tanks, and the efficiency of such systems depends on the quality of mixing, which has been a subject of research for many years. For solid-liquid mixing, traditionally the research efforts were geared towards determining mixing features such as off-bottom solid suspension using experimental techniques. In a few studies that focused on the determination of solids concentration distribution, some methods that have been used have not be...
CFD Simulation of Twin Vertical Axis Tidal Turbines System
Syed Shah Khalid; Zhang Liang; Sheng Qi-hu
2013-01-01
As concerns about rising fossil-fuel prices, energy security and climate-change increase, renewable energy can play a vital role in producing local, clean and inexhaustible energy to supply world rising demand for electricity. In this study, hydrodynamic analysis of vertical axis tidal turbine operating side-by-side is numerically analyzed. Two-dimensional numerical modeling of the unsteady flow through the blades of the turbine is performed using ANSYS CFX, hereafter CFX; this is based on a ...
3D CFD simulation of flashing flows in a converging-diverging nozzle
Energy Technology Data Exchange (ETDEWEB)
Liao, Yixiang, E-mail: y.liao@hzdr.de; Lucas, Dirk
2015-10-15
Highlights: • Flashing flow in a converging-diverging nozzle simulated. • Three-dimensional CFD simulation using two-fluid model used. • Satisfactory agreement in cross-section averaged parameters. • Reasons for discrepancies in radial profiles discussed. • Obvious improvement in comparison to 1D calculations. - Abstract: Flashing of initially sub-cooled water in a vertical circular converging-diverging nozzle is simulated with two-fluid model incorporating drag and non-drag forces. Phase change is assumed to be induced only by interphase heat transfer while pressure jump across the interface is ignored. The reliability of CFD simulations is confirmed by comparison with experimental data and one-dimensional results basing on a drift-flux model. Satisfactory prediction of mass flow rate and cross-section averaged parameters is achieved. The predicted radial distribution of void fraction is however much more flat than the measured one. The discrepancy is found to be caused by the effect of lift force and the reversal of relative velocity. Cases characterised with large pressure-undershoot exhibit significant pressure non-equilibrium effect in form of a pressure recovery process. Sensitivity tests on bubble number density, heat transfer coefficient as well as nucleation are performed.
CFD simulation of non-Newtonian fluid flow in anaerobic digesters.
Wu, Binxin; Chen, Shulin
2008-02-15
A general mathematical model that predicts the flow fields in a mixed-flow anaerobic digester was developed. In this model, the liquid manure was assumed to be a non-Newtonian fluid, and the flow governed by the continuity, momentum, and k-epsilon standard turbulence equations, and non-Newtonian power law model. The commercial computational fluid dynamics (CFD) software, Fluent, was applied to simulate the flow fields of lab-scale, scale-up, and pilot-scale anaerobic digesters. The simulation results were validated against the experimental data from literature. The flow patterns were qualitatively compared for Newtonian and non-Newtonian fluids flow in a lab-scale digester. Numerical simulations were performed to predict the flow fields in scale-up and pilot-scale anaerobic digesters with different water pump power inputs and different total solid concentration (TS) in the liquid manure. The optimal power inputs were determined for the pilot-scale anaerobic digester. Some measures for reducing dead and low velocity zones were proposed based upon the CFD simulation results. PMID:17705227
On the modelling of bubble entrainment by impinging jets in CFD-simulations
International Nuclear Information System (INIS)
This contribution presents different approaches for the modeling of air entrainment under water by plunging jets in CFD codes. In simulations which include the full length of the jet and its environment, the process of bubble generation cannot be resolved due to computational limitations. This is why the air entrainment has to be modeled in meso-scale simulations. In the frame of an Euler- Euler simulation, the local morphology of the phases has to be considered in the drag model. In the impinging jet configuration, the air is a continuous phase above the water level but bubbly below the water level. Various drag models are implemented in the CFD solver CFX11 and their influence on the gas void fraction below the water level is discussed. The algebraic interface area density (AIAD) model applies a drag coefficient for bubbles and a different drag coefficient for the free surface. If the AIAD model is used for the simulation of impinging jets, the gas entrainment depends on the free parameters included in this model. The calculated gas entrainment can be adapted via these parameters. Therefore, an advanced AIAD approach could be used in future for the implementation of models (e.g. correlations) for the gas entrainment. (authors)
CFD Simulation of Casing Treatment of Axial Flow Compressors
DeWitt, Kenneth
2005-01-01
A computational study is carried out to understand the physical mechanism responsible for the improvement in stall margin of an axial flow rotor due to the circumferential casing grooves. It is shown that the computational tool used predicts an increase in operating range of the rotor when casing grooves are present. A budget of the axial momentum equation is carried out at the rotor casing in the tip gap in order to uncover the physical process behind this stall margin improvement. It is shown that for the smooth casing the net axial pressure force . However in the presence of casing grooves the net axial shear stress force acting at the casing is augmented by the axial force due to the radial transport of axial momentum, which occurs across the grooves and power stream interface. This additional force adds to the net axial viscous sheer force and thus leads to an increase in the stall margin of the rotor.
Figueredo-Cardero, Alvio; Chico, Ernesto; Castilho, Leda R; Medronho, Ricardo A
2009-11-01
In the present work Computational Fluid Dynamics (CFD) was used to study the flow field and particle dynamics in an internal spin-filter (SF) bioreactor system. Evidence of a radial exchange flow through the filter mesh was detected, with a magnitude up to 130-fold higher than the perfusion flow, thus significantly contributing to radial drag. The exchange flow magnitude was significantly influenced by the filter rotation rate, but not by the perfusion flow, within the ranges evaluated. Previous reports had only given indirect evidences of this exchange flow phenomenon in spin-filters, but the current simulations were able to quantify and explain it. Flow pattern inside the spin-filter bioreactor resembled a typical Taylor-Couette flow, with vortices being formed in the annular gap and eventually penetrating the internal volume of the filter, thus being the probable reason for the significant exchange flow observed. The simulations also showed that cells become depleted in the vicinity of the mesh due to lateral particle migration. Cell concentration near the filter was approximately 50% of the bulk concentration, explaining why cell separation achieved in SFs is not solely due to size exclusion. The results presented indicate the power of CFD techniques to study and better understand spin-filter systems, aiming at the establishment of effective design, operation and scale-up criteria. PMID:19998058
Energy Technology Data Exchange (ETDEWEB)
Corley, Richard A; Minard, Kevin R; Kabilan, Senthil; Einstein, Daniel R; Kuprat, Andrew P; harkema, J R; Kimbell, Julia; Gargas, M L; Kinzell, John H
2009-06-01
The percentages of total airflows over the nasal respiratory and olfactory epithelium of female rabbits were calculated from computational fluid dynamics (CFD) simulations of steady-state inhalation. These airflows calculations, along with nasal airway geometry determinations, are critical parameters for hybrid CFD/physiologically based pharmacokinetic models that describe the nasal dosimetry of water-soluble or reactive gases and vapors in rabbits. CFD simulations were based upon three-dimensional computational meshes derived from magnetic resonance images of three adult female New Zealand White (NZW) rabbits. In the anterior portion of the nose, the maxillary turbinates of rabbits are considerably more complex than comparable regions in rats, mice, monkeys, or humans. This leads to a greater surface area to volume ratio in this region and thus the potential for increased extraction of water soluble or reactive gases and vapors in the anterior portion of the nose compared to many other species. Although there was considerable interanimal variability in the fine structures of the nasal turbinates and airflows in the anterior portions of the nose, there was remarkable consistency between rabbits in the percentage of total inspired airflows that reached the ethmoid turbinate region (~50%) that is presumably lined with olfactory epithelium. These latter results (airflows reaching the ethmoid turbinate region) were higher than previous published estimates for the male F344 rat (19%) and human (7%). These differences in regional airflows can have significant implications in interspecies extrapolations of nasal dosimetry.
Cfd Simulation of Capillary Rise of Liquid in Cylindrical Container with Lateral Vanes
Liu, Xiaolin; Huang, Yiyong; Li, Guangyu
2016-06-01
Orbit refueling is one of the most significant technologies, which has vital strategic meaning. It can enhance the flexibility and prolong the lifetime of the spacecrafts. Space propellant management is one of the key technologies in orbit refueling. Based on the background of space propellant management, CFD simulations of capillary rise of liquid in Cylindrical container with lateral vanes in space condition were carried out in this paper. The influence of the size and the number of the vanes to the capillary flow were analyzed too. The results can be useful to the design and optimization of the propellant management device in the vane type surface tension tank.
DET3D - A CFD tool for simulating hydrogen combustion in nuclear reactor safety
International Nuclear Information System (INIS)
In this paper, the CFD code DET3D is described which has been used for simulating assumed accident scenarios in nuclear reactors (fission and fusion, see e.g. [4, 5, 11]) involving hydrogen detonations in complex 3-dimensional geometries. Two validation calculations against experiments are discussed in detail: (i) a hydrogen-air detonation in a 12 m long straight tube with a truly 3-dimensional inner obstacle, and (ii) a pure radiolytic gas detonation in a 5 m long U-shaped tube at 44 bar initial pressure. (author)
International Nuclear Information System (INIS)
Highlights: • We use CFD model to simulate air temperature in an industrial-scale paint curing oven. • Comparison of temperature is made for two proposed options to achieve energy saving. • Both proposed options provide the increase in average air temperature for the oven. - Abstract: An oven has been commonly employed to cure powder painted on metal parts for an air-conditioning production. There are many options to improve efficiency in fuel use for the paint curing oven; however some options need deep understanding to prove the possibility of thermal performance. In this work, computational fluid dynamic (CFD) modeling and simulation have been applied to study the temperature distribution and the flow pattern in the paint curing oven on a large scale. The CFD model has been validated against real data. The validated CFD model is used to investigate the temperature distribution and the flow pattern for two proposed options: eliminating stored heat and rearranging airflow. Results demonstrate that both cases provide temperature increase of 1.9 and 1.3 °C for air compared to the present paint curing oven. It can be concluded that the two proposed options are applicable for further implementation to the present paint curing oven
On the wind-induced undercatch in rainfall measurement using CFD-based simulations
Colli, Matteo; Lanza, Luca
2016-04-01
The reliability of liquid atmospheric precipitation measurements is a basic requirement since rainfall data represent the fundamental input variables of many scientific applications (hydrologic models, weather forecasting data assimilation, climate change studies, calibration of weather radar, etc.). The scientific community and the National Meteorological Services worldwide are facing the issue of improving the accuracy of precipitation measurements, with an increased focus on retrieving the information at a high temporal resolution. The rainfall intensity is indeed fundamental information for the precise quantification of the markedly time-varying behavior of precipitation events. Environmental conditions have a relevant impact on the rain collection/sensing efficiency. Among other effects, wind is recognized as a major source of underestimation since it reduces the collection efficiency of the catching-type gauges (Nespor and Sevruk, 1999), the most common type of instruments used worldwide in the national observation networks. The collection efficiency is usually obtained by comparing the rainfall amounts measured by the gauge with the reference, which was defined by EN-13798 standard (CEN, 2002) as a gauge placed below the ground level inside a pit. A lot of scatter can be observed for a given wind speed, which is mainly caused by comparability issues among the tested gauges. An additional source of uncertainty is the drops size distribution (DSD) of the rain, which varies on an event-by-event basis. The goal of this study is to understand the role of the physical characteristics of precipitation particles on the wind-induced rainfall underestimation observed for catching-type gauges. To address this issue, a detailed analysis of the flow field in the vicinity of the gauge is conducted using time-averaged computational fluid dynamics (CFD) simulations (Colli et al., 2015). Using a Lagrangian model, which accounts for the hydrodynamic behavior of liquid
CFD Simulation and Optimisation of a Low Energy Ventilation and Cooling System
John Kaiser Calautit; Dominic O'Connor; Polytimi Sofotasiou; Ben Richard Hughes
2015-01-01
Mechanical Heating Ventilation and Air-Conditioning (HVAC) systems account for 60% of the total energy consumption of buildings. As a sector, buildings contributes about 40% of the total global energy demand. By using passive technology coupled with natural ventilation from wind towers, significant amounts of energy can be saved, reducing the emissions of greenhouse gases. In this study, the development of Computational Fluid Dynamics (CFD) analysis in aiding the development of wind towers wa...
CFD Simulation of Polydispersed Bubbly Two-Phase Flow around an Obstacle
E. Krepper; Ruyer, P.; Beyer, M.; Lucas, D.; H.-M. Prasser; Seiler, N
2009-01-01
This paper concerns the model of a polydispersed bubble population in the frame of an ensemble averaged two-phase flow formulation. The ability of the moment density approach to represent bubble population size distribution within a multi-dimensional CFD code based on the two-fluid model is studied. Two different methods describing the polydispersion are presented: (i) a moment density method, developed at IRSN, to model the bubble size distribution function and (ii) a population balance meth...
Case studies from the REHVA CFD guide book
DEFF Research Database (Denmark)
Nielsen, Peter V.
2008-01-01
This paper presents CFD predictions which are used at different levels, from the evaluation of an idea to the design of a system, or for the analysing work on an existing building.......This paper presents CFD predictions which are used at different levels, from the evaluation of an idea to the design of a system, or for the analysing work on an existing building....
International Nuclear Information System (INIS)
This study presents a new modelling methodology for three-dimensional simulation of a reheating furnace of steel billets with natural gas burners. The movement of the billets inside the furnace is a periodically transient phenomenon. A modification in the energy transport equation is introduced through source terms in the billet region to convert the transient movements of the billets into a steady-state simulation, which significantly reduces the computational time without any loss of information. The combustion simulation inside the burners is performed using a global combustion mechanism that takes into account the combustion of the main gaseous species present in natural gas following a kinetic and turbulent control of the reaction through the Eddy Dissipation Concept (EDC). The results are contrasted and validated with the data obtained in a real facility though the SCADA of the plant. Some parameters, such as the surface temperatures of billets at the outlet and the distribution of power supplied by the fuel inside the furnace are reasonably close to the real case data obtained in temperature fields of both billets and the gas phase as well as the energy balance, leading to the conclusion that the proposed methodology is adequate for the purpose of simulating this system. - Highlights: • A new methodology is described in the CFD simulation of a reheating furnace in steady-state condition. • The movement of billets is performed by modifying the energy transport equation. • The method achieves a reduction in calculation time compared with transient modelling method. • CFD simulation has been compared with a real case with reasonably close results. • The method can be applicable to predict performance following geometrical and operational modifications
Directory of Open Access Journals (Sweden)
J. Govardhan, G.V.S. Rao, J. Narasaiah
2011-09-01
Full Text Available As part of an investigation few experiments were conducted to study the enhanced heat transfer rate and increased furnace efficiency in a diesel fired crucible furnace with oscillating combustion. The results of experimental investigations of temperature distribution inside the crucible furnace during oscillating combustion are validated with the numerical simulation CFD code. At first pragmatic study of temperature distribution inside a furnace was carried out with conventional mode of combustion at certain conditions and later transient behavior similar to that is conducted with oscillating combustion mode with the same conditions. There found to be enhanced heat transfer rate, reduced processing time and increased furnace efficiency with visibly clean emissions during the oscillating combustion mode than the conventional combustion mode. In the present paper the temperatures inside the furnace at few designated points measured by suitable K type thermo-couples are compared with the CFD code. The geometric models were created in ANSYS and the configuration was an asymmetric one for computational reason. The experimental and numerical investigations produce similar acceptable results. The presented results show that the 3D transient model appeared to be an effective numerical tool for the simulation of the crucible furnace for melting processes.
Energy Technology Data Exchange (ETDEWEB)
Pal, Eshita [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Kumar, Mukesh [Reactor Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India); Joshi, Jyeshtharaj B., E-mail: jbjoshi@gmail.com [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Department of Chemical Engineering, Institute of Chemical Technology, Matunga, Mumbai 400019 India (India); Nayak, Arun K. [Reactor Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India); Vijayan, Pallippattu K., E-mail: vijayanp@barc.gov.in [Reactor Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India)
2015-10-15
Highlights: • CFD simulations in the Calandria of an advanced reactor under natural circulation. • Under natural convection, majority of the flow recirculates within the Calandria. • Maximum temperature is located at the top and center of the fuel channel matrix. • During SBO, temperature inside Calandria is stratified. - Abstract: Passive systems are being examined for the future Advanced Nuclear Reactor designs. One of such concepts is the Passive Moderator Cooling System (PMCS), which is designed to remove heat from the moderator in the Calandria vessel passively in case of an extended Station Black Out condition. The heated heavy-water moderator (due to heat transferred from the Main Heat Transport System (MHTS) and thermalization of neutrons and gamma from radioactive decay of fuel) rises upward due to buoyancy, gets cooled down in a heat exchanger and returns back to Calandria, completing a natural circulation loop. The natural circulation should provide sufficient cooling to prevent the increase of moderator temperature and pressure beyond safe limits. In an earlier study, a full-scale 1D transient simulation was performed for the reactor including the MHTS and the PMCS, in the event of a station blackout scenario (Kumar et al., 2013). The results indicate that the systems remain within the safe limits for 7 days. However, the flow inside a geometry like Calandria is quite complex due to its large size and inner complexities of dense fuel channel matrix, which was simplified as a 1D pipe flow in the aforesaid analysis. In the current work, CFD simulations are performed to study the temperature distributions and flow distribution of moderator inside the Calandria vessel using a three-dimensional CFD code, OpenFoam 2.2.0. First, a set of steady state simulation was carried out for a band of inlet mass flow rates, which gives the minimum mass flow rate required for removing the maximum heat load, by virtue of prediction of hot spots inside the Calandria
International Nuclear Information System (INIS)
Highlights: • CFD simulations in the Calandria of an advanced reactor under natural circulation. • Under natural convection, majority of the flow recirculates within the Calandria. • Maximum temperature is located at the top and center of the fuel channel matrix. • During SBO, temperature inside Calandria is stratified. - Abstract: Passive systems are being examined for the future Advanced Nuclear Reactor designs. One of such concepts is the Passive Moderator Cooling System (PMCS), which is designed to remove heat from the moderator in the Calandria vessel passively in case of an extended Station Black Out condition. The heated heavy-water moderator (due to heat transferred from the Main Heat Transport System (MHTS) and thermalization of neutrons and gamma from radioactive decay of fuel) rises upward due to buoyancy, gets cooled down in a heat exchanger and returns back to Calandria, completing a natural circulation loop. The natural circulation should provide sufficient cooling to prevent the increase of moderator temperature and pressure beyond safe limits. In an earlier study, a full-scale 1D transient simulation was performed for the reactor including the MHTS and the PMCS, in the event of a station blackout scenario (Kumar et al., 2013). The results indicate that the systems remain within the safe limits for 7 days. However, the flow inside a geometry like Calandria is quite complex due to its large size and inner complexities of dense fuel channel matrix, which was simplified as a 1D pipe flow in the aforesaid analysis. In the current work, CFD simulations are performed to study the temperature distributions and flow distribution of moderator inside the Calandria vessel using a three-dimensional CFD code, OpenFoam 2.2.0. First, a set of steady state simulation was carried out for a band of inlet mass flow rates, which gives the minimum mass flow rate required for removing the maximum heat load, by virtue of prediction of hot spots inside the Calandria
DEFF Research Database (Denmark)
wake, and it is compared to the predictions from the Dynamic Wake Meandering model, for a selected 10 minutes dataset. Secondly, the average wake expansion in the fixed frame of reference is determined from measurements and compared to results from CFD simulations. The CFD simulations were conducted...... using the EllipSys3D flow solver using Large Eddy Simulation (LES) and Actuator Line Technique (ACL) to model the rotor. Discrepancies due to the uncertainties on the wake advection velocity are observed and discussed....
DEFF Research Database (Denmark)
Machefaux, Ewan; Larsen, Gunner Chr.; Troldborg, Niels;
2013-01-01
wake, and it is compared to the predictions from the Dynamic Wake Meandering model, for a selected 10 minutes dataset. Secondly, the average wake expansion in the fixed frame of reference is determined from measurements and compared to results from CFD simulations. The CFD simulations were conducted...... using the EllipSys3D flow solver using Large Eddy Simulation (LES) and Actuator Line Technique (ACL) to model the rotor. Discrepancies due to the uncertainties on the wake advection velocity are observed and discussed....
Salim, S M; Viswanathan, Shekar; Ray, Madhumita Bhowmick
2006-12-01
Dispersion of airborne contaminants in indoor air was evaluated employing physical measurement, empirical models, and computer simulation methods. Field data collected from a tray of evaporating solvent in the laboratory were compared with computational fluid dynamics (CFD) simulations coupled with evaporation models. The results indicated that mathematical models of evaporation can be coupled with CFD simulations to produce reasonable qualitative predictions of airborne contaminant levels. The airflow pattern within a room is primarily determined by the room layout and the position of the air supply diffusers. Variations in ventilation rate did not alter the airflow pattern, thus generating a characteristic concentration profile of the airborne contaminants. PMID:17050350
Application of CFD code for simulation of an inclined snow chute flow
Directory of Open Access Journals (Sweden)
R K Aggarwal
2013-03-01
Full Text Available In this paper, 2-D simulation of a 61 m long inclined snow chute flow and its interaction with a catch dam type obstacle has been carried out at Dhundhi field research station near Manali, Himachal Pradesh (India using a commercially available computational fluid dynamics (CFD code ANSYS Fluent. Eulerian non-granular multiphase model was chosen to model the snow flow in the surrounding atmospheric air domain. Both air and snow were assumed as laminar and incompressible fluids. User defined functions(UDF were written for the computation of bi-viscous Bingham fluid viscosity and wall shear stress of snow to account for the slip at the interface between the flowing snow and the stationary snow chute surface. Using the proposed CFD model, the velocity, dynamic pressure and debris deposition were simulatedfor flowing snow mass in the chute. Experiments were performed on the snow chute to validate the simulated results. On comparison, the simulated results were found in good agreement with the experimental results.
A multiscale methodology for CFD simulation of catalytic distillation bale packings
Directory of Open Access Journals (Sweden)
Ding Huidian
2016-03-01
Full Text Available A multiscale model for simulating the hydrodynamic behavior of catalytic bale packings has been proposed. This model combines computational fluid dynamics (CFD and macroscopic calculation. At small scale calculation, the CFD model includes 3-D volume-of-fluid (VOF simulation within representative elementary unit (REU under unsteady-state conditions. The REU constitutes gauze and catalyst domain, and porous media model is applied. At large scale calculation, a new mechanistic model deduced from the unit network model is employed. Based on liquid split proportion from small scale calculation, liquid distribution of the entire bale packing can be predicted. To evaluate different packing design, three common bale arrangements, i.e. one-bale, nine-bales and seven-bales, are compared. The area-weighted Christiansen uniformity coefficient is introduced to assess the distribution performance. A comparison between simulation and experimental results is made to validate the multiscale model. The present methodology is proved to be effective to analysis and design of catalytic distillation columns.
CFD SIMULATION OF AIR ION REGIME IN WORK AREAS AT CONDITION OF ARTIFICIAL AIR IONIZATION
Directory of Open Access Journals (Sweden)
M. M. Biliaiev
2016-04-01
Full Text Available Purpose. The paper supposes creation of a CFD model for calculating the air ion regime in the premises and in work areas at artificial ionization of the air by the ionizer installation indoors with considering the most important physical factors that influence the formation of ions concentration field. Methodology. The proposed CFD model for calculation of the air ion regime in work areas at artificial ionization of the air by installing ionizer indoors is based on the application of aerodynamics, electrostatics and mass transfer equations. The mass transfer equation takes into account the interaction of different polarities of ions with each other and with the dust particles. The calculation of air flow rate in the room is realized on the basis of the potential flow model by using the Laplace equation for the stream function. Poisson equation for the electric potential is used for calculation of the charged particles drift in an electric field. At the simulation to take into account: 1 influence of the working area geometric characteristics; 2 location of the ventilation holes; 3 placement of furniture and equipment; 4 ventilation regime in the room; 5 presence of obstacles on the ions dispersion process; 6 specific location of dust particles emission and ions of different polarity, and their interaction in the room and in the working zones. Findings. The developed CFD model allows determining the concentration of negative ions in the room and in the area of the human respiratory organs. The distribution of the negative ions concentration is presented in the form of concentration field isolines. Originality. The 2D CFD model for calculating the air ion regime in working areas, providing the ability to determine the ions concentration in a given place in the room was created. The proposed model is developed taking into account: placement of furniture and equipment in the room; geometric characteristics of the room; location of dust emissions
Zhang, Ye; van Zuijlen, Alexander; van Bussel, Gerard
2014-06-01
In this paper, three dimensional flow over non-rotating MEXICO blades is simulated by CFD methods. The numerical results are compared with the latest MEXICO wind turbine blades measurements obtained in the low speed low turbulence (LTT) wind tunnel of Delft University of Technology. This study aims to validate CFD codes by using these experimental data measured in well controlled conditions. In order to avoid use of wind tunnel corrections, both the blades and the wind tunnel test section are modelled in the simulations. The ability of Menter's k - ω shear stress transport (SST) turbulence model is investigated at both attached flow and massively separated flow cases. Steady state Reynolds averaged Navier Stokes (RANS) equations are solved in these computations. The pressure distribution at three measured sections are compared under the conditions of different inflow velocities and a range of angles of attack. The comparison shows that at attached flow condition, good agreement can be obtained for all three airfoil sections. Even with massively separated flow, still fairly good pressure distribution comparison can be found for the DU and NACA airfoil sections, although the RISØ section shows poor comparison. At the near stall case, considerable deviations exists on the forward half part of the upper surface for all three sections.
Computational Fluid Dynamics (CFD) Simulations of a Humvee Airdropped from Aircraft
Reyes, Phillip M.
Military airdrop is a means of transporting and delivering cargo to inaccessible locales faster and more efficiently. The Humvee, an all-terrain truck, is one such payload that the U.S. Army drops routinely. Here, interesting physics occurs both structurally and aerodynamically. From a fluid dynamics and trajectory standpoint, determining the aerodynamic forces and moments acting on the parachute and payload is crucial particularly for trajectory prediction. This study primarily used Computational Fluid Dynamics (CFD) to simulate the aerodynamics of an airdrop Humvee model in two regimes of fall, namely, right after clearing the aircraft ramp, and during descent under parachute. This study was performed at a Reynolds number of 3.07x10. 6 and at an airspeedof 9.144m/s (30ft/s). The first humvee part of the study analyzed the aerodynamic coefficients drag, lift, and pitching moment over a 360 degree range of pitch angles for the Humvee configured for extraction. The second set of humvee simulations focused on the aerodynamic coefficients at pitch angles of -40 degrees to +40 degrees with the platform and vehicle configured for descent under parachute. The Humvee after ramp tip-off has a parachute pack on its hood, but lacks one during the descent phase. The numerical data was compared with the results of geometries from previous studies. These geometries include: the flat plate, Type-V LVADS and 10K-JPADS containers, and a cargo-carrying platform outfitted with a bumper. Our results clearly show the effects of the many angular features that characterize the shape of a Humvee in comparison to those of a simple cuboid, particularly with regards to the loss of lift in a sub-range of pitch angle (-45 degrees to -180 degrees). First, the aerodynamic coefficients were calculated over one full-revolution of the humvee (-180 degrees to +180 degrees static pitch angles with respect to the humvee's platform) best matched in lift, drag, and moment those of the type V LVADS
Coupled full core neutron transport/CFD simulations of pressurized water reactors
International Nuclear Information System (INIS)
Recently as part of the CASL project, a capability to perform 3D whole-core coupled neutron transport and computational fluid dynamics (CFD) calculations was demonstrated. This work uses the 2D/1D transport code DeCART and the commercial CFD code STAR-CCM+. It builds on previous CASL work demonstrating coupling for smaller spatial domains. The coupling methodology is described along with the problem simulated and results are presented for fresh hot full power conditions. An additional comparison is made to an equivalent model that uses lower order T/H feedback to assess the importance and cost of high fidelity feedback to the neutronics problem. A simulation of a quarter core Combustion Engineering (CE) PWR core was performed with the coupled codes using a Fixed Point Gauss-Seidel iteration technique. The total approximate calculation requirements are nearly 10,000 CPU hours and 1 TB of memory. The problem took 6 coupled iterations to converge. The CFD coupled model and low order T/H feedback model compared well for global solution parameters, with a difference in the critical boron concentration and average outlet temperature of 14 ppm B and 0.94 deg. C, respectively. Differences in the power distribution were more significant with maximum relative differences in the core-wide pin peaking factor (Fq) of 5.37% and average relative differences in flat flux region power of 11.54%. Future work will focus on analyzing problems more relevant to CASL using models with less approximations. (authors)
Coupled full core neutron transport/CFD simulations of pressurized water reactors
Energy Technology Data Exchange (ETDEWEB)
Kochunas, B.; Stimpson, S.; Collins, B.; Downar, T. [Dept. of Nuclear Engineering and Radiological Sciences, Univ. of Michigan, 2200 Bonisteel Blvd, Ann Arbor, MI 48104 (United States); Brewster, R.; Baglietto, E. [CD-adapco, 60 Broadhollow Road, Melville, NY 11747 (United States); Yan, J. [Westinghouse Electric Company LLC, Columbia, SC (United States)
2012-07-01
Recently as part of the CASL project, a capability to perform 3D whole-core coupled neutron transport and computational fluid dynamics (CFD) calculations was demonstrated. This work uses the 2D/1D transport code DeCART and the commercial CFD code STAR-CCM+. It builds on previous CASL work demonstrating coupling for smaller spatial domains. The coupling methodology is described along with the problem simulated and results are presented for fresh hot full power conditions. An additional comparison is made to an equivalent model that uses lower order T/H feedback to assess the importance and cost of high fidelity feedback to the neutronics problem. A simulation of a quarter core Combustion Engineering (CE) PWR core was performed with the coupled codes using a Fixed Point Gauss-Seidel iteration technique. The total approximate calculation requirements are nearly 10,000 CPU hours and 1 TB of memory. The problem took 6 coupled iterations to converge. The CFD coupled model and low order T/H feedback model compared well for global solution parameters, with a difference in the critical boron concentration and average outlet temperature of 14 ppm B and 0.94 deg. C, respectively. Differences in the power distribution were more significant with maximum relative differences in the core-wide pin peaking factor (Fq) of 5.37% and average relative differences in flat flux region power of 11.54%. Future work will focus on analyzing problems more relevant to CASL using models with less approximations. (authors)
Feasibility Study of a 3D CFD Solution for FSI Investigations on NREL 5MW Wind Turbine Blade
Bernardi, Giacomo
2015-01-01
With the increase in length of wind turbine blades flutter is becoming a potential design constrain, hence the interest in computational tools for fluid-structure interaction studies. The general approach to this problem makes use of simplified aerodynamic computational tools. Scope of this work is to investigate the outcomes of a 3D CFD simulation of a complete wind turbine blade, both in terms of numerical results and computational cost. The model studied is a 5MW theoretical wind turbine f...
CFD simulation of IPR-R1 Triga subchannels fluid flow
Energy Technology Data Exchange (ETDEWEB)
Silva, Vitor V.; Santos, A.; Mesquita, Amir Z.; Silva, P.S. da, E-mail: vitors@cdtn.br, E-mail: aacs@cdtn.br, E-mail: amir@cdtn.br, E-mail: psblsg@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN - MG), Belo Horizonte, MG (Brazil); Pereira, C., E-mail: claubia@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear
2013-07-01
Computational fluid dynamics (CFD) codes have been extensively used in engineering problems, with increasing use in nuclear engineering. One of these computer codes is OpenFOAM. It is freely distributed with source code and offers a great flexibility in simulating particular conditions like those found in many problems in nuclear reactor analysis. The aim of this work is to simulate fluid flow and heat flux in three different configurations of subchannels of IPR-R1 TRIGA reactor using OpenFOAM. The data will be then validated against real experimental data obtained during the operation of the reactor at 100kW. This validation process is fundamental to allow the use of the software and associated model to simulate reactor's operation at different conditions, namely different power e fluid flow velocities. (author)
CFD simulation of IPR-R1 Triga subchannels fluid flow
International Nuclear Information System (INIS)
Computational fluid dynamics (CFD) codes have been extensively used in engineering problems, with increasing use in nuclear engineering. One of these computer codes is OpenFOAM. It is freely distributed with source code and offers a great flexibility in simulating particular conditions like those found in many problems in nuclear reactor analysis. The aim of this work is to simulate fluid flow and heat flux in three different configurations of subchannels of IPR-R1 TRIGA reactor using OpenFOAM. The data will be then validated against real experimental data obtained during the operation of the reactor at 100kW. This validation process is fundamental to allow the use of the software and associated model to simulate reactor's operation at different conditions, namely different power e fluid flow velocities. (author)
Advanced CFD simulation for the assessment of nuclear safety issues at EDF. Some examples
International Nuclear Information System (INIS)
EDF R and D has computer power that puts it amongst the top industrial research centers in the world. Its supercomputers and in-house codes as well as its experts represent important capabilities to support EDF activities (safety analyses, support to the design of new reactors, analysis of accidental situations non reproducible by experiments, better understanding of physics or complex system response, effects of uncertainties and identification of prominent parameters, qualification and optimization of processes and materials...). Advanced numerical simulation is a powerful tool allowing EDF to increase its competitiveness, improve its performance and the safety of its plants. On this issue, EDF made the choice to develop its own in-house codes, instead of using commercial software, in order to be able to capitalize its expertise and methodologies. This choice allowed as well easier technological transfer to the concerned business units or engineering divisions, fast adaptation of our simulation tools to emerging needs and the development of specific physics or functionalities not addressed by the commercial offer. During the last ten years, EDF has decided to open its in-house codes, through the Open Source way. This is the case for Code–Aster (structure analysis), Code–Saturne (computational fluid dynamics, CFD), TELEMAC (flow calculations in aquatic environment), SALOME (generic platform for Pre and Post-Processing) and SYRTHES (heat transfer in complex geometries), among others. The 3 open source software: Code–Aster, Code–Saturne and TELEMAC, are certified by the French Nuclear Regulatory Authority for many «Important to Safety» studies. Advanced simulation, which treats complex, multi-field and multi-physics problems, is of great importance for the assessment of nuclear safety issues. This paper will present 2 examples of advanced simulation using Code–Saturne for safety issues of nuclear power plants in the fields of R and D and engineering: 1
An improved CFD tool to simulate adiabatic and diabatic two-phase flows
International Nuclear Information System (INIS)
contact lines. For such cases a dynamic contact angle scheme should be implemented. In this study, FLUENT was used to model adiabatic and diabatic, time dependent two-phase flows. Since FLUENT already contains a VOF method, a LS method was implemented and coupled with VOF into FLUENT via UDFs. Furthermore, since the LS function, used to compute the surface tension force, ceases to be a signed distance to the interface even after one time step, a re-initialization equation was solved after each time step. This involved using a fifth order WENO (Weighted Essentially Non Oscillatory) scheme to discretize the space derivatives (otherwise oscillations of the interface occurred), and a first order Euler method for the time integration. In another part of the study, a 3D dynamic contact angle model based on volume fraction, interface reconstruction, and experimentally available advancing and receding static contact angles was also developed and implemented into FLUENT via UDFs. Several validations for the developed CLSVOF method and dynamic contact angle model are presented in this thesis, these includes a static bubble, a bubble rising in a stagnant liquid for Morton numbers ranging from 102 to 10-11, droplet deformation due to a vortex flow field, droplets spreading over a wall under the gravity effect and droplets sliding over a wall due to gravity. These validations demonstrated the high accuracy and the stability of our methods for modeling these phenomena. A heat and mass transfer model was also implemented into the commercial CFD code FLUENT for simulating of boiling (and condensation) heat transfer. Several simulations were presented with water and R134a as working fluids. The influence of the contact angle and the wall superheat was also studied. (author)
Pre-Test CFD Analysis of a Bypass Flow Experiment for VHTR Simulation
Energy Technology Data Exchange (ETDEWEB)
Yoon, Churl; Kim, Min Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2011-05-15
To investigate the flow characteristics through a prismatic HTGR(High Temperature Gas-cooled Reactor) core, a bypass flow model has been designed and is being constructed for installation in INL(Idaho National Laboratory)'s MIR(Matched Index of Refraction) test facility. The flow in the MIR facility is necessarily isothermal to achieve matching of the indices of refraction of the quartz used to construct the model and the mineral oil used as the working fluid; this provides significant optical advantages for the application of particle image velocimetry that will be used to take the detailed velocity data. The model is designed to represent the gaps and some normal coolant channels near the junction of three hexagonal prismatic blocks of a prismatic VHTR(Very High Temperature Reactor). The model can be adjusted to have (vertical) gaps of 2, 4, and 10 mm, representing 1, 2, and 5 mm in the actual reactor core. (The scale factor is about two times larger than actual size.) The purpose of this study is to develop a CFD(Computational Fluid Dynamics) model for analyzing the bypass flows through the graphite block of a VHTR, and to validate the CFD model against the experimental data. Since any experimental data has not yet been produced from the INL MIR facility, basic validities of the developed CFD model has been examined in the current stage
Predictions in CFD simulations of wire-wrapped SFR fuel assemblies
International Nuclear Information System (INIS)
In response to the goals outlined by the U.S. Department of Energy's Advanced Fuel Cycle Initiative, an effort has been initiated to create an integrated multi-physics, multi-resolution thermal-hydraulic simulation tool package for the evaluation of nuclear power plant design and safety. As part of this effort, a variety of thermal-hydraulic analysis methods are being evaluated for application to the prediction of heat transfer and fluid dynamics in the wire-wrapped fuel-rod assemblies found in a sodium-cooled fast reactor core. The work described herein is an initial assessment of the capabilities of the general-purpose commercial RANS-based computational fluid dynamics (CFD) code Star-CD for prediction of fluid dynamic characteristics in a wire-wrapped, fast reactor fuel assembly. Wire-wrapped fuel rod assemblies containing 7, 19 or 37 pins based on the dimensions of fuel elements in the conceptual design of the Advanced Burner Test Reactor (ABTR) were simulated for different mesh densities and distortions, and domain configurations. Expanding on previously completed benchmarking comparisons with high-order numerical methods, specifically large eddy simulation-based NEK5000, an initial dynamic pressure loss validation effort has been completed using the pressure loss correlations developed by Cheng and Todreas. This commonly used correlation was numerically developed and fitted to available experimental data. The agreement between the CFD predictions and the correlation improves as the pin number increases. The 7-pin bundle simulations predict dimensionless pressure loss coefficients that are 60% higher than the predictions of the correlation. The large deviation is not unexpected since the fundamental flow in this case is dominated by the swirl of the coolant in the edge channels, and this small assembly is outside the specified range of the correlation. The 19- and 37-pin simulations predict dimensionless pressure loss coefficients that are within the
International Nuclear Information System (INIS)
The main objective of this work was to investigate sensitivities of the heated wall temperature and radial velocity distribution predictions on selected model parameters, in water flow under supercritical conditions. The study was focused on cases in which deterioration of heat transfer occurs. Numerical simulations of the turbulent, upward flow in a circular tube were performed using the commercial CFD code ANSYS CFX 12.1. Implementation of water properties was according to IAPWS IF97. The model sensitivities were examined on the mesh discretization, boundary conditions and numerical parameters. Results of simulations were compared with the available experimental data. A significant sensitivity was recognized especially for changes of heat flux and mass flux. It was found out that the model is much less sensitive to changes of boundary conditions for high values of mass flux and heat flux than for low mass and heat fluxes. (author)
Wu, Kenan; Huai, Ying; Jia, Shuqin; Jin, Yuqi
2011-12-19
Coupled simulation based on intracavity partially coherent light model and 3D CFD model is firstly achieved in this paper. The dynamic equation of partially coherent intracavity field is derived based on partially coherent light theory. A numerical scheme for the coupled simulation as well as a method for computing the intracavity partially coherent field is given. The presented model explains the formation of the sugar scooping phenomenon, and enables studies on the dependence of the spatial mode spectrum on physical parameters of laser cavity and gain medium. Computational results show that as the flow rate of iodine increases, higher order mode components dominate in the partially coherent field. Results obtained by the proposed model are in good agreement with experimental results. PMID:22274214
CFD simulation of gas and non-Newtonian fluid two-phase flow in anaerobic digesters.
Wu, Binxin
2010-07-01
This paper presents an Eulerian multiphase flow model that characterizes gas mixing in anaerobic digesters. In the model development, liquid manure is assumed to be water or a non-Newtonian fluid that is dependent on total solids (TS) concentration. To establish the appropriate models for different TS levels, twelve turbulence models are evaluated by comparing the frictional pressure drops of gas and non-Newtonian fluid two-phase flow in a horizontal pipe obtained from computational fluid dynamics (CFD) with those from a correlation analysis. The commercial CFD software, Fluent12.0, is employed to simulate the multiphase flow in the digesters. The simulation results in a small-sized digester are validated against the experimental data from literature. Comparison of two gas mixing designs in a medium-sized digester demonstrates that mixing intensity is insensitive to the TS in confined gas mixing, whereas there are significant decreases with increases of TS in unconfined gas mixing. Moreover, comparison of three mixing methods indicates that gas mixing is more efficient than mixing by pumped circulation while it is less efficient than mechanical mixing. PMID:20627353
CFD Simulations in Support of Shuttle Orbiter Contingency Abort Aerodynamic Database Enhancement
Papadopoulos, Periklis E.; Prabhu, Dinesh; Wright, Michael; Davies, Carol; McDaniel, Ryan; Venkatapathy, E.; Wercinski, Paul; Gomez, R. J.
2001-01-01
Modern Computational Fluid Dynamics (CFD) techniques were used to compute aerodynamic forces and moments of the Space Shuttle Orbiter in specific portions of contingency abort trajectory space. The trajectory space covers a Mach number range of 3.5-15, an angle-of-attack range of 20deg-60deg, an altitude range of 100-190 kft, and several different settings of the control surfaces (elevons, body flap, and speed brake). Presented here are details of the methodology and comparisons of computed aerodynamic coefficients against the values in the current Orbiter Operational Aerodynamic Data Book (OADB). While approximately 40 cases have been computed, only a sampling of the results is provided here. The computed results, in general, are in good agreement with the OADB data (i.e., within the uncertainty bands) for almost all the cases. However, in a limited number of high angle-of-attack cases (at Mach 15), there are significant differences between the computed results, especially the vehicle pitching moment, and the OADB data. A preliminary analysis of the data from the CFD simulations at Mach 15 shows that these differences can be attributed to real-gas/Mach number effects. The aerodynamic coefficients and detailed surface pressure distributions of the present simulations are being used by the Shuttle Program in the evaluation of the capabilities of the Orbiter in contingency abort scenarios.
Computational fluid dynamics (CFD) simulation of a newly designed passive particle sampler.
Sajjadi, H; Tavakoli, B; Ahmadi, G; Dhaniyala, S; Harner, T; Holsen, T M
2016-07-01
In this work a series of computational fluid dynamics (CFD) simulations were performed to predict the deposition of particles on a newly designed passive dry deposition (Pas-DD) sampler. The sampler uses a parallel plate design and a conventional polyurethane foam (PUF) disk as the deposition surface. The deposition of particles with sizes between 0.5 and 10 μm was investigated for two different geometries of the Pas-DD sampler for different wind speeds and various angles of attack. To evaluate the mean flow field, the k-ɛ turbulence model was used and turbulent fluctuating velocities were generated using the discrete random walk (DRW) model. The CFD software ANSYS-FLUENT was used for performing the numerical simulations. It was found that the deposition velocity increased with particle size or wind speed. The modeled deposition velocities were in general agreement with the experimental measurements and they increased when flow entered the sampler with a non-zero angle of attack. The particle-size dependent deposition velocity was also dependent on the geometry of the leading edge of the sampler; deposition velocities were more dependent on particle size and wind speeds for the sampler without the bend in the leading edge of the deposition plate, compared to a flat plate design. Foam roughness was also found to have a small impact on particle deposition. PMID:27108045
CFD Simulation and Optimization of Very Low Head Axial Flow Turbine Runner
Directory of Open Access Journals (Sweden)
Yohannis Mitiku Tobo
2015-10-01
Full Text Available The main objective of this work is Computational Fluid Dynamics (CFD modelling, simulation and optimization of very low head axial flow turbine runner to be used to drive a centrifugal pump of turbine-driven pump. The ultimate goal of the optimization is to produce a power of 1kW at head less than 1m from flowing river to drive centrifugal pump using mechanical coupling (speed multiplier gear directly. Flow rate, blade numbers, turbine rotational speed, inlet angle are parameters used in CFD modeling, simulation and design optimization of the turbine runner. The computed results show that power developed by a turbine runner increases with increasing flow rate. Pressure inside the turbine runner increases with flow rate but, runner efficiency increases for some flow rate and almost constant thereafter. Efficiency and power developed by a runner drops quickly if turbine speed increases due to higher pressure losses and conversion of pressure energy to kinetic energy inside the runner. Increasing blade number increases power developed but, efficiency does not increase always. Efficiency increases for some blade number and drops down due to the fact that change in direction of the relative flow vector at the runner exit, which decreases the net rotational momentum and increases the axial flow velocity.
Cho, Y. J.; Zullah, M. A.; Faizal, M.; Choi, Y. D.; Lee, Y. H.
2012-11-01
A variety of technologies has been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales. Due to the complexity of most offshore wave energy devices and their motion response in different sea states, physical tank tests are common practice for WEC design. Full scale tests are also necessary, but are expensive and only considered once the design has been optimized. Computational Fluid Dynamics (CFD) is now recognized as an important complement to traditional physical testing techniques in offshore engineering. Once properly calibrated and validated to the problem, CFD offers a high density of test data and results in a reasonable timescale to assist with design changes and improvements to the device. The purpose of this study is to investigate the performance of a newly developed direct drive hydro turbine (DDT), which will be built in a caisson for extraction of wave energy. Experiments and CFD analysis are conducted to clarify the turbine performance and internal flow characteristics. The results show that commercial CFD code can be applied successfully to the simulation of the wave motion in the water tank. The performance of the turbine for wave energy converter is studied continuously for a ongoing project.
CFD simulation of blood flow inside the corkscrew collaterals of the Buerger’s disease
Sharifi, Alireza; Charjouei Moghadam, Mohammad
2016-01-01
Introduction: Buerger’s disease is an occlusive arterial disease that occurs mainly in medium and small vessels. This disease is associated with Tobacco usage. The existence of corkscrew collateral is one of the established characteristics of the Buerger’s disease. Methods: In this study, the computational fluid dynamics (CFD) simulation of blood flow within the corkscrew artery of the Buerger’s disease is conducted. The geometry of the artery is constructed based on the actual corkscrew artery of a patient diagnosed with the Buerger’s disease. The blood properties are the same as the actual blood properties of the patient. The blood flow rate is taken from the available experimental data in the literature. Results: The local velocity patterns, pressure and kinematic viscosity distributions in different segments of the corkscrew collateral artery was demonstrated and discussed for the first time for this kind of artery. The effects of non-Newtonian consideration for the blood viscosity behavior were investigated in different segments of the artery. Moreover, the variations of the blood flow patterns along the artery were investigated in details for each segment. Conclusion: It was found that the flow patterns were affected by the complex geometry of this artery in such a way that it could lead to the presence of sites that were prone to the accumulation of the flowing particles in blood like nicotine. Furthermore, due to the existence of many successive bends in this artery, the variations of kinematic viscosity along this artery were significant, therefore the non-Newtonian behavior of the blood viscosity must be considered. PMID:27340623
Simulating Flow and Dispersion by Using WRF-CFD Coupled Model in a Built-Up Area of Shenyang, China
Directory of Open Access Journals (Sweden)
Yijia Zheng
2015-01-01
Full Text Available Results are presented from a series of numerical studies designed to investigate the atmospheric boundary layer structure, ambient wind, and pollutant source location and their impacts on the wind field and pollutant distribution within the built-up areas of Shenyang, China. Two models, namely, Open Source Field Operation and Manipulation (OpenFOAM software package and Weather Research and Forecasting (WRF model, are used in the present study. Then the high resolution computational fluid dynamics (CFD numerical experiments were performed under the typical simulated atmospheric boundary conditions. It was found that the atmospheric boundary structure played a crucial role in the pollution within the building cluster, which determined the potential turbulent diffusion ability of the atmospheric surface layer; the change of the ambient wind direction can significantly affect the dispersion pattern of pollutants, which was a more sensitive factor than the ambient wind speed; under a given atmospheric state, the location of the pollution sources would dramatically determine the pollution patterns within built-up areas. The WRF-CFD numerical evaluation is a reliable method to understand the complicated flow and dispersion within built-up areas.
CFD Study of an Annular-Ducted Fan Lift System for VTOL Aircraft
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Yun Jiang
2015-09-01
Full Text Available The present study aimed at assessing a novel annular-ducted fan lift system for VTOL aircraft through computational fluid dynamics (CFD simulations. The power and lift efficiency of the lift fan system in hover mode, the lift and drag in transition mode, the drag and flight speed of the aircraft in cruise mode and the pneumatic coupling of the tip turbine and jet exhaust were studied. The results show that the annular-ducted fan lift system can have higher lift efficiency compared to the rotor of the Apache helicopter; the smooth transition from vertical takeoff to cruise flight needs some extra forward thrust to overcome a low peak of drag; the aircraft with the lift fan system enclosed during cruise flight theoretically may fly faster than helicopters and tiltrotors based on aerodynamic drag prediction, due to the elimination of rotor drag and compressibility effects on the rotor blade tips; and pneumatic coupling of the tip turbine and jet exhaust of a 300 m/s velocity can provide enough moment to spin the lift fan. The CFD results provide insight for future experimental study of the annular-ducted lift fan VTOL aircraft.
cfd modelling and experimental study on the fluid flow and heat transfer in copper heat sink design
Karimpourian, Bijan
2007-01-01
Abstract This thesis is studying the heatsinks new designs for copper heatsinks which utilizes modelling and simulation by CFD, construction of prototypes and experimental works. Challenges and complications in manufacturing of copper heatsinks are expressed and finding the solutions to these hindrances involve in this work. Numerical efforts supported by fluent are made to promote investigation and approaching the goal in which serves the new opportunities for wider application of copper mat...
CFD simulation of transient stage of continuous countercurrent hydrolysis of canola oil
Wang, Weicheng
2012-08-01
Computational Fluid Dynamic (CFD) modeling of a continuous countercurrent hydrolysis process was performed using ANSYS-CFX. The liquid properties and flow behavior such as density, specific heats, dynamic viscosity, thermal conductivity, and thermal expansivity as well as water solubility of the hydrolysis components triglyceride, diglyceride, monoglyceride, free fatty acid, and glycerol were calculated. Chemical kinetics for the hydrolysis reactions were simulated in this model by applying Arrhenius parameters. The simulation was based on actual experimental reaction conditions including temperature and water-to-oil ratio. The results not only have good agreement with experimental data but also show instantaneous distributions of concentrations of every component in hydrolysis reaction. This model provided visible insight into the continuous countercurrent hydrolysis process. © 2012 Elsevier Ltd.
Wind Turbine Rotor Simulation via CFD Based Actuator Disc Technique Compared to Detailed Measurement
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Esmail Mahmoodi
2015-10-01
Full Text Available In this paper, a generalized Actuator Disc (AD is used to model the wind turbine rotor of the MEXICO experiment, a collaborative European wind turbine project. The AD model as a combination of CFD technique and User Defined Functions codes (UDF, so-called UDF/AD model is used to simulate loads and performance of the rotor in three different wind speed tests. Distributed force on the blade, thrust and power production of the rotor as important designing parameters of wind turbine rotors are focused to model. A developed Blade Element Momentum (BEM theory as a code based numerical technique as well as a full rotor simulation both from the literature are included into the results to compare and discuss. The output of all techniques is compared to detailed measurements for validation, which led us to final conclusions.
CFD simulation of vertical seven-rod bundle cooled with supercritical Freon-12
Energy Technology Data Exchange (ETDEWEB)
Huang, X.; Podila, K.; Rao, Y.F., E-mail: podilak@aecl.ca [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada)
2014-06-15
In this paper, a seven-rod bare bundle was simulated using ANSYS Fluent 6.3.26 to accurately predict the fluid flow and heat transfer behaviour under supercritical flow conditions. Seven turbulence models were compared to identify the appropriate model to predict the experiments performed at the Institute of Physics and Power Engineering on a vertically oriented seven-rod bare bundle cooled with supercritical Freon-12. It was found that predictions of wall temperatures and heat transfer coefficients are sensitive to the choice of turbulence model as well as to the near-wall treatment. Overall, the CFD simulations were able to predict the measured sheath temperature profiles along the length of the bundle within reasonable accuracy. (author)
Wang, Xu; Ding, Jie; Guo, Wan-Qian; Ren, Nan-Qi
2010-12-01
Investigating how a bioreactor functions is a necessary precursor for successful reactor design and operation. Traditional methods used to investigate flow-field cannot meet this challenge accurately and economically. Hydrodynamics model can solve this problem, but to understand a bioreactor in sufficient depth, it is often insufficient. In this paper, a coupled hydrodynamics-reaction kinetics model was formulated from computational fluid dynamics (CFD) code to simulate a gas-liquid-solid three-phase biotreatment system for the first time. The hydrodynamics model is used to formulate prediction of the flow field and the reaction kinetics model then portrays the reaction conversion process. The coupled model is verified and used to simulate the behavior of an expanded granular sludge bed (EGSB) reactor for biohydrogen production. The flow patterns were visualized and analyzed. The coupled model also demonstrates a qualitative relationship between hydrodynamics and biohydrogen production. The advantages and limitations of applying this coupled model are discussed. PMID:20727741
CFD Simulation of an Anaerobic Membrane BioReactor (AnMBR to Treat Industrial Wastewater
Directory of Open Access Journals (Sweden)
Laura C. Zuluaga
2015-06-01
Full Text Available A Computational Fluid Dynamics (CFD simulation has been developed for an Anaerobic Membrane BioReactor (AnMBR to treat industrial wastewater. As the process consists of a side-stream MBR, two separate simulations were created: (i reactor and (ii membrane. Different cases were conducted for each one, so the surrounding temperature and the total suspended solids (TSS concentration were checked. For the reactor, the most important aspects to consider were the dead zones and the mixing, whereas for the ceramic membrane, it was the shear stress over the membrane surface. Results show that the reactor's mixing process was adequate and that the membrane presented higher shear stress in the 'triangular' channel.
International Nuclear Information System (INIS)
The SINQ HETSS (Heat Emitting Temperature Sensing Surface) experiments were designed to study the heat transfer process between flowing mercury and a heated surface in a suitable geometry closely resembling that of the MEGAPIE target, which is currently being constructed for insertion in the PSI SINQ neutron source. This target, which utilizes liquid lead-bismuth eutectic as the coolant fluid, is being designed with strong support from Computational Fluid Dynamics (CFD), with a major contribution being made by PSI. One SINQ HETSS experiment has been simulated using the CFD codes CFX-4 and CFX-5, to assess the validity of the calculations currently been undertaken for MEGAPIE, partially in regard to the predicted temperatures over the beam window. Results from the validation exercise give an indication of the best turbulence models and degrees of mesh refinement to use. The information is of particular relevance to MEGAPIE, and of more general interest for the application of this type of target in an Accelerator Driven System (ADS), an innovative design of nuclear reactor which can be used for the production of energy as well as for the burning and reduction of toxic reactor waste. (author)
Experiment and CFD simulation of hybrid SNCR-SCR using urea solution in a pilot-scale reactor
Energy Technology Data Exchange (ETDEWEB)
Nguyen, T.D.B.; Lim, Y.I.; Eom, W.H.; Kim, S.J.; Yoo, K.S. [Hankyong National University, Gyonggi Do (Republic of Korea). Dept. of Chemical Engineering
2010-10-12
The urea-based selective non-catalytic reduction (SNCR) experiment and modeling previously presented by Nguyen, Lim, et al. (2008) was extended in this study to the hybrid SNCR-SCR process for nitrogen oxides (NOx) removal in a pilot-scale flow reactor. The 5 wt% urea-water solution was sprayed into the SNCR zone and a commercial V{sub 2}O{sub 5}-WO{sub 3}/TiO{sub 2} catalyst in the form of monolith honeycomb was applied in the SCR zone. The NOx reduction efficiency of 91% was obtained from hybrid SNCR-SCR experiments, while 81% of NOx was reduced from the SNCR zone at 940{sup o}C and a normalized stoichiometric ratio (NSR) of 2.0. The turbulent reacting flow computational fluid dynamics (CFD) model with a nonuniform droplet size distribution was used, incorporating with the reduced seven-step reactions of SNCR and one Arrhenius-type SCR kinetics. The CFD simulation results showed a reasonable agreement with the experimental data in the temperature range between 900 and 980{sup o}C.
CFD simulation of MSW combustion and SNCR in a commercial incinerator
International Nuclear Information System (INIS)
Highlights: • Presented a CFD scheme for modeling MSW incinerator including SNCR process. • Performed a sensitivity analysis of SNCR operating conditions. • Non-uniform distributions of gas velocity, temperature and NOx in the incinerator. • The injection position of reagent was critical for a desirable performance of SNCR. • A NSR 1.5 was recommended as a compromise of NOx reduction rates and NH3 slip. - Abstract: A CFD scheme was presented for modeling municipal solid waste (MSW) combustion in a moving-grate incinerator, including the in-bed burning of solid wastes, the out-of-bed burnout of gaseous volatiles, and the selective non-catalytic reduction (SNCR) process between urea (CO(NH2)2) and NOx. The in-bed calculations provided 2-D profiles of the gas–solid temperatures and the gas species concentrations along the bed length, which were then used as inlet conditions for the out-of-bed computations. The over-bed simulations provided the profiles of incident radiation heat flux on the top of bed. A 3-dimensional benchmark simulation was conducted with a 750 t/day commercial incinerator using the present coupling scheme incorporating with a reduced SNCR reduction mechanism. Numerical tests were performed to investigate the effects of operating parameters such as injection position, injection speed and the normalized stoichiometric ratio (NSR) on the SNCR performance. The simulation results showed that the distributions of gas velocity, temperature and NOx concentration were highly non-uniform, which made the injection position one of the most sensitive operating parameters influencing the SNCR performance of moving grate incinerators. The simulation results also showed that multi-layer injections were needed to meet the EU2000 standard, and a NSR 1.5 was suggested as a compromise of a satisfactory NOx reduction and reasonable NH3 slip rates. This work provided useful guides to the design and operation of SNCR process in moving-grate incinerators
Energy Technology Data Exchange (ETDEWEB)
Moussiere, S
2006-12-15
Supercritical water oxidation is an innovative process to treat organic liquid waste which uses supercritical water properties to mix efficiency the oxidant and the organic compounds. The reactor is a stirred double shell reactor. In the step of adaptation to nuclear constraints, the computational fluid dynamic modeling is a good tool to know required temperature field in the reactor for safety analysis. Firstly, the CFD modeling of tubular reactor confirms the hypothesis of an incompressible fluid and the use of k-w turbulence model to represent the hydrodynamic. Moreover, the EDC model is as efficiency as the kinetic to compute the reaction rate in this reactor. Secondly, the study of turbulent flow in the double shell reactor confirms the use of 2D axisymmetric geometry instead of 3D geometry to compute heat transfer. Moreover, this study reports that water-air mixing is not in single phase. The reactive turbulent flow is well represented by EDC model after adaptation of initial conditions. The reaction rate in supercritical water oxidation reactor is mainly controlled by the mixing. (author)
Kumar, Mayank
2009-01-01
In this work, we use a CFD package to model the operation of a coal gasifier with the objective of assessing the impact of devolatilization and char consumption models on the accuracy of the results. Devolatilization is modeled using the Chemical Percolation Devolitilization (CPD) model. The traditional CPD models predict the rate and the amount of volatiles released but not their species composition. We show that the knowledge of devolatilization rates is not sufficient for the accurate prediction of char consumption and a quantitative description of the devolatilization products, including the chemical composition of the tar, is needed. We incorporate experimental data on devolatilization products combined with modeling of the tar composition and reactions to improve the prediction of syngas compositions and carbon conversion. We also apply the shrinking core model and the random pore model to describe char consumption in the CFD simulations. Analysis of the results indicates distinct regimes of kinetic and diffusion control depending on the particle radius and injection conditions for both char oxidation and gasification reactions. The random pore model with Langmuir-Hinshelwood reaction kinetics are found to be better at predicting carbon conversion and exit syngas composition than the shrinking core model with Arrhenius kinetics. In addition, we gain qualitative and quantitative insights into the impact of the ash layer surrounding the char particle on the reaction rate. Copyright © 2010 by ASME.
An integral CFD approach for the thermal simulation of the PBMR Reactor Unit
Energy Technology Data Exchange (ETDEWEB)
Janse van Rensburg, J.J., E-mail: cobusjvr1@gmail.com [North-West University, Potchefstroom Campus (South Africa); Parsons Brinckerhoff Africa, Craighall (South Africa); Kleingeld, M. [North-West University (South Africa)
2011-08-15
Highlights: > Establishment of a modeling capability to simulate the integral thermal operation of an HTR. > The focus was on the capability rather than improving the assumptions and correlations. > All assumptions and correlations applied were taken from previous credible research. > It was shown that it is possible to establish such a capability using current information. > With this capability, it is now possible to test updated correlations and determine the integral effect. - Abstract: A CFD method was developed to conduct integral thermal reactor analysis for the complete Reactor Unit of the Pebble Bed Modular Reactor (Pty) Ltd (PBMR). The requirement was however also to include very detailed aspects such as leakage and bypass flow paths through the reflector blocks and sleeves. The aim was therefore to investigate the influence of leakage and bypass flow on the thermal performance of the Reactor Unit in an integral fashion. The focus of this paper is to discuss the methodology that was developed. The discussion will firstly highlight all the required inputs, elaborate briefly on the underlying theory and how this was implemented into the CFD modeling capability. Results will be discussed briefly, but the focus is on the methodology.
Thermal radiation of di-tert-butyl peroxide pool fires-Experimental investigation and CFD simulation
Energy Technology Data Exchange (ETDEWEB)
Chun, Hyunjoo [Umicore Korea Limited, 410 Chaam-dong, Cheonan-city, Chungnam, 330-200 (Korea, Republic of); Wehrstedt, Klaus-Dieter [Federal Institute for Materials Research and Testing (BAM), Working Group ' Explosive Substances of Chemical Industries' , Unter den Eichen 87, D-12205 Berlin (Germany); Vela, Iris [University of Duisburg-Essen, Institute for Chemical Engineering I, Universitaetsstrasse 5, D-45141 Essen (Germany); Schoenbucher, Axel, E-mail: axel.schoenbucher@uni-due.de [University of Duisburg-Essen, Institute for Chemical Engineering I, Universitaetsstrasse 5, D-45141 Essen (Germany)
2009-08-15
Instantaneous and time averaged flame temperatures T-bar, surface emissive power SEP-bar and time averaged irradiances E-bar of di-tert-butyl peroxide (DTBP) pool fires with d = 1.12 and 3.4 m are investigated experimentally and by CFD simulation. Predicted centerline temperature profiles for d = 1.12 m are in good agreement with the experimental emission temperature profiles for x/d > 0.9. For d = 3.4 m the CFD predicted maximum centerline temperature at x/d = 1.4 is 1440 K whereas the emission temperature experimentally determined from thermograms at x/d {approx} 1.3 is 1560 K. The predicted surface emissive power for d = 1.12 m is 115 kW/m{sup 2} in comparison to the measured surface emissive power of 130 kW/m{sup 2} whereas for d = 3.4 m these values are 180 and 250 kW/m{sup 2}. The predicted distance dependent irradiances agree well with the measured irradiances.
Chun, Hyunjoo; Wehrstedt, Klaus-Dieter; Vela, Iris; Schönbucher, Axel
2009-08-15
Instantaneous and time averaged flame temperatures T , surface emissive power SEP and time averaged irradiances E of di-tert-butyl peroxide (DTBP) pool fires with d=1.12 and 3.4m are investigated experimentally and by CFD simulation. Predicted centerline temperature profiles for d=1.12m are in good agreement with the experimental emission temperature profiles for x/d>0.9. For d=3.4m the CFD predicted maximum centerline temperature at x/d=1.4 is 1440 K whereas the emission temperature experimentally determined from thermograms at x/d approximately 1.3 is 1560 K. The predicted surface emissive power for d=1.12m is 115 kW/m(2) in comparison to the measured surface emissive power of 130 kW/m(2) whereas for d=3.4m these values are 180 and 250 kW/m(2). The predicted distance dependent irradiances agree well with the measured irradiances. PMID:19185989
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John White
2012-01-01
Full Text Available The application of computational fluid dynamics (CFD in the area of porous media and adsorption cooling system is becoming more practical due to the significant improvement in computer power. The results from previous studies have shown that CFD can be useful tool for predicting the water vapour flow pattern, temperature, heat transfer, flow velocity, and adsorption rate. This paper investigates the effect of silica gel granular size on the water adsorption rate using computational fluid dynamics.
CFD simulation of short-range plume dispersion from a point release in an urban like environment
Kumar, Pramod; Feiz, Amir-Ali; Ngae, Pierre; Singh, Sarvesh Kumar; Issartel, Jean-Pierre
2015-12-01
An accurate simulation of the short-range plume dispersion of a hazardous pollutant in a geometrically complex urban region is a prerequisite in emergency preparedness and to assist regulators for developing effective policies. This study critically examines the real predictive capability of a three-dimensional Computational Fluid Dynamics (CFD) model, Fluidyn-PANACHE, to apply it in emergency contexts of an accidental or deliberate airborne release in urban regions. The model is evaluated with the Mock Urban Setting Test (MUST) field experiment of a continuous point source release in an idealized urban geometry of a regular array of shipping containers in various atmospheric stability varying from neutral to stable, and very stable conditions. The simulations are performed using three combinations (cases 1, 2, & 3) of inflow boundary conditions for wind and turbulence profiles. A detailed analysis with statistical measures shows that the performance of the Fluidyn-PANACHE against MUST experiment with all the three cases of the inflow boundary conditions is well achieved within the acceptable standards for air quality applications. The model with three cases 1, 2, & 3 predicts respectively 52.8%, 59.9%, and 67.9% of the total concentrations within a factor of two and shows an overall under-prediction. The sampling line maximum concentrations are better simulated by the CFD model with case-3 (95% within a factor of two) in comparison to other cases 1 & 2. A comparative statistical analysis is also performed with other evaluation studies in the literature for the averaged and sampling line maximum concentrations. The present evaluation of the Fluidyn-PANACHE strengthen the evidence that it is capable of dealing properly with the dispersion phenomena in geometrically complex urban environments.
CFD simulations on two-phase distribution in rod bundles with grid spacers
International Nuclear Information System (INIS)
Considering the bubble coalescence and break-up, the CFD simulations for air/water two-phase flow in 3 × 3 rod bundles with grid spacers have been performed with MUSIG model. The simulation is sensitive with the bubble diameter size but not with the inlet void fraction. The small diameter bubbles are the main effect of void fraction distribution nearby the downstream of the space grid, while the large diameter bubbles are main effect of void fraction distribution at the farther downstream of the space grid. Considering the effect of inlet air-water flow quality, geometry and pressure on bubble max diameter, this paper gives a relation for simulating the bubble with maximum diameter based on which is dealt with numerical simulation for rod bundles with grid spacers is set, and the advice of simulation method and model setting is given. The calculation results show that the shape and peak of void fraction distribution accord well with the experiment, and this simulation method can predict rationally the distribution of two phase flow in complicated channels. (authors)
Study of tip loss corrections using CFD rotor computations
DEFF Research Database (Denmark)
Shen, Wen Zhong; Zhu, Wei Jun; Sørensen, Jens Nørkær
2014-01-01
computations for wind turbines with sharp tip. Using the technique of determination of angle of attack and the CFD results for a NordTank 500 kW rotor, airfoil data are extracted and a new tip loss function on airfoil data is derived. To validate, BEM computations with the new tip loss function are carried out...
International Nuclear Information System (INIS)
In design studies of Japanese sodium-cooled fast reactors, a compact size reactor vessel is expected to be employed for economical advantages. However, such a design makes coolant velocity higher and may result in occurrence of gas entrainment (GE) phenomena. Since the GE is highly non-linear and too difficult to predict its onset condition by theoretical methods, we are developing a high-precision CFD method to evaluate the GE accurately. The CFD method is formulated on unstructured meshes to establish accurate geometric modeling of complicated reactor systems. As for two-phase flow simulations, a high-precision volume-of-fluid algorithm was employed and newly formulated on unstructured meshes. In the formulation process, a volume-conservative algorithm and a new formulation establishing the mechanical balance between pressure and surface tension were introduced. The developed CFD method was verified by solving well-known driven-cavity and Zalesak's slotted disk rotation problems to show the simulation accuracy. Then, we simulated a rising bubble in liquid under Bhaga et al.'s experimental conditions. As a result, the developed method showed good agreement with the experiment. Finally, the developed method was validated by simulating the GE phenomena in the basic experiment. The developed method succeeded in reproducing the occurrence of the GE under the experimental GE condition. (authors)
Cfd Simulation Of Swirling Effect In S-Shaped Diffusing Duct By Swirl Angle 200
Directory of Open Access Journals (Sweden)
Ramazan
2013-07-01
Full Text Available The present study involves the CFD analysis for the prediction of swirl effect on the characteristics of a steady, incompressible flow through an S-shaped diffusing duct. The curved diffuser considered in the present case has Sshaped diffusing duct having an area ratio of 1.9, length of 300 mm and turning angle of 22.5°/22.5°. The static pressure, total pressure, velocity and turbulence intensity were accounted. The improvement is observed for both, clockwise and anti-clockwise swirl, the improvement being higher for clockwise swirl. Flow uniformity at the exit is more uniform for clockwise swirl at the inlet.
DEFF Research Database (Denmark)
Dannemand, Mark; Fan, Jianhua; Furbo, Simon;
2014-01-01
Computational Fluid Dynamics (CFD) model. The CFD calculated temperatures are compared to measured temperatures internally in the box to validate the CFD model. Four cases are investigated; heating the test module with the sodium acetate water mixture in solid phase from ambient temperature to 52˚C; heating the...... the crystallization, ending at ambient temperature with the sodium acetate water mixture in solid phase. Comparisons have shown reasonable good agreement between experimental measurements and theoretical simulation results for the investigated scenarios....
Advanced CFD simulations of turbulent flows around appendages in CANDU fuel bundles
International Nuclear Information System (INIS)
Computational Fluid Dynamics (CFD) was used to simulate the coolant flow in a modified 37-element CANDU fuel bundle, in order to investigate the effects of the appendages on the flow field. First, a subchannel model was created to qualitatively analyze the capabilities of different turbulence models such as k.ε, Reynolds Normalization Group (RNG), Shear Stress Transport (SST) and Large Eddy Simulation (LES). Then, the turbulence model with the acceptable quality was used to investigate the effects of positioning appendages, normally used in CANDU 37-element Critical Heat Flux (CHF) experiments, on the flow field. It was concluded that the RNG and SST models both show improvements over the k.ε method by predicting cross flow rates closer to those predicted by the LES model. Also the turbulence effects in the k.ε model dissipate quickly downstream of the appendages, while in the RNG and SST models appear at longer distances similar to the LES model. The RNG method simulation time was relatively feasible and as a result was chosen for the bundle model simulations. In the bundle model simulations it was shown that the tunnel spacers and leaf springs, used to position the bundles inside the pressure tubes in the experiments, have no measureable dominant effects on the flow field. The flow disturbances are localized and disappear at relatively short streamwise distances. (author)
Skřínský, Jan; Vereš, Ján; Ševčíková, Silvie Petránková
2016-06-01
Aqueous solutions of binary and ternary mixtures of alcohols are of considerable interest for a wide range of scientists and technologists. Simple dimensionless experimental formulae based on rational reciprocal and polynomial functions are proposed for correlation of the flashpoint data of binary mixtures of two components. The formulae are based on data obtained from flashpoint experiments and predictions. The main results are the derived experimental flashpoint values for ternary mixtures of two aqueous-organic solutions and the model prediction of maximum explosion pressure values for the studied mixtures. Potential application for the results concerns the assessment of fire and explosion hazards, and the development of inherently safer designs for chemical processes containing binary and ternary partially miscible mixtures of an aqueous-organic system. The goal of this article is to present the results of modelling using these standard models and to demonstrate its importance in the area of CFD simulation.
Directory of Open Access Journals (Sweden)
P.MANOJ KUMAR,
2011-04-01
Full Text Available In direct injection (DI diesel engines the effect of injector Orientation on velocity vector Components have high influence on engine performance as well as exhaust gas emissions. The fuelinjector orientation plays very important role in fuel air mixing. A single cylinder four stroke DI diesel engine with fuel injector having multi-hole nozzle injector is considered for the analysis and acomputational fluid dynamics (CFD code, STAR-CD is used for the simulation. In the present study, various injector orientations are considered for the analysis. It is shown that there is an optimal injector orientation for the fuel in-cylinder fluid flow through velocity vectors at 950, 1000 and 1100 are discussed
Akherat, S M Javid Mahmoudzadeh
2016-01-01
Considerations on implementation of the stress-strain constitutive relations applied in Computational Fluid dynamics (CFD) simulation of cardiovascular flows have been addressed extensively in the literature. However, the matter is yet controversial. The author suggests that the choice of non-Newtonian models and the consideration of non-Newtonian assumption versus the Newtonian assumption is very application oriented and cannot be solely dependent on the vessel size. In the presented work, where a renal disease patient-specific geometry is used, the non-Newtonian effects manifest insignificant, while the vessel is considered to be medium to small which, according to the literature, suggest a strict use of non-Newtonian formulation. The insignificance of the non-Newtonian effects specially manifests in Wall Shear Stress (WSS) along the walls of the numerical domain, where the differences between Newtonian calculated WSS and non-Newtonian calculated WSS is barely visible.
Energy Technology Data Exchange (ETDEWEB)
Wardle, K.E. [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States)
2013-07-01
Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A hybrid multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. Simulations of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor are reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup.
OpenDx programs for visualization of computational fluid dynamics (CFD) simulations
International Nuclear Information System (INIS)
The search for high performance and low cost hardware and software solutions always guides the developments performed at the IEN parallel computing laboratory. In this context, this dissertation about the building of programs for visualization of computational fluid dynamics (CFD) simulations using the open source software OpenDx was written. The programs developed are useful to produce videos and images in two or three dimensions. They are interactive, easily to use and were designed to serve fluid dynamics researchers. A detailed description about how this programs were developed and the complete instructions of how to use them was done. The use of OpenDx as development tool is also introduced. There are examples that help the reader to understand how programs can be useful for many applications. (author)
International Nuclear Information System (INIS)
Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A hybrid multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. Simulations of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor are reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup
CFD simulation and experiment research of pipe downstream with orifice and jet impingement
International Nuclear Information System (INIS)
In nuclear power plants, the flow accelerated corrosion (FAC) occurs mainly in the secondary circuit, causing a significant impact on production practice. Straight pipes with an orifice and jet impingement were simulated by CFD at 250℃ and 273℃, achieving flow patterns and shear force distributions on the surfaces of plates and in the internal of pipes, and identifying weak points caused by pipe thinning with an orifice and influence of jet impingement angle. The results show that the orifice diameter ratio in the straight pipe changing has little effect on the maximum point of shear stress. With smaller crashing angle, the greater the shear force is, and the stronger the mechanical action is. (authors)
CFD simulation of fibre material transport in a PWR core under loss of coolant conditions
Energy Technology Data Exchange (ETDEWEB)
Hoehne, Thomas; Grahn, Alexander; Kliem, Soeren [Helmholtz-Zentrum Dresden-Rossendorf (HZDR) e.V., Dresden (Germany); Weiss, Frank-Peter [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS), Garching (Germany)
2011-03-15
During a postulated cold leg LOCA with hot leg ECC injection, a limited amount of small fractions of the insulation material after passing the sump strainers can enter the upper plenum and can accumulate at the fuel element spacer grids, preferably at the uppermost grid level. This effect might affect the ECC flow into the core and could result in degradation of core cooling. The CFD simulations show that after starting the sump mode, the ECC water injected through the hot legs flows down into the core at so-called 'brake through channels' located at the outer core region where the downward leg of the convection role had established. The hotter, lighter coolant rises in the center of the core. As a consequence, the insulation material is preferably deposited at the uppermost spacer grids positioned in the break through zones. This means that at the beginning the fibers are not uniformly deposited over the core cross section. (orig.)
CFD simulation of vertical linear motion mixing in anaerobic digester tanks.
Meroney, Robert N; Sheker, Robert E
2014-09-01
Computational fluid dynamics (CFD) was used to simulate the mixing characteristics of a small circular anaerobic digester tank (diameter 6 m) equipped sequentially with 13 different plunger type vertical linear motion mixers and two different type internal draft-tube mixers. Rates of mixing of step injection of tracers were calculated from which active volume (AV) and hydraulic retention time (HRT) could be calculated. Washout characteristics were compared to analytic formulae to estimate any presence of partial mixing, dead volume, short-circuiting, or piston flow. Active volumes were also estimated based on tank regions that exceeded minimum velocity criteria. The mixers were ranked based on an ad hoc criteria related to the ratio of AV to unit power (UP) or AV/UP. The best plunger mixers were found to behave about the same as the conventional draft-tube mixers of similar UP. PMID:25327022
CFD simulation of the gas flow in a pulse tube cryocooler with two pulse tubes
Yin, C. L.
2015-12-01
In this paper, in order to instruct the next optimization work, a two-dimension Computational Fluid Dynamics (CFD) model is developed to simulate temperature distribution and velocity distribution of oscillating fluid in the DPTC by individual phase-shifting. It is found that the axial temperature distribution of regenerator is generally uniform and the temperatures near the center at the same cross setion of two pulse tubes are obviously higher than their near wall temperatures. The wall temperature difference about 0-7 K exists between the two pulse tubes. The velocity distribution near the center of the regenerator is uniform and there is obvious injection stream coming at the center of the pulse tubes from the hot end. The formation reason of temperature distribution and velocity distribution is explained.
Parallel CFD simulation of flow in a 3D model of vibrating human vocal folds
Czech Academy of Sciences Publication Activity Database
Šidlof, Petr; Horáček, Jaromír; Řidký, V.
2013-01-01
Roč. 80, č. 1 (2013), s. 290-300. ISSN 0045-7930 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional research plan: CEZ:AV0Z20760514 Keywords : numerical simulation * vocal folds * glottal airflow * inite volume method * parallel CFD Subject RIV: BI - Acoustics Impact factor: 1.532, year: 2013 http://www.sciencedirect.com/science?_ob=ArticleListURL&_method=list&_ArticleListID=-268060849&_sort=r&_st=13&view=c&_acct=C000034318&_version=1&_urlVersion=0&_userid=640952&md5=7c5b5539857ee9a02af5e690585b3126&searchtype=a
International Nuclear Information System (INIS)
The present paper contains a comprehensive literature survey on helicopter flow analyses and describes some true unsteady flows past helicopter rotors obtained using low and high order CFD models. The low order model is based on a panel method coupled with a viscous boundary layer approach and a compressibility correction. The USAERO software is used for the computations. The high order model is based on Euler and Navier-Stokes equations. For the high order models, a true unsteady scheme, as implemented in the CFD-FASTRAN code using the Euler equations, is considered for flows past hovering rotor. On the other hand, a quasi-steady approach, using the WIND code with the Navier-Stokes equations and the SST turbulence model, is used to assess the validity of the approach for the simulation of flows past a helicopter in forward flight conditions. When using the high order models, a Chimera grid technique is used to describe the blade motions within the parent stationary grid. Comparisons with experimental data are performed and the true unsteady simulations provide a reasonable agreement with the available experimental data. The panel method and the quasisteady approach are found to overestimate the loads on the helicopter rotors. The USAERO panel code is found to produce more thrust owing to some error sources in the computations when a wake-surface collision occurs, as the blades interact with their own wakes. The automatic cutting of the wake sheets, as they approach the model surface, is not working properly at every time step. (author)
CFD simulation of particle deposition on an array of spheres using an Euler/Lagrange approach
Energy Technology Data Exchange (ETDEWEB)
Dehbi, A., E-mail: abdel.dehbi@psi.ch [Laboratory for Thermal-Hydraulics, Paul Scherrer Institut, Villigen 5232 (Switzerland); Martin, S., E-mail: simon.martin@ec-lyon.f [Laboratoire de Mecanique des Fluides et d' Acoustique, Ecole Centrale de Lyon, 69130 Ecully (France)
2011-08-15
Highlights: > We use CFD to simulate particulate deposition around arrays of spheres and compare results with experimental data. > The Continuous Random Walk (CRW) is employed to supply fluctuating fluid velocity components. > Model predictions of particle deposition rates are generally within the scatter of the data. - Abstract: The Generation IV Pebble Bed Modular Reactor (PBMR) is being considered as a promising concept to produce electricity or process heat with high efficiencies and unique safety features. The PBMR is a high-temperature, helium-cooled, graphite moderated reactor. The fuel elements consist of 6 cm diameter spherical graphite 'pebbles' containing each thousands of uranium dioxide microspheres. As the pebbles continually rub against one another in the core, a significant quantity of graphite dust can be released in the reactor coolant system. These dust particles, which contain some amounts of fission products, are transported and deposited on pebbles as well as primary circuit surfaces. It is therefore of great safety interest to develop and benchmark numerical approaches for predicting deposition of dust particles in the various locations of the PBMR primary circuit. In this investigation, we use the ANSYS-Fluent CFD code to simulate particulate flows around linear arrays of spheres and compare deposition rates against experiments. It is found that the Reynolds Stress Model (RSM) combined with the Continuous Random Walk (CRW) to supply fluctuating velocity components predicts deposition rates that are generally within the scatter of the data. The methodology developed here can therefore be used to predict to first order the graphite dust deposition rates on pebbles in PBMR-type reactors.
Accuracy quantification metrics for CFD simulation of in-vessel flows
Energy Technology Data Exchange (ETDEWEB)
Moretti, Fabio, E-mail: f.moretti@ing.unipi.it; D’Auria, Francesco
2014-11-15
Highlights: • CFD code validation involves accuracy quantification. • Accuracy evaluation requires metrics for comparison of multi-variable data. • Proposal of possible metrics, based on a set of quantitative parameters. • Providing examples applied to distribution of coolant properties at core inlet. • Applying the proposed set of parameters to a number of code validation cases. - Abstract: Within more general frameworks dealing with uncertainty evaluation and code assessment, well assessed methodologies exist for the accuracy evaluation of system thermal hydraulic analysis results. As long as multi-dimensional transient data is involved, such as space and time distributions obtained from CFD calculations and experiments, the task of quantifying the accuracy and defining acceptance criteria becomes harder, and there seems to be a lack of systematic approaches available to that purpose. An example of such multi-dimensional data is represented by the time and space distribution of coolant properties (e.g. temperature, boron concentration) at the reactor core inlet, which is relevant to reactor safety as local perturbations potentially induce power excursions. An attempt is made here to tackle the accuracy quantification issue for that class of data, in a somewhat empirical way, i.e. by proposing a set of parameters that can be used, after proper qualitative analysis of measured data and code simulation results, to characterize the target variable time and space distributions, and to quantify the deviation of the simulation from the experimental data. The advantage of using such kind of metrics based on many parameters relies in the ability to cover different relevant features of the target variables and thus provide a more complete assessment and allow statements about the overall agreement.
Institute of Scientific and Technical Information of China (English)
李大美; 王祥三; 赖永根
2001-01-01
Schistosomiasis is a parasitic disease. They propagate in the Yangtze River valley of Chi-na. The spread of the disease is solely through a middle-agent named oncomelania, so the spread ofschistosomiasis by oncomelania can be controlled by properly designing water intakes which preventoncomelania from entering the farming land or residential areas. In this paper, a successful design pro-cess is reported and a new oncomelania-free intake device is demonstrated in the laboratory. The de-sign of the new intake is based on a sound research program in which an extensive experimental stud-ies have been carried out to gain knowledge of oncomelania eco-hydraulic behaviors and a detailed flowfield information is obtained through CFD simulation.
Li, Jun-De
2013-02-01
This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected. PMID:24850953
Directory of Open Access Journals (Sweden)
Nils Koliha
2015-09-01
Full Text Available Real-time rendering in the realm of computational fluid dynamics (CFD in particular and scientific high performance computing (HPC in general is a comparably young field of research, as the complexity of most problems with practical relevance is too high for a real-time numerical simulation. However, recent advances in HPC and the development of very efficient numerical techniques allow running first optimized numerical simulations in or near real-time, which in return requires integrated and optimized visualization techniques that do not affect performance. In this contribution, we present concepts, implementation details and several application examples of a minimally-invasive, efficient visualization tool for the interactive monitoring of 2D and 3D turbulent flow simulations on commodity hardware. The numerical simulations are conducted with ELBE, an efficient lattice Boltzmann environment based on NVIDIA CUDA (Compute Unified Device Architecture, which provides optimized numerical kernels for 2D and 3D computational fluid dynamics with fluid-structure interactions and turbulence.
CFD simulation of pressure and discharge surge in Francis turbine at off-design conditions
Chirkov, D.; Avdyushenko, A.; Panov, L.; Bannikov, D.; Cherny, S.; Skorospelov, V.; Pylev, I.
2012-11-01
A hybrid 1D-3D CFD model is developed for the numerical simulation of pressure and discharge surge in hydraulic power plants. The most essential part - the turbine itself - is simulated directly using 3D unsteady equations of turbulent motion of fluid-vapor mixture, while the rest of the hydraulic system is simulated in frames of 1D hydro-acoustic model. Thus the model accounts for the main factors responsible for excitation and propagation of pressure and discharge waves in hydraulic power plant. Boundary conditions at penstock inlet and draft tube outlet are discussed in detail. Then simulations of dynamic behavior at part load and full load operating points are performed. It is shown that the numerical model is able to capture self-excited oscillations in full load conditions. The influence of penstock length and flow structure behind the runner are investigated. The presented approach seems to be a promising tool for prediction and investigation the dynamic behavior in hydraulic power plants.
CFD simulations of thermal comfort in naturally ventilated primary school classrooms
Directory of Open Access Journals (Sweden)
Stevanović Žana Ž.
2016-01-01
Full Text Available The purpose of Thermal Comfort is to specify the combinations of indoor space environment and personal factors that will produce thermal environment conditions acceptable to 80% or more of the occupants within a space. Naturally ventilated indoors has a very complex air movement, which depends on numerous variables such as: outdoor interaction, intensity of infiltration, the number of openings, the thermal inertia of walls, occupant behaviors, etc. The most important mechanism for naturally ventilated indoors is the intensity of infiltration and thermal buoyancy mechanism. In this study the objective was to determine indicators of thermal comfort for children, by the CFD model based on experimental measurements with modification on turbulent and radiant heat transfer mathematical model. The case study was selected on school children aged 8 and 9 years in primary school „France Prešern“, Belgrade. The purpose was to evaluate the relationships between the indoor environment and the subjective responses. Also there was analysis of infiltration and stack effect based on meterological data on site. The main parameters that were investigated are: operative temperature, radiant temperature, concentration of CO2 and air velocity. The new correction of turbulence and radiative heat transfer models has been validated by comparison with experimental data using additional statistical indicators. It was found that both turbulence model correct and the new radiative model of nontransparent media have a significant influence on CFD data set accuracy.
A CFD STUDY OF CAVITATION IN REAL SIZE DIESEL INJECTORS
PATOUNA, STAVROULA
2012-01-01
In Diesel engines, the internal flow characteristics in the fuel injection nozzles, such as the turbulence level and distribution, the cavitation pattern and the velocity profile affect significantly the air-fuel mixture in the spray and subsequently the combustion process. Since the possibility to observe experimentally and measure the flow inside real size Diesel injectors is very limited, Computational Fluid Dynamics (CFD) calculations are generally used to obtain the relevant informati...
CFD and experimental study of aerodynamic degradation of iced airfoils
Czech Academy of Sciences Publication Activity Database
Horák, V.; Rozehnal, D.; Chára, Zdeněk; Hyll, A.
Praha: Ústav termomechaniky AV ČR v. v. i, 2008 - (Jonáš, P.; Uruba, V.), č. 007 ISBN 978-80-87012-14-7. [Colloquium FLUID DYNAMICS 2008. Praha (CZ), 22.10.2008-24.10.2008] R&D Projects: GA ČR GA103/07/0136; GA MPO FT-TA4/044 Institutional research plan: CEZ:AV0Z20600510 Keywords : CFD * lift coefficient * iced airfoil Subject RIV: BK - Fluid Dynamics
Multi-scale Model Coupling for CFD Simulations of Discharge Dispersion in the Sea
Robinson, D.; Wood, M.; Piggott, M. D.; Gorman, G.
2014-12-01
nodes adjusting to efficiently concentrate computational effort only on those areas of the flow that are influential to model accuracy. The simulation results are used to give a pragmatic cost / benefit analysis of the various coupling methods, comparing their accuracy and speed where used in outfall design studies.
CFD simulation of a particle loaded coolant flow in the sump and in the condensation chamber
International Nuclear Information System (INIS)
A collaborative project funded by the BMBF in the framework of the R and D program ''Energie 2020+'' by 4 Universities, 2 Research Centres and ANSYS was coordinated by Helmholtz- Zentrum Dresden-Rossendorf (HZDR). The present report describes the contributions of HZDR done from September 2009 to January 2013. The project was directed towards the development and validation of CFD models of boiling processes in PWR in the range from subcooled nucleate boiling up to the critical heat flux. The report describes the developed and used models. Main achievements were a comprehensive study of the boiling process itself and a better description of the interfacial area by coupling of wall boiling with a population balance model. The model extensions are validated and the present capabilities of CFD for wall boiling are investigated. By means of rod bundle experiments was shown that the measured cross sectional averaged values can be reproduced well with a single set of calibrated model parameters for different tests cases. For the reproduction of patterns of void distribution cross sections attention has to be focussed on the modelling of turbulence in the narrow channel. The experimental work was focussed on the investigation of the flow in a rod bundle. Using a rod bundle test rig the turbulent single phase flow field (PIV) and the average gas volume fraction (gamma densitometry) are measured. The timely and spatial resolved gas fraction was measured applying the ''High speed x-ray tomography'', developed in Rossendorf.
A CFD study on the effectiveness of trees to disperse road traffic emissions at a city scale
Jeanjean, A. P. R.; Hinchliffe, G.; McMullan, W. A.; Monks, P. S.; Leigh, R. J.
2015-11-01
This paper focuses on the effectiveness of trees at dispersing road traffic emissions on a city scale. CFD simulations of air-pollutant concentrations were performed using the OpenFOAM software platform using the k-ε model. Results were validated against the CODASC wind tunnel database before being applied to a LIDAR database of buildings and trees representing the City of Leicester (UK). Most other CFD models in the literature typically use idealised buildings to model wind flow and pollution dispersion. However, the methodology used in this study uses real buildings and trees data from LIDAR to reconstruct a 3D representation of Leicester City Centre. It focuses on a 2 × 2 km area which is on a scale larger than those usually used in other CFD studies. Furthermore, the primary focus of this study is on the interaction of trees with wind flow dynamics. It was found that in effect, trees have a regionally beneficial impact on road traffic emissions by increasing turbulence and reducing ambient concentrations of road traffic emissions by 7% at pedestrian height on average. This was an important result given that previous studies generally concluded that trees trapped pollution by obstructing wind flow in street canyons. Therefore, this study is novel both in its methodology and subsequent results, highlighting the importance of combining local and regional scale models for assessing the impact of trees in urban planning.
3 × 3 rod bundle investigations, CFD single-phase numerical simulations
International Nuclear Information System (INIS)
Highlights: • CFD simulations of the flow around a 3 × 3 rod bundle were conducted. • Single-phase calculations performed as pre-investigation of future boiling applications. • The influence of the geometry details (inlet vessel, grid spacers) was investigated. • Turbulent patterns of these flows were analyzed (secondary flows, vortices, flow asymmetries). - Abstract: The work here presented has been performed in the framework of a research project aimed to investigate two-phase (boiling) flows in pressurized water reactors (PWR). CFD investigations of a rod bundle have been conducted while a new experimental facility (ROFEX) was constructed in Helmholtz Zentrum Dresden-Rossendorf (HZDR) for the generation of quality validation data. The apparatus consists of a 3 × 3 rod bundle inside a Plexiglas vertical pipe. The results summarized in this paper are considered as a pre-investigation, being the final goal to be able to predict accurately boiling water flows under high pressure around rods. For this purpose, three steps were defined: analysis of single-phase flows in such geometry, analysis of the multiphase flow when using a refrigerant as a working fluid and, finally, the analysis of a multiphase flow using water. The single-phase approach allows gaining experience regarding the turbulence behaviour of the flow, while the multiphase investigation of the refrigerant simplifies the experimental conditions since it is possible to get boiling situations at lower pressure level. At the moment of writing this paper, the authors were focused on the first step (single-phase flows at low pressure), since this not only made possible to better understand the turbulence in that geometry, but it also resulted in valuable feedback to the experimentalists on improving the construction of the facility. In parallel, HZDR researchers have been developing a new tomography measurement technique to measure gas content in multiphase flows
3 × 3 rod bundle investigations, CFD single-phase numerical simulations
Energy Technology Data Exchange (ETDEWEB)
Lifante, C., E-mail: Conxita.Lifante@ansys.com [ANSYS Germany GmbH, Staudenfeldweg 12, Otterfing D-83624 (Germany); Krull, B., E-mail: Benjamin.Krull@ansys.com [ANSYS Germany GmbH, Staudenfeldweg 12, Otterfing D-83624 (Germany); Frank, Th., E-mail: Thomas.Frank@ansys.com [ANSYS Germany GmbH, Staudenfeldweg 12, Otterfing D-83624 (Germany); Franz, R., E-mail: r.franz@hzdr.de [Experimentelle Thermofluiddynamik, Helmholtz Zentrum Dresden-Rossendorf, POB 510 119, Dresden D-01314 (Germany); Hampel, U., E-mail: u.hampel@hzdr.de [Experimentelle Thermofluiddynamik, Helmholtz Zentrum Dresden-Rossendorf, POB 510 119, Dresden D-01314 (Germany)
2014-11-15
Highlights: • CFD simulations of the flow around a 3 × 3 rod bundle were conducted. • Single-phase calculations performed as pre-investigation of future boiling applications. • The influence of the geometry details (inlet vessel, grid spacers) was investigated. • Turbulent patterns of these flows were analyzed (secondary flows, vortices, flow asymmetries). - Abstract: The work here presented has been performed in the framework of a research project aimed to investigate two-phase (boiling) flows in pressurized water reactors (PWR). CFD investigations of a rod bundle have been conducted while a new experimental facility (ROFEX) was constructed in Helmholtz Zentrum Dresden-Rossendorf (HZDR) for the generation of quality validation data. The apparatus consists of a 3 × 3 rod bundle inside a Plexiglas vertical pipe. The results summarized in this paper are considered as a pre-investigation, being the final goal to be able to predict accurately boiling water flows under high pressure around rods. For this purpose, three steps were defined: analysis of single-phase flows in such geometry, analysis of the multiphase flow when using a refrigerant as a working fluid and, finally, the analysis of a multiphase flow using water. The single-phase approach allows gaining experience regarding the turbulence behaviour of the flow, while the multiphase investigation of the refrigerant simplifies the experimental conditions since it is possible to get boiling situations at lower pressure level. At the moment of writing this paper, the authors were focused on the first step (single-phase flows at low pressure), since this not only made possible to better understand the turbulence in that geometry, but it also resulted in valuable feedback to the experimentalists on improving the construction of the facility. In parallel, HZDR researchers have been developing a new tomography measurement technique to measure gas content in multiphase flows.
Simulation of two-phase flows in vertical tubes with the CFD code FLUBOX
International Nuclear Information System (INIS)
The Computational Fluid Dynamics (CFD) code FLUBOX is developed at GRS for the multidimensional simulation of two-phase flows. The single-pressure two-fluid model is used as basis of the simulation. A basic mathematical property of the two-fluid model of FLUBOX is the hyperbolic character of the convection. The numerical solution methods of FLUBOX make explicit use of the hyperbolic structure of the coefficient matrices. The simulation of two-phase flow phenomena needs, apart from the conservation equations for each phase, an additional transport equation for the interfacial area concentration. The concentration of the interfacial area is one of the key parameters for the modelling of interfacial friction forces and interfacial transfer terms. A new transport equation for the interfacial area concentration is in development. It describes the dynamic change of the interfacial area concentration due to mass exchange and a force balance at the phase boundary. Results from FLUBOX calculations for different experiments of two-phase flows in vertical tubes are presented as part of the validation. (authors)