Experimental studies and CFD simulations of conical spouted bed hydrodynamics
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.
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
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
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
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
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.
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)
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
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
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
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.
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
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.
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...
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)
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
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
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
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
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
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
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
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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
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
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...
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
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
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
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.
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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)
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
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
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
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.)
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.)
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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
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.
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
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
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
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
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
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
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
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
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
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
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
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.
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
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
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.
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
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
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
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
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
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
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
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....
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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 ...