Development of CFD-based icing model for wind turbines
DEFF Research Database (Denmark)
Pedersen, Marie Cecilie; Martinez, Benjamin; Yin, Chungen
2015-01-01
Operation of wind turbines in cold climate areas is challenged by icing-induced problems, such as loss of production, safety issues and blade fatique. Production losses are especially a big issue in Sweden, and due to difficulties with on-site measurements, simulations are often used to get an...... understanding and to predict icing events. In this paper a case study of modeling icing using Computational Fluid Dynamics (CFD) is proposed. The case study aims to form the basic of a general CFD model for icing on wind turbine blade sections....
International Nuclear Information System (INIS)
Highlights: • A CFD based model developed in ANSYS-FLUENT for simulating the distribution of hydrogen in the containment of a nuclear power plant during a severe accident is validated against four large-scale experiments. • The successive formation and mixing of a stratified gas-layer in experiments performed in the THAI and PANDA facilities are predicted well by the CFD model. • The pressure evolution and related condensation rate during different mixed convection flow conditions in the TOSQAN facility are predicted well by the CFD model. • The results give confidence in the general applicability of the CFD model and model settings. - Abstract: In the event of core degradation during a severe accident in water-cooled nuclear power plants (NPPs), large amounts of hydrogen are generated that may be released into the reactor containment. As the hydrogen mixes with the air in the containment, it can form a flammable mixture. Upon ignition it can damage relevant safety systems and put the integrity of the containment at risk. Despite the installation of mitigation measures, it has been recognized that the temporary existence of combustible or explosive gas clouds cannot be fully excluded during certain postulated accident scenarios. The distribution of hydrogen in the containment and mitigation of the risk are, therefore, important safety issues for NPPs. Complementary to lumped parameter code modelling, Computational Fluid Dynamics (CFD) modelling is needed for the detailed assessment of the hydrogen risk in the containment and for the optimal design of hydrogen mitigation systems in order to reduce this risk as far as possible. The CFD model applied by NRG makes use of the well-developed basic features of the commercial CFD package ANSYS-FLUENT. This general purpose CFD package is complemented with specific user-defined sub-models required to capture the relevant thermal-hydraulic phenomena in the containment during a severe accident as well as the effect of
Development of a compartment model based on CFD simulations for description of mixing in bioreactors
Directory of Open Access Journals (Sweden)
Crine, M.
2010-01-01
Full Text Available Understanding and modeling the complex interactions between biological reaction and hydrodynamics are a key problem when dealing with bioprocesses. It is fundamental to be able to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. CFD can provide detailed modeling about hydrodynamics and mixing. However, it is computationally intensive, especially when reactions are taken into account. Another way to predict hydrodynamics is the use of "Compartment" or "Multi-zone" models which are much less demanding in computation time than CFD. However, compartments and fluxes between them are often defined by considering global quantities not representative of the flow. To overcome the limitations of these two methods, a solution is to combine compartment modeling and CFD simulations. Therefore, the aim of this study is to develop a methodology in order to propose a compartment model based on CFD simulations of a bioreactor. The flow rate between two compartments can be easily computed from the velocity fields obtained by CFD. The difficulty lies in the definition of the zones in such a way they can be considered as perfectly mixed. The creation of the model compartments from CFD cells can be achieved manually or automatically. The manual zoning consists in aggregating CFD cells according to the user's wish. The automatic zoning defines compartments as regions within which the value of one or several properties are uniform with respect to a given tolerance. Both manual and automatic zoning methods have been developed and compared by simulating the mixing of an inert scalar. For the automatic zoning, several algorithms and different flow properties have been tested as criteria for the compartment creation.
Towards a CFD-based mechanistic deposit formation model for straw-fired boilers
DEFF Research Database (Denmark)
Kær, Søren Knudsen; Rosendahl, Lasse Aistrup; Baxter, L.L.
2006-01-01
in the reminder of the paper. The growth of deposits on furnace walls and super heater tubes is treated including the impact on heat transfer rates determined by the CFD code. Based on the commercial CFD code FLUENTe, the overall model is fully implemented through the User Defined Functions. The...... model is configured entirely through a graphical user interface integrated in the standard FLUENTe interface. The model considers fine and coarse mode ash deposition and sticking mechanisms for the complete deposit growth, as well as an influence on the local boundary conditions for heat transfer due to...
CFD-based Evaluation of Interfacial Flows
Ito, Kei; Ohshima, Hiroyuki; Sakai, Takaaki; Kunugi, Tomoaki
2010-01-01
As an example of the evaluation of interfacial flows, two methodologies were proposed for the evaluation of the GE phenomena. One is the CFD-based prediction methodology and the other is the high-precision numerical simulation of interfacial flows. In the development of the CFD-based prediction methodology, the vortical flow model was firstly constructed based on the Burgers theory. Then, the accuracy of the CFD results, which are obtained on relatively coarse computational mesh without consi...
Developing an Accurate CFD Based Gust Model for the Truss Braced Wing Aircraft
Bartels, Robert E.
2013-01-01
The increased flexibility of long endurance aircraft having high aspect ratio wings necessitates attention to gust response and perhaps the incorporation of gust load alleviation. The design of civil transport aircraft with a strut or truss-braced high aspect ratio wing furthermore requires gust response analysis in the transonic cruise range. This requirement motivates the use of high fidelity nonlinear computational fluid dynamics (CFD) for gust response analysis. This paper presents the development of a CFD based gust model for the truss braced wing aircraft. A sharp-edged gust provides the gust system identification. The result of the system identification is several thousand time steps of instantaneous pressure coefficients over the entire vehicle. This data is filtered and downsampled to provide the snapshot data set from which a reduced order model is developed. A stochastic singular value decomposition algorithm is used to obtain a proper orthogonal decomposition (POD). The POD model is combined with a convolution integral to predict the time varying pressure coefficient distribution due to a novel gust profile. Finally the unsteady surface pressure response of the truss braced wing vehicle to a one-minus-cosine gust, simulated using the reduced order model, is compared with the full CFD.
A CFD-based wind solver for a fast response transport and dispersion model
Energy Technology Data Exchange (ETDEWEB)
Gowardhan, Akshay A [Los Alamos National Laboratory; Brown, Michael J [Los Alamos National Laboratory; Pardyjak, Eric R [UNIV OF UTAH; Senocak, Inanc [BOISE STATE UNIV
2010-01-01
In many cities, ambient air quality is deteriorating leading to concerns about the health of city inhabitants. In urban areas with narrow streets surrounded by clusters of tall buildings, called street canyons, air pollution from traffic emissions and other sources is difficult to disperse and may accumulate resulting in high pollutant concentrations. For various situations, including the evacuation of populated areas in the event of an accidental or deliberate release of chemical, biological and radiological agents, it is important that models should be developed that produce urban flow fields quickly. For these reasons it has become important to predict the flow field in urban street canyons. Various computational techniques have been used to calculate these flow fields, but these techniques are often computationally intensive. Most fast response models currently in use are at a disadvantage in these cases as they are unable to correlate highly heterogeneous urban structures with the diagnostic parameterizations on which they are based. In this paper, a fast and reasonably accurate computational fluid dynamics (CFD) technique that solves the Navier-Stokes equations for complex urban areas has been developed called QUIC-CFD (Q-CFD). This technique represents an intermediate balance between fast (on the order of minutes for a several block problem) and reasonably accurate solutions. The paper details the solution procedure and validates this model for various simple and complex urban geometries.
CFD simulation of aerosol deposition in an anatomically based human large-medium airway model.
Ma, Baoshun; Lutchen, Kenneth R
2009-02-01
Quantitative data on aerosol deposition in the human respiratory tract are useful for understanding the causes of certain lung diseases and for designing efficient drug delivery systems via inhalation. In this study, aerosol deposition in a 3D anatomically based human large-medium airway model was simulated using computational fluid dynamics (CFD). The model extended from mouth to generation 10 and included two-thirds of the airways obtained by multi-detector row computed tomography (MDCT) imaging on normal healthy human subjects. Steady oral inhalation (15, 30, and 60 L/min) and aerosol (1-30 micrometer) deposition were computed by CFD using the realizable k-epsilon turbulence model. Based on the mean turbulence flow field, the computed extrathoracic deposition, ratio of left to right lung deposition, and deposition efficiency at each generation compared favorably with existing in vivo and in vitro experiments. The significant deposition in the large-medium airway model showed that the total tracheobronchial deposition is dominated by the large-medium airways for micrometer-sized aerosol particles. These quantitative data and the methods developed in this study provided valuable means toward subject-specific modeling of aerosol deposition in the human lung based on realistic lung geometry. PMID:19082892
CFD based combustion model for sewage sludge gasification in a fluidized bed
Institute of Scientific and Technical Information of China (English)
Yiqun WANG; Lifeng YAN
2009-01-01
Gasification is one potential way to use sewage sludge as renewable energy and solve the environmental problems caused by the huge amount of sewage sludge. In this paper, a three-dimensional Computational Fluid Dynamics (CFD) model has been developed to simulate the sewage sludge gasification process in a fluidized bed. The model describes the complex physical and chemical phenomena in the gasifier including turbulent flow, heat and mass transfer, and chemical reactions. The model is based on the Eulerian-Lagrangian concept using the non-premixed combustion modeling approach. In terms of the CFD software FLUENT, which represents a powerful tool for gasifIer analysis, the simulations provide detailed information on the gas products and temperature distribution in the gasifier. The model sensitivity is analyzed by performing the model in a laboratory-scale fluidized bed in the literature, and the model validation is carried out by comparing with experimental data from the literature. Results show that reasonably good agreement was achieved. Effects of temperature and Equivalence Ratio (ER) on the quality of product syngas (H2 + CO) are also studied.
Active-passive measurements and CFD based modelling for indoor radon dispersion study
International Nuclear Information System (INIS)
Computational fluid dynamics (CFD) play a significant role in indoor pollutant dispersion study. Radon is an indoor pollutant which is radioactive and inert gas in nature. The concentration level and spatial distribution of radon may be affected by the dwelling's ventilation conditions. Present work focus at the study of indoor radon gas distribution via measurement and CFD modeling in naturally ventilated living room. The need of the study is the prediction of activity level and to study the effect of natural ventilation on indoor radon. Two measurement techniques (Passive measurement using pin-hole dosimeters and active measurement using continuous radon monitor (SRM)) were used for the validation purpose of CFD results. The CFD simulation results were compared with the measurement results at 15 points, 3 XY planes at different heights along with the volumetric average concentration. The simulation results found to be comparable with the measurement results. The future scope of these CFD codes is to study the effect of varying inflow rate of air on the radon concentration level and dispersion pattern. - Highlights: • The distribution of radon gas in indoor environment was simulated using CFD modelling. • The distribution of radon was found to be more homogenous in open room condition. • The radon concentration level in open room was low as compare to closed room due to enhanced ventilation rate. • Simulation results are in agreement with active and passive measurements results
Assessment of CFD URANS models for buoyancy driven mixing flows based on ROCOM experiments
International Nuclear Information System (INIS)
An assessment of STAR-CCM+ Computational Fluid Dynamics (CFD) models of a KONVOI type Reactor Pressure Vessel (RPV) has been performed based on experimental data collected at the ROssendorf COolant Mixing (ROCOM) test facility as part of the OECD-NEA PKL 2 Project. Three different experimental configurations typical of Main Steam Line Break (MSLB) with Loss-Of-Offsite-Power (LOOP) scenarios are investigated (i.e. Test 1.1, 2.1 and 2.2). The transport of the mixing scalar is based on an equivalent thermal model of the isothermal experimental system. The focus of the study is on the modeling of the physical properties and the turbulent heat flux (closure term) needed by the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. Results show that a standard Constant Turbulent Prandtl number (CTP) and the chosen Variable Turbulent Prandtl number (VTP) models are capable of describing qualitatively and quantitatively well the time-evolution of the temperature field in the core inlet zone (Test 1.1). When large density differences of the coolant are present in the system, the VTP model outperforms the CTP model in predicting the elevation of the thermal stratification line that builds up in the downcomer due to incomplete mixing. Nevertheless, the CTP model performs very well when the density difference is very low (Test 2.1). No significant changes have been observed for Test 2.2 when idealized boundary conditions are used instead of the experimental ones. (author)
Development of CFD analysis method based on droplet tracking model for BWR fuel assemblies
International Nuclear Information System (INIS)
It is well known that the minimum critical power ratio (MCPR) of the boiling water reactor (BWR) fuel assembly depends on the spacer grid type. Recently, improvement of the critical power is being studied by using a spacer grid with mixing devices attaching various types of flow deflectors. In order to predict the critical power of the improved BWR fuel assembly, we have developed an analysis method based on the consideration of detailed thermal-hydraulic mechanism of annular mist flow regime in the subchannels for an arbitrary spacer type. The proposed method is based on a computational fluid dynamics (CFD) model with a droplet tracking model for analyzing the vapor-phase turbulent flow in which droplets are transported in the subchannels of the BWR fuel assembly. We adopted the general-purpose CFD software Advance/FrontFlow/red (AFFr) as the base code, which is a commercial software package created as a part of Japanese national project. AFFr employs a three-dimensional (3D) unstructured grid system for application to complex geometries. First, AFFr was applied to single-phase flows of gas in the present paper. The calculated results were compared with experiments using a round cellular spacer in one subchannel to investigate the influence of the choice of turbulence model. The analyses using the large eddy simulation (LES) and re-normalisation group (RNG) k-ε models were carried out. The results of both the LES and RNG k-ε models show that calculations of velocity distribution and velocity fluctuation distribution in the spacer downstream reproduce the experimental results qualitatively. However, the velocity distribution analyzed by the LES model is better than that by the RNG k-ε model. The velocity fluctuation near the fuel rod, which is important for droplet deposition to the rod, is also simulated well by the LES model. Then, to examine the effect of the spacer shape on the analytical result, the gas flow analyses with the RNG k-ε model were performed
Improvement of core effective thermal conductivity model of GAMMA+ code based on CFD analysis
International Nuclear Information System (INIS)
Highlights: • We assessed the core effective thermal conductivity (ETC) model of GAMMA+ code. • The analytical model of GAMMA+ code was compared with the result of CFD analysis. • Effects of material property of composite and geometric configuration were studied. • The GAMMA+ model agreed with the CFD result when the fuel gap is ignored. • The GAMMA+ model was improved by the ETC model of fuel compact including fuel gap. - Abstract: The GAMMA+ code has been developed for the thermo-fluid and safety analyses of a high temperature gas-cooled reactor (HTGR). In order to calculate the core effective thermal conductivity, this code adopts a heterogeneous model derived from the Maxwell’s theory that accounts for three distinct materials in a fuel block of the reactor core. In this model, the fuel gap is neglected since the gap thickness is quite small. In addition, the configuration of the fuel block is assumed to be homogeneous, and the volume fraction and material properties of each component are taken into account. In the accident condition, the conduction and radiation are major heat transfer mechanism. Therefore, the core effective thermal conductivity model should be validated in order to estimate the heat transfer in the core appropriately. In this regard, the objective of this study is to validate the core effective thermal conductivity model of the GAMMA+ code by a computational fluid dynamics (CFD) analysis using a commercial CFD code, CFX-13. The effects of the temperature condition, material property and geometric modeling on the core effective thermal conductivity were investigated. When the fuel gap is not modeled in the CFD analysis, the result of the GAMMA+ code shows a good agreement with the CFD result. However, when the fuel gap is modeled, the GAMMA+ model overestimates the core effective thermal conductivity considerably for all cases. This is because of the increased thermal resistance by the fuel gap which is not taken into account in
Wu, Kenan; Huai, Ying; Jia, Shuqin; Jin, Yuqi
2011-12-19
Coupled simulation based on intracavity partially coherent light model and 3D CFD model is firstly achieved in this paper. The dynamic equation of partially coherent intracavity field is derived based on partially coherent light theory. A numerical scheme for the coupled simulation as well as a method for computing the intracavity partially coherent field is given. The presented model explains the formation of the sugar scooping phenomenon, and enables studies on the dependence of the spatial mode spectrum on physical parameters of laser cavity and gain medium. Computational results show that as the flow rate of iodine increases, higher order mode components dominate in the partially coherent field. Results obtained by the proposed model are in good agreement with experimental results. PMID:22274214
A CFD model for orbital gerotor motor
International Nuclear Information System (INIS)
In this paper, a full 3D transient CFD model for orbital gerotor motor is described in detail. One of the key technologies to model such a fluid machine is the mesh treatment for the dynamically changing rotor fluid volume. Based on the geometry and the working mechanism of the orbital gerotor, a moving/deforming mesh algorithm was introduced and implemented in a CFD software package. The test simulations show that the proposed algorithm is accurate, robust, and efficient when applied to industrial orbital gerotor motor designs. Simulation results are presented in the paper and compared with experiment test data.
Efficient Turbulence Modeling for CFD Wake Simulations
DEFF Research Database (Denmark)
van der Laan, Paul
Wind turbine wakes can cause 10-20% annual energy losses in wind farms, and wake turbulence can decrease the lifetime of wind turbine blades. One way of estimating these effects is the use of computational fluid dynamics (CFD) to simulate wind turbines wakes in the atmospheric boundary layer. Since...... wind farm, the simulated results cannot be compared directly with wind farm measurements that have a high uncertainty in the measured reference wind direction. When this uncertainty is used to post-process the CFD results, a fairer comparison with measurements is achieved....... this flow is in the high Reynolds number regime, it is mainly dictated by turbulence. As a result, the turbulence modeling in CFD dominates the wake characteristics, especially in Reynolds-averaged Navier-Stokes (RANS). The present work is dedicated to study and develop RANS-based turbulence models...
Directory of Open Access Journals (Sweden)
K.C. Ghanta
2010-12-01
Full Text Available An attempt has been made in the present study to develop a generalized slurry flow model using CFD and utilize the model to predict concentration profile. The purpose of the CFD model is to gain better insight into the solid liquid slur¬ry flow in pipelines. Initially a three-dimensional model problem was developed to understand the influence of the particle drag coefficient on the solid concen¬tration profile. The preliminary simulations highlighted the need for correct mo¬delling of the inter phase drag force. The various drag correlations available in the literature were incorporated into a two-fluid model (Euler-Euler along with the standard k- turbulence model with mixture properties to simulate the tur¬bulent solid-liquid flow in a pipeline. The computational model was mapped on to a commercial CFD solver FLUENT6.2 (of Fluent Inc., USA. To push the en¬velope of applicability of the simulation, recent data from Kaushal (2005 (with solid concentration up to 50% was selected to validate the three dimensional simulations. The experimental data consisted of water-glass bead slurry at 125 and 440-micron particle with different flow velocity (from 1 to 5 m/s and overall concentration up to 10 to 50% by volume. The predicted pressure drop and concentration profile were validated by experimental data and showed excel-lent agreement. Interesting findings came out from the parametric study of ve-locity and concentration profiles. The computational model and results discus¬sed in this work would be useful for extending the applications of CFD models for simulating large slurry pipelines.
International Nuclear Information System (INIS)
This paper describes a CFD based strategy for the modeling of stratified two-phase flows with heat and mass transfer across a moving steam-water interface due to direct contact condensation. Such flows have been of major importance for example in connection with the analysis of nuclear reactor safety systems, in particular during two-phase Pressurized Thermal Shock (PTS) scenarios. The approach is based on the two-fluid phase-average model. The interfacial friction was modeled by using an Algebraic Interfacial Area Density (AIAD) framework where the drag coefficient is a function of the local flow characteristics. To show the impact of the modeling of interfacial friction the simulation with the AIAD model was compared with a simulation where a constant drag coefficient of 0.44 was used in the whole domain. For the modeling of interfacial heat and mass transfer two correlations for the water heat transfer coefficient based on the penetration theory were utilized. The CFD simulations were validated against a steady-state TOPFLOW-PTS steam/water experiment. In the experiment, very detailed temperature measurements were conducted using special thermocouple lances and infrared thermography. Total condensation rate was determined indirectly by using three different methods. The simulations have shown that the results obtained with the AIAD model are considerably closer to the experimental observations than the results obtained with the constant drag coefficient. The condensation models used in the current study predict quite different total condensation rates. That caused significant differences in the temperature field. The simulations of the TOPFLOW-PTS steam/water experiment with condensation have shown that the proposed CFD modeling approach can be successfully applied for the prediction of temperature field and condensation rate during two-phase Pressurized Thermal Shock scenarios. However, the modeling of turbulent interfacial heat transfer should be improved
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...
Temperature Field-Wind Velocity Field Optimum Control of Greenhouse Environment Based on CFD Model
Directory of Open Access Journals (Sweden)
Yongbo Li
2014-01-01
Full Text Available The computational fluid dynamics technology is applied as the environmental control model, which can include the greenhouse space. Basic environmental factors are set to be the control objects, the field information is achieved via the division of layers by height, and numerical characteristics of each layer are used to describe the field information. Under the natural ventilation condition, real-time requirements, energy consumption, and distribution difference are selected as index functions. The optimization algorithm of adaptive simulated annealing is used to obtain optimal control outputs. A comparison with full-open ventilation shows that the whole index can be reduced at 44.21% and found that a certain mutual exclusiveness exists between the temperature and velocity field in the optimal course. All the results indicate that the application of CFD model has great advantages to improve the control accuracy of greenhouse.
International Nuclear Information System (INIS)
Chemical Looping Combustion is an energy efficient combustion technology for the inherent separation of carbon dioxide for both gaseous and solid fuels. For scale up and further development of this process multi-phase CFD-based simulations have a strong potential which rely on kinetic models for the solid/gaseous reactions. Reaction models are usually simple in structure in order to keep the computational cost low. They are commonly derived from thermogravimetric experiments. With only few CFD-based simulations performed on chemical looping combustion, there is a lack in understanding of the role and of the sensitivity of the applied chemical reaction model on the outcome of a simulation. The aim of this investigation is therefore the study of three different carrier materials CaSO4, Mn3O4 and NiO with the gaseous fuels H2 and CH4 in a batch type reaction vessel. Four reaction models namely the linear shrinking core, the spherical shrinking core, the Avrami-Erofeev and a recently proposed multi parameter model are applied and compared on a case by case basis. (authors)
International Nuclear Information System (INIS)
Traditional applications of the commercial CFD package FLUENT include modelling of gas and liquid flows, combustion processes, thermal radiation exchange, particle dynamics and related processes of industrial interest. Recently, however, the area of applications of this package has been extended to modelling of new processes such as CO2 laser discharges and the solution of the Boltzmann equation. Results of this modelling were reported at XXI International Conference on Phenomena in Ionized gases in Bochum and were later published in a number of research papers. The aim of this report is to summarize some further latest developments of the FLUENT package aimed to adjust it to the needs of modelling of plasma processes including those in ionized gases. The simplest way to modify this package is to include Amper force into Navier-Stokes equation and Ohm heating term into the enthalpy equation. In most cases, however, electric currents and electric and magnetic fields used in these equations cannot be assumed to be a priori known as they depend on plasma dynamics (distribution of velocities and pressures) and thermodynamics (distribution of temperatures) which implicitly enter into Maxwell or any equivalent electromagnetic equations. This makes it necessary to include these electromagnetic equations into the general iteration loop used in FLUENT
Miyawaki, Shinjiro; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long
2014-11-01
The authors have developed a method to automatically generate non-uniform CFD mesh for image-based human airway models. The sizes of generated tetrahedral elements vary in both radial and longitudinal directions to account for boundary layer and multiscale nature of pulmonary airflow. The proposed method takes advantage of our previously developed centerline-based geometry reconstruction method. In order to generate the mesh branch by branch in parallel, we used the open-source programs Gmsh and TetGen for surface and volume meshes, respectively. Both programs can specify element sizes by means of background mesh. The size of an arbitrary element in the domain is a function of wall distance, element size on the wall, and element size at the center of airway lumen. The element sizes on the wall are computed based on local flow rate and airway diameter. The total number of elements in the non-uniform mesh (10 M) was about half of that in the uniform mesh, although the computational time for the non-uniform mesh was about twice longer (170 min). The proposed method generates CFD meshes with fine elements near the wall and smooth variation of element size in longitudinal direction, which are required, e.g., for simulations with high flow rate. NIH Grants R01-HL094315, U01-HL114494, and S10-RR022421. Computer time provided by XSEDE.
Directory of Open Access Journals (Sweden)
Takanori Uchida
2011-01-01
Full Text Available Because a significant portion of the topography in Japan is characterized by steep, complex terrain, which results in a complex spatial distribution of wind speed, great care is necessary for selecting a site for the construction of wind turbine generators (WTG. We have developed a CFD model for unsteady flow called RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, computational prediction of airflow over complex terrain. The RIAM-COMPACT CFD model is based on large eddy simulation (LES. The computational domain of RIAM-COMPACT can extend from several meters to several kilometers, and RIAM-COMPACT can predict airflow and gas diffusion over complex terrain with high accuracy. The present paper proposes a technique for evaluating the deployment location of a WTG. The proposed technique employs the RIAM-COMPACT CFD model and simulates a continuous wind direction change over 360 degrees.
DEFF Research Database (Denmark)
Tajsoleiman, Tannaz; J. Abdekhodaie, Mohammad; Gernaey, Krist;
2016-01-01
the main bottlenecks in this type of processes. In this regard, mathematical modelling and computational fluid dynamics simulation (CFD) are powerful tools to identify an efficient and optimized design by providing reliable insights of the process. This study presents a mathematical model and CFD...... simulation of cartilage cell culture under a perfusion flow, which allows not only to characterize the supply of nutrients and metabolic products inside a fibrous scaffold, but also to assess the overall culture condition and predict the cell growth rate. Afterwards, the simulation results supported finding...
Wind modelling over complex terrain using CFD
Avila, Matias; Owen, Herbert; Folch, Arnau; Prieto, Luis; Cosculluela, Luis
2015-04-01
The present work deals with the numerical CFD modelling of onshore wind farms in the context of High Performance Computing (HPC). The CFD model involves the numerical solution of the Reynolds-Averaged Navier-Stokes (RANS) equations together with a κ-É turbulence model and the energy equation, specially designed for Atmospheric Boundary Layer (ABL) flows. The aim is to predict the wind velocity distribution over complex terrain, using a model that includes meteorological data assimilation, thermal coupling, forested canopy and Coriolis effects. The modelling strategy involves automatic mesh generation, terrain data assimilation and generation of boundary conditions for the inflow wind flow distribution up to the geostrophic height. The CFD model has been implemented in Alya, a HPC multi physics parallel solver able to run with thousands of processors with an optimal scalability, developed in Barcelona Supercomputing Center. The implemented thermal stability and canopy physical model was developed by Sogachev in 2012. The k-É equations are of non-linear convection diffusion reaction type. The implemented numerical scheme consists on a stabilized finite element formulation based on the variational multiscale method, that is known to be stable for this kind of turbulence equations. We present a numerical formulation that stresses on the robustness of the solution method, tackling common problems that produce instability. The iterative strategy and linearization scheme is discussed. It intends to avoid the possibility of having negative values of diffusion during the iterative process, which may lead to divergence of the scheme. These problems are addressed by acting on the coefficients of the reaction and diffusion terms and on the turbulent variables themselves. The k-É equations are highly nonlinear. Complex terrain induces transient flow instabilities that may preclude the convergence of computer flow simulations based on steady state formulation of the
Liquid rocket propulsion impeller CFD modeling
Ratcliff, Mark L.; Athavale, Mahesh M.; Thomas, Matthew E.; Williams, Robert W.
1993-01-01
Steady-state impeller geometric modeling and typical Navier-Stokes CFD algorithm analysis procedures are assessed using two benchmark quality impeller data sets. Two geometric modeling and grid generation software packages, ICEM-CFD and PATRAN, are considered. Results show that a significant advantage of PATRAN's open-ended architecture is the potential interaction between CFD and structural/thermal analysts inside the mechanical computer-aided engineering environment. However the time required to construct the inducer grid would be unacceptable in a design and engineering environment. The ICEM-CFD package is considered to be more appropriate for structural grid generation but lacks the mature link to structural/thermal analysis arena as compared to PATRAN.
3D CFD computations of transitional flows using DES and a correlation based transition model
DEFF Research Database (Denmark)
Sørensen, Niels N.
process can be important for the aerodynamic performance. Today, the most widespread approach is to use fully turbulent computations, where the transitional process is ignored and the entire boundary layer on the wings or airfoils is handled by the turbulence model. The correlation based transition model...... has lately shown promising results, and the present paper describes the application of the model to predict the drag and shedding frequency for flow around a cylinder from sub to super-critical Reynolds numbers. Additionally, the model is applied to the flow around the DU-96 airfoil, at high angles of...
3D CFD computations of trasitional flows using DES and a correlation based transition model
DEFF Research Database (Denmark)
Sørensen, Niels N.; Bechmann, Andreas; Zahle, Frederik
2011-01-01
The present article describes the application of the correlation based transition model of Menter et al. in combination with the Detached Eddy Simulation (DES) methodology to two cases with large degree of flow separation typically considered difficult to compute. Firstly, the flow is computed over...
Study of indoor radon distribution using measurements and CFD modeling
International Nuclear Information System (INIS)
Measurement and/or prediction of indoor radon (222Rn) concentration are important due to the impact of radon on indoor air quality and consequent inhalation hazard. In recent times, computational fluid dynamics (CFD) based modeling has become the cost effective replacement of experimental methods for the prediction and visualization of indoor pollutant distribution. The aim of this study is to implement CFD based modeling for studying indoor radon gas distribution. This study focuses on comparison of experimentally measured and CFD modeling predicted spatial distribution of radon concentration for a model test room. The key inputs for simulation viz. radon exhalation rate and ventilation rate were measured as a part of this study. Validation experiments were performed by measuring radon concentration at different locations of test room using active (continuous radon monitor) and passive (pin-hole dosimeters) techniques. Modeling predictions have been found to be reasonably matching with the measurement results. The validated model can be used to understand and study factors affecting indoor radon distribution for more realistic indoor environment. - Highlights: • Indoor radon distribution has been studied using active and passive measurements and CFD simulation. • At low ventilation, non-uniformity of radon concentration was observed. • Measured wall radon flux and ventilation rate has been used in simulations. • CFD simulation results were found to be close to measurements
CFD modelling of moisture interactions between air and constructions
DEFF Research Database (Denmark)
Mortensen, Lone Hedegaard; Woloszyn, Monika; Hohota, Raluca;
2005-01-01
There is a strong demand for accurate moisture modelling since moisture poses a risk for both the constructions and the indoor climate. Thus, in this investigation there is special focus on moisture modelling. The paper describes a new model based on a CFD tool that is enhanced to include both...
DEFF Research Database (Denmark)
Dannemand, Mark; Fan, Jianhua; Furbo, Simon;
2014-01-01
Computational Fluid Dynamics (CFD) model. The CFD calculated temperatures are compared to measured temperatures internally in the box to validate the CFD model. Four cases are investigated; heating the test module with the sodium acetate water mixture in solid phase from ambient temperature to 52˚C; heating the...... the crystallization, ending at ambient temperature with the sodium acetate water mixture in solid phase. Comparisons have shown reasonable good agreement between experimental measurements and theoretical simulation results for the investigated scenarios....
Linearised CFD Models for Wakes
DEFF Research Database (Denmark)
Ott, Søren; Berg, Jacob; Nielsen, Morten
from generic look{up tables. Three dierent models, based on three dierent closures, are examined: - the 'simple closure' using an unperturbed eddy viscosity uz - the mixing length closure - the E-ε closure Model results are evaluated against oshore wind farm production data from Horns Rev I and the......This report describes the development of a fast and reasonably accurate model for the prediction of energy production in oshore wind farms taking wake eects into account. The model has been implemented as a windows application called Fuga which can run in batch mode or as a graphical user interface....... Fuga is brie y described. The model is based on alinearization technique which is described in some detail, and linearized, governing equations are derived and written in a standard form based on a mixed{spectral formulation. A new solution method is used to solve the equations which involves intensive...
CFD based extraction column design-Chances and challenges
Institute of Scientific and Technical Information of China (English)
Mark W Hlawitschka; Menwer M Attarakih; Samer S Alzyod; Hans-Jrg Bart
2016-01-01
This paper shows that one-dimensional (1-D) [and three-dimensional (3-D) computational fluid dynamics (CFD)] simulations can replace the state-of-the-art usage of pseudo-homogeneous dispersion or back mixing models. This is based on standardized lab-scale cel experiments for the determination of droplet rise, breakage, coalescence and mass transfer parameters in addition to a limited number of additional mini-plant experiments with original fluids. Alternatively, the hydrodynamic parameters can also be derived using more sophisticated 3-D CFD simulations. Computational 1-D modeling served as a basis to replace pilot-plant experiments in any column geometry. The combination of 3-D CFD simulations with droplet population balance models (DPBM) increased the accuracy of the hydrodynamic simulations and gave information about the local droplet size. The high computational costs can be reduced by open source CFD codes when using a flexible mesh generation. First combined simulations using a three way coupled CFD/DPBM/mass-transfer solver pave the way for a safer design of industrial-sized columns, where no correlations are available.
Modelling Complex Inlet Geometries in CFD
DEFF Research Database (Denmark)
Skovgaard, M.; Nielsen, Peter V.
field. In order to apply CFD for this purpose it is essential to be able to model the inlet conditions precisely and effectively, in a way which is comprehensible to the manufacturer of inlet devices and in a way which can be coped with by the computer. In this paper a universal method is presented and...
Tip studies using CFD and comparison with tip loss models
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Johansen, J.
The flow past a rotating LM8.2 blade equipped with two different tips are computed using CFD. The different tip flows are analysed and a comparison with two different tip loss models is made. Keywords: tip flow, aerodynamics, CFD......The flow past a rotating LM8.2 blade equipped with two different tips are computed using CFD. The different tip flows are analysed and a comparison with two different tip loss models is made. Keywords: tip flow, aerodynamics, CFD...
International Nuclear Information System (INIS)
A sodium cooled fast reactor is one of the attractive concepts for the 4th generation nuclear reactors. For the safety of a sodium cooled fast reactor, sodium-air and sodium-water reactions must be avoided. A sodium-air reaction typically occurs in two dominant modes, namely the spray fire and the pool fire. To avoid sodium-air accidents and to deal with their consequences, it is essential to understand the physical phenomena. Numerical modeling is one of the methods, which can be used to understand all the physics involved. This paper will present new numerical methods to model sodium pool combustion based on advanced state-of-the-art Computational Fluid Dynamics techniques. The models have been developed, implemented and validated against available experimental data of Newman and Payne. (author)
International Nuclear Information System (INIS)
Highlights: • A CFD based method proposed in the previous article is used for the simulation of the effect of CO2–He dilution on hydrogen deflagration. • A theoretical study is presented to verify whether CO2–He diluent can be used as a replacement for H2O as diluent. • CFD model used for the validation work is described. • TFC combustion model results are in good agreement with large-scale homogeneous hydrogen–air–CO2–He experiments. - Abstract: Large quantities of hydrogen can be generated and released into the containment during a severe accident in a PWR. The generated hydrogen, when mixed with air, can lead to hydrogen combustion. The dynamic pressure loads resulting from hydrogen combustion can be detrimental to the structural integrity of the reactor safety systems and the reactor containment. Therefore, accurate prediction of these pressure loads is an important safety issue. In our previous article, a CFD based method to determine these pressure loads was presented. This CFD method is based on the application of a turbulent flame speed closure combustion model. The method was validated against three uniform hydrogen–air deflagration experiments with different blockage ratio performed in the ENACCEF facility. It was concluded that the maximum pressures were predicted within 13% accuracy, while the rate of pressure rise dp/dt was predicted within about 30%. The eigen frequencies of the residual pressure wave phenomena were predicted within a few %. In the present article, we perform additional validation of the CFD based method against three uniform hydrogen–air–CO2–He deflagration experiments with three different concentrations of the CO2–He diluent. The trends of decrease in the flame velocity, the intermediate peak pressure, the rate of pressure rise dp/dt, and the maximum value of the mean pressure with an increase in the CO2–He dilution are captured well in the simulations. From the presented validation analyses, it can be
CFD Based Erosion Modelling of Abrasive Waterjet Nozzle using Discrete Phase Method
Hakim Kamarudin, Naqib; Prasada Rao, A. K.; Azhari, Azmir
2016-02-01
In Abrasive Waterjet (AWJ) machining, the nozzle is the most critical component that influences the performance, precision and economy. Exposure to a high speed jet and abrasives makes it susceptible to wear erosion which requires for frequent replacement. The present works attempts to simulate the erosion of the nozzle wall using computational fluid dynamics. The erosion rate of the nozzle was simulated under different operating conditions. The simulation was carried out in several steps which is flow modelling, particle tracking and erosion rate calculation. Discrete Phase Method (DPM) and K-ε turbulence model was used for the simulation. Result shows that different operating conditions affect the erosion rate as well as the flow interaction of water, air and abrasives. The simulation results correlates well with past work.
Linearised CFD models for wakes
Energy Technology Data Exchange (ETDEWEB)
Ott, S.; Berg, J.; Nielsen, Morten
2011-12-15
This report describes the development of a fast and reasonably accurate model for the prediction of energy production in offshore wind farms taking wake effects into account. The model has been implemented as a windows application called Fuga which can run in batch mode or as a graphical user interface. Fuga is briefly described. The model is based on a linearization technique which is described in some detail, and linearized, governing equations are derived and written in a standard form based on a mixed-spectral formulation. A new solution method is used to solve the equations which involves intensive use of look-up tables for storage of intermediate results. Due to the linearity of the model, multiple wakes from many turbines can be constructed from the wake of a single, solitary turbine. These are in turn constructed from Fourier components by a fast Fourier integral transform of results derived from generic look-up tables. Three different models, based on three different closures, are examined: 1) the 'simple closure' using an unperturbed eddy viscosity kucentre dotz. 2) the mixing length closure. 3) the E-epsilon closure. Model results are evaluated against offshore wind farm production data from Horns Rev I and the Nysted wind farm, and a comparison with direct wake measurements in an onshore turbine (Nibe B) is also made. A very satisfactory agreement with data is found for the simple closure. The exception is the near wake, just behind the rotor, where all three linearized models fail. The mixing length closure underestimates wake effects in all cases. The E-epsilon closure overestimates wake losses in the offshore farms while it predicts a too shallow and too wide the wake in the onshore case. The simple closure performs distinctly better than the other two. Wind speed data from the the Horns rev met masts are used to further validate Fuga results with the 'simple' closure. Finally, Roedsand 1 and 2 are used as an example to illustrate
Application of Simple CFD Models in Smoke Ventilation Design
DEFF Research Database (Denmark)
Brohus, Henrik; Nielsen, Peter Vilhelm; la Cour-Harbo, Hans;
2004-01-01
The paper examines the possibilities of using simple CFD models in practical smoke ventilation design. The aim is to assess if it is possible with a reasonable accuracy to predict the behaviour of smoke transport in case of a fire. A CFD code mainly applicable for “ordinary” ventilation design is...... used for the examination. The CFD model is compared with benchmark tests and results from a special application fire simulation CFD code. Apart from benchmark tests two practical applications are examined in shape of modelling a fire in a theatre and a double façade, respectively. The simple CFD model...
CFD modeling of fouling in crude oil pre-heaters
International Nuclear Information System (INIS)
Highlights: ► A conceptual CFD-based model to predict fouling in industrial crude oil pre-heaters. ► Tracing fouling formation in the induction and developing continuation periods. ► Effect of chemical components, shell-side HTC and turbulent flow on the fouling rate. - Abstract: In this study, a conceptual procedure based on the computational fluid dynamic (CFD) technique has been developed to predict fouling rate in an industrial crude oil pre-heater. According to the developed CFD concept crude oil was assumed to be composed of three pseudo-components comprising of petroleum, asphaltene and salt. The binary diffusion coefficients were appropriately categorized into five different groups. The species transport model was applied to simulate the mixing and transport of chemical species. The possibility of adherence of reaction products to the wall was taken into account by applying a high viscosity for the products in competition with the shear stress on the wall. Results showed a reasonable agreement between the model predictions and the plant data. The CFD model could be applied to new operating conditions to investigate the details of the crude oil fouling in the industrial pre-heaters.
Modeling Pulse Tube Cryocoolers with CFD
Flake, Barrett; Razani, Arsalan
2004-06-01
A commercial computational fluid dynamics (CFD) software package is used to model the oscillating flow inside a pulse tube cryocooler. Capabilities for modeling pulse tubes are demonstrated with preliminary case studies and the results presented. The 2D axi-symmetric simulations demonstrate the time varying temperature and velocity fields in the tube along with computation of the heat fluxes at the hot and cold heat exchangers. The only externally imposed boundary conditions are a cyclically moving piston wall at one end of the tube and constant temperature or heat flux boundaries at the external walls of the hot and cold heat exchangers.
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 modeling of the EPR primary circuit
International Nuclear Information System (INIS)
Highlights: • A RANS CFD computation of almost all of the EPR reactor primary circuit is demonstrated. • Comparison with experimental data of the obtained results is carried out. • Hydraulic decoupling between main vessel elements in normal operation is pointed out. • Promising results are found out with regards to nuclear plants’ safety demonstration. - Abstract: The present paper deals with the feasibility of a RANS CFD computation of almost all of the primary circuit of a EPR PWR reactor. The developed model includes the vessel, the core, the steam generators and the associated piping. The flow in the primary circuit is studied under normal operations with balanced flow rates between loops. The k–ε realizable model is retained for the turbulence modeling, and standard wall functions are used as wall treatment. The constructed grid contains about 181,000,000 elements, mainly hexahedrons. The computation is performed with the commercial CFD code STAR-CD, and despite the relatively large amount of cells, such kind of computation is fully accessible at an industrial scale with today available computational resources. A comparison with experimental data of the obtained results is carried out. The simulation results in the vessel are confronted to measurements issued from JULIETTE and ROMEO mock-ups, representative of the EPR lower and upper internals respectively. Regarding the steam generators, a benchmark with the dedicated code GENEPI is also performed. An overall good agreement with the reference data is underlined. The potential up-and-downstream effects of the different modeled components brought interesting knowledge, especially with regards to safety issues. These encouraging results allow in testing, in a near future, this model in other configurations such as unbalanced operation or accidental transients
Method for Lumped Parameter simulation of Digital Displacement pumps/motors based on CFD
DEFF Research Database (Denmark)
Rømer, Daniel; Johansen, Per; Pedersen, Henrik C.;
2013-01-01
design and control of digital displacement machines, there is a need for simulation models, preferably models with low computational cost. Therefore, a low computational cost generic lumped parameter model of digital displacement machine is presented, including a method for determining the needed model...... parameters based on steady CFD results, in order to take detailed geometry information into account. The response of the lumped parameter model is compared to a computational expensive transient CFD model for an example geometry....
A Large Interface Model for two-phase CFD
International Nuclear Information System (INIS)
Highlights: ► CFD of PTS involves interfaces generally much larger than the computational cells. ► A two-phase model is developed to better take them into account. ► It includes interface recognition, friction, heat and mass transfer. ► The models are written in a three-cell stencil in a wall law-like format. -- Abstract: In the context of the Pressurized Thermal Shock (PTS) studies related to PWR life extension, a two-phase CFD (Eulerian two-field 3D transient) approach has been developed and validated during the last decade. The PTS CFD involves interfaces between liquid and vapour which are generally much larger than the computational cells size: the large interfaces. Special models to deal with them were developed and implemented in the NEPTUNECFD code: it is the Large Interface Model (LIM). It includes large interface recognition, interfacial transfer of momentum (friction), heat and mass transfer with direct contact condensation. The LIM takes into account large interfaces which can be smooth, wavy or rough. The models are written within a three-cell stencil around the large interface position. This stencil is used to calculate, on both the liquid and gas sides, the distance from the first computational cell to the large interface. Both distances are used in the models written in a wall law-like format. Some assumptions made to write the LIM were deduced from the picture given by the experimental data base which was defined for the CFD validation in the context of the PTS issue
A CFD model for pollutant dispersion in rivers
Directory of Open Access Journals (Sweden)
Modenesi K.
2004-01-01
Full Text Available Studies have shown that humankind will experience a water shortage in the coming decades. It is therefore paramount to develop new techniques and models with a view to minimizing the impact of pollution. It is important to predict the environmental impact of new emissions in rivers, especially during periods of drought. Computational fluid dynamics (CFD has proved to be an invaluable tool to develop models able to analyze in detail particle dispersion in rivers. However, since these models generate grids with thousands (even millions of points to evaluate velocities and concentrations, they still require powerful machines. In this context, this work contributes by presenting a new three-dimensional model based on CFD techniques specifically developed to be fast, providing a significant improvement in performance. It is able to generate predictions in a couple of hours for a one-thousand-meter long section of river using Pentium IV computers. Commercial CFD packages would require weeks to solve the same problem. Another innovation inb this work is that a half channel with a constant elliptical cross section represents the river, so the Navier Stokes equations were derived for the elliptical system. Experimental data were obtained from REPLAN (PETROBRAS refining unit on the Atibaia River in São Paulo, Brazil. The results show good agreement with experimental data.
CFD and FEM Model of an Underwater Vehicle Propeller
Directory of Open Access Journals (Sweden)
Chruściel Tadeusz
2014-10-01
Full Text Available Within the framework of the project for design and optimization of the Remotely Operated Vehicle (ROV, research on its propulsion has been carried out. Te entire project was supported by CFD and FEM calculations taking into account the characteristics of the underwater vehicle. One of the tasks was to optimize the semi-open duct for horizontal propellers, which provided propulsion and controllability in horizontal plane. In order to create a measurable model of this task it was necessary to analyze numerical methodology of propeller design, along with the structure of a propellers with nozzles and contra-rotating propellers. It was confronted with theoretical solutions which included running of the analyzed propeller near an underwater vehicle. Also preliminary qualitative analyses of a simplified system with contra-rotating propellers and a semi-open duct were carried out. Te obtained results enabled to make a decision about the ROVs duct form. Te rapid prototyping SLS (Selective Laser Sintering method was used to fabricate a physical model of the propeller. As a consequence of this, it was necessary to verify the FEM model of the propeller, which based on the load obtained from the CFD model. Te article contains characteristics of the examined ROV, a theoretical basis of propeller design for the analyzed cases, and the results of CFD and FEM simulations.
Simultaneous Excitation of Multiple-Input Multiple-Output CFD-Based Unsteady Aerodynamic Systems
Silva, Walter A.
2008-01-01
A significant improvement to the development of CFD-based unsteady aerodynamic reduced-order models (ROMs) is presented. This improvement involves the simultaneous excitation of the structural modes of the CFD-based unsteady aerodynamic system that enables the computation of the unsteady aerodynamic state-space model using a single CFD execution, independent of the number of structural modes. Four different types of inputs are presented that can be used for the simultaneous excitation of the structural modes. Results are presented for a flexible, supersonic semi-span configuration using the CFL3Dv6.4 code.
Balakin, Boris V.; Hoffmann, Alex C.; Kosinski, Pawel; Istomin, Vladimir A.; Chuvilin, Evgeny M.
2010-09-01
A combined computational fluid dynamics/population balance model (CFD-PBM) is developed for gas hydrate particle size prediction in turbulent pipeline flow. The model is based on a one-moment population balance technique, which is coupled with flow field parameters computed using commercial CFD software. The model is calibrated with a five-moment, off-line population balance model and validated with experimental data produced in a low-pressure multiphase flow loop.
Modelling of Air Flow trough a Slatted Floor by CFD
DEFF Research Database (Denmark)
Svidt, Kjeld; Bjerg, Bjarne; Morsing, Svend;
In this paper two different CFD-approaches are investigated to model the airflow through a slatted floor. Experiments are carried out in a full-scale test room. The computer simulations are carried out with the CFD-code FLOVENT, which solves the time-averaged Navier-Stokes equations by use of the k...
Qualification of CFD-models for multiphase flows
Energy Technology Data Exchange (ETDEWEB)
Lucas, Dirk [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany)
2016-05-15
While Computational Fluid Dynamics (CFD) is already an accepted industrial tool for single phase flows it is not yet mature for two-phase flows. For this reason the qualification of CFD for reactor safety relevant applications which involve multiphase flows is a present topic of research. At the CFD division of Helmholtz-Zentrum Dresden-Rossendorf (HZDR) hereby beside an application-oriented model development and validation also more generic investigations are done. Thus, the baseline model strategy aims on the consolidation of the CFD-modelling for multiphase to enable reliable predictions for well-defined flow pattern in future. In addition the recently developed GENTOP-concept broadens the range of applicability of CFD. Different flow morphologies including transitions between them can be considered in frame of this concept.
Qualification of CFD-models for multiphase flows
International Nuclear Information System (INIS)
While Computational Fluid Dynamics (CFD) is already an accepted industrial tool for single phase flows it is not yet mature for two-phase flows. For this reason the qualification of CFD for reactor safety relevant applications which involve multiphase flows is a present topic of research. At the CFD division of Helmholtz-Zentrum Dresden-Rossendorf (HZDR) hereby beside an application-oriented model development and validation also more generic investigations are done. Thus, the baseline model strategy aims on the consolidation of the CFD-modelling for multiphase to enable reliable predictions for well-defined flow pattern in future. In addition the recently developed GENTOP-concept broadens the range of applicability of CFD. Different flow morphologies including transitions between them can be considered in frame of this concept.
Directory of Open Access Journals (Sweden)
Cabezón D.
2014-01-01
Full Text Available Wake effect represents one of the main sources of energy loss and uncertainty when designing offshore wind farms. Traditionally analytical models have been used to optimize and estimate power deficits. However these models have shown to underestimate wake effect and consequently overestimate output power [1, 2]. This means that analytical models can be very helpful at optimizing preliminary layouts but not as accurate as needed for an ultimate fine design. Different techniques can be found in the literature to study wind turbine wakes that include simplified kinematic models and more advanced field models, that solve flow equations with different turbulence closure schemes. See the review papers of Crespo et al. [3], Vermeer et al. [4], and Sanderse et al. [5]. Purely elliptic Computational Fluid Dynamics (CFD models based on the actuator disk technique have been developed during the last years [6–8]. They consider wind turbine rotor as a disk where a distribution of axial forces act over the incoming air. It is a fair approach but it can still be computationally expensive for big wind farms in an operative mode. With this technique still active, an alternative approach inspired on the parabolic wake models [9, 10] is proposed. Wind turbine rotors continue to be represented as actuator disks but now the domain is split into subdomains containing one or more wind turbines. The output of each subdomain is mapped onto the input boundary of the next one until the end of the domain is reached, getting a considerable decrease on computational time, by a factor of order 10. As the model is based on the open source CFD solver OpenFOAM, it can be parallelized to speed-up convergence. The near wake is calculated so no initial wind speed deficit profiles have to be supposed as in totally parabolic models and alternative turbulence models, such as the anisotropic Reynolds Stress Model (RSM can be used. Traditional problems of elliptic models related to
CFD modeling of passive autocatalytic recombiners*
Directory of Open Access Journals (Sweden)
Orszulik Magdalena
2015-06-01
Full Text Available This study deals with numerical modeling of passive autocatalytic hydrogen recombiners (PARs. Such devices are installed within containments of many nuclear reactors in order to remove hydrogen and convert it to steam. The main purpose of this work is to develop a numerical model of passive autocatalytic recombiner (PAR using the commercial computational fluid dynamics (CFD software ANSYS-FLUENT and tuning the model using experimental results. The REKO 3 experiment was used for this purpose. Experiment was made in the Institute for Safety Research and Reactor Technology in Julich (Germany. It has been performed for different hydrogen concentrations, different flow rates, the presence of steam, and different initial temperatures of the inlet mixture. The model of this experimental recombiner was elaborated within the framework of this work. The influence of mesh, gas thermal conductivity coefficient, mass diffusivity coefficients, and turbulence model was investigated. The best results with a good agreement with REKO 3 data were received for k-ɛ model of turbulence, gas thermal conductivity dependent on the temperature and mass diffusivity coefficients taken from CHEMKIN program. The validated model of the PAR was next implemented into simple two-dimensional simulations of hydrogen behavior within a subcompartment of a containment building.
CFD and FEM modeling of PPOOLEX experiments
Energy Technology Data Exchange (ETDEWEB)
Paettikangas, T.; Niemi, J.; Timperi, A. (VTT Technical Research Centre of Finland (Finland))
2011-01-15
Large-break LOCA experiment performed with the PPOOLEX experimental facility is analysed with CFD calculations. Simulation of the first 100 seconds of the experiment is performed by using the Euler-Euler two-phase model of FLUENT 6.3. In wall condensation, the condensing water forms a film layer on the wall surface, which is modelled by mass transfer from the gas phase to the liquid water phase in the near-wall grid cell. The direct-contact condensation in the wetwell is modelled with simple correlations. The wall condensation and direct-contact condensation models are implemented with user-defined functions in FLUENT. Fluid-Structure Interaction (FSI) calculations of the PPOOLEX experiments and of a realistic BWR containment are also presented. Two-way coupled FSI calculations of the experiments have been numerically unstable with explicit coupling. A linear perturbation method is therefore used for preventing the numerical instability. The method is first validated against numerical data and against the PPOOLEX experiments. Preliminary FSI calculations are then performed for a realistic BWR containment by modeling a sector of the containment and one blowdown pipe. For the BWR containment, one- and two-way coupled calculations as well as calculations with LPM are carried out. (Author)
CFD modeling of a boiler's tubes rupture
International Nuclear Information System (INIS)
This paper reports the results of a study on the reason for tubes damage in the superheater Platen section of the 320 MW Bisotoun power plant, Iran. The boiler has three types of superheater tubes and the damage occurs in a series of elbows belongs to the long tubes. A three-dimensional modeling was performed using an in-house computational fluid dynamics (CFD) code in order to explore the reason. The code has ability of simultaneous solving of the continuity, the Reynolds-Averaged Navier-Stokes (RANS) equations and employing the turbulence, combustion and radiation models. The whole boiler including; walls, burners, air channels, three types of tubes, etc., was modeled in the real scale. The boiler was meshed into almost 2,000,000 tetrahedral control volumes and the standard k-ε turbulence model and the Rosseland radiation model were used in the model. The theoretical results showed that the inlet 18.9 MPa saturated steam becomes superheated inside the tubes and exit at a pressure of 17.8 MPa. The predicted results showed that the temperature of the steam and tube's wall in the long tubes is higher than the short and medium size tubes. In addition, the predicted steam mass flow rate in the long tube was lower than other ones. Therefore, it was concluded that the main reason for the rupture in the long tubes elbow is changing of the tube's metal microstructure due to working in a temperature higher than the design temperature. In addition, the structural fatigue tension makes the last elbow of the long tube more ready for rupture in comparison with the other places. The concluded result was validated by observations from the photomicrograph of the tube's metal samples taken from the damaged and undamaged sections
CFD model of an aerating hydrofoil
International Nuclear Information System (INIS)
Improving water quality in the tailrace below hydroelectric dams has become a priority in many river systems. In warm climates, water drawn by the turbine from deep in a reservoir can be deficient in dissolved oxygen (DO), a critical element in maintaining a healthy aquatic ecosystem. Many different solutions have been proposed in order to increase the DO levels in turbine discharge, including: turbine aeration systems (adding air to the water through either the turbine hub, the periphery or through distributed aeration in the runner blades); bubble diffusers in the reservoir or in the tailrace; aerating weirs downstream of the dams; and surface water pumps in the reservoir near the dam. There is a significant potential to increase the effectiveness of these solutions by improving the way that oxygen is introduced into the water; better distributions of bubbles will result in better oxygen transfer. In the present study, a two-phase Computational Fluid Dynamics model has been formulated using a commercial code to study the distribution of air downstream of a simple aerating hydrofoil. The two-phase model uses the Eulerian-Eulerian approach. Appropriate relations are used to model the interphase forces, including the Grace drag force model, the Favre averaged drag force and the Sato enhanced eddy viscosity. The model is validated using experimental results obtained in the water tunnel at the University of Minnesota's Saint Anthony Falls Laboratory. Results are obtained for water velocities between 5 and 10 m/s, air flow rates between 0.5 and 1.5 sL/min and for angles of attack between 0° and -8°. The results of this study show that the CFD model provides a good qualitative comparison to the experimental results by well predicting the wake location at the different flow rates and angles of attack used
Mustafa, Mohamad; Xu, Yizhong
2015-01-01
Physical experiments have difficulties to thoroughly investigate the full structure of air flow behind a porous fence. Physical measurement sensors have their limitations of data acquisitions in turbulent air flow. Computational Fluid Dynamics (CFD) technique provides an infinite number of virtual sensors that allows producing quantitative CFD based virtual sensors data for users. In this paper, a 3D CFD model is assessed by the physical sensors data, and the simulation has provid...
Energy Technology Data Exchange (ETDEWEB)
Soerensen, Niels N.
2009-07-15
The report describes the application of the correlation based transition model of Menter et. al. [1, 2] to the cylinder drag crisis and the stalled flow over an DU-96-W-351 airfoil using the DES methodology. When predicting the flow over airfoils and rotors, the laminar-turbulent transition process can be important for the aerodynamic performance. Today, the most widespread approach is to use fully turbulent computations, where the transitional process is ignored and the entire boundary layer on the wings or airfoils is handled by the turbulence model. The correlation based transition model has lately shown promising results, and the present paper describes the application of the model to predict the drag and shedding frequency for flow around a cylinder from sub to super-critical Reynolds numbers. Additionally, the model is applied to the flow around the DU-96 airfoil, at high angles of attack. (au)
Immersive visualization of dynamic CFD model results
International Nuclear Information System (INIS)
With immersive visualization the engineer has the means for vividly understanding problem causes and discovering opportunities to improve design. Software can generate an interactive world in which collaborators experience the results of complex mathematical simulations such as computational fluid dynamic (CFD) modeling. Such software, while providing unique benefits over traditional visualization techniques, presents special development challenges. The visualization of large quantities of data interactively requires both significant computational power and shrewd data management. On the computational front, commodity hardware is outperforming large workstations in graphical quality and frame rates. Also, 64-bit commodity computing shows promise in enabling interactive visualization of large datasets. Initial interactive transient visualization methods and examples are presented, as well as development trends in commodity hardware and clustering. Interactive, immersive visualization relies on relevant data being stored in active memory for fast response to user requests. For large or transient datasets, data management becomes a key issue. Techniques for dynamic data loading and data reduction are presented as means to increase visualization performance. (author)
Coupling a CFD code with neutron kinetics and pin thermal models for nuclear reactor safety analyses
International Nuclear Information System (INIS)
Highlights: • A CFD/neutron kinetics coupled code FLUENT/PK for nuclear reactor transient safety was developed. • The mathematical models and coupling methods of FLUENT/PK were described. • The code-to-code validation between FLUENT/PK and SIMMER-III was conducted. - Abstract: Most system codes are based on the one-dimensional lumped-parameter method, which is unsuitable to simulate multi-dimensional thermal-hydraulics problems. CFD method is a good tool to simulate multi-dimensional thermal-hydraulics phenomena in the nuclear reactor, which can increase the accuracy of analysis results. However, since there is no neutron kinetics model and pin thermal model in current CFD codes, the application of the CFD method in the area of nuclear reactor safety analyses is still limited. Coupling a CFD code with the neutron kinetics model (PKM) and the pin thermal model (PTM) is a good way to use CFD code to simulate multi-dimensional thermal-hydraulics problems of nuclear reactors. The motivation for this work is to develop a CFD/neutron kinetics coupled code named FLUENT/PK for nuclear reactor safety analyses by coupling the commercial CFD code named FLUENT with the point kinetics model (PKM) and the pin thermal model (PTM). The mathematical models and the coupling method are described and the unprotected transient overpower (UTOP) accident of a liquid metal cooled fast reactor (LMFR) is chosen as an application case. As a general validation, the calculated results are used to compare with that of another multi-physics coupled code named SIMMER-III and good agreements are achieved for various characteristic parameters
Modelling of a CFD Microscale Model and Its Application in Wind Energy Resource Assessment
Directory of Open Access Journals (Sweden)
Yue Jie-shun
2016-01-01
Full Text Available The prediction of a wind farm near the wind turbines has a significant effect on the safety as well as economy of wind power generation. To assess the wind resource distribution within a complex terrain, a computational fluid dynamics (CFD based wind farm forecast microscale model is developed. The model uses the Reynolds Averaged Navier-Stokes (RANS model to characterize the turbulence. By using the results of Weather Research and Forecasting (WRF mesoscale weather forecast model as the input of the CFD model, a coupled model of CFD-WRF is established. A special method is used for the treatment of the information interchange on the lateral boundary between two models. This established coupled model is applied in predicting the wind farm near a wind turbine in Hong Gang-zi, Jilin, China. The results from this simulation are compared to real measured data. On this basis, the accuracy and efficiency of turbulence characterization schemes are discussed. It indicates that this coupling system is easy to implement and can make these two separate models work in parallel. The CFD model coupled with WRF has the advantage of high accuracy and fast speed, which makes it valid for the wind power generation.
CFD modelling of Stirling engines with complex design topologies
Alexakis, Thanos
2013-01-01
This research is in the field of CFD modelling of heat engines, particularly the advanced CFD methodologies for the performance characterization of solar Stirling Engines with complex geometrical topologies. The research aims to investigate whether these methods can provide a more inclusive picture of the engine performance and how this information can be used for the design improvement of Stirling engines and the investigation of more complex engine topologies.
International Nuclear Information System (INIS)
Highlights: • We outline a new coupling of the ASBM model with one equation SA closure. • We provide mathematical implementation details and a Fortran module. • The numerical stability and convergence characteristics of ASBM-SA are comparable to that of SA. • The ASBM-SA model provides full Reynolds stress anisotropy information unlike the SA model. • Overall, predictions os ASBM-SA shows moderate accuracy improvements relative to those of SA. - Abstract: Structure-based turbulence models (SBM) carry information about the turbulence structure that is needed for the prediction of complex non-equilibrium flows. SBM have been successfully used to predict a number of canonical flows, yet their adoption rate in engineering practice has been relatively low, mainly because of their departure from standard closure formulations, which hinders easy implementation in existing codes. Here, we demonstrate the coupling between the Algebraic Structure-Based Model (ASBM) and the one-equation Spalart–Allmaras (SA) model, which provides an easy route to bringing structure information in engineering turbulence closures. As the ASBM requires correct predictions of two turbulence scales, which are not taken into account in the SA model, Bradshaw relations and numerical optimizations are used to provide the turbulent kinetic energy and dissipation rate. Attention is paid to the robustness and accuracy of the hybrid model, showing encouraging results for a number of simple test cases. An ASBM module in Fortran-90 is provided along with the present paper in order to facilitate the testing of the model by interested readers
Gorrepati, Devi Prasad
A Modular Data Center (MDC) is a portable method of deploying a data center's capacity. As an alternative to the traditional data center, an MDC can be placed anywhere data capacity is required. The purpose of this study is to reduce the damage or loss of performance caused to the data centers that use free cooling, by mitigating high-speed winds. The Modular Data centers which use free cooling and that are located in open regions are subjected to various environmental risks such as very high-speed winds. As this wind blows over these data centers, the pressure difference generated within and outside the enclosure can have a drastic effect on the free cooling. Therefore, by using a wind fence which basically acts as a barrier to the upstream wind and reduces the mean velocity of air downstream of the wind fence, we reduce the pressure difference created and also the wind induced loading on the objects situated behind the fence. Although wind fences are used in many agricultural and farming practices, their usage pertaining to MDCs is very limited. The challenge is to reduce wind speed from 100 mph to 10 mph. This has been achieved by iteratively designing and analyzing a wind fence using CFD simulations to come up with a few wind fence options that have defined properties such as height, perforation and location (distance from the inlet of MDC) of the wind fence.
Unsteady wind loads for TMT: replacing parametric models with CFD
MacMartin, Douglas G.; Vogiatzis, Konstantinos
2014-08-01
Unsteady wind loads due to turbulence inside the telescope enclosure result in image jitter and higher-order image degradation due to M1 segment motion. Advances in computational fluid dynamics (CFD) allow unsteady simulations of the flow around realistic telescope geometry, in order to compute the unsteady forces due to wind turbulence. These simulations can then be used to understand the characteristics of the wind loads. Previous estimates used a parametric model based on a number of assumptions about the wind characteristics, such as a von Karman spectrum and frozen-flow turbulence across M1, and relied on CFD only to estimate parameters such as mean wind speed and turbulent kinetic energy. Using the CFD-computed forces avoids the need for assumptions regarding the flow. We discuss here both the loads on the telescope that lead to image jitter, and the spatially-varying force distribution across the primary mirror, using simulations with the Thirty Meter Telescope (TMT) geometry. The amplitude, temporal spectrum, and spatial distribution of wind disturbances are all estimated; these are then used to compute the resulting image motion and degradation. There are several key differences relative to our earlier parametric model. First, the TMT enclosure provides sufficient wind reduction at the top end (near M2) to render the larger cross-sectional structural areas further inside the enclosure (including M1) significant in determining the overall image jitter. Second, the temporal spectrum is not von Karman as the turbulence is not fully developed; this applies both in predicting image jitter and M1 segment motion. And third, for loads on M1, the spatial characteristics are not consistent with propagating a frozen-flow turbulence screen across the mirror: Frozen flow would result in a relationship between temporal frequency content and spatial frequency content that does not hold in the CFD predictions. Incorporating the new estimates of wind load characteristics
MODELLING MANTLE TANKS FOR SDHW SYSTEMS USING PIV AND CFD
DEFF Research Database (Denmark)
Shah, Louise Jivan; Morrison, G.L.; Behnia, Masud
1999-01-01
mantle is buoyancy dominated. The numerically predicted flow distribution was found to be in good agreement with the experimental results. The numerical results were also found to be independent of the grid system used to model the convection processes on either side of the mantle heat transfer wall.......Characteristics of vertical mantle heat exchanger tanks for SDHW systems have been investigated experimentally and theoretically using particle image velocimetry (PIV) and CFD modelling. A glass model of a mantle heat exchanger tank was constructed so that the flow distribution in the mantle could...... be studied using the PIV test facility. Two transient three-dimensional CFD-models of the glass model mantle tank were developed using the CFD-programmes CFX and FLUENT.The experimental results illustrate that the mantle flow structure in the mantle is complicated and the distribution of flow in the...
Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat; Plósz, Benedek Gy
2015-10-15
The present study aims at using statistically designed computational fluid dynamics (CFD) simulations as numerical experiments for the identification of one-dimensional (1-D) advection-dispersion models - computationally light tools, used e.g., as sub-models in systems analysis. The objective is to develop a new 1-D framework, referred to as interpreted CFD (iCFD) models, in which statistical meta-models are used to calculate the pseudo-dispersion coefficient (D) as a function of design and flow boundary conditions. The method - presented in a straightforward and transparent way - is illustrated using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor screening study and system understanding, 50 different sets of design and flow conditions are selected using Latin Hypercube Sampling (LHS). The boundary condition sets are imposed on a 2-D axi-symmetrical CFD simulation model of the SST. In the framework, to degenerate the 2-D model structure, CFD model outputs are approximated by the 1-D model through the calibration of three different model structures for D. Correlation equations for the D parameter then are identified as a function of the selected design and flow boundary conditions (meta-models), and their accuracy is evaluated against D values estimated in each numerical experiment. The evaluation and validation of the iCFD model structure is carried out using scenario simulation results obtained with parameters sampled from the corners of the LHS experimental region. For the studied SST, additional iCFD model development was carried out in terms of (i) assessing different density current sub-models; (ii) implementation of a combined flocculation, hindered, transient and compression settling velocity function; and (iii
Institute of Scientific and Technical Information of China (English)
任立波; 韩吉田
2014-01-01
Based on MPI (Message Passing Interface)platform of FLUENT software,the parallel technique for coupled CFD (computational fluid dynamics)-DEM(discrete element method)model is implemented by user defined functions in the framework of secondary development,which has good scalability and acceleration performance with the increase of CPU number.The convergence of the governing equations is improved by constructing the void fraction scalar field and reorganizing the governing equations of the gas phase which follow the volume-averaged form of the two-fluid mod-el.Inter-particle and particle-wall interactions are determined with the soft-sphere model and the two phases are coupled based on the drag model.The parallel coupled CFD-DEM model is applied to the simulation of gas-particle two-phase flow in a conical-base spouted bed.Simulation results show that this model could well simulate gas-flow behavior in the spouted bed.Two distinct regions can be identified:the start-up and stable fluidization stage.In the stable fluidization stage,an oscillation cy-cle period can be observed,and the characteristics of the time-averaged particle velocity are obtained on the basis of the instantaneous particle velocity field.%基于 FLUENT 软件的 MPI 平台，在二次开发框架内通过用户自定义函数文件实现了CFD-DEM耦合并行算法。该并行算法具有随CPU核数增加的较佳扩展性能和良好加速性能。通过构建空隙率标量场、重组基于局部平均并考虑气固相互作用的气相控制方程，提高了气相控制方程的求解稳定性与收敛性；通过软球模型确定颗粒颗粒及颗粒壁面间的相互作用，以曳力模型为基础建立了相间相互作用关系。将该CFD-DEM耦合并行模型应用于锥形喷动床气固两相流动的数值模拟中，结果表明：该CFD-DEM耦合并行模型能较好地模拟锥形喷动床内气固流动行为；锥形喷动床内的颗粒流动经历了鼓泡阶段
A Transient 3D-CFD Model Incorporating Biological Processes for Use in Tissue Engineering
DEFF Research Database (Denmark)
Krühne, Ulrich; Wendt, D.; Martin, I.;
2010-01-01
In this article a mathematical model is presented in which the fluid dynamic interaction between the liquid flow in a scaffold and growing cells is simulated. The model is based on a computational fluid dynamic (CFD) model for the representation of the fluid dynamic conditions in the scaffold. It...... after 2, 8 and 13 days. The development of the cells is compared to the simulated growth of cells and it is attempted to draw a conclusion about the impact of the shear stress on the cell growth. Keyword: Computational fluid dynamics (CFD),Micro pores,Scaffold,Bioreactor,Fluid structure interaction...
CFD-model of the mass transfer in the vertical settler
Directory of Open Access Journals (Sweden)
E. K. Nagornaya
2013-02-01
Full Text Available Purpose. Nowadays the mathematical models of the secondary settlers are intensively developed. As a rule the engineers use the 0-D models or 1-D models to design settlers. But these models do not take into account the hydrodynamics process inside the settler and its geometrical form. That is why the CFD-models based on Navier - Stokes equations are not widely used in practice now. The use of CFD-models based on Navier - Stokes equations needs to incorporate very refine grid. It is very actually now to develop the CFD-models which permit to take into account the geometrical form of the settler, the most important physical processes and needs small computer time for calculation. That is why the development of the 2-D numerical model for the investigation of the waste waters transfer in the vertical settlers which permits to take into account the geometrical form and the constructive features of the settler is essential. Methodology. The finite - difference schemes are applied. Findings. The new 2-D-CFD-model was developed, which permits to perform the CFD investigation of the vertical settler. This model takes into account the geometrical form of the settler, the central pipe inside it and others peculiarities. The method of «porosity technique» is used to create the geometrical form of the settler in the numerical model. This technique permits to build any geometrical form of the settler for CFD investigation. Originality. Making of CFD-model which permits on the one hand to take into account the geometrical form of the settler, basic physical processes of mass transfer in construction and on the other hand requiring the low time cost in order to obtain results. Practical value. CFD-model is designed and code which is constructed on its basis allows at low cost of computer time and about the same as in the calculation of the 1-D model to solve complex multiparameter problems that arise during the design of vertical settlers with their shape and
Global hydroelastic model for springing and whipping based on a free-surface CFD code (OpenFOAM
Directory of Open Access Journals (Sweden)
Seng Sopheak
2014-12-01
Full Text Available The theoretical background and a numerical solution procedure for a time domain hydroelastic code are presented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solver where the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in a local floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frame undergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preserves the coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide the total fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forces and the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show that the VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responses accurately.
CFD model of multiphase flow in the abrasive water jet tool
Říha, Zdeněk
2015-01-01
The possibility of using CFD fluid flow modeling in area of tools with abrasive water jet is described in the paper. The correct function of such tool is based on proper setting of multiphase flow of water, air and solid particles in the inner space of the tool. The multiphase fluid flow numerical simulation can provide information which show relation between the geometry and the flow field. Then, this stable CFD model of multiphase flow creates key to design of the tool able to work wi...
Comparison of mesh-based and particle-based CFD coupling with DEM
Markauskas, D; Sivanesapillai, R; Steeb, H
2016-01-01
A comparative study on mesh-based and particle-based computational fluid dynamics (CFD) coupling with a discrete element method (DEM) is presented. As the mesh-based CFD method a finite volume method (FVM) is used. A smoothed particle hydrodynamics (SPH) method represents particle-based CFD. An unresolved fluid model with locally averaged Navier-Stokes equations for the fluid is used. A newly developed model of boundary conditions for the SPH is described and the validation tests are performed. With the help of the performed comparative tests, the similarities and differences of particle movements in both DEM-FVM and DEM-SPH methods are discussed. Three test cases, namely a single particle sedimentation test, flow through a porous block and sedimentation of a porous block, are performed using DEM-FVM and DEM-SPH methods. The drag force acting onto the solid particles highly depends on the fluid fraction. To be able to compare both methods, the size of the cell in FVM is chosen to give the same fluid fraction ...
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-based System Identification%基于CFD的系统辨识方法
Institute of Scientific and Technical Information of China (English)
孟庆龙; 官燕玲; 谢安生
2011-01-01
The principle of CFD (computational fluid dynamics) simulation and system identification were summarized, including the presentation of "grey-box" modeling method and steps of CFD-based system identification ; some applications in practice were analyzed to point out potential problems and its developing trends.%概述了计算流体力学(CFD)数值模拟和系统辨识的原理,详细阐述了基于CFD数值模拟的系统辨识“灰箱”建模方法的基本原理和实现步骤,对近几年该方法的应用案例进行分析,指出该建模方法存在的问题及发展方向.
Guo, Yuan; Deng, Baoqing; Ge, Daqiang; Shen, Xiuzhong
2015-08-01
CFD simulations of gas-solid fluidized beds have been performed in Euler-Euler framework. Green-Gauss Cell Based gradient approximation can predict the solid velocity well among gradient approximations. The dispersed choice in the turbulence model can reproduce the solid velocity correctly while the mixture and per phase choices cannot. The standard k-ɛ model, RNG k-ɛ model and SST k-ω model with the dispersed choice can predict the solid velocity well.
Isothermal CFD-model of Peirce-Smith converting process
Energy Technology Data Exchange (ETDEWEB)
Vaarno, J.; Pitkaelae, J.; Ahokainen, T.; Jokilaakso, A.
1997-12-31
The Peirce-Smith converter has been a dominating copper and nickel matte refining process since 1905. Due to extremely difficult process conditions, very little measured data has been available for studying interactions of the gas injection and molten sulphide matte. Detailed information on fluid dynamics of the gas injection is needed in solving gas injection related problems like refractory wear, accretion growth and tuyere blockage as well as optimising the efficiency of momentum and mass transfer created by the gas jets. A commercial CFD-code PHOENICS was used to solve isothermal flow field of gas and liquid in a Peirce-Smith converter. An Euler-Euler based algorithm was chosen for modelling fluid dynamics and evaluating controlling forces of a submerged gas injection generally. Predictions were made with a {kappa}-{epsilon} turbulence model in the body fitted co-ordinate system. The model has been verified with a 1/4 scale water model, and a parametric study with the mathematical model of submerged gas injection was made for the PS-process and the ladle injection processes. Limits of the modelling technique used were recognised, but calculated results indicates that the present model predicts the general flow field with reasonable accuracy and it can be used as input for more detailed mathematical models of gas plumes. Predicted bubble distribution, pattern of the flow field and magnitude of flow velocities were also used to evaluate scaling factors of physical models and general flow conditions of an industrial PS-converter. (orig.) 28 refs.
International Nuclear Information System (INIS)
Drastic urbanization and manhattanization are causing various problems in wind environment. This study suggests a CFD simulation method to evaluate wind environment in the early design stage of high-rise buildings. The CFD simulation of this study is not a traditional in-depth simulation, but a method to immediately evaluate wind environment for each design alternative and provide guidelines for design modification. Thus, the CFD simulation of this study to evaluate wind environments uses BIM-based CFD tools to utilize building models in the design stage. This study examined previous criteria to evaluate wind environment for pedestrians around buildings and selected evaluation criteria applicable to the CFD simulation method of this study. Furthermore, proper mesh generation method and CPU time were reviewed to find a meaningful CFD simulation result for determining optimal design alternative from the perspective of wind environment in the design stage. In addition, this study is to suggest a wind environment evaluation method through a BIM-based CFD simulation.
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 Modeling in Development of Renewable Energy Applications
Directory of Open Access Journals (Sweden)
Maher A.R. Sadiq Al-Baghdadi
2013-01-01
Full Text Available Chapter 1: A Multi-fluid Model to Simulate Heat and Mass Transfer in a PEM Fuel Cell. Torsten Berning, Madeleine Odgaard, Søren K. Kær Chapter 2: CFD Modeling of a Planar Solid Oxide Fuel Cell (SOFC for Clean Power Generation. Meng Ni Chapter 3: Hydrodynamics and Hydropower in the New Paradigm for a Sustainable Engineering. Helena M. Ramos, Petra A. López-Jiménez Chapter 4: Opportunities for CFD in Ejector Solar Cooling. M. Dennis Chapter 5: Three Dimensional Modelling of Flow Field Around a Horizontal Axis Wind Turbine (HAWT. Chaouki Ghenai, Armen Sargsyan, Isam Janajreh Chapter 6: Scaling Rules for Hydrodynamics and Heat Transfer in Jetting Fluidized-Bed Biomass Gasifiers. K. Zhang, J. Chang, P. Pei, H. Chen, Y. Yang Chapter 7: Investigation of Low Reynolds Number Unsteady Flow around Airfoils in Pitching, Plunging and Flapping Motions. M.R. Amiralaei, H. Alighanbari, S.M. Hashemi Chapter 8: Justification of Computational Fluid Dynamics Simulation for Flat Plate Solar Energy Collector. Mohamed Selmi, Mohammed J. Al-Khawaja, Abdulhamid Marafia Chapter 9: Comparative Performance of a 3-Bladed Airfoil Chord H-Darrieus and a 3-Bladed Straight Chord H-Darrieus Turbines using CFD. R. Gupta, Agnimitra Biswas Chapter 10: Computational Fluid Dynamics for PEM Fuel Cell Modelling. A. Iranzo, F. Rosa Chapter 11: Analysis of the Performance of PEM Fuel Cells: Tutorial of Major Functional and Constructive Characteristics using CFD Analysis. P.J. Costa Branco, J.A. Dente Chapter 12: Application of Techniques of Computational Fluid Dynamics in the Design of Bipolar Plates for PEM Fuel Cells. A.P. Manso, F.F. Marzo, J. Barranco, M. Garmendia Mujika.
CFD and FEM Model of an Underwater Vehicle Propeller
Chruściel Tadeusz; Ciba Ewelina; Dopke Julita
2014-01-01
Within the framework of the project for design and optimization of the Remotely Operated Vehicle (ROV), research on its propulsion has been carried out. Te entire project was supported by CFD and FEM calculations taking into account the characteristics of the underwater vehicle. One of the tasks was to optimize the semi-open duct for horizontal propellers, which provided propulsion and controllability in horizontal plane. In order to create a measurable model of this task it was necessary to ...
A Quasi-One-Dimensional CFD Model for Multistage Turbomachines
Institute of Scientific and Technical Information of China (English)
Olivier Léonard; Olivier Adam
2008-01-01
The objective of this paper is to present a fast and reliable CFD model that is able to simulate stationary and transient operations of multistage compressors and turbines. This analysis tool is based on an adapted version of the Euler equations solved by a time-marching, finite-volume method. The Euler equations have been extended by including source terms expressing the blade-flow interactions. These source terms are determined using the velocity triangles and a row-by-row representation of the blading at mid-span. The losses and deviations undergone by the fluid across each blade row are supplied by correlations. The resulting flow solver is a performance prediction tool based only on the machine geometry, offering the possibility of exploring the entire characteristic map of a multistage compressor or turbine. Its efficiency in terms of CPU time makes it possible to couple it to an optimization algorithm or to a gas turbine performance tool. Different test-cases are presented for which the calculated characteristic maps are compared to experimental ones.
Energy Technology Data Exchange (ETDEWEB)
Wanninger, Andreas; Ceuca, Sabin Cristian; Macian-Juan, Rafael [Technische Univ. Muenchen, Garching (Germany). Dept. of Nuclear Engineering
2013-07-01
Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)
International Nuclear Information System (INIS)
Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)
CFD based draft tube hydraulic design optimization
International Nuclear Information System (INIS)
The draft tube design of a hydraulic turbine, particularly in low to medium head applications, plays an important role in determining the efficiency and power characteristics of the overall machine, since an important proportion of the available energy, being in kinetic form leaving the runner, needs to be recovered by the draft tube into static head. For large units, these efficiency and power characteristics can equate to large sums of money when considering the anticipated selling price of the energy produced over the machine's life-cycle. This same draft tube design is also a key factor in determining the overall civil costs of the powerhouse, primarily in excavation and concreting, which can amount to similar orders of magnitude as the price of the energy produced. Therefore, there is a need to find the optimum compromise between these two conflicting requirements. In this paper, an elaborate approach is described for dealing with this optimization problem. First, the draft tube's detailed geometry is defined as a function of a comprehensive set of design parameters (about 20 of which a subset is allowed to vary during the optimization process) and are then used in a non-uniform rational B-spline based geometric modeller to fully define the wetted surfaces geometry. Since the performance of the draft tube is largely governed by 3D viscous effects, such as boundary layer separation from the walls and swirling flow characteristics, which in turn governs the portion of the available kinetic energy which will be converted into pressure, a full 3D meshing and Navier-Stokes analysis is performed for each design. What makes this even more challenging is the fact that the inlet velocity distribution to the draft tube is governed by the runner at each of the various operating conditions that are of interest for the exploitation of the powerhouse. In order to determine these inlet conditions, a combined steady-state runner and an initial draft tube analysis
Advanced subgrid modeling for Multiphase CFD in CASL VERA tools
International Nuclear Information System (INIS)
This work introduces advanced modeling capabilities that are being developed to improve the accuracy and extend the applicability of Multiphase CFD. Specifics of the advanced and hardened boiling closure model are described in this work. The development has been driven by new physical understanding, derived from the innovative experimental techniques available at MIT. A new experimental-based mechanistic approach to heat partitioning is proposed. The model introduces a new description of the bubble evaporation, sliding and interaction on the heated surface to accurately capture the evaporation occurring at the heated surface, while also tracking the local surface conditions. The model is being assembled to cover an extended application area, up to Critical Heat Flux (CHF). The accurate description of the bubble interaction, effective microlayer and dry surface area are considered to be the enabling quantities towards innovated CHF capturing methodologies. Further, improved mechanistic force-balance models for bubble departure predictions and lift-off diameter predictions are implemented in the model. Studies demonstrate the influence of the newly implemented partitioning components. Finally, the development work towards a more consistent and integrated hydrodynamic closure is presented. The main objective here is to develop a set of robust momentum closure relations which focuses on the specific application to PWR conditions, but will facilitate the application to other geometries, void fractions, and flow regimes. The innovative approach considers local flow conditions on a cell-by-cell basis to ensure robustness. Closure relations of interest initially include drag, lift, and turbulence dispersion, with near wall corrections applied for both drag and lift. (author)
Modeling and verification of hemispherical solar still using ANSYS CFD
Directory of Open Access Journals (Sweden)
Hitesh N. Panchal, P. K. Shah
2013-01-01
Full Text Available In every efficient solar still design, water temperature, vapor temperature and distillate output, and difference between water temperature and inner glass cover temperatures are very important. Here, two dimensional three phase model of hemispherical solar still is made for evaporation as well as condensation process in ANSYS CFD. Simulation results like water temperature, vapor temperature, distillate output compared with actual experimental results of climate conditions of Mehsana (latitude of 23° 59’ and longitude of 72° 38 of hemispherical solar still. Water temperature and distillate output were good agreement with actual experimental results. Study shows that ANSYS-CFD is very powerful as well as efficient tool for design, comparison purpose of hemispherical solar still.
Modeling and verification of hemispherical solar still using ANSYS CFD
Energy Technology Data Exchange (ETDEWEB)
Panchal, Hitesh N. [KSV University, Gujarat Power Engineering and Research Institute, Mehsana (India); Shah, P.K. [Silver Oak College of Engineering and Technology, Ahmedabad, Gujarat (India)
2013-07-01
In every efficient solar still design, water temperature, vapor temperature and distillate output, and difference between water temperature and inner glass cover temperatures are very important. Here, two dimensional three phase model of hemispherical solar still is made for evaporation as well as condensation process in ANSYS CFD. Simulation results like water temperature, vapor temperature, distillate output compared with actual experimental results of climate conditions of Mehsana (latitude of 23° 59’ and longitude of 72° 38) of hemispherical solar still. Water temperature and distillate output were good agreement with actual experimental results. Study shows that ANSYS-CFD is very powerful as well as efficient tool for design, comparison purpose of hemispherical solar still.
CFD modeling of the test 25 of the PANDA experiment
International Nuclear Information System (INIS)
A large amount of steam and Hydrogen gas is expected to be released within the dry containment of a pressurized water reactor (PWR), after the hypothetical beginning of a severe accident leading to the melting of the core. The accurate modeling of gas distribution in a PWR containment concerns phenomena such as wall condensation, hydrogen accumulation, gas stratification and transport in the different compartments of the containment. The paper presents numerical assessments of CFD solvers NEPTUNE-CFD and Code-Saturne, and is focused on the analysis and the understanding of gas stratification and transport phenomena. NEPTUNE-CFD is dedicated to the simulation of incompressible and compressible multi-component/multi-phase flows, whereas Code-Saturne is dedicated to homogeneous incompressible or low Mach number compressible flows, with only one momentum equation representing the mixture of gases, liquid and particles. NEPTUNE-CFD is mainly used for nuclear engineering, whereas Code-Saturne is used either for nuclear and fossil energy engineering, and for environment (geophysical flows). The NEPTUNE-CFD code is developed within the framework of the NEPTUNE project, financially supported by CEA (Commissariat a l'energie Atomique), EDF, IRSN (Institut de Radioprotection et de Surete Nucleaire) and AREVA-NP. Both codes are validated and compared with experimental data corresponding to the test 25 of the PANDA experiment. This test concerns the distribution of mixture of gases (Helium as a simulant of hydrogen and condensing steam) in air over two vertical and cylindrical vessels, interconnected by a horizontal and cylindrical pipe. The overall dimensions of the experiment (Diameter ∼4 m, Height 8 m, Volume of the 2 vessels ∼180 m3) are not yet representative of the true scale of the reactors, but they already provide valuable information when compared to smaller scales (as experience TOSQAN∼7 m3). The computational results with Code-Saturne and NEPTUNE-CFD compare
CFD Wake Modelling with a BEM Wind Turbine Sub-Model
Directory of Open Access Journals (Sweden)
Anders Hallanger
2013-01-01
Full Text Available Modelling of wind farms using computational fluid dynamics (CFD resolving the flow field around each wind turbine's blades on a moving computational grid is still too costly and time consuming in terms of computational capacity and effort. One strategy is to use sub-models for the wind turbines, and sub-grid models for turbulence production and dissipation to model the turbulent viscosity accurately enough to handle interaction of wakes in wind farms. A wind turbine sub-model, based on the Blade Momentum Theory, see Hansen (2008, has been implemented in an in-house CFD code, see Hallanger et al. (2002. The tangential and normal reaction forces from the wind turbine blades are distributed on the control volumes (CVs at the wind turbine rotor location as sources in the conservation equations of momentum. The classical k-epsilon turbulence model of Launder and Spalding (1972 is implemented with sub-grid turbulence (SGT model, see Sha and Launder (1979 and Sand and Salvesen (1994. Steady state CFD simulations were compared with flow and turbulence measurements in the wake of a model scale wind turbine, see Krogstad and Eriksen (2011. The simulated results compared best with experiments when stalling (boundary layer separation on the wind turbine blades did not occur. The SGT model did improve turbulence level in the wake but seems to smear the wake flow structure. It should be noted that the simulations are carried out steady state not including flow oscillations caused by vortex shedding from tower and blades as they were in the experiments. Further improvement of the simulated velocity defect and turbulence level seems to rely on better parameter estimation to the SGT model, improvements to the SGT model, and possibly transient- instead of steady state simulations.
A Multi-Model Approach for Uncertainty Propagation and Model Calibration in CFD Applications
Wang, Jian-xun; Xiao, Heng
2015-01-01
Proper quantification and propagation of uncertainties in computational simulations are of critical importance. This issue is especially challenging for CFD applications. A particular obstacle for uncertainty quantifications in CFD problems is the large model discrepancies associated with the CFD models used for uncertainty propagation. Neglecting or improperly representing the model discrepancies leads to inaccurate and distorted uncertainty distribution for the Quantities of Interest. High-fidelity models, being accurate yet expensive, can accommodate only a small ensemble of simulations and thus lead to large interpolation errors and/or sampling errors; low-fidelity models can propagate a large ensemble, but can introduce large modeling errors. In this work, we propose a multi-model strategy to account for the influences of model discrepancies in uncertainty propagation and to reduce their impact on the predictions. Specifically, we take advantage of CFD models of multiple fidelities to estimate the model ...
CFD Based Study of Heterogeneous Microclimate in a Typical Chinese Greenhouse in Central China
Institute of Scientific and Technical Information of China (English)
WANG Xiao-wei; LUO Jin-yao; LI Xiao-ping
2013-01-01
Indoor microclimate is important for crop production and quality in greenhouse cultivation. This paper focuses on microclimate study based on a computational fluid dynamics (CFD) model of a typical plastic greenhouse (with a sector shape vertical cross-section) popularly used in central China. A radiation model is added into the CFD model so as to simulate coupling of convective transfers and radiative exchanges at the cover and the roof, instead of using the usual coupling approach based on energy balance. In addition, a fractal permeability model is innovatively adopted in the modeling of the crop canopy. Compared the numerical results with measured experimental data, the model simulation is proved with success. This model then is used to explore the microclimate variable distributions in the greenhouse. It shows that the airflow pattern, temperature and humidity profiles are different from those in a sawtooth Mediterranean-type greenhouse. The study suggests that this deliberately developed CFD model can be served as a useful tool in macroclimate research and greenhouse design investigating.
Development of a three-dimensional CFD model for rotary lime kilns
Energy Technology Data Exchange (ETDEWEB)
Lixin Tao; Blom, Roger (FS Dynamics Sweden AB, Goeteborg (Sweden)); Nordgren, Daniel (Innventia, Stockholm (Sweden))
2010-11-15
In the calcium loop of the recovery cycle in a Kraft process of pulp and paper production, rotary lime kilns are used to convert the lime mud, mainly CaCO3, back to quick lime, CaO, for re-use in the causticizing process. The lime kilns are one of the major energy consumption devices for paper and pulp industry. Because of the rising oil price and new emission limits, the pulp mills have been forced to look for alternative fuels for their lime kilns. One interesting alternative to oil, often easily available at pulp mills, is biofuels such as sawdust and bark. However the practical kiln operation often encounters some difficulties because of the uncertainties around the biofuel impact on the lime kiln performance. A deeper understanding of the flame characteristics is required when shifting from oil to biofuels. Fortunately recent advances in modern Computational Fluid Dynamics, CFD, have provided the possibility to study and predict the detailed flame characteristics regarding the lime kiln performance. In this project a three-dimensional CFD model for rotary lime kilns has been developed. To simulate a rotary lime kiln the developed CFD model integrates the three essential sub-models, i.e. the freeboard hot flow model, the lime bed model and the rotating refractory wall model and it is developed based on the modern CFD package: FLUENT which is commercially available on the market. The numerical simulations using the developed CFD model have been performed for three selected kiln operations fired with three different fuel mixtures. The predicted results from the CFD modelling are presented and discussed in order to compare the impacts on the kiln performance due to the different firing conditions. During the development, the lime kiln at the Soedra Cell Moensteraas mill has been used as reference kiln. To validate the CFD model, in-plant measurements were carried out in the Moensteraas lime kiln during an experiment campaign. The results obtained from the
CFD Modelling of Abdominal Aortic Aneurysm on Hemodynamic Loads Using a Realistic Geometry with CT
Loong, T. H.; Maurizio Bordone; Uei Pua; Sriram Narayanan; Eduardo Soudah; E. Y. K. Ng
2013-01-01
The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA) geometric parameters, wall stress shear (WSS), abdominal flow patterns, intraluminal thrombus (ILT), and AAA arterial wall rupture using computational fluid dynamics (CFD). Real AAA 3D models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetr...
CFD Modelling of Abdominal Aortic Aneurysm on Hemodynamic Loads Using a Realistic Geometry with CT
Directory of Open Access Journals (Sweden)
Eduardo Soudah
2013-01-01
Full Text Available The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA geometric parameters, wall stress shear (WSS, abdominal flow patterns, intraluminal thrombus (ILT, and AAA arterial wall rupture using computational fluid dynamics (CFD. Real AAA 3D models were created by three-dimensional (3D reconstruction of in vivo acquired computed tomography (CT images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m3 and a kinematic viscosity of 4×10-3 Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index (β, saccular index (γ, deformation diameter ratio (χ, and tortuosity index (ε and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation.
CFD Modelling of Abdominal Aortic Aneurysm on Hemodynamic Loads Using a Realistic Geometry with CT
Ng, E. Y. K.; Loong, T. H.; Bordone, Maurizio; Pua, Uei; Narayanan, Sriram
2013-01-01
The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA) geometric parameters, wall stress shear (WSS), abdominal flow patterns, intraluminal thrombus (ILT), and AAA arterial wall rupture using computational fluid dynamics (CFD). Real AAA 3D models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m3 and a kinematic viscosity of 4 × 10−3 Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index (β), saccular index (γ), deformation diameter ratio (χ), and tortuosity index (ε)) and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation. PMID:23864906
CFD modeling of airflow for indoor comfort in the tropics
International Nuclear Information System (INIS)
In humid tropical environments air movement is a common means to achieving indoor thermal comfort. In many locations closer to the equator, breezes are weaker and less reliable. Whatever the source of air movement it is important to quantity its potential in terms of the percentage of time the air movement will be available and the likely speed of the air movement in occupied zone of a building. It is also important to establish appropriate thermal comfort criteria with respect to air temperature, humidity and air movement. There are a number of techniques for modeling air movement inside naturally ventilated buildings. Boundary layer wind tunnels provide an opportunity to both measure and visually observe such airflow through model building. It is important to model adjacent buildings and any significant landscaping features that will influence outdoor airflow patterns. Such studies are relatively expensive. The recent availability of computational fluid dynamics (CFD) software for personal computers offers an alternative method for modeling air movement inside naturally ventilated buildings. Very expensive versions of this software have been available for large computers and work stations for many years but they have only recently become available for smaller computers. There are some features of such software that should be compared before purchasing a copy or a license. This paper discusses such features in detail. It is important in the case of natural ventilation that adjacent buildings and any significant landscaping features that will influence outdoor airflow patterns are included in the modeling. This paper also stresses the importance of calibrating the CFD software output against some physical measurements or wind tunnel modeling to ensure that the CFD results are realistic
Cfd modeling of a synthetic jet actuator
International Nuclear Information System (INIS)
Synthetic jet actuators show good promise as an enabling technology for innovative boundary layer flow control applied to external surfaces, like airplane wings, and to internal flows, like those occurring in a curved engine inlet. The appealing characteristics of a synthetic jet are zero-net-mass flux operation and an efficient control effect that takes advantages of unsteady fluid phenomena. The formation of a synthetic jet in a quiescent external air flow is only beginning to be understood and a rational understanding of these devices is necessary before they can be applied to the control of flows outside of the laboratory. The synthetic jet flow generated by a planar orifice is investigated here using computational approach. Computations of the 2D synthetic jet are performed with unsteady RANS modeled with the Realizable κ - ε turbulence model available in FLUENT environment. In this present work, the ability of the first order turbulence model, employed in our computations, to model the formation of the counter-rotating-vortex pair (CVP) that appears in the flow-field was investigated. Computational results were in good agreement with experimental measurements. The effectiveness of such control actuator was tested on separated boundary layer. Preliminary investigation were presented and discussed
CFD code fluent turbulence models application. Ansaldo's prototype modeling
International Nuclear Information System (INIS)
Among others, one of the main activities in the Nuclear Engineering and Fluid Mechanics Department of the Engineering School in Bilbao, is the study of liquid metals behavior. And for this purpose the CFD code FLUENT is being used. Currently, the code is being applied to the use of Lead-Bismuth eutectic (LBE) as the coolant of an accelerator driven system (ADS) and also as the target for a neutron source. In this paper, ANSALDO's Energy Amplifier Demonstration Facility is simulated, paying attention only on the coolant. As it will be later explained, natural convection is a very important issue, because the philosophy for safety systems in nuclear devices tends to consider passive technologies. The purpose is to avoid electrical machines like pumps, so the core should remain coolable, even if there is a blackout. To get this natural circulation, heat transfer plays a main role, and as turbulence enhances the heat transfer, it is important to choose a good turbulence model to correctly simulate this ADS's coolant system. (author)
CFD modeling of sodium spray combustion
International Nuclear Information System (INIS)
A sodium cooled fast reactor is one of the attractive concept for the IVth generation advanced reactor designs. For the safety of a sodium cooled fast reactor, sodium-air and sodium-water reactions must be avoided. A sodium-air reaction typically occurs in two dominant modes, namely the spray fire and pool fire. The focus of the paper will be on spray fires. To avoid sodium-air accidents and to mitigate the consequences if a sodium fire occurs, it is essential to understand all the physical phenomena involved in sodium spray combustion. Numerical modeling is one of the methods, which can be used to understand all the physics involved. The goal of the work presented in this paper is to propose a numerical method to simulate sodium spray combustion and to validate this method against experiments. Free falling single droplet sodium spray combustion experiments are used as a validation case for the proposed numerical method. The trend obtained using our numerical simulations matches well with the experimental data. Further validation needs to be performed, before the presented modeling can be used for sodium fast reactor safety analyses. (author)
CFD modeling of dust dispersion through Najaf historic city centre
Directory of Open Access Journals (Sweden)
Maher A.R. Sadiq Al-Baghdadi
2014-01-01
Full Text Available The aim of this project is to study the influences of the wind flow and dust particles dispersion through Najaf historic city centre. Two phase Computational Fluid Dynamics (CFD model using a Reynolds Average Navier Stokes (RANS equations has been used to simulate the wind flow and the transport and dispersion of the dust particles through the historic city centre. This work may provide useful insight to urban designers and planners interested in examining the variation of city breathability as a local dynamic morphological parameter with the local building packing density.
Lime Kiln Modeling. CFD and One-dimensional simulations
Energy Technology Data Exchange (ETDEWEB)
Svedin, Kristoffer; Ivarsson, Christofer; Lundborg, Rickard
2009-03-15
The incentives for burning alternative fuels in lime kilns are growing. An increasing demand on thorough investigations of alternative fuel impact on lime kiln performance have been recognized, and the purpose of this project has been to develop a lime kiln CFD model with the possibility to fire fuel oil and lignin. The second part of the project consists of three technical studies. Simulated data from a one-dimensional steady state program has been used to support theories on the impact of biofuels and lime mud dryness. The CFD simulations was carried out in the commercial code FLUENT. Due to difficulties with the convergence of the model the calcination reaction is not included. The model shows essential differences between the two fuels. Lignin gives a different flame shape and a longer flame length compared to fuel oil. Mainly this depends on how the fuel is fed into the combustion chamber and how much combustion air that is added as primary and secondary air. In the case of lignin combustion the required amount of air is more than in the fuel oil case. This generates more combustion gas and a different flow pattern is created. Based on the values from turbulent reaction rate for the different fuels an estimated flame length can be obtained. For fuel oil the combustion is very intense with a sharp peak in the beginning and a rapid decrease. For lignin the combustion starts not as intense as for the fuel oil case and has a smoother shape. The flame length appears to be approximately 2-3 meter longer for lignin than for fuel oil based on turbulent reaction rate in the computational simulations. The first technical study showed that there are many benefits of increasing dry solids content in the lime mud going into a kiln such as increased energy efficiency, reduced TRS, and reduced sodium in the kiln. However, data from operating kilns indicates that these benefits can be offset by increasing exit gas temperature that can limit kiln production capacity. Simulated
CFD Modeling of Particulate Matter Dispersion from Kerman Cement Plant
Directory of Open Access Journals (Sweden)
M. Panahandeh
2010-04-01
Full Text Available "n "n "nBackgrounds and Objectives: The dispersion of particulate matter has been known as the most serious environmental pollution of cement plants. In the present work, dispersion of the particulate matter from stack of Kerman Cement Plant was investigated using Computational Fluid Dynamics (CFD modeling."nMaterials and Methods: In order to study the dispersion of particulate matter from the stack, a calculation domain with dimensions of 8000m × 800m × 400m was considered. The domain was divided to 936781 tetrahedral control volumes. The mixture two-phase model was employed to model the interaction of the particulate matter (dispersed phase and air (continuous phase. The Large Eddy Simulation (LES method was used for turbulence modeling."nResults: The concentration of particulate matter in the whole calculation domain was computed. The predicted concentrations were compared to the measured values from the literature and a good agreement was observed. The predicted concentration profiles at different cross sections were analyzed."nConclusion:The results of the present work showed that CFD is a useful tool for understanding the dispersion of particulate matter in air. Although the obtained results were promising, more investigations on the properties of the dispersed phase, turbulent parameters and the boundary layer effect is needed to obtain more accurate results.
Directory of Open Access Journals (Sweden)
Kruggel-Emden H.
2011-03-01
Full Text Available Chemical Looping Combustion is an energy efficient combustion technology for the inherent separation of carbon dioxide for both gaseous and solid fuels. For scale up and further development of this process multi-phase CFD-based simulations have a strong potential which rely on kinetic models for the solid/gaseous reactions. Reaction models are usually simple in structure in order to keep the computational cost low. They are commonly derived from thermogravimetric experiments. With only few CFD-based simulations performed on chemical looping combustion, there is a lack in understanding of the role and of the sensitivity of the applied chemical reaction model on the outcome of a simulation. The aim of this investigation is therefore the study of three different carrier materials CaSO4, Mn3O4 and NiO with the gaseous fuels H2 and CH4 in a batch type reaction vessel. Four reaction models namely the linear shrinking core, the spherical shrinking core, the Avrami-Erofeev and a recently proposed multi parameter model are applied and compared on a case by case basis. La combustion en boucle chimique (Chemical Looping Combustion est une technologie de combustion efficace permettant le captage in situ du CO2 pour des charges gazeuses ou solides. Dans l’optique du développement et de l’extrapolation du procédé, la CFD est un outil de simulation à fort potentiel qui s’appuie notamment sur des modèles cinétiques pour décrire les réactions gaz-solide. Ces modèles décrivant les réactions sont généralement assez simples pour limiter les temps de simulation et sont obtenus à partir d’expérimentations en thermobalance. Il y a encore peu de travaux de modélisation CFD du procédé CLC et il est difficile d’estimer l’importance du modèle décrivant les réactions chimiques sur les résultats des simulations. Le but de ce travail est donc d’étudier la combustion de charges gazeuses H2 et CH4 dans des réacteurs en batch en consid
Integration of CFD codes and advanced combustion models for quantitative burnout determination
Energy Technology Data Exchange (ETDEWEB)
Javier Pallares; Inmaculada Arauzo; Alan Williams [University of Zaragoza, Zaragoza (Spain). Centre of Research for Energy Resources and Consumption (CIRCE)
2007-10-15
CFD codes and advanced kinetics combustion models are extensively used to predict coal burnout in large utility boilers. Modelling approaches based on CFD codes can accurately solve the fluid dynamics equations involved in the problem but this is usually achieved by including simple combustion models. On the other hand, advanced kinetics combustion models can give a detailed description of the coal combustion behaviour by using a simplified description of the flow field, this usually being obtained from a zone-method approach. Both approximations describe correctly general trends on coal burnout, but fail to predict quantitative values. In this paper a new methodology which takes advantage of both approximations is described. In the first instance CFD solutions were obtained of the combustion conditions in the furnace in the Lamarmora power plant (ASM Brescia, Italy) for a number of different conditions and for three coals. Then, these furnace conditions were used as inputs for a more detailed chemical combustion model to predict coal burnout. In this, devolatilization was modelled using a commercial macromolecular network pyrolysis model (FG-DVC). For char oxidation an intrinsic reactivity approach including thermal annealing, ash inhibition and maceral effects, was used. Results from the simulations were compared against plant experimental values, showing a reasonable agreement in trends and quantitative values. 28 refs., 4 figs., 4 tabs.
A CFD-informed quasi-steady model of flapping wing aerodynamics
Nakata, Toshiyuki; Liu, Hao; Bomphrey, Richard J.
2016-01-01
Aerodynamic performance and agility during flapping flight are determined by the combination of wing shape and kinematics. The degree of morphological and kinematic optimisation is unknown and depends upon a large parameter space. Aimed at providing an accurate and computationally inexpensive modelling tool for flapping-wing aerodynamics, we propose a novel CFD (computational fluid dynamics)-informed quasi-steady model (CIQSM), which assumes that the aerodynamic forces on a flapping wing can be decomposed into the quasi-steady forces and parameterised based on CFD results. Using least-squares fitting, we determine a set of proportional coefficients for the quasi-steady model relating wing kinematics to instantaneous aerodynamic force and torque; we calculate power with the product of quasi-steady torques and angular velocity. With the quasi-steady model fully and independently parameterised on the basis of high-fidelity CFD modelling, it is capable of predicting flapping-wing aerodynamic forces and power more accurately than the conventional blade element model (BEM) does. The improvement can be attributed to, for instance, taking into account the effects of the induced downwash and the wing tip vortex on the force generation and power consumption. Our model is validated by comparing the aerodynamics of a CFD model and the present quasi-steady model using the example case of a hovering hawkmoth. It demonstrates that the CIQSM outperforms the conventional BEM while remaining computationally cheap, and hence can be an effective tool for revealing the mechanisms of optimization and control of kinematics and morphology in flapping-wing flight for both bio-flyers and unmanned air systems.
A CFD model of the wake of an offshore wind farm: Using a prescribed wake inflow
DEFF Research Database (Denmark)
Réthoré, P.-E.; Bechmann, Andreas; Sørensen, Niels N.;
2007-01-01
An CFD model of the wake of an offshore wind farm, expanding existing measurements is proposed. The method is based on solving the Navier Stokes equation in a large domain downstream an offshore wind farm. The inflow of the domain is estimated using existing met mast measurements from both free...... stream and directly in-wake conditions. A comparison between the simulation results and measurements from a met mast are presented and the shortcomings of the methods are discussed. ...
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 modeling of multiphase reacting flow in blast furnace shaft with layered burden
International Nuclear Information System (INIS)
The ironmaking blast furnace is a counter-current chemical reactor which includes the ascending gas flow and the counter-current descending porous bed (burden). A Computational Fluid Dynamics (CFD) model has been developed to simulate the multiphase reacting flow in blast furnace shaft. The gas flow dynamics, burden movement, chemical reactions, heat and mass transfer between the gas phase and burden phase are included in the CFD model. The blast furnace burden consists of alternative layers of iron ore and coke. A novel methodology is proposed to efficiently model the effects of alternative burden layer structure on gas flow, heat transfer, mass transfer and chemical reactions. Different reactions and heat transfer characteristics are applied for difference types of layer. In addition, the layered CFD model accurately predicts the Cohesive Zone (CZ) shape where the melting of solid burden taking place. The shape and location of the CZ are determined by an iterative method based on the ore temperature distribution. The theoretical formation and the methodology of the CFD model are presented and the model is applied to simulate industry blast furnaces. The proposed method can be applied to investigate the blast furnace shaft process and other moving bed system with periodic burden structure configuration. - Highlights: •A novel methodology is proposed to efficiently model the blast furnace shaft with layered burden. •The effects of layered burden on flow, heat transfer, and chemical reactions are considered in the model. •The shape and location of the cohesive zone is determined by an iterative method
Validation of NEPTUNE-CFD two-phase flow models using experimental data
Jorge Pérez Mañes; Victor Hugo Sánchez Espinoza; Sergio Chiva Vicent; Michael Böttcher; Robert Stieglitz
2014-01-01
This paper deals with the validation of the two-phase flow models of the CFD code NEPTUNEC-CFD using experimental data provided by the OECD BWR BFBT and PSBT Benchmark. Since the two-phase models of CFD codes are extensively being improved, the validation is a key step for the acceptability of such codes. The validation work is performed in the frame of the European NURISP Project and it was focused on the steady state and transient void fraction tests. The influence of different NEPTUNE-CFD ...
Numerical modelling of pressure suppression pools with CFD and FEM codes
Energy Technology Data Exchange (ETDEWEB)
Paettikangas, T.; Niemi, J.; Timperi, A. (VTT Technical Research Centre of Finland (Finland))
2011-06-15
Experiments on large-break loss-of-coolant accident for BWR is modeled with computational fluid (CFD) dynamics and finite element calculations. In the CFD calculations, the direct-contact condensation in the pressure suppression pool is studied. The heat transfer in the liquid phase is modeled with the Hughes-Duffey correlation based on the surface renewal model. The heat transfer is proportional to the square root of the turbulence kinetic energy. The condensation models are implemented with user-defined functions in the Euler-Euler two-phase model of the Fluent 12.1 CFD code. The rapid collapse of a large steam bubble and the resulting pressure source is studied analytically and numerically. Pressure source obtained from simplified calculations is used for studying the structural effects and FSI in a realistic BWR containment. The collapse results in volume acceleration, which induces pressure loads on the pool walls. In the case of a spherical bubble, the velocity term of the volume acceleration is responsible of the largest pressure load. As the amount of air in the bubble is decreased, the peak pressure increases. However, when the water compressibility is accounted for, the finite speed of sound becomes a limiting factor. (Author)
Modal Decomposition of Synthetic Jet Flow Based on CFD Computation
Directory of Open Access Journals (Sweden)
Hyhlík Tomáš
2015-01-01
Full Text Available The article analyzes results of numerical simulation of synthetic jet flow using modal decomposition. The analyzes are based on the numerical simulation of axisymmetric unsteady laminar flow obtained using ANSYS Fluent CFD code. Three typical laminar regimes are compared from the point of view of modal decomposition. The first regime is without synthetic jet creation with Reynolds number Re = 76 and Stokes number S = 19.7. The second studied regime is defined by Re = 145 and S = 19.7. The third regime of synthetic jet work is regime with Re = 329 and S = 19.7. Modal decomposition of obtained flow fields is done using proper orthogonal decomposition (POD where energetically most important modes are identified. The structure of POD modes is discussed together with classical approach based on phase averaged velocities.
Engineering-Based Thermal CFD Simulations on Massive Parallel Systems
Frisch, Jérôme
2015-05-22
The development of parallel Computational Fluid Dynamics (CFD) codes is a challenging task that entails efficient parallelization concepts and strategies in order to achieve good scalability values when running those codes on modern supercomputers with several thousands to millions of cores. In this paper, we present a hierarchical data structure for massive parallel computations that supports the coupling of a Navier–Stokes-based fluid flow code with the Boussinesq approximation in order to address complex thermal scenarios for energy-related assessments. The newly designed data structure is specifically designed with the idea of interactive data exploration and visualization during runtime of the simulation code; a major shortcoming of traditional high-performance computing (HPC) simulation codes. We further show and discuss speed-up values obtained on one of Germany’s top-ranked supercomputers with up to 140,000 processes and present simulation results for different engineering-based thermal problems.
Engineering-Based Thermal CFD Simulations on Massive Parallel Systems
Directory of Open Access Journals (Sweden)
Jérôme Frisch
2015-05-01
Full Text Available The development of parallel Computational Fluid Dynamics (CFD codes is a challenging task that entails efficient parallelization concepts and strategies in order to achieve good scalability values when running those codes on modern supercomputers with several thousands to millions of cores. In this paper, we present a hierarchical data structure for massive parallel computations that supports the coupling of a Navier–Stokes-based fluid flow code with the Boussinesq approximation in order to address complex thermal scenarios for energy-related assessments. The newly designed data structure is specifically designed with the idea of interactive data exploration and visualization during runtime of the simulation code; a major shortcoming of traditional high-performance computing (HPC simulation codes. We further show and discuss speed-up values obtained on one of Germany’s top-ranked supercomputers with up to 140,000 processes and present simulation results for different engineering-based thermal problems.
Two Phase Flow Models and Numerical Methods of the Commercial CFD Codes
Energy Technology Data Exchange (ETDEWEB)
Bae, Sung Won; Jeong, Jae Jun; Chang, Seok Kyu; Cho, Hyung Kyu
2007-11-15
The use of commercial CFD codes extend to various field of engineering. The thermal hydraulic analysis is one of the promising engineering field of application of the CFD codes. Up to now, the main application of the commercial CFD code is focused within the single phase, single composition fluid dynamics. Nuclear thermal hydraulics, however, deals with abrupt pressure changes, high heat fluxes, and phase change heat transfer. In order to overcome the CFD limitation and to extend the capability of the nuclear thermal hydraulics analysis, the research efforts are made to collaborate the CFD and nuclear thermal hydraulics. To achieve the final goal, the current useful model and correlations used in commercial CFD codes should be reviewed and investigated. This report gives the summary information about the constitutive relationships that are used in the FLUENT, STAR-CD, and CFX. The brief information of the solution technologies are also enveloped.
Two Phase Flow Models and Numerical Methods of the Commercial CFD Codes
International Nuclear Information System (INIS)
The use of commercial CFD codes extend to various field of engineering. The thermal hydraulic analysis is one of the promising engineering field of application of the CFD codes. Up to now, the main application of the commercial CFD code is focused within the single phase, single composition fluid dynamics. Nuclear thermal hydraulics, however, deals with abrupt pressure changes, high heat fluxes, and phase change heat transfer. In order to overcome the CFD limitation and to extend the capability of the nuclear thermal hydraulics analysis, the research efforts are made to collaborate the CFD and nuclear thermal hydraulics. To achieve the final goal, the current useful model and correlations used in commercial CFD codes should be reviewed and investigated. This report gives the summary information about the constitutive relationships that are used in the FLUENT, STAR-CD, and CFX. The brief information of the solution technologies are also enveloped
CFD Simulation of Nanosufur Crystallization Incorporating Population Balance Modeling
Directory of Open Access Journals (Sweden)
Fatemeh Golkhou
2013-01-01
Full Text Available A physical vapor condensation process for synthesizing nanosized sulfur powder as a precursor for various industries was simulated by the use of computational ?uid dynamic (CFD modeling. The phase change, swirl flow and heat transfer taking place inside the cyclone are analyzed along with particle formation via gas condensation method. The population balance model is a mathematical framework for the modeling of crystal size distribution (CSD and the study of gas-phase changes leading to nucleation of the first solid particles. In this paper the Direct Quadrature Method of Moments is used for solving the transport equations of the moments of the size distribution. The temperature, velocity and particle size distribution ranges inside the cyclone were computed. The results show the formation of nanosulfur particles in 1-7 nm range.
CFD-aided modelling of activated sludge systems - A critical review.
Karpinska, Anna M; Bridgeman, John
2016-01-01
Nowadays, one of the major challenges in the wastewater sector is the successful design and reliable operation of treatment processes, which guarantee high treatment efficiencies to comply with effluent quality criteria, while keeping the investment and operating cost as low as possible. Although conceptual design and process control of activated sludge plants are key to ensuring these goals, they are still based on general empirical guidelines and operators' experience, dominated often by rule of thumb. This review paper discusses the rationale behind the use of Computational Fluid Dynamics (CFD) to model aeration, facilitating enhancement of treatment efficiency and reduction of energy input. Several single- and multiphase approaches commonly used in CFD studies of aeration tank operation, are comprehensively described, whilst the shortcomings of the modelling assumptions imposed to evaluate mixing and mass transfer in AS tanks are identified and discussed. Examples and methods of coupling of CFD data with biokinetics, accounting for the actual flow field and its impact on the oxygen mass transfer and yield of the biological processes occurring in the aeration tanks, are also critically discussed. Finally, modelling issues, which remain unaddressed, (e.g. coupling of the AS tank with secondary clarifier and the use of population balance models to simulate bubbly flow or flocculation of the activated sludge), are also identified and discussed. PMID:26615385
Strategy for the Development of a DNB Local Predictive Approach Based on Neptune CFD Software
International Nuclear Information System (INIS)
The NEPTUNE project constitutes the thermal-hydraulics part of a long-term joint development program for the next generation of nuclear reactor simulation tools. This project is being carried through by EDF (Electricite de France) and CEA (Commissariat a l'Energie Atomique), with the co-sponsorship of IRSN (Institut de Radioprotection et de Surete Nucleaire) and AREVA NP. NEPTUNE is a multi-phase flow software platform that includes advanced physical models and numerical methods for each simulation scale (CFD, component, system). NEPTUNE also provides new multi-scale and multi-disciplinary coupling functionalities. This new generation of two-phase flow simulation tools aims at meeting major industrial needs. DNB (Departure from Nucleate Boiling) prediction in PWRs is one of the high priority needs, and this paper focuses on its anticipated improvement by means of a so-called 'Local Predictive Approach' using the NEPTUNE CFD code. We firstly present the ambitious 'Local Predictive Approach' anticipated for a better prediction of DNB, i.e. an approach that intends to result in CHF correlations based on relevant local parameters as provided by the CFD modeling. The associated requirements for the two-phase flow modeling are underlined as well as those for the good level of performance of the NEPTUNE CFD code; hence, the code validation strategy based on different experimental data base types (including separated effect and integral-type tests data) is depicted. Secondly, we present comparisons between low pressure adiabatic bubbly flow experimental data obtained on the DEDALE experiment and the associated numerical simulation results. This study anew shows the high potential of NEPTUNE CFD code, even if, with respect to the aforementioned DNB-related aim, there is still a need for some modeling improvements involving new validation data obtained in thermal-hydraulics conditions representative of PWR ones. Finally, we deal with one of these new experimental data needs
Investigation of Microclimate by CFD Modeling of Moisture Interactions between Air and Constructions
DEFF Research Database (Denmark)
Mortensen, Lone Hedegaard; Woloszyn, Monika; Rode, Carsten;
2007-01-01
There is a strong demand for accurate moisture modeling since moisture poses a risk for both the constructions and the indoor climate. This investigation has special focus on moisture modeling. The paper describes a new model based on a CFD tool enhanced to include both detailed modeling of...... airflows in rooms and heat and moisture transfer in walls by applying them as fluid walls. In a 3D configuration it is investigated what the impacts are of different boundary conditions and how this influences microclimates in rooms. The studied microclimate is a piece of furniture placed near a cold...
Data-Driven CFD Modeling of Turbulent Flows Through Complex Structures
Wang, Jian-Xun
2016-01-01
The growth of computational resources in the past decades has expanded the application of Computational Fluid Dynamics (CFD) from the traditional fields of aerodynamics and hydrodynamics to a number of new areas. Examples range from the heat and fluid flows in nuclear reactor vessels and in data centers to the turbulence flows through wind turbine farms and coastal vegetation plants. However, in these new applications complex structures are often exist (e.g., rod bundles in reactor vessels and turbines in wind farms), which makes fully resolved, first-principle based CFD modeling prohibitively expensive. This obstacle seriously impairs the predictive capability of CFD models in these applications. On the other hand, a limited amount of measurement data is often available in the systems in the above-mentioned applications. In this work we propose a data-driven, physics-based approach to perform full field inversion on the effects of the complex structures on the flow. This is achieved by assimilating observati...
CFD modelling of subcooled flow boiling for nuclear engineering applications
International Nuclear Information System (INIS)
In this work a general-purpose CFD code CFX-5 was used for simulations of subcooled flow boiling. The subcooled boiling model, available in a custom version of CFX-5, uses a special treatment of the wall boiling boundary, which assures the grid invariant solution. The simulation results have been validated against the published experimental data [1] of high-pressure flow boiling in a vertical pipe covering a wide range of conditions (relevant to the pressurized water reactor). In general, a good agreement with the experimental data has been achieved. To adequately predict the lateral distribution of two-phase flow parameters, the modelling of two-phase flow turbulence and non-drag forces under wall boiling conditions have been also investigated in the paper. (author)
CFD modelling of condensers for freeze-drying processes
Indian Academy of Sciences (India)
Miriam Petitti; Antonello A Barresi; Daniele L Marchisio
2013-12-01
The aim of the present research is the development of a computational tool for investigating condensation processes and equipment with particular attention to freeze-dryers. These condensers in fact are usually operated at very low pressures, making it difficult to experimentally acquire quantitative knowledge of all the variables involved. Mathematical modelling and CFD (Computational Fluid Dynamics) simulations are used here to achieve a better comprehension of the flow dynamics and of the process of ice condensation and deposition in the condenser, in order to evaluate condenser efficiency and gain deeper insights of the process to be used for the improvement of its design. Both a complete laboratory-scale freeze-drying apparatus and an industrial-scale condenser have been investigated in this work, modelling the process of water vapour deposition. Different operating conditions have been considered and the influence exerted by the inert gas as well as other parameters has been investigated.
A CFD Modeling Study for the Design of an Advanced HANARO Reactor Core Structure
Energy Technology Data Exchange (ETDEWEB)
Park, Jong-Hark; Chae, Hee-Teak; Park, Cheol; Kim, Heo-Nil [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2007-07-01
AHR(Advanced HANARO Reactor) based on HANARO has been under a conceptually designed with new ideas to implement new findings, which have been revealed from twelve years operation of HANARO. For example, a perforated structure to reduce the FIV(Flow Induced Vibration) of a fuel assembly has been considered to install. And a change of dual outlets to a single outlet has also been investigated to promote the accessibility and to work easily in the reactor pool. Those investigations have been conducted by the CFD (Computational Fluid Dynamics) method, which can provide us with an good understanding of three dimensional flow fields influenced by design changes without an experiment. In this study a CFD modeling study for an AHR core structure design is described.
A CFD Modeling Study for the Design of an Advanced HANARO Reactor Core Structure
International Nuclear Information System (INIS)
AHR(Advanced HANARO Reactor) based on HANARO has been under a conceptually designed with new ideas to implement new findings, which have been revealed from twelve years operation of HANARO. For example, a perforated structure to reduce the FIV(Flow Induced Vibration) of a fuel assembly has been considered to install. And a change of dual outlets to a single outlet has also been investigated to promote the accessibility and to work easily in the reactor pool. Those investigations have been conducted by the CFD (Computational Fluid Dynamics) method, which can provide us with an good understanding of three dimensional flow fields influenced by design changes without an experiment. In this study a CFD modeling study for an AHR core structure design is described
CFD modeling of a UV-LED photocatalytic odor abatement process in a continuous reactor
International Nuclear Information System (INIS)
Highlights: ► A CFD model is developed for a UV-LED based photocatalytic deodorization reactor. ► Radiation field model and Langmuir–Hinshelwood kinetics are integrated in the model. ► The model can predict the pollutant concentration profile and the reactor performance. ► LED distance is predicted to be a critical parameter in photocatalytic reactor design. - Abstract: This paper presents a model study of a UV light-emitting-diode (UV-LED) based photocatalytic odor abatement process. It integrated computational fluid dynamics (CFD) modeling of the gas flow in the reactor with LED-array radiation field calculation and Langmuir–Hinshelwood reaction kinetics. It was applied to simulate the photocatalytic degradation of dimethyl sulfide (DMS) in a UV-LED reactor based on experimentally determined chemical kinetic parameters. A non-linear power law relating reaction rate to irradiation intensity was adopted. The model could predict the steady state DMS concentration profiles by calculating the advection, diffusion and Langmuir–Hinshelwood reaction kinetics. By affecting the radiation intensity and uniformity, the position of the LED array relative to the catalyst appeared to be a critical parameter determining DMS removal efficiency. Too small distances might yield low quantum efficiency and consequently poor abatement performance. This study provided an example of LED-based photocatalytic process modeling and gave insights into the optimization of light source design for photocatalytic applications.
Model test and CFD calculation of a cavitating bulb turbine
Energy Technology Data Exchange (ETDEWEB)
Necker, J; Aschenbrenner, T, E-mail: joerg.necker@voith.co [Voith Hydro Holding GmbH and Co. KG Alexanderstrasse 11, 89522 Heidenheim (Germany)
2010-08-15
The flow in a horizontal shaft bulb turbine is calculated as a two-phase flow with a commercial Computational Fluid Dynamics (CFD-)-code including cavitation model. The results are compared with experimental results achieved at a closed loop test rig for model turbines. On the model test rig, for a certain operating point (i.e. volume flow, net head, blade angle, guide vane opening) the pressure behind the turbine is lowered (i.e. the Thoma-coefficient {sigma} is lowered) and the efficiency of the turbine is recorded. The measured values can be depicted in a so-called {sigma}-break curve or {eta}- {sigma}-diagram. Usually, the efficiency is independent of the Thoma-coefficient up to a certain value. When lowering the Thoma-coefficient below this value the efficiency will drop rapidly. Visual observations of the different cavitation conditions complete the experiment. In analogy, several calculations are done for different Thoma-coefficients {sigma}and the corresponding hydraulic losses of the runner are evaluated quantitatively. For a low {sigma}-value showing in the experiment significant efficiency loss, the the change of volume flow in the experiment was simulated. Besides, the fraction of water vapour as an indication of the size of the cavitation cavity is analyzed qualitatively. The experimentally and the numerically obtained results are compared and show a good agreement. Especially the drop in efficiency can be calculated with satisfying accuracy. This drop in efficiency is of high practical importance since it is one criterion to determine the admissible cavitation in a bulb-turbine. The visual impression of the cavitation in the CFD-analysis is well in accordance with the observed cavitation bubbles recorded on sketches and/or photographs.
Energy Technology Data Exchange (ETDEWEB)
Corley, Richard A; Minard, Kevin R; Kabilan, Senthil; Einstein, Daniel R; Kuprat, Andrew P; harkema, J R; Kimbell, Julia; Gargas, M L; Kinzell, John H
2009-06-01
The percentages of total airflows over the nasal respiratory and olfactory epithelium of female rabbits were calculated from computational fluid dynamics (CFD) simulations of steady-state inhalation. These airflows calculations, along with nasal airway geometry determinations, are critical parameters for hybrid CFD/physiologically based pharmacokinetic models that describe the nasal dosimetry of water-soluble or reactive gases and vapors in rabbits. CFD simulations were based upon three-dimensional computational meshes derived from magnetic resonance images of three adult female New Zealand White (NZW) rabbits. In the anterior portion of the nose, the maxillary turbinates of rabbits are considerably more complex than comparable regions in rats, mice, monkeys, or humans. This leads to a greater surface area to volume ratio in this region and thus the potential for increased extraction of water soluble or reactive gases and vapors in the anterior portion of the nose compared to many other species. Although there was considerable interanimal variability in the fine structures of the nasal turbinates and airflows in the anterior portions of the nose, there was remarkable consistency between rabbits in the percentage of total inspired airflows that reached the ethmoid turbinate region (~50%) that is presumably lined with olfactory epithelium. These latter results (airflows reaching the ethmoid turbinate region) were higher than previous published estimates for the male F344 rat (19%) and human (7%). These differences in regional airflows can have significant implications in interspecies extrapolations of nasal dosimetry.
Inertisation options for BG method and optimisation using CFD modelling
Institute of Scientific and Technical Information of China (English)
Morla Ramakrishna; Balusu Rao; Tanguturi Krishna; Ting Ren
2015-01-01
Spontaneous combustion (sponcom) is one of the issues of concern with the blasting gallery (BG) method of coal mining and has the potential to cause fires, and impact on production and safety, greenhouse gas (GHG) emissions and huge costs involved in controlling the aftermath situations. Some of the research attempts made to prevent and control coal mine fires and spontaneous combustion in thick seams worked with bord and pillar mining methods are presented in this paper. In the study, computational fluid dynamics (CFD) modelling techniques were used to simulate and assess the effects of various mining methods, layouts, designs, and different operational and ventilation parameters on the flow of goaf gases in BG panels. A wide range of parametric studies were conducted to develop proactive strategies to control and prevent ingress of oxygen into the goaf area preventing spontaneous combustion and mine fires.
On the accuracy of CFD-based pressure drop predictions for right-angle ducts
Brankovic, Andreja
1993-07-01
The predictive capability of computational fluid dynamics (CFD) codes for turbulent flow through curved ducts is of significant importance to the design and performance analysis of modern rocket engine flowpaths. Code calibration and validation studies for this class of flow are desireable to estimate the performance margin and operating range of components designed using Navier-Stokes methods. Parametric experimental studies such as that of Weske (NACA ARR W-39) provided a wealth of performance data for the design of single- and compound elbow configurations with various cross-sections, curvature and aspect ratios at varying Reynolds numbers. In that work, the majority of data is presented in the form of loss coefficients, characterizing pressure losses due to duct curvature, and including losses due to wall friction. Using measured friction coefficients, losses of equivalent straight lengths of duct are subtracted, resulting in performance curves useful for design computations. These data are currently used in a CFD-based parametric study covering a broad range of operating conditions. Of particular interest for the accuracy of CFD predictions are the effects on pressure loss due to inlet boundary layer thickness (dependent on upstream development length), and the wall treatment for the turbulence equations (conventional wall functions vs. wall integration using a two-layer model). The experimental data are reassessed in the form of an error analysis, and are compared with CFD predictions for 18 computational cases. Grid-independence, grid spacing, and convergence requirements of the cases are discussed. Conclusions regarding the relative importance of the parametric variables will be presented.
CFD modeling and experience of waste-to-energy plant burning waste wood
DEFF Research Database (Denmark)
Rajh, B.; Yin, Chungen; Samec, N.;
2013-01-01
Computational Fluid Dynamics (CFD) is being increasingly used in industry for in-depth understanding of the fundamental mixing, combustion, heat transfer and pollutant formation in combustion processes and for design and optimization of Waste-to-Energy (WtE) plants. In this paper, CFD modeling...... of waste wood combustion in a 13 MW grate-fired boiler in a WtE plant is presented. As a validation effort, the temperature profiles at a number of ports in the furnace are measured and the experimental results are compared with the CFD predictions. In the simulation, a 1D model is developed to simulate...... the conversion of the waste wood in the fuel bed on the grate, which provides the appropriate inlet boundary condition for the freeboard 3D CFD simulation. The CFD analysis reveals the detailed mixing and combustion characteristics in the waste wood-fired furnace, pinpointing how to improve the design...
A coupled DEM-CFD method for impulse wave modelling
Zhao, Tao; Utili, Stefano; Crosta, GiovanBattista
2015-04-01
Rockslides can be characterized by a rapid evolution, up to a possible transition into a rock avalanche, which can be associated with an almost instantaneous collapse and spreading. Different examples are available in the literature, but the Vajont rockslide is quite unique for its morphological and geological characteristics, as well as for the type of evolution and the availability of long term monitoring data. This study advocates the use of a DEM-CFD framework for the modelling of the generation of hydrodynamic waves due to the impact of a rapid moving rockslide or rock-debris avalanche. 3D DEM analyses in plane strain by a coupled DEM-CFD code were performed to simulate the rockslide from its onset to the impact with still water and the subsequent wave generation (Zhao et al., 2014). The physical response predicted is in broad agreement with the available observations. The numerical results are compared to those published in the literature and especially to Crosta et al. (2014). According to our results, the maximum computed run up amounts to ca. 120 m and 170 m for the eastern and western lobe cross sections, respectively. These values are reasonably similar to those recorded during the event (i.e. ca. 130 m and 190 m respectively). In these simulations, the slope mass is considered permeable, such that the toe region of the slope can move submerged in the reservoir and the impulse water wave can also flow back into the slope mass. However, the upscaling of the grains size in the DEM model leads to an unrealistically high hydraulic conductivity of the model, such that only a small amount of water is splashed onto the northern bank of the Vajont valley. The use of high fluid viscosity and coarse grain model has shown the possibility to model more realistically both the slope and wave motions. However, more detailed slope and fluid properties, and the need for computational efficiency should be considered in future research work. This aspect has also been
A CFD Approach to Modeling Spacecraft Fuel Slosh
Marsell, Brandon; Gangadharan, Sathya; Chatman, Yadira; Sudermann, James; Schlee, Keith; Ristow, James E.
2009-01-01
Energy dissipation and resonant coupling from sloshing fuel in spacecraft fuel tanks is a problem that occurs in the design of many spacecraft. In the case of a spin stabilized spacecraft, this energy dissipation can cause a growth in the spacecrafts' nutation (wobble) that may lead to disastrous consequences for the mission. Even in non-spinning spacecraft, coupling between the spacecraft or upper stage flight control system and an unanticipated slosh resonance can result in catastrophe. By using a Computational Fluid Dynamics (CFD) solver such as Fluent, a model for this fuel slosh can be created. The accuracy of the model must be tested by comparing its results to an experimental test case. Such a model will allow for the variation of many different parameters such as fluid viscosity and gravitational field, yielding a deeper understanding of spacecraft slosh dynamics. In order to gain a better understanding of the dynamics behind sloshing fluids, the Launch Services Program (LSP) at the NASA Kennedy Space Center (KSC) is interested in finding ways to better model this behavior. Thanks to past research, a state-of-the-art fuel slosh research facility was designed and fabricated at Embry Riddle Aeronautical University (ERAU). This test facility has produced interesting results and a fairly reliable parameter estimation process to predict the necessary values that accurately characterize a mechanical pendulum analog model. The current study at ERAU uses a different approach to model the free surface sloshing of liquid in a spherical tank using Computational Fluid Dynamics (CFD) methods. Using a software package called Fluent, a model was created to simulate the sloshing motion of the propellant. This finite volume program uses a technique called the Volume of Fluid (VOF) method to model the interaction between two fluids [4]. For the case of free surface slosh, the two fluids are the propellant and air. As the fuel sloshes around in the tank, it naturally
Development of a Cartesian grid based CFD solver (CARBS)
International Nuclear Information System (INIS)
Formulation for 3D transient incompressible CFD solver is developed. The solution of variable property, laminar/turbulent, steady/unsteady, single/multi specie, incompressible with heat transfer in complex geometry will be obtained. The formulation can handle a flow system in which any number of arbitrarily shaped solid and fluid regions are present. The solver is based on the use of Cartesian grids. A method is proposed to handle complex shaped objects and boundaries on Cartesian grids. Implementation of multi-material, different types of boundary conditions, thermo physical properties is also considered. The proposed method is validated by solving two test cases. 1st test case is that of lid driven flow in inclined cavity. 2nd test case is the flow over cylinder. The 1st test case involved steady internal flow subjected to WALL boundaries. The 2nd test case involved unsteady external flow subjected to INLET, OUTLET and FREE-SLIP boundary types. In both the test cases, non-orthogonal geometry was involved. It was found that, under such a wide conditions, the Cartesian grid based code was found to give results which were matching well with benchmark data. Convergence characteristics are excellent. In all cases, the mass residue was converged to 1E-8. Based on this, development of 3D general purpose code based on the proposed approach can be taken up. (author)
A quantitative CFD benchmark for Sodium Fast Reactor fuel assembly modeling
International Nuclear Information System (INIS)
Highlights: • A CFD model is benchmarked against the ORNL 19-pin Sodium Test assembly. • Sensitivity was tested for cell size, turbulence model, and wire contact model. • The CFD model was found to be appropriately representing the experiment. • CFD was then used as a predictive tool to help understand experimental uncertainty. • Comparison to subchannel results were carried out as well. - Abstract: This paper details a CFD model of a 19-pin wire-wrapped sodium fuel assembly experiment conducted at Oak Ridge National Laboratory in the 1970s. Model sensitivities were tested for cell size, turbulence closure, wire-wrap contact, inlet geometry, outlet geometry, and conjugate heat transfer. The final model was compared to the experimental results quantitatively to establish confidence in the approach. The results were also compared to the sub-channel analysis code COBRA-IV-I-MIT. Experiment and CFD computations were consistent inside the bundle. Comparison between experimental temperature measurements from thermocouples embedded in the heated length of the bundle are consistently reproducible with CFD code predictions across a wide range of operating conditions. The demonstrated agreement provides confidence in the predictive capabilities of the approach. However significant discrepancy between the CFD code predictions and the experimental data was found at the bundle outlet. Further sensitivity studies are presented to support the conclusion that this discrepancy is caused by significant uncertainty associated with the experimental data reported for the bundle outlet
Development and validation of a CFD model predicting the backfill process of a nuclear waste gallery
Energy Technology Data Exchange (ETDEWEB)
Gopala, Vinay Ramohalli, E-mail: gopala@nrg.eu [Nuclear Research and consultancy Group (NRG), P.O. Box 25, 1755 ZG Petten (Netherlands); Lycklama a Nijeholt, Jan-Aiso [Nuclear Research and consultancy Group (NRG), P.O. Box 25, 1755 ZG Petten (Netherlands); Bakker, Paul [Van Hattum en Blankevoort, Woerden (Netherlands); Haverkate, Benno [Nuclear Research and consultancy Group (NRG), P.O. Box 25, 1755 ZG Petten (Netherlands)
2011-07-15
Research highlights: > This work presents the CFD simulation of the backfill process of Supercontainers with nuclear waste emplaced in a disposal gallery. > The cement-based material used for backfill is grout and the flow of grout is modelled as a Bingham fluid. > The model is verified against an analytical solution and validated against the flowability tests for concrete. > Comparison between backfill plexiglas experiment and simulation shows a distinct difference in the filling pattern. > The numerical model needs to be further developed to include segregation effects and thixotropic behavior of grout. - Abstract: Nuclear waste material may be stored in underground tunnels for long term storage. The example treated in this article is based on the current Belgian disposal concept for High-Level Waste (HLW), in which the nuclear waste material is packed in concrete shielded packages, called Supercontainers, which are inserted into these tunnels. After placement of the packages in the underground tunnels, the remaining voids between the packages and the tunnel lining is filled-up with a cement-based material called grout in order to encase the stored containers into the underground spacing. This encasement of the stored containers inside the tunnels is known as the backfill process. A good backfill process is necessary to stabilize the waste gallery against ground settlements. A numerical model to simulate the backfill process can help to improve and optimize the process by ensuring a homogeneous filling with no air voids and also optimization of the injection positions to achieve a homogeneous filling. The objective of the present work is to develop such a numerical code that can predict the backfill process well and validate the model against the available experiments and analytical solutions. In the present work the rheology of Grout is modelled as a Bingham fluid which is implemented in OpenFOAM - a finite volume-based open source computational fluid dynamics
Development and validation of a CFD model predicting the backfill process of a nuclear waste gallery
International Nuclear Information System (INIS)
Research highlights: → This work presents the CFD simulation of the backfill process of Supercontainers with nuclear waste emplaced in a disposal gallery. → The cement-based material used for backfill is grout and the flow of grout is modelled as a Bingham fluid. → The model is verified against an analytical solution and validated against the flowability tests for concrete. → Comparison between backfill plexiglas experiment and simulation shows a distinct difference in the filling pattern. → The numerical model needs to be further developed to include segregation effects and thixotropic behavior of grout. - Abstract: Nuclear waste material may be stored in underground tunnels for long term storage. The example treated in this article is based on the current Belgian disposal concept for High-Level Waste (HLW), in which the nuclear waste material is packed in concrete shielded packages, called Supercontainers, which are inserted into these tunnels. After placement of the packages in the underground tunnels, the remaining voids between the packages and the tunnel lining is filled-up with a cement-based material called grout in order to encase the stored containers into the underground spacing. This encasement of the stored containers inside the tunnels is known as the backfill process. A good backfill process is necessary to stabilize the waste gallery against ground settlements. A numerical model to simulate the backfill process can help to improve and optimize the process by ensuring a homogeneous filling with no air voids and also optimization of the injection positions to achieve a homogeneous filling. The objective of the present work is to develop such a numerical code that can predict the backfill process well and validate the model against the available experiments and analytical solutions. In the present work the rheology of Grout is modelled as a Bingham fluid which is implemented in OpenFOAM - a finite volume-based open source computational fluid
Optimization the design of venturi gas mixer for syngas engine using three-dimensional CFD modeling
International Nuclear Information System (INIS)
A venturi mixer prototype is developed for mixing air and synthesis gas or 'syngas' as a fuel. Syngas is recognized as a viable energy source worldwide, particularly for stationary power generation. It has a very low energy density, so a mixer with λ (ratio of actual to stoichiometric air-fuel ratio) in the range of 1.1 to 1.7 is expected. In this study, three-dimensional computational fluid dynamics (CFD) modeling is used to investigate and analyze the influence of the throat diameter, gas chamber thickness and gas exits diameter on mixer characteristics and performance. Attention is focused on the effect of venturi mixer geometry on the air-fuel ratio, pressure loss and mixing quality. Based on the numerical results, an optimized design of venturi gas mixer is made. The optimized design has λ in the range of 1.2 to 1.3, and gives very good mixing quality and acceptable pressure loss. The CFD results are validated with experimental data. The CFD results show good agreement with experimental data
Simulation of a MW rotor equipped with vortex generators using CFD and an actuator shape model
DEFF Research Database (Denmark)
Troldborg, Niels; Zahle, Frederik; Sørensen, Niels N.
2015-01-01
This article presents a comparison of CFD simulations of the DTU 10 MW reference wind turbine with and without vortex generators installed on the inboard part of the blades. The vortex generators are modelled by introducing body forces determined using a modified version of the so-called BAY model....... The vortex generator model is validated by applying it for modelling an array of VGs on an airfoil section compared to both wind tunnel measurements and fully gridded CFD....
CFD-based Analysis of Aeroelastic behavior of Supersonic Fins
Directory of Open Access Journals (Sweden)
Tianxing Cai
2011-02-01
Full Text Available The main goal of this paper is to analyze the flutter boundary, transient loads of a supersonic fin, and the flutter with perturbation. Reduced order mode (ROM based on Volterra Series is presented to calculate the flutter boundary, and CFD/CSD coupling is used to compute the transient aerodynamic load. The Volterra-based ROM is obtained using the derivative of unsteady aerodynamic step-response, and the infinite plate spline is used to perform interpolation of physical quantities between the fluid and the structural grids. The results show that inertia force plays a significant role in the transient loads, the moment cause by inertia force is lager than the aerodynamic force, because of the huge transient loads, structure may be broken by aeroelasticity below the flutter dynamic pressure. Perturbations of aircraft affect the aeroelastic response evident, the reduction of flutter dynamic pressure by rolling perturbation form 15.4% to 18.6% when Mach from 2.0 to 3.0. It is necessary to analyze the aeroelasticity behaviors under the compositive force environment.
DEFF Research Database (Denmark)
Andersen, Morten Q.; Mortensen, Kasper; Nielsen, Daniel E.;
2009-01-01
This paper describes a proposed CFD model to simulate the wind conditions on a forested site. The model introduces porous subdomains representing the forests in the terrain. Obtained simulation values are compared to field measurements in- and outside a forest. Initial results are very promising...
CFD Modeling of Free-Piston Stirling Engines
Ibrahim, Mounir B.; Zhang, Zhi-Guo; Tew, Roy C., Jr.; Gedeon, David; Simon, Terrence W.
2001-01-01
NASA Glenn Research Center (GRC) is funding Cleveland State University (CSU) to develop a reliable Computational Fluid Dynamics (CFD) code that can predict engine performance with the goal of significant improvements in accuracy when compared to one-dimensional (1-D) design code predictions. The funding also includes conducting code validation experiments at both the University of Minnesota (UMN) and CSU. In this paper a brief description of the work-in-progress is provided in the two areas (CFD and Experiments). Also, previous test results are compared with computational data obtained using (1) a 2-D CFD code obtained from Dr. Georg Scheuerer and further developed at CSU and (2) a multidimensional commercial code CFD-ACE+. The test data and computational results are for (1) a gas spring and (2) a single piston/cylinder with attached annular heat exchanger. The comparisons among the codes are discussed. The paper also discusses plans for conducting code validation experiments at CSU and UMN.
Two-dimensional CFD modeling of wave rotor flow dynamics
Welch, Gerard E.; Chima, Rodrick V.
1993-01-01
A two-dimensional Navier-Stokes solver developed for detailed study of wave rotor flow dynamics is described. The CFD model is helping characterize important loss mechanisms within the wave rotor. The wave rotor stationary ports and the moving rotor passages are resolved on multiple computational grid blocks. The finite-volume form of the thin-layer Navier-Stokes equations with laminar viscosity are integrated in time using a four-stage Runge-Kutta scheme. The Roe approximate Riemann solution scheme or the computationally less expensive Advection Upstream Splitting Method (AUSM) flux-splitting scheme are used to effect upwind-differencing of the inviscid flux terms, using cell interface primitive variables set by MUSCL-type interpolation. The diffusion terms are central-differenced. The solver is validated using a steady shock/laminar boundary layer interaction problem and an unsteady, inviscid wave rotor passage gradual opening problem. A model inlet port/passage charging problem is simulated and key features of the unsteady wave rotor flow field are identified. Lastly, the medium pressure inlet port and high pressure outlet port portion of the NASA Lewis Research Center experimental divider cycle is simulated and computed results are compared with experimental measurements. The model accurately predicts the wave timing within the rotor passage and the distribution of flow variables in the stationary inlet port region.
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...
DEFF Research Database (Denmark)
Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat;
2015-01-01
using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor...... discretization both in 2-D and 1-D was undertaken. Results suggest that the iCFD model developed for the SST through the proposed methodology is able to predict solid distribution with high accuracy – taking a reasonable computational effort – when compared to multi-dimensional numerical experiments, under a...
National Aeronautics and Space Administration — The project will be developing a CFD approach that can handle the additional complexities needed in a NTP testing facility when modeling the combustion processes in...
CFD MODELING ANALYSIS OF MECHANICAL DRAFT COOLING TOWER
Energy Technology Data Exchange (ETDEWEB)
Lee, S; Alfred Garrett, A; James02 Bollinger, J; Larry Koffman, L
2008-03-03
Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has a MDCT consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to conduct a parametric study for cooling tower performance under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model to achieve the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of the modeling calculations was performed to investigate the impact of ambient and operating conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was benchmarked against the literature data and the SRS test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be presented here.
CFD Modeling of LNG Spill: Humidity Effect on Vapor Dispersion
Giannissi, S. G.; Venetsanos, A. G.; Markatos, N.
2015-09-01
The risks entailed by an accidental spill of Liquefied Natural Gas (LNG) should be indentified and evaluated, in order to design measures for prevention and mitigation in LNG terminals. For this purpose, simulations are considered a useful tool to study LNG spills and to understand the mechanisms that influence the vapor dispersion. In the present study, the ADREA-HF CFD code is employed to simulate the TEEX1 experiment. The experiment was carried out at the Brayton Fire Training Field, which is affiliated with the Texas A&M University system and involves LNG release and dispersion over water surface in open- obstructed environment. In the simulation the source was modeled as a two-phase jet enabling the prediction of both the vapor dispersion and the liquid pool spreading. The conservation equations for the mixture are solved along with the mass fraction for natural gas. Due to the low prevailing temperatures during the spill ambient humidity condenses and this might affect the vapor dispersion. This effect was examined in this work by solving an additional conservation equation for the water mass fraction. Two different models were tested: the hydrodynamic equilibrium model which assumes kinetic equilibrium between the phases and the non hydrodynamic equilibrium model, in order to assess the effect of slip velocity on the prediction. The slip velocity is defined as the difference between the liquid phase and the vapor phase and is calculated using the algebraic slip model. Constant droplet diameter of three different sizes and a lognormal distribution of the droplet diameter were applied and the results are discussed and compared with the measurements.
Gott, Kevin
This research endeavors to better understand the physical vapor deposition (PVD) vapor transport process by determining the most appropriate fluidic model to design PVD coating manufacturing. An initial analysis was completed based on the calculation of Knudsen number from titanium vapor properties. The results show a dense Navier-Stokes solver best describes flow near the evaporative source, but the material properties suggest expansion into the chamber may result in a strong drop in density and a rarefied flow close to the substrate. A hybrid CFD-DSMC solver is constructed in OpenFOAM for rapidly rarefying flow fields such as PVD vapor transport. The models are patched together combined using a new patching methodology designed to take advantage of the one-way motion of vapor from the CFD region to the DSMC region. Particles do not return to the dense CFD region, therefore the temperature and velocity can be solved independently in each domain. This novel technique allows a hybrid method to be applied to rapidly rarefying PVD flow fields in a stable manner. Parameter studies are performed on a CFD, Navier-Stokes continuum based compressible solver, a Direct Simulation Monte Carlo (DSMC) rarefied particle solver, a collisionless free molecular solver and the hybrid CFD-DSMC solver. The radial momentum at the inlet and radial diffusion characteristics in the flow field are shown to be the most important to achieve an accurate deposition profile. The hybrid model also shows sensitivity to the shape of the CFD region and rarefied regions shows sensitivity to the Knudsen number. The models are also compared to each other and appropriate experimental data to determine which model is most likely to accurately describe PVD coating deposition processes. The Navier-Stokes solvers are expected to yield backflow across the majority of realistic inlet conditions, making their physics unrealistic for PVD flow fields. A DSMC with improved collision model may yield an accurate
CFD MODEL OF THE CNG DIRECT INJECTION ENGINE
Directory of Open Access Journals (Sweden)
Zbigniew Czyż
2014-09-01
Full Text Available The paper presents CFD analysis of fuel flow in the CNG injector. The issues such a pressure drop along an injector channel, mass flow through the key sections of the injector geometry, flow rates, the impact of the needle shape on the deflection of the sprayed gas cone and the impact of the wall head are analyzed in the article. The simulation was made in the transient states conditions for full injection process, including the opening and closing of the injector. An injection time of 6 ms, velocity of 0.33 mm/ms and a lift of 0.5 mm were selected for opening and closing of injector based on experimental test. The simulation shows that the volume inside the injector is a kind of fuel accumulator, and the opening process of the needle influence the flow parameters in an inlet cross-section after a certain time, depending on a channel cross section. The calculations allowed to select the ratio of an injector duct cross sectional area to the aperture area of the injection capable of the reducing pressure loss. The unusual location of the injector in the socket of a glow plug in the Andoria ADCR engine makes a stream be impaired by a part of the head. This research result would be useful in developing an injector construction which will be used for an investigation of CNG addition into diesel engine.
Indoor/outdoor climate design by CFD based on the Software Platform
International Nuclear Information System (INIS)
The difficulties in CFD analysis of indoor/outdoor environments is described in this paper and new techniques in CFD for overcoming these difficulties are developed. A 'Software Platform' is proposed that integrates various numerical analysis tools and that is able to give a complete evaluation of indoor/outdoor climates. A number of case studies on designing indoor/outdoor climates are reported based on this newly developed Software Platform
Simulation and Scale-up of Barium Sulphate Precipitation Process Using CFD Modeling
Institute of Scientific and Technical Information of China (English)
龚俊波; 卫宏远; 王静康; JohnGarsideb
2005-01-01
Some empirical mixing models were used to describe the imperfect mixing in precipitation process.However, the models can not, in general, reflect the details of interactions between mixing and crystallization in a vessel. In this study, CFD (computational fluid dynamics) technique were developed by simulating the precipitation of barium sulphate in stirred tanks by integration of population balance equations with a CFD solver. Two typical impellers, Rushton and pitched blade turbines, were employed for agitation. The influence of feed concentration and position on crystal product properties was investigated by CFD simulation. The scale-up of these precipitators was systematically studied. Significant effect on the crystal properties was found for the scale-up under some conditions.Keywords simulation, scale up, precipitation, CFD(computational fluid dynamics)
DEFF Research Database (Denmark)
Rong, Li; Nielsen, Peter Vilhelm; Bjerg, Bjarne;
2016-01-01
scale pig barns was simulated to show the procedures of validating a CFD simulation in livestock buildings. After summarizing the guideline and/or best practice for CFD modeling, the authors addressed the issues related to numerical methods and the governing equations, which were limited to RANS models......, simulating domain etc. This information is particularly important for the readers to evaluate the quality of the CFD simulation results.......Computational Fluid Dynamics (CFD) is increasingly used to study airflow around and in livestock buildings, to develop technologies to mitigate emissions and to predict the contaminant dispersion from livestock buildings. In this paper, an example of air flow distribution in a room with two full...
A CFD Model for High Pressure Liquid Poison Injection for CANDU-6 Shutdown System No. 2
International Nuclear Information System (INIS)
In CANDU reactor one of the two reactor shutdown systems is the liquid poison injection system which injects the highly pressurized liquid neutron poison into the moderator tank via small holes on the nozzle pipes. To ensure the safe shutdown of a reactor it is necessary for the poison curtains generated by jets provide quick, and enough negative reactivity to the reactor during the early stage of the accident. In order to produce the neutron cross section necessary to perform this work, the poison concentration distribution during the transient is necessary. In this study, a set of models for analyzing the transient poison concentration induced by this high pressure poison injection jet activated upon the reactor trip in a CANDU-6 reactor moderator tank has been developed and used to generate the poison concentration distribution of the poison curtains induced by the high pressure jets injected into the vacant region between the pressure tube banks. The poison injection rate through the jet holes drilled on the nozzle pipes is obtained by a 1-D transient hydrodynamic code called, ALITRIG, and this injection rate is used to provide the inlet boundary condition to a 3-D CFD model of the moderator tank based on CFX4.3, a CFD code, to simulate the formation of the poison jet curtain inside the moderator tank. For validation, an attempt was made to validate this model against a poison injection experiment performed at BARC. As conclusion this set of models is judged to be appropriate. (authors)
Wind Turbine Rotor Simulation via CFD Based Actuator Disc Technique Compared to Detailed Measurement
Directory of Open Access Journals (Sweden)
Esmail Mahmoodi
2015-10-01
Full Text Available In this paper, a generalized Actuator Disc (AD is used to model the wind turbine rotor of the MEXICO experiment, a collaborative European wind turbine project. The AD model as a combination of CFD technique and User Defined Functions codes (UDF, so-called UDF/AD model is used to simulate loads and performance of the rotor in three different wind speed tests. Distributed force on the blade, thrust and power production of the rotor as important designing parameters of wind turbine rotors are focused to model. A developed Blade Element Momentum (BEM theory as a code based numerical technique as well as a full rotor simulation both from the literature are included into the results to compare and discuss. The output of all techniques is compared to detailed measurements for validation, which led us to final conclusions.
Evaluation of gas radiation models in CFD modeling of oxy-combustion
International Nuclear Information System (INIS)
Highlights: • CFD modeling of a typical industrial water tube boiler is conducted. • Different combustion processes were considered including air and oxy-fuel combustion. • SGG, EWBM, Leckner, Perry and WSGG radiation models were considered in the study. • EWBM is the most accurate model and it’s considered to be the benchmark model. • Characteristics of oxy-fuel combustion are compared to those of air–fuel combustion. - Abstract: Proper determination of the radiation energy is very important for proper predictions of the combustion characteristics inside combustion devices using CFD modeling. For this purpose, different gas radiation models were developed and applied in the present work. These radiation models vary in their accuracy and complexity according to the application. In this work, a CFD model for a typical industrial water tube boiler was developed, considering three different combustion environments. The combustion environments are air–fuel combustion (21% O2 and 79% N2), oxy-fuel combustion (21% O2 and 79% CO2) and oxy-fuel combustion (27% O2 and 73% CO2). Simple grey gas (SGG), exponential wide band model (EWBM), Leckner, Perry and weighted sum of grey gases (WSGG) radiation models were examined and their influences on the combustion characteristics were evaluated. Among those radiation models, the EWBM was found to provide close results to the experimental data for the present boiler combustion application. The oxy-fuel combustion characteristics were analyzed and compared with those of air–fuel combustion
Calibration of the k- ɛ model constants for use in CFD applications
Glover, Nina; Guillias, Serge; Malki-Epshtein, Liora
2011-11-01
The k- ɛ turbulence model is a popular choice in CFD modelling due to its robust nature and the fact that it has been well validated. However it has been noted in previous research that the k- ɛ model has problems predicting flow separation as well as unconfined and transient flows. The model contains five empirical model constants whose values were found through data fitting for a wide range of flows (Launder 1972) but ad-hoc adjustments are often made to these values depending on the situation being modeled. Here we use the example of flow within a regular street canyon to perform a Bayesian calibration of the model constants against wind tunnel data. This allows us to assess the sensitivity of the CFD model to changes in these constants, find the most suitable values for the constants as well as quantifying the uncertainty related to the constants and the CFD model as a whole.
CFD modeling of the HTR reactor cavity cooling system
International Nuclear Information System (INIS)
This report describes the heat transport under accident conditions from the reactor vessel wall of the INCOGEN installation to the environment. For this purpose, the heat transfer mechanisms as well as the flow patterns inside the cavity and the Reactor Cavity Cooling System (RCCS) have been calculated by the CFD (Computational Fluid Dynamics) code called CFDS-FLOW3D. The main purpose of the calculations is to determine the vessel wall temperature at which the power produced in the vessel is removed. An important assumption of the calculations is that a total of 1 MW of decay power and fission power has to be removed by the RCCS under accident conditions. In the reference calculation, about 80% of the heat is transported by radiation to the RCCS, while the remaining 20% is transported by convection of the gas in the cavity. The maximum calculated temperature on the outside of the vessel in 634 K. The reference calculation is assessed by a number of sensitivity calculations. In these calculations, the influence of the following parameters on the reactor vessel wall temperature has been determined: The turbulence model, the properties of the inlet and the outlet structures, the heat loss from the reactor vessel wall, the emissivity of structures, and the interaction between gas and radiation. Most of the parameters investigated have a small influence on the reactor vessel wall temperature. The following changes result in an increase of the reactor vessel wall temperature by 25 K or more: An increase of the heat loss from 1 MW to 2 MW, an increase of the inlet temperature from 300 K to 350 K, a decrease of the emissivity of the reactor vessel wall from 0.8 to 0.6, or very high concentrations of scattering aerosol particles. (orig.)
Modeling chemical reactions in the indoor environment by CFD
DEFF Research Database (Denmark)
Sørensen, Dan Nørtoft; Weschler, Charles J.
2002-01-01
The concentrations of ozone and a terpene that react in the gas-phase to produce a hypothetical product were investigated by computational fluid dynamics (CFD) for two different air exchange rates. Ozone entered the room with the ventilation air. The terpenes were introduced as a localized source...
Directory of Open Access Journals (Sweden)
Vítek Oldřich
2016-06-01
Full Text Available The paper deals with CCV knowledge transfer from reference data (either experiments or 3-D CFD data into system simulation SW tools (based on 0-D/1-D CFD. It was verified that CCV phenomenon can be modeled by means of combustion model perturbations. The proposed methodology consists of two major steps. First, individual cycle data have to be matched with the 0-D/1-D model, i.e., combustion model parameters are varied to achieve the best possible match of in-cylinder pressure traces. Second, the combustion model parameters (obtained in previous step are statistically evaluated to obtain PDFs and cross-correlations. Then such information is imposed to the 0-D/1-D tool to mimic pressure traces CCV. Good correspondence with the reference data is achieved only if both PDFs and cross-correlations are imposed simultaneously.
CFD modelling of an industrial air diffuser - predicting velocity and temperature in the near zone
Energy Technology Data Exchange (ETDEWEB)
Einberg, G.; Holmberg, S. [Royal Institute of Technology, Haninge (Sweden). Department of Constructional Engineering and Design; Hagstroem, K.; Mustakallio, P. [Halton OY, Kausala (Finland); Koskela, H. [Finnish Institute of Occupational Health, Turku (Finland)
2005-05-15
This article describes experimental and modelling results from CFD simulation of an air diffuser for industrial spaces. The main objective of this paper is to validate a manufacturer model of the diffuser. In the air diffuser, the low velocity part is placed on top of a multi-cone diffuser in order to increase airflow rates and maximize the cooling capacity of a single diffuser unit. This kind of configuration should ensure appropriate performance of industrial air diffusers, which is discussed briefly at the end of the article. The paper illustrates the importance of a simulation model jointly with the manufacturer's product model and the grid layout near the ventilation device to achieve accurate results. Parameters for diffuser modelling were adapted from literature and manufacturer's product data. Correct specification of diffuser geometry and numerical boundary conditions for CFD simulations are critical for prediction. The standard {kappa}-{epsilon} model was chosen to model turbulence because it represents the best-known model utilized and validated for air diffuser performance. CFD simulations were compared systematically with data from laboratory measurements; air velocity was measured by ultrasonic sensors. Results show that CFD simulation with a standard {kappa}-{epsilon} model accurately predicts non-isothermal airflow around the diffuser. Additionally, smoke tests revealed that the flow around the diffuser is not completely symmetrical as predicted by CFD. The cause of the observed asymmetry was not identified. This was the main reason why some simulation results deviate from the measured values. (author)
From Detailed Description of Chemical Reacting Carbon Particles to Subgrid Models for CFD
Directory of Open Access Journals (Sweden)
Schulze S.
2013-04-01
Full Text Available This work is devoted to the development and validation of a sub-model for the partial oxidation of a spherical char particle moving in an air/steam atmosphere. The particle diameter is 2 mm. The coal particle is represented by moisture- and ash-free nonporous carbon while the coal rank is implemented using semi-global reaction rate expressions taken from the literature. The submodel includes six gaseous chemical species (O2, CO2, CO, H2O, H2, N2. Three heterogeneous reactions are employed, along with two homogeneous semi-global reactions, namely carbon monoxide oxidation and the water-gas-shift reaction. The distinguishing feature of the subgrid model is that it takes into account the influence of homogeneous reactions on integral characteristics such as carbon combustion rates and particle temperature. The sub-model was validated by comparing its results with a comprehensive CFD-based model resolving the issues of bulk flow and boundary layer around the particle. In this model, the Navier-Stokes equations coupled with the energy and species conservation equations were used to solve the problem by means of the pseudo-steady state approach. At the surface of the particle, the balance of mass, energy and species concentration was applied including the effect of the Stefan flow and heat loss due to radiation at the surface of the particle. Good agreement was achieved between the sub-model and the CFD-based model. Additionally, the CFD-based model was verified against experimental data published in the literature (Makino et al. (2003 Combust. Flame 132, 743-753. Good agreement was achieved between numerically predicted and experimentally obtained data for input conditions corresponding to the kinetically controlled regime. The maximal discrepancy (10% between the experiments and the numerical results was observed in the diffusion-controlled regime. Finally, we discuss the influence of the Reynolds number, the ambient O2 mass fraction and the ambient
CFD modeling of a spouted bed with a porous draft tube
Institute of Scientific and Technical Information of China (English)
Salar Azizi; Seyyed Hossein Hosseini; M. Moraveji; Goodarz Ahmadi
2010-01-01
Spouted bed with a porous draft tube is used for drying of grains and chemical products and thermal disinfestations process. This work provides a computational fluid dynamics (CFD) simulation of binary mixtures of glass particles in a spouted bed with a porous draft tube. The simulation used the multi-fluid Eulerian-Eulerian approach based on kinetic theory of granular flows, incorporating a kinetic-frictional constitutive model for dense assemblies of particulate solids and Gidaspow's drag model for the inter-action between gas and particles. Influences of solids mass fraction and inlet gas flow rate on pressure distribution, gas and particle velocities were studied. The modeling results were compared with the exper-imental work of Ishikura, Nagashima, and lde (2003) for the flow condition along the axis of the spouted bed. Good agreement between the modeling results and experimental data was observed.
A 2.5D Single Passage CFD Model for Centrifugal Pumps
Nakamura S.; Ding, W.; Yano, K.
1998-01-01
This paper describes the single passage model based on CFD to analyze the flow in blade passages of a centrifugal pump. The model consists of the flow passage between two impeller blades and the spaces in the inlet eye as well as in the volute. The incompressible Navier-Stokes equations in the conservation form are solved by a finite difference method. The code is designed to investigate the velocity and pressure distributions and intended to investigate how the pump design affects fluid flow through the rotor as well as the pump performance. An early part of the paper investigates the behavior of the model as well as validity of the assumptions made in the model. Then, applications to a rotodynamic heart pump are presented.
Investigation of furnace processes in power steam generators based on CFD simulation tools
Energy Technology Data Exchange (ETDEWEB)
Risto V. Filkoski; Ilija J. Petrovski [University ' Sts. Cyril & Metodius' , Skopje (Macedonia)
2004-07-01
This article presents the overall frame and principal steps in the numerical modelling of combustion chamber of pulverised coal-fired power boiler OB-380, with tangential disposition of the burners. Commercial CFD software is utilised for creation of a three dimensional model of the boiler furnace, including the platen superheater installed in the upper part of the furnace. The methodology used to perform numerical modelling is briefly described. A standard steady semi-empirical {kappa}-{epsilon} model is employed for description of the turbulent flow. The coupling of velocity and pressure is achieved by the SIMPLE method. Coal combustion is modelled by the mixture fraction/PDF approach for the reaction chemistry, with equilibrium assumption applied for description of the system chemistry. Radiation heat transfer is computed by means of the simplified P-N model, based on the expansion of the radiation intensity into an orthogonal series of spherical harmonics. Some distinctive results concerning the examined boiler performance are presented graphically. On a basis of comparison between the simulation predictions and available site measurements on temperature and heat flux in the furnace, a conclusion can be drawn that the model produces realistic insight into the furnace processes. Qualitative agreement indicates reasonability of the calculations and validates the employed sub-models. The described test case and other experiences with CFD stress the advantages over a purely field data study, such as the ability to quickly and cheaply analyse a variety of design options without actually modifying the object and the availability of significantly more data to interpret the results. 22 refs., 9 figs., 5 tabs.
Indoor radon level and dispersion study due to different type of building materials using CFD model
International Nuclear Information System (INIS)
Indoor radon is known for the contributing factor to natural radiation exposure to mankind. Radon progeny gets deposited into the lungs and increase the probability of lung cancer. The underneath soil is the main source of indoor radon. There are several pathways by which radon can migrate from the soil to indoor environment which can accumulate into the less ventilated room or dwellings. The diffusing barriers for radon entry from soil and indoor environment interface depends upon the type of building martial used for the flooring purpose. For this purpose the radon exhalation rates from different type of flooring was taken from the literature. The floors made of soil, marble, concrete and granite are main types of floors which are studied during the present work. The values of radon exhalation rate corresponding to the different type building material used for the construction of floor are used as the input parameter in CFD based model to study out the radon levels and dispersion pattern in less ventilated room. It has been found that CFD modeling is a good method to estimate the radon behavior under different situations. The indoor radon levels are found to be high for the mud flooring compare to other type of flooring. The visualization of indoor radon gas is also different for the different types of building materials. (author)
International Nuclear Information System (INIS)
Highlights: • CFD is used to model triangular-pitch rod bundle. • The Reynolds stress model with different pressure–strain models is used in this investigation. • Predicting the secondary flow characteristics and made comparisons with measured data. • Predicting the position of vortex center and the distribution of normal stresses. • The distribution trends of normal stresses have good agreements. - Abstract: With the dramatic progress in the computer processing power, computational fluid dynamics (CFD) methodology can be applied in investigating the detailed knowledge of thermal–hydraulic characteristics in the rod bundles. These localized information, including flow, turbulence, and heat transfer characteristics, can assist in the design and the improvement of rod bundles for nuclear power plants. In this paper, a three-dimensional (3-D) CFD model with the Reynolds stresses turbulence model is proposed simulating the flowing characteristics within the rod bundles and subsequently to investigate the effects of different mesh distributions and pressure–strain models on the turbulent mixing. Based on the CFD simulations, the secondary flow can be reasonably captured in the rod bundle. However, different pressure–strain models would affect the distributions of normal stresses and lead to be non-uniform distribution for using Linear Pressure–Strain (LPS) model. In addition, the predicted results with RSM–LPS model would be larger than that using other models for axial velocity and normal stresses. The main reason is the wall-reflection effect added on RSM–LPS model. The wall-reflection effect also would affect the position of the vortex center. The predicted position with the Quadratic Pressure–Strain (QPS) model has good agreement compared with the experiments
Microtomography-based CFD analysis of transport in open-cell aluminum metal foams
International Nuclear Information System (INIS)
Nowadays, the need for developing more effective heat exchange technologies and innovative materials, capable of increasing performances while keeping power consumption, size and cost at reasonable levels, is well recognized. Under this perspective, metal foams have a great potential for enhancing the thermal efficiency of heat transfer devices, while allowing for the use of smaller and lighter equipments. However, for practical applications, it is necessary to compromise between the augmented heat transfer rate and the increased pressure drop induced by the tortuous flow passages. For design purposes, the estimation of the flow permeability and the thermal conductivity of the foam is fundamental, but far from simple. From this perspective, besides classical transport models and correlations, computational fluid dynamics (CFD) at the pore scale, although challenging, is becoming a promising approach, especially if coupled with a realistic description of the foam structure. For precisely recovering the microstructure of the foams, a 3D X-ray computed microtomography (μ-CT) can be adopted. In this work, the results of μ-CT-based CFD simulations performed on different open-cell aluminum foams samples, for laminar flow regime, will be discussed. The results demonstrate that open-cell aluminum foams are effective means for enhancing heat transfer.
CFD Based Determination of Dynamic Stability Derivatives in Yaw for a Bird
Institute of Scientific and Technical Information of China (English)
M. A. Moelyadi; G. Sachs
2007-01-01
Dynamic yaw stability derivatives of a gull bird are determined using Computational Fluid Dynamics(CFD) method. Two kinds of motions are applied for calculating the dynamic yaw stability derivatives CNr and CNβ. The first one relates to a lateral translation and, separately, to a yaw rotation. The second one consists of a combined translational and rotational motion. To determine dynamic yaw stability derivatives, the simulation of an unsteady flow with a bird model showing a harmonic motion is performed. The flow solution for each time step is obtained by solving unsteady Euler equations based on a finite volume approach for a small reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using harmonic Fourier analysis. The results of the dynamic yaw stability derivatives for both simulations of the model show a good agreement.
Validation of cfd and simplified models with experimental data for multiphase flow in bends
Nennie, E.D.; Belfroid, S.P.C.; O'Mahoney, T.S.D.
2013-01-01
In this paper details of the measurement results of the forces on the bends in a 4" setup are compared to two models. The first model is a simple analytical model and is used to estimate the forces. In the second model, CFD is used. In the experiments only resulting forces, including upstream and do
Diffusion-Based Coarse Graining in Hybrid Continuum--Discrete Solvers: Applications in CFD--DEM
Sun, Rui
2014-01-01
In this work, a coarse graining method previously proposed by the authors based on solving diffusion equations is applied to CFD--DEM simulations, where coarse graining is used to obtain solid volume fraction, particle phase velocity, and fluid--particle interaction forces. By examining the conservation requirements, the variables to solve diffusion equations for in CFD--DEM simulations are identified. The algorithm is then implemented to a CFD--DEM solver based on OpenFOAM and LAMMPS, the former being a general-purpose, three-dimensional CFD solver based on unstructured meshes. Numerical simulations are performed for a fluidized bed by using the CFD--DEM solver with the diffusion-based coarse graining algorithm. Converged results are obtained on successively refined meshes, even for meshes with cell sizes comparable to or smaller than the particle diameter. This is a critical advantage of the proposed method over many existing coarse graining methods, and would be particularly valuable when small cells are r...
SYSTEM FOR TORQUE CONVERTER DESIGN AND ANALYSIS BASED ON CAD/CFD INTEGRATED PLATFORM
Institute of Scientific and Technical Information of China (English)
WU Guangqiang; YAN Peng
2008-01-01
A 3D torque converter design system is developed based on numerical investigation into flow field and CAD technology. The 3D steady-state flow field simulation is undertaken by using time averaged Reynolds equation and k-epsilon turbulence model, with mixing-plane boundary conditions at three section interfaces. The blades are designed according to the flow field characteristics by using a reverse design method in the system. The accurateness of numerical analysis and the validity of design system are verified by the fluid field experiment of desingn example of the torque converter. This kind of design and analysis system for torque converter based on integration of comput ationol fluid dynamics (CFD) and CAD is a powerful tool for torque converter manufacturing, but also a prettg important significance for research and development.
Two-phase CFD modeling of flow causing the heater vibration
International Nuclear Information System (INIS)
Vibrations of heater rods were observed in a heated annulus with water flow under boiling conditions. In order to find out the cause of such vibrations, CFD model of this annulus has been prepared in CFD code STAR-CCM+. Two-phase flow in the annulus was described using a two-fluid model with number of sub-models to describe the mass, momentum and energy transfer between phases. The model was validated using experimental data from reference. The validated model was used to perform a steady state calculation of flow parameters under different conditions. Results of CFD simulations were compared to experimentally detected vibration offset. It was found out that vibration increase caused by heating the channel is connected with the vibration offset. The results and their extension to nuclear safety were discussed. (author)
CFD model of diabatic annular two-phase flow using the Eulerian–Lagrangian approach
International Nuclear Information System (INIS)
Highlights: • A CFD model of annular two-phase flow with evaporating liquid film has been developed. • A two-dimensional liquid film model is developed assuming that the liquid film is sufficiently thin. • The liquid film model is coupled to the gas core flow, which is represented using the Eulerian–Lagrangian approach. - Abstract: A computational fluid dynamics (CFD) model of annular two-phase flow with evaporating liquid film has been developed based on the Eulerian–Lagrangian approach, with the objective to predict the dryout occurrence. Due to the fact that the liquid film is sufficiently thin in the diabatic annular flow and at the pre-dryout conditions, it is assumed that the flow in the wall normal direction can be neglected, and the spatial gradients of the dependent variables tangential to the wall are negligible compared to those in the wall normal direction. Subsequently the transport equations of mass, momentum and energy for liquid film are integrated in the wall normal direction to obtain two-dimensional equations, with all the liquid film properties depth-averaged. The liquid film model is coupled to the gas core flow, which currently is represented using the Eulerian–Lagrangian technique. The mass, momentum and energy transfers between the liquid film, gas, and entrained droplets have been taken into account. The resultant unified model for annular flow has been applied to the steam–water flow with conditions typical for a Boiling Water Reactor (BWR). The simulation results for the liquid film flow rate show favorable agreement with the experimental data, with the potential to predict the dryout occurrence based on criteria of critical film thickness or critical film flow rate
Design of a decay tank for a pool type research reactor with a CFD model
International Nuclear Information System (INIS)
A conceptual primary cooling system (PCS) was designed for adequate cooling of the core of a research reactor. The primary coolant after passing through the reactor core contains many kinds of radio-nuclides. A decay tank provides a delayed transit time to ensure that the N-16 activity decreases enough before the coolant leaves the decay tank's shielding room. The size of the decay tank should be enlarged to provide sufficient transit time. However, there was a limitation: to minimize the tank size, it should be designed with an internal baffle, which affects the pressure loss in the system and net positive suction head (NPSH) of the PCS pump. Therefore, the decay tank should be optimized for size and the internal baffle. A vertical type decay tank was chosen to optimize the geometrical arrangement of PCS and the vertical internal baffle was installed to minimize the number of internal structures. The preliminary geometry of the tank and the internal baffle were determined to satisfy the required delayed transit time by calculating the maximum velocity and the flow path length of the circular and the annular sections of the tank. The commercially available CFD model, FLUENT, which solves the Navier-Stokes and turbulent models, was used to specifically design the decay tank with the preliminarily calculated geometry and the related flow rate. Several turbulence models, standard k-ε model, renormalization group (RNG) model, and realizable k-ε model, were conducted to isolate the root cause of these differences. By comparing the results of the velocity profile and the characteristics of each model, a detailed design study was simulated using the realizable k-ε model. A user-defined scalar equation was solved to estimate the delayed transit time. The size and the internal baffle that satisfy the required transit time were determined based on the CFD results. (author)
CFD Analysis of a Slug Mixing Experiment Conducted on a VVER-1000 Model
Directory of Open Access Journals (Sweden)
F. Moretti
2009-01-01
Full Text Available A commercial CFD code was applied, for validation purposes, to the simulation of a slug mixing experiment carried out at OKB “Gidropress” scaled facility in the framework of EC TACIS project R2.02/02: “Development of safety analysis capabilities for VVER-1000 transients involving spatial variations of coolant properties (temperature or boron concentration at core inlet.” Such experimental model reproduces a VVER-1000 nuclear reactor and is aimed at investigating the in-vessel mixing phenomena. The addressed experiment involves the start-up of one of the four reactor coolant pumps (the other three remaining idle, and the presence of a tracer slug on the starting loop, which is thus transported to the reactor pressure vessel where it mixes with the clear water. Such conditions may occur in a boron dilution scenario, hence the relevance of the addressed phenomena for nuclear reactor safety. Both a pretest and a posttest CFD simulations of the mentioned experiment were performed, which differ in the definition of the boundary conditions (based either on nominal quantities or on measured quantities, resp.. The numerical results are qualitatively and quantitatively analyzed and compared against the measured data in terms of space and time tracer distribution at the core inlet. The improvement of the results due to the optimization of the boundary conditions is evidenced, and a quantification of the simulation accuracy is proposed.
CFD Model of Dense Gas-solid Systems in Jetting Fl uidized Beds
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A CFD code has been developed based on the conservation principles describing gas and solid flow in fluidized beds. This code is employed to simulate not only the spatiotemporal gas- and solid-phase velocities and voidage profiles in a two-dimensional bed but also fluid dynamics in the jet region. The computational results show that gas flow direction is upward in the entire bed accompanied with random local circulations, whilst solid flow direction is upward at the center and downward near the wall. The radical reason of strong back-mixing of solid particles and good transfer behavior between two phases is that the jet entrains solid particles. Numerical calculation indicates that gas velocity, solid velocity and pressure profile have a significant change when the voidage is 0. 8. The simulated time-averaged voidage profiles agree with the experimental results and simulated data reported by Gidaspow and Ettehadieh(1983). Therefore, CFD model can be regarded as a useful tool to study the jet characteristics in dense gas-solid fluidized beds.
CFD aided analysis of a scaled down model of the Brazilian Multipurpose Reactor (RMB) pool
International Nuclear Information System (INIS)
Research reactors are commonly built inside deep pools that provide radiological and thermal protection and easy access to its core. Reactors with thermal power in the order of MW usually use an auxiliary thermal-hydraulic circuit at the top of its pool to create a purified hot water layer (HWL). Thermal-hydraulic analysis of the flow configuration in the pool and HWL is paramount to insure radiological protection. A useful tool for these analyses is the application of CFD (Computational Fluid Dynamics). To obtain satisfactory results using CFD it is necessary the verification and validation of the CFD numerical model. Verification is divided in code and solution verifications. In the first one establishes the correctness of the CFD code implementation and in the former estimates the numerical accuracy of a particular calculation. Validation is performed through comparison of numerical and experimental results. This paper presents a dimensional analysis of the RMB (Brazilian Multipurpose Reactor) pool to determine a scaled down experimental installation able to aid in the HWL numerical investigation. Two CFD models were created one with the same dimensions and boundary conditions of the reactor prototype and the other with 1/10 proportion size and boundary conditions set to achieve the same inertial and buoyant forces proportions represented by Froude Number between the two models. Results comparing the HWL thickness show consistence between the prototype and the scaled down model behavior. (author)
CFD aided analysis of a scaled down model of the Brazilian Multipurpose Reactor (RMB) pool
Energy Technology Data Exchange (ETDEWEB)
Schweizer, Fernando L.A.; Lima, Claubia P.B.; Costa, Antonella L.; Veloso, Maria A.F., E-mail: ando.schweizer@gmail.com, E-mail: claubia@nuclear.ufmg.br, E-mail: antonella@nuclear.ufmg.br, E-mail: mdora@nuclear.ufmg.br [Universidade Federal de Minas Gerais (DEN/UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Santos, Andre A.C.; Costa, Antonio C.L., E-mail: aacs@cdtn.br, E-mail: aclc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN/-MG), Belo Horizonte, MG (Brazil)
2013-07-01
Research reactors are commonly built inside deep pools that provide radiological and thermal protection and easy access to its core. Reactors with thermal power in the order of MW usually use an auxiliary thermal-hydraulic circuit at the top of its pool to create a purified hot water layer (HWL). Thermal-hydraulic analysis of the flow configuration in the pool and HWL is paramount to insure radiological protection. A useful tool for these analyses is the application of CFD (Computational Fluid Dynamics). To obtain satisfactory results using CFD it is necessary the verification and validation of the CFD numerical model. Verification is divided in code and solution verifications. In the first one establishes the correctness of the CFD code implementation and in the former estimates the numerical accuracy of a particular calculation. Validation is performed through comparison of numerical and experimental results. This paper presents a dimensional analysis of the RMB (Brazilian Multipurpose Reactor) pool to determine a scaled down experimental installation able to aid in the HWL numerical investigation. Two CFD models were created one with the same dimensions and boundary conditions of the reactor prototype and the other with 1/10 proportion size and boundary conditions set to achieve the same inertial and buoyant forces proportions represented by Froude Number between the two models. Results comparing the HWL thickness show consistence between the prototype and the scaled down model behavior. (author)
Application of CFD based wave loads in aeroelastic calculations
DEFF Research Database (Denmark)
Schløer, Signe; Paulsen, Bo Terp; Bredmose, Henrik
2014-01-01
Two fully nonlinear irregular wave realizations with different significant wave heights are considered. The wave realizations are both calculated in the potential flow solver Ocean-Wave3D and in a coupled domain decomposed potential-flow CFD solver. The surface elevations of the calculated wave...... realizations compare well with corresponding surface elevations from laboratory experiments. In aeroelastic calculations of an offshore wind turbine on a monopile foundation the hydrodynamic loads due to the potential flow solver and Morison’s equation and the hydrodynamic loads calculated by the coupled...
Parametric sensitivity of a CFD model concerning the hydrodynamics of trickle-bed reactor (TBR
Directory of Open Access Journals (Sweden)
Janecki Daniel
2016-03-01
Full Text Available The aim of the present study was to investigate the sensitivity of a multiphase Eulerian CFD model with respect to relations defining drag forces between phases. The mean relative error as well as standard deviation of experimental and computed values of pressure gradient and average liquid holdup were used as validation criteria of the model. Comparative basis for simulations was our own data-base obtained in experiments carried out in a TBR operating at a co-current downward gas and liquid flow. Estimated errors showed that the classical equations of Attou et al. (1999 defining the friction factors Fjk approximate experimental values of hydrodynamic parameters with the best agreement. Taking this into account one can recommend to apply chosen equations in the momentum balances of TBR.
CFD MODELING OF FINE SCALE FLOW AND TRANSPORT IN THE HOUSTON METROPOLITAN AREA, TEXAS
Fine scale modeling of flows and air quality in Houston, Texas is being performed; the use of computational fluid dynamics (CFD) modeling is being applied to investigate the influence of morphologic structures on the within-grid transport and dispersion of sources in grid models ...
CFD modelling of DC casting of aluminium alloys
International Nuclear Information System (INIS)
Casting and solidification of metals is a process in which transport phenomena as heat flow, mass flow and fluid flow are highly coupled. The major drive for casting modelling is to improve the insight how process parameters affect casting performance and a major part of current solidification modelling applications is used for the prevention of casting defects. Solidification modelling activities are dope at nearly all the size scales for the physical processes involved: nucleation, dendrite tip growth, liquid metal flow through a mushy semi-solid dendritic network, etc.. In this paper we will concentrate on the coupled fluid flow effects during DC casting. Compositional differences over the whole cross-section of an ingot, defined as macrosegregation, can have a significant impact on the properties of the finished product, in particular for strong alloy applications. There are several hypotheses possible to explain macrosegregation, although they all have in common the attributed effect of fluid flow. A reliable calculation of macrosegregation during the casting of alloys depends on the accurate modelling of the associated physical mechanisms. Besides that the particular microsegregation model (Scheil, lever-rule) is of importance, the relative movement of the liquid and solid phase inside the mushy zone controls the amount of macrosegregation. In solving the solute concentration equation, the accuracy of the velocity field is thus of great concern. From the literature on computational fluid dynamics, we also know that in high Peclet number flows, the incorrect treatment of the convection terms causes numerical diffusion, which can completely overshadow the actual physical diffusion. Throughout the history of CFD, a great number of differencing schemes for the convection term have been proposed in order to reduce the numerical diffusion. In the current research several of these schemes are examined on their ability to correctly predict macrosegregation in the DC
Validation of Neptune CFD two phase flow models using the OECD/NRC BFBT benchmark database
International Nuclear Information System (INIS)
In this work the flow within a fuel assembly of a boiling water reactor was modeled using NEPTUNE-CFD. The most important parameters to define the flow like the incipient boiling condition, the heat flux partitioning and the heat transfer models are identified and tested against experimental data from BFBT bundle test. Different heat transfer models are applied for the water/steam interface. Additionally the heat conduction is solved for the insulator and cladding of the heater rods by coupling NEPTUNE-CFD with the SYRTHES package. The calculated average void fractions are in good agreement with the experimental data and the areas for future improvements are identified. (author)
Hristov, Y.; Oxley, G.; Žagar, M.
2014-06-01
The Bolund measurement campaign, performed by Danish Technical University (DTU) Wind Energy Department (also known as RISØ), provided significant insight into wind flow modeling over complex terrain. In the blind comparison study several modelling solutions were submitted with the vast majority being steady-state Computational Fluid Dynamics (CFD) approaches with two equation k-epsilon turbulence closure. This approach yielded the most accurate results, and was identified as the state-of-the-art tool for wind turbine generator (WTG) micro-siting. Based on the findings from Bolund, further comparison between CFD and field measurement data has been deemed essential in order to improve simulation accuracy for turbine load and long-term Annual Energy Production (AEP) estimations. Vestas Wind Systems A/S is a major WTG original equipment manufacturer (OEM) with an installed base of over 60GW in over 70 countries accounting for 19% of the global installed base. The Vestas Performance and Diagnostic Centre (VPDC) provides online live data to more than 47GW of these turbines allowing a comprehensive comparison between modelled and real-world energy production data. In previous studies, multiple sites have been simulated with a steady neutral CFD formulation for the atmospheric surface layer (ASL), and wind resource (RSF) files have been generated as a base for long-term AEP predictions showing significant improvement over predictions performed with the industry standard linear WAsP tool. In this study, further improvements to the wind resource file generation with CFD are examined using an unsteady diurnal cycle approach with a full atmospheric boundary layer (ABL) formulation, with the unique stratifications throughout the cycle weighted according to mesoscale simulated sectorwise stability frequencies.
International Nuclear Information System (INIS)
The Bolund measurement campaign, performed by Danish Technical University (DTU) Wind Energy Department (also known as RISØ), provided significant insight into wind flow modeling over complex terrain. In the blind comparison study several modelling solutions were submitted with the vast majority being steady-state Computational Fluid Dynamics (CFD) approaches with two equation k-ε turbulence closure. This approach yielded the most accurate results, and was identified as the state-of-the-art tool for wind turbine generator (WTG) micro-siting. Based on the findings from Bolund, further comparison between CFD and field measurement data has been deemed essential in order to improve simulation accuracy for turbine load and long-term Annual Energy Production (AEP) estimations. Vestas Wind Systems A/S is a major WTG original equipment manufacturer (OEM) with an installed base of over 60GW in over 70 countries accounting for 19% of the global installed base. The Vestas Performance and Diagnostic Centre (VPDC) provides online live data to more than 47GW of these turbines allowing a comprehensive comparison between modelled and real-world energy production data. In previous studies, multiple sites have been simulated with a steady neutral CFD formulation for the atmospheric surface layer (ASL), and wind resource (RSF) files have been generated as a base for long-term AEP predictions showing significant improvement over predictions performed with the industry standard linear WAsP tool. In this study, further improvements to the wind resource file generation with CFD are examined using an unsteady diurnal cycle approach with a full atmospheric boundary layer (ABL) formulation, with the unique stratifications throughout the cycle weighted according to mesoscale simulated sectorwise stability frequencies
International Nuclear Information System (INIS)
A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, operating potential, steam-electrode gas composition, oxygen-electrode gas composition, current density and hydrogen production over a range of stack operating conditions. Single-cell and five-cell results will be presented. Flow distribution through both models is discussed. Flow enters from the bottom, distributes through the inlet plenum, flows across the cells, gathers in the outlet plenum and flows downward making an upside-down ''U'' shaped flow pattern. Flow and concentration variations exist downstream of the inlet holes. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, oxygen-electrode and steam-electrode current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicate the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal
Directory of Open Access Journals (Sweden)
Mimoun Maurice
2011-03-01
Full Text Available Abstract Background Controlling airborne contamination is of major importance in burn units because of the high susceptibility of burned patients to infections and the unique environmental conditions that can accentuate the infection risk. In particular the required elevated temperatures in the patient room can create thermal convection flows which can transport airborne contaminates throughout the unit. In order to estimate this risk and optimize the design of an intensive care room intended to host severely burned patients, we have relied on a computational fluid dynamic methodology (CFD. Methods The study was carried out in 4 steps: i patient room design, ii CFD simulations of patient room design to model air flows throughout the patient room, adjacent anterooms and the corridor, iii construction of a prototype room and subsequent experimental studies to characterize its performance iv qualitative comparison of the tendencies between CFD prediction and experimental results. The Electricité De France (EDF open-source software Code_Saturne® (http://www.code-saturne.org was used and CFD simulations were conducted with an hexahedral mesh containing about 300 000 computational cells. The computational domain included the treatment room and two anterooms including equipment, staff and patient. Experiments with inert aerosol particles followed by time-resolved particle counting were conducted in the prototype room for comparison with the CFD observations. Results We found that thermal convection can create contaminated zones near the ceiling of the room, which can subsequently lead to contaminate transfer in adjacent rooms. Experimental confirmation of these phenomena agreed well with CFD predictions and showed that particles greater than one micron (i.e. bacterial or fungal spore sizes can be influenced by these thermally induced flows. When the temperature difference between rooms was 7°C, a significant contamination transfer was observed to
International Nuclear Information System (INIS)
Results presented on application of a CFD technique for determination of the thermal state of a Lynx overhead conductor, used in power distribution networks. The thermal state of the Lynx conductor is mainly defined by the magnitude of the transmitted electrical current, ambient temperature, wind velocity and its direction and also by solar radiation. CFD modelling provides engineers with a capability to fully reflect in the process of numerical simulations variations of the above parameters over a range which is typical for real exploitation conditions. Results for both the steady-state and transient responses have been obtained and compared to those predicted by industrial standards and available from experimental data. Time constant values were obtained for various scenarios in which there was an instantaneous change in the magnitude of the electrical current or wind velocity. Analysis of numerical results demonstrate that the CFD technique provides an adequate level of accuracy in predicting the thermal state of the overhead conductor and could be a viable option for the dynamic analysis of distribution networks with a number of renewable energy generators, operating under varying electrical load and weather conditions. -- Highlights: • The thermal state of the Lynx overhead conductor was studied using CFD modelling. • Steady and transient thermal states were studied for a range of operating conditions. • CFD results were compared to that from industrial standards and experiments. • Time constant values were obtained for changes in the current and wind velocity
International Nuclear Information System (INIS)
Computational Fluid Dynamics (CFD), as a tool, is successfully being applied in different application fields involving fluid flow problems mainly because of the versatile nature of the equations involved to accommodate domain specific phenomena. Application of CFD in atmospheric flow and pollutant dispersion problems has been the focus of professionals in the field of environment and risk, the reasons being the availability of more specific input data in addition to the high end computational resources in the recent times. Atmospheric flow field at a given site is generally driven by the large scale weather system, within which local scale site specific flow field is embedded due to the local topographic effects and also due to the non-homogeneity of the surface conditions. The Numerical Weather Prediction (NWP) models, such as MM5, are ideally suited for predicting 3-dimensional flow field conditions over a regional scale or meso-scale range; however, it may give poor forecast for local flow conditions due to the coarse resolution of the model. On the contrary, CFD based models are well suited for generating local scale flow fields, using locally measured data, however, they lack information about the large scale flow field in which the local scale flow field is embedded. Thus, it was felt that proper coupling of the two may give more realistic flow filed simulation as well as pollutant dispersion for the site under consideration. Moreover, the NWP model being predictive, coupling of the NWP with CFD based local scale model could be a very effective tool for analyzing the consequences of accidental releases in advance and can help in emergency preparedness of the industry under consideration. This paper discusses an effort made to generate an interface between a CFD based dispersion model (Fluidyn-PANEPR) and a meso-scale meteorological model (MM5) to cater to the problems of the kind as discussed above. The NWP model MM5 takes initial and boundary conditions data
Towards a generic, reliable CFD modelling methodology for waste-fired grate boilers
DEFF Research Database (Denmark)
Rajh, Boštjan; Yin, Chungen; Samec, Niko;
Computational Fluid Dynamics (CFD) is increasingly used in industry for detailed understanding of the combustion process and for appropriate design and optimization of Waste–to–Energy (WtE) plants. In this paper, CFD modelling of waste wood combustion in a 13 MW grate-fired boiler in a WtE plant is...... presented. To reduce the risk of slagging, optimize the temperature control and enhance turbulent mixing, part of the flue gas is recycled into the grate boiler. In the simulation, a 1D in–house bed model is developed to simulate the conversion of the waste wood in the fuel bed on the grate, which provides...
Comparing different CFD wind turbine modelling approaches with wind tunnel measurements
International Nuclear Information System (INIS)
The performance of a model wind turbine is simulated with three different CFD methods: actuator disk, actuator line and a fully resolved rotor. The simulations are compared with each other and with measurements from a wind tunnel experiment. The actuator disk is the least accurate and most cost-efficient, and the fully resolved rotor is the most accurate and least cost-efficient. The actuator line method is believed to lie in between the two ends of the scale. The fully resolved rotor produces superior wake velocity results compared to the actuator models. On average it also produces better results for the force predictions, although the actuator line method had a slightly better match for the design tip speed. The open source CFD tool box, OpenFOAM, was used for the actuator disk and actuator line calculations, whereas the market leading commercial CFD code, ANSYS/FLUENT, was used for the fully resolved rotor approach
Comparing different CFD wind turbine modelling approaches with wind tunnel measurements
Kalvig, Siri; Manger, Eirik; Hjertager, Bjørn
2014-12-01
The performance of a model wind turbine is simulated with three different CFD methods: actuator disk, actuator line and a fully resolved rotor. The simulations are compared with each other and with measurements from a wind tunnel experiment. The actuator disk is the least accurate and most cost-efficient, and the fully resolved rotor is the most accurate and least cost-efficient. The actuator line method is believed to lie in between the two ends of the scale. The fully resolved rotor produces superior wake velocity results compared to the actuator models. On average it also produces better results for the force predictions, although the actuator line method had a slightly better match for the design tip speed. The open source CFD tool box, OpenFOAM, was used for the actuator disk and actuator line calculations, whereas the market leading commercial CFD code, ANSYS/FLUENT, was used for the fully resolved rotor approach.
A physical approach of the short-term wind power prediction based on CFD pre-calculated flow fields
Institute of Scientific and Technical Information of China (English)
LI Li; LIU Yong-qian; YANG Yong-ping; HAN Shuang; WANG Yi-mei
2013-01-01
A physical approach of the wind power prediction based on the CFD pre-calculated flow fields is proposed in this paper.The flow fields are obtained based on a steady CFD model with the discrete inflow wind conditions as the boundary conditions,and a database is established containing the important parameters including the inflow wind conditions,the flow fields and the corresponding wind power for each wind turbine.The power is predicted via the database by taking the Numerical Weather Prediction (NWP)wind as the input data.In order to evaluate the approach,the short-term wind power prediction for an actual wind farm is conducted as an example during the period of the year 2010.Compared with the measured power,the predicted results enjoy a high accuracy with the annual Root Mean Square Error (RMSE) of 15.2％ and the annual MAE of 10.80％.A good performance is shown in predicting the wind power's changing trend.This approach is independent of the historical data and can be widely used for all kinds of wind farms including the newly-built wind farms.At the same time,it does not take much computation time while it captures the local air flows more precisely by the CFD model.So it is especially practical for engineering projects.
Befrui, Bizhan A.
1995-01-01
This viewgraph presentation discusses the following: STAR-CD computational features; STAR-CD turbulence models; common features of industrial complex flows; industry-specific CFD development requirements; applications and experiences of industrial complex flows, including flow in rotating disc cavities, diffusion hole film cooling, internal blade cooling, and external car aerodynamics; and conclusions on turbulence modeling needs.
A CFD Analysis of Complex Flow Distribution in KSNP Reactor Vessel Lower Structures Based on 3D CAD
International Nuclear Information System (INIS)
During design period and commercial operation of a nuclear power plants (NPP) lots of safety analyses are performed because nuclear regulatory body requires the vendor and utility to report lots of simulation results in order to ensure the safe operation of the NPP. In general, the simulations are carried out using vendor-specific design codes and best-estimate system analysis codes. The thermal-hydraulic system codes have powerful features such as multi-phase flow model, phase-change model and event programming. During the past decade, however, computing power has been dramatically enhanced in terms of speed, capability and expenses. On the other hand, mechanistic computational fluid dynamics(CFD) codes also made a progress during these days. Nowadays, commercial CFD programs are applied to very large and complex systems design such as core design, HVAC design and chemical plant buildings. In spite of the recent progress in computing hardware and software the nuclear industry still uses conventional system codes based on lumped parameter model. It is believed to be beneficial to take advantage of advanced commercial CFD codes in safety analysis and design of NPPs
International Nuclear Information System (INIS)
Background: Based on general purpose CFD code Fluent, the PBMR-400 full load nominal condition thermal-hydraulics performance was studied by applying local thermal non-equilibrium porous media model. Purpose: In thermal hydraulics study of the gas cooled pebble bed reactor, the core of the reactor can be treated as macroscopic porous media with strong inner heat source, and the original Fluent code can not handle it properly. Methods: By introducing a UDS in the calculation domain of the reactor core and subjoining a new resistance term, we develop a non-equilibrium porous media model which can give an accurate description of the core of the pebble bed. The mesh of CFD code is finer than that of the traditional pebble bed reactor thermal hydraulics analysis code such as THERMIX and TINTE, thus more information about coolant velocity fields, temperature field and solid phase temperature field can be acquired. Results: The nominal condition calculation results of the CFD code are compared to those of the well-established thermal-hydraulic code THERMIX and TINTE, and show a good consistency. Conclusion: The extended local thermal non-equilibrium model can be used to analyse thermal-hydraulics of high temperature pebble bed type reactor. (authors)
Energy Technology Data Exchange (ETDEWEB)
Martin-Valdepenas, J.M.; Jimenez, M.A.; Martin-Fuertes, F. [Universidad Politecnica de Madrid, Department of Nuclear Engineering, Jose Gutierrez Abascal, 2, E-28006, Madrid (Spain); Benitez, J.A. Fernandez [Universidad Politecnica de Madrid, Departamento de Ingenieria Energetica y Fluidomecanica, Jose Gutierrez Abascal, 2, E-28006, Madrid (Spain)
2005-09-01
Several film condensation models in presence of non-condensable gases are presented. They have been implemented in a CFD code and compared with experimental data. The aim was to improve the code for simulating the gas mixing process in large containment buildings involving steam. The models based on correlation are more robust and simpler, but they work badly out of their experimental conditions. The mechanistic models, based on the diffusion layer theory, work well in numerous conditions but the algorithm are more complicated. Moreover, they run badly when the convective heat transfer is not well predicted by the code. (orig.)
CFD simulations in the nuclear containment using the DES turbulence models
Energy Technology Data Exchange (ETDEWEB)
Ding, Peng [School of Engineering, Sun Yat-Sen University, Guangzhou (China); Chen, Meilan [China Nuclear Power Technology Research Institute, Shenzhen (China); Li, Wanai, E-mail: liwai@mail.sysu.edu.cn [Sino-French Institute of Nuclear Engineering & Technology, Sun Yat-Sen University, Guangzhou (China); Liu, Yulan [School of Engineering, Sun Yat-Sen University, Guangzhou (China); Wang, Biao [Sino-French Institute of Nuclear Engineering & Technology, Sun Yat-Sen University, Guangzhou (China)
2015-06-15
Highlights: • The k-ε based DES model is used in the nuclear containment simulation. • The comparison of results between different turbulent models is obtained. • The superiority of DES models is analyzed. • The computational efficiency with the DES turbulence models is explained. - Abstract: Different species of gases would be released into the containment and cause unpredicted disasters during the nuclear severe accidents. It is important to accurately predict the transportation and stratification phenomena of these gas mixtures. CFD simulations of these thermal hydraulic issues in nuclear containment are investigated in this paper. The main work is to study the influence of turbulence model on the calculation of gas transportation and heat transfer. The k-ε based DES and other frequently used turbulence models are used in the steam and helium release simulation in THAI series experiment. This paper will show the superiority of the DES turbulence model in terms of computational efficiency and accuracy with the experimental results, and analyze the necessities of DES model to simulate the large-scale containment flows with both laminar and turbulence regions.
Richardson, Brian; Kenny, Jeremy
2015-01-01
Injector design is a critical part of the development of a rocket Thrust Chamber Assembly (TCA). Proper detailed injector design can maximize propulsion efficiency while minimizing the potential for failures in the combustion chamber. Traditional design and analysis methods for hydrocarbon-fuel injector elements are based heavily on empirical data and models developed from heritage hardware tests. Using this limited set of data produces challenges when trying to design a new propulsion system where the operating conditions may greatly differ from heritage applications. Time-accurate, Three-Dimensional (3-D) Computational Fluid Dynamics (CFD) modeling of combusting flows inside of injectors has long been a goal of the fluid analysis group at Marshall Space Flight Center (MSFC) and the larger CFD modeling community. CFD simulation can provide insight into the design and function of an injector that cannot be obtained easily through testing or empirical comparisons to existing hardware. However, the traditional finite-rate chemistry modeling approach utilized to simulate combusting flows for complex fuels, such as Rocket Propellant-2 (RP-2), is prohibitively expensive and time consuming even with a large amount of computational resources. MSFC has been working, in partnership with Streamline Numerics, Inc., to develop a computationally efficient, flamelet-based approach for modeling complex combusting flow applications. In this work, a flamelet modeling approach is used to simulate time-accurate, 3-D, combusting flow inside a single Gas Centered Swirl Coaxial (GCSC) injector using the flow solver, Loci-STREAM. CFD simulations were performed for several different injector geometries. Results of the CFD analysis helped guide the design of the injector from an initial concept to a tested prototype. The results of the CFD analysis are compared to data gathered from several hot-fire, single element injector tests performed in the Air Force Research Lab EC-1 test facility
Modelling of massive particulates for breakwater engineering using coupled FEMDEM and CFD
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The seaward slope of many breakwaters consists of thousands of interlocking units of rock or concrete comprising a massive granular system of large elements each weighing tens of tonnes.The dumped quarry materials in the core are protected by progressively coarser particulates.The outer armour layer of freely placed units is intended to both dissipate wave energy and remain structurally stable as strong flows are drawn in and out of the particulate core.Design guidance on the mass and shape of these units is based on empirical equations derived from sealed physical model tests.The main failure mode for armour layers exposed to severe storms is hydraulic instability where the armour units of concrete or rock are subjected to uplift and drag forces which can in turn lead to rocking,displacement and collisions sufficient to cause breakage of units.Recently invented armour unit designs making up such granular layered system owe much of their success to the desirable emergent properties of interlock and porosity and how these combine with individual unit structural strength and inertial mass. Fundamental understanding of the forces governing such wave-structure interaction remains poor.We use discrete element and combined finite-discrete element methods to model the granular solid skeleton of randomly packed units coupled to a CFD code which resolves the wave dynamics through an interface tracking technique.The CFD code exploits several methods including a compressive advection scheme, node movement, and general mesh optimization.We provide the engineering context and report progress towards the numerical modelling of instability in these massive granular systems.
Energy Technology Data Exchange (ETDEWEB)
Arastoopour, Hamid [Illinois Inst. of Technology, Chicago, IL (United States); Abbasian, Javad [Illinois Inst. of Technology, Chicago, IL (United States)
2014-07-31
This project describes the work carried out to prepare a highly reactive and mechanically strong MgO based sorbents and to develop a Population Balance Equations (PBE) approach to describe the evolution of the particle porosity distribution that is linked with Computational Fluid Dynamics (CFD) to perform simulations of the CO2 capture and sorbent regeneration. A large number of MgO-based regenerable sorbents were prepared using low cost and abundant dolomite as the base material. Among various preparation parameters investigated the potassium/magnesium (K/Mg) ratio was identified as the key variable affecting the reactivity and CO2 capacity of the sorbent. The optimum K/Mg ratio is about 0.15. The sorbent formulation HD52-P2 was identified as the “best” sorbent formulation and a large batch (one kg) of the sorbent was prepared for the detailed study. The results of parametric study indicate the optimum carbonation and regeneration temperatures are 360° and 500°C, respectively. The results also indicate that steam has a beneficial effect on the rate of carbonation and regeneration of the sorbent and that the reactivity and capacity of the sorbent decreases in the cycling process (sorbent deactivation). The results indicate that to achieve a high CO2 removal efficiency, the bed of sorbent should be operated at a temperature range of 370-410°C which also favors production of hydrogen through the WGS reaction. To describe the carbonation reaction kinetics of the MgO, the Variable Diffusivity shrinking core Model (VDM) was developed in this project, which was shown to accurately fit the experimental data. An important advantage of this model is that the changes in the sorbent conversion with time can be expressed in an explicit manner, which will significantly reduce the CFD computation time. A Computational Fluid Dynamic/Population Balance Equations (CFD/PBE) model was developed that accounts for the particle (sorbent) porosity distribution and a new version of
International Nuclear Information System (INIS)
In a previous work we presented an analysis approach developed to effectively and accurately assess thermal loads on vessel and structures in a Boiling Water Reactor (BWR) lower head during a severe accident. Central to the assessment is the Effective Convectivity Model (ECM) that makes use of experimental heat transfer correlations to capture the effect of turbulent natural convection in a volumetrically heated liquid pool, while retaining the pool three-dimensional energy splitting and ability to represent local heat transfer effects. Thanking to its features, the ECM is unique in enabling calculations of complex heat transfer phenomena during long severe accident transients that would not be otherwise feasible using higher-fidelity methods such as Computational Fluid Dynamics (CFD). Efficiency notwithstanding, the natural questions are: (i) how good are those ECM-calculated results, and, (ii) if required, what can be done (with the highest return-on-investment) to improve the quality of ECM prediction results. The approach refers to experiments and CFD simulations as the main resources to address (i) and (ii). However, validation of ECM against simulant-fluid experiments by itself does not reveal deficiencies (due to non-prototypicality factors). In the present work we focus on the use of CFD-based numerical 'experiments' to identify and quantify source of epistemic uncertainty in the calculated thermal loads due to modeling assumptions in ECM. Specifically, heat transfer correlations that underlie the ECM are obtained as surface-averaged (even though implemented as spatially distributed) and derived from experiments conducted at different geometries and using fluids that are not reactor prototypical (molten corium in the present case of severe accident). The CFD simulations exhibit so-called fluid Prandtl number effect on local peaking of the pool's downward heat flux for corium as working fluid. The main premise is a synergistic use of a fast-running model
CFD based propeller modelling and optimization
Greco, Luca; Testa, Claudio; Leone, Stefania; Salvatore, Francesco; Peri, Daniele; Mauro, Salvatore
2012-01-01
This report is written in fulfilment of deliverable D3.3 of the EU-FP7 project HyMAR. Aim of the project is to develop innovative hybrid drive train systems for small and medium size marine vehicles, by exploiting self-pitching propellers. In this context, the present report describes an automated optimal design procedure developed in the project and presents the results of applying this methodology to a practical self-pitching propeller design exercise. The proposed design procedure combines...
CFD modeling and experience of waste-to-energy plant burning waste wood
Rajh, B.; Yin, Chungen; Samec, N.; M. HRIBERSEK; Kokalj, F.
2013-01-01
Computational Fluid Dynamics (CFD) is being increasingly used in industry for in-depth understanding of the fundamental mixing, combustion, heat transfer and pollutant formation in combustion processes and for design and optimization of Waste-to-Energy (WtE) plants. In this paper, CFD modeling of waste wood combustion in a 13 MW grate-fired boiler in a WtE plant is presented. As a validation effort, the temperature profiles at a number of ports in the furnace are measured and the experimental...
Pollock, Michael; Colli, Matteo; Stagnaro, Mattia; Lanza, Luca; Quinn, Paul; Dutton, Mark; O'Donnell, Greg; Wilkinson, Mark; Black, Andrew; O'Connell, Enda
2016-04-01
observed in the vicinity of the collector, compared to the standard gauge shapes. Both the air velocity and the turbulent kinetic energy fields present structures that may improve the interception of particles by the aerodynamic gauge collector. To provide empirical validation, a field-based experimental campaign was undertaken at four UK research stations to compare the results of aerodynamic and conventional gauges, mounted in juxtaposition. The reference measurement is recorded using a rain gauge pit, as specified by the WMO. The results appear to demonstrate how the effect of the wind on rainfall measurements is influenced by the gauge shape and the mounting height. Significant undercatch is observed compared to the reference measurement. Aerodynamic gauges mounted on the ground catch more rainfall than juxtaposed straight-sided gauges, in most instances. This appears to provide some preliminary validation of the CFD model. The indication that an aerodynamic profile improves the gauge catching capability could be confirmed by tracking the hydrometeor trajectories with a Lagrangian method, based on the available set of airflows; and investigating time-dependent aerodynamic features by means of dedicated CFD simulations. Furthermore, wind-tunnel tests could be carried out to provide more robust physical validation of the CFD model.
Integrated DEM–CFD modeling of the contact charging of pneumatically conveyed powders
Korevaar, M.W.; Padding, J.T.; Hoef, van der M.A.; Kuipers, J.A.M.
2014-01-01
A model is proposed that incorporates contact charging (also known as triboelectric charging) of pneumatically conveyed powders in a DEM–CFD framework, which accounts for the electrostatic interactions, both between particles and between the particles and conducting walls. The simulation results rev
Aspects of Using CFD for Wind Comfort Modeling Around Tall Buildings
DEFF Research Database (Denmark)
Rasmussen, Michael R.; Andersen, Lars
2008-01-01
The Light*House complex is investigated for uncomfortable wind climate and dangerous winds at pedestrian level. A CFD model is used for simulating the wind effect for 12 different directions and correlated to the wind statistics of a nearby meteorological station. Comparing to practical standards...
Numerical simulation and CFD-Based Correlation of Erosion Threshold Gas Velocity in Pipe Bends
Directory of Open Access Journals (Sweden)
K A Ibrahim1
2010-04-01
Full Text Available
This paper presents numerical simulation of sand erosion phenomena in curved ducts. The Eulerian-Lagrangian approach is used to simulate the gas-solid two-phase flow while semi-empirical model is used to calculate the erosion rate. The effect of solid phase on the gas phase is included in the model. The model prediction is validated with the available experimental data and good agreement was obtained. Based on many predictions of the maximum penetration rate, a CFD based correlation is developed to calculate the penetration rate in bends. From this equation a model to predict the erosional velocity was developed. The present results showed that the flow velocity should be decreased as the mass loading ratio, particle size, pipe diameter increase in order to avoid failure.
Comparison of CFD Simulation of a Hyundai I20 Model with Four Different Turbulence Models
Directory of Open Access Journals (Sweden)
Vivekanandan
2016-07-01
Full Text Available This article describes the CFD analysis of a Hyundai i20 car Model. The focus of this study is to investigate the aerodynamics characteristics of Hyundai i20 car model and the flow obtained by solving the steady-state governing continuity equations as well as the momentum conservation equations combined with one of four turbulence models (1.Spalart-Allmaras 2.k-ε Standard 3.Transition k-kl-ω 4.Transition Shear Stress Transport (SST and the solutions obtained using these different models were compared. Except transition k-kl-ω model, other three models show nearly similar velocity variations plot. Pressure variation plot are almost similar with K-ε and transition-SST models. Eddy viscosity plot are almost similar with K-ε and transition k-kl-ω models
Numerical modeling of immiscible two-phase flow in micro-models using a commercial CFD code
Energy Technology Data Exchange (ETDEWEB)
Crandall, Dustin; Ahmadia, Goodarz; Smith, Duane H.
2009-01-01
Off-the-shelf CFD software is being used to analyze everything from flow over airplanes to lab-on-a-chip designs. So, how accurately can two-phase immiscible flow be modeled flowing through some small-scale models of porous media? We evaluate the capability of the CFD code FLUENT{trademark} to model immiscible flow in micro-scale, bench-top stereolithography models. By comparing the flow results to experimental models we show that accurate 3D modeling is possible.
Optimization of centrifugal pump cavitation performance based on CFD
Xie, S. F.; Wang, Y.; Liu, Z. C.; Zhu, Z. T.; Ning, C.; Zhao, L. F.
2015-01-01
In order to further improve the cavitation performance of a centrifugal pump, slots on impeller blade near inlet were studied and six groups of hydraulic model were designed. Base on cavitating flow feature inside a centrifugal pump, bubble growth and implosion are calculated from the Rayleigh-Plesset equation which describes the dynamic behavior of spherical bubble and RNG κ-epsilon model was employed to simulate and analyze the internal two-phase flow of the model pump under the same conditions. The simulation results show that slots on blade near inlet could improve the cavitation performance and cavitation performance improvement of the second group was more obvious. Under the same conditions, the pressure on the back of blade near inlet was higher than the pressure on the back of unmodified blade near inlet, and energy distribution in the flow channel between the two blades was more uniform with a small change of head.
Development of a CFD Model for Secondary Final Settling Tanks in Water Pollution Control Plants
Gong, Minwei; Xanthos, Savvas; Ramalingam, Krish; Fillos, John
2007-11-01
To assess performance and evaluate alternatives to improve efficiency of the New York City the Wards Island Water Pollution Control Plant (WPCP) FSTs at peak loads, a 3D CFD model has been developed. Fluent was utilized as the base platform, where sub-models of the Suspended Solids (SS), settling characteristics, density currents and SS flocculation were incorporated. This was supplemented by field and bench scale experiments to quantify the coefficients integral to the sub-models. Model calibration and validation have been carried out by using the extensive set of data collected. The model can be used to evaluate different modes of operation, alternate hydraulic and solids loading rates, as well as addition of auxiliary components such as baffles to improve process performance. The model is being used to compare potential benefits for different alternatives of design and operation of the existing FSTs. After comparing series of inlet baffles, a baffle with 4 horizontal and 7 vertical slots has been recommended for installation in the FSTs. Additional baffle type, configurations and locations within the tank are also being evaluated to improve the performance of the FSTs especially during periods of poor settling and peak flow conditions.
Multiphase CFD modeling of nearfield fate of sediment plumes
DEFF Research Database (Denmark)
Saremi, Sina; Hjelmager Jensen, Jacob
2014-01-01
. The two-phase mixture solution based on the drift-flux method is evaluated for 3D simulation of material disposal and overflow discharge from the hoppers. The model takes into account the hindrance and resistance mechanisms in the mixture and is capable of describing the flow details within the plumes...
International Nuclear Information System (INIS)
In order to comprehensively study the hydrodynamic characteristics of diffuser for marine current turbine with a postpositive bulb, a geometric model of the turbine was established. Three-dimensional CFD simulation of turbulent flow was performed based on the incompressible continuity equation, the Navier-Stokes equations and the Spalart-Allmaras turbulence model. The influence of diffuser was calculated and analyzed by numerical results, which were also compared with model test results. Results showed that the numerical results agree fairly well with model test and the maximum error of impeller efficiency and power is 1.5% and 1.8% in the rated water velocity condition, which are less than 5.8% and 5.5% under other cases respectively. The new type marine current turbine with a bulb for erecting motor which is different from regular, and the diffuser can aggregate water flow, raise inlet water velocity more than 3% and efficiency of impeller effectively increased. After diffuser was added, the power coefficient curve rose over the full range, so the high power area became widely, and then remarkably prolonged power time as well as increased generated energy, it is also significant for efficient utilization of marine current energy and environmental pollution remission
Institute of Scientific and Technical Information of China (English)
Zhou Lihong; Pritchard Christopher; Zheng Yi
2015-01-01
Knowledge of the airflow patterns and methane distributions at a continuous miner face under different ventilation conditions can minimize the risks of explosion and injury to miners by accurately forecasting potentially hazardous face methane levels. This study focused on validating a series of computational fluid dynamics (CFD) models using full-scale ventilation gallery data that assessed how curtain setback distance impacted airflow patterns and methane distributions at an empty mining face (no continuous miner present). Three CFD models of face ventilation with 4.6, 7.6 and 10.7 m (15, 25, and 35 ft) blowing curtain setback distances were constructed and validated with experimental data collected in a full-scale ventilation test facility. Good agreement was obtained between the CFD simulation results and this data. Detailed airflow and methane distribution information are provided. Elevated methane zones at the working faces were identified with the three curtain setback distances. Visualization of the setback dis-tance impact on the face methane distribution was performed by utilizing the post-processing capability of the CFD software.
CFD modeling of natural convection within dry spent nuclear fuel storage canisters
International Nuclear Information System (INIS)
One of the interim storage configurations being considered for aluminum-clad foreign research reactor fuel, such as the Material and Testing Reactor (MTR) design, is in a dry storage facility. To support design studies of storage options, a computational and experimental program was conducted at the Savannah River Site (SRS). The objective was to develop computational fluid dynamics (CFD) models which would be benchmarked using data obtained from a full scale heat transfer experiment conducted in the SRS Experimental Thermal Fluids Laboratory. The current work documents the CFD approach and presents comparison of results with experimental data. CFDS-FLOW3D (version 3.3) CFD code has been used to model the 3-dimensional convective velocity and temperature distributions within a single dry storage canister of MTR fuel elements. The analysis was made for the cases with q double-prime ' = 100 or 137 watts per MTR fuel element (equivalent to 25 or 35 kW/m3) using different convective boundary conditions around the canister wall and different cooling gases (N2 or He). For the present analysis, the Boussinesq approximation was used for the consideration of buoyancy-driven natural convection. Comparison of the CFD code can be used to predict reasonably accurate flow and thermal behavior of a typical foreign research reactor fuel stored in a dry storage facility
CFD modeling of the turbulent precipitation of plutonium oxalate in a vortex reactor
International Nuclear Information System (INIS)
Full text of publication follows:The nuclear fuel reprocessing, as it is done in La Hague COGEMA's plant, involves a precipitation in an un-baffled stirred tank to turn plutonium nitrate into plutonium oxalate prior to a calcination for using it in MOX fuel (Mixed Oxides). In every crystallization and precipitation (reactive crystallization), the key variable is sur-saturation, resulting from either a chemical reaction between two liquids, a liquid and a solid, a gas and a solid, or a decrease in the product solubility induced by temperature gradient or mixing of a solvent and an anti-solvent. According to the local sur-saturation degree, different mechanisms may occur leading to the solid dispersed phase: nucleation, growth and eventually aggregation, breakage and ripening. The challenge in that kind of modeling lies in the non linear behavior of the physical and chemical phenomenons, and in the different time and length scales involved which can not be solved without resorting to computational fluid dynamics (CFD). The modeling philosophy used here is divided in two parts: (1) a lower mesh statistical mixing model (FM-PDF) and a liquid energy spectrum model coupled to the RANS equations, for taking into account the continuous liquid phase mixing at various levels: reactor scale, turbulent dispersion and molecular diffusion; (2) a population balance model for the solid dispersed phase to link flow pattern to the morphology and chemical properties of particles. Many approaches have been developed so far to solve PBE but the recent breakthrough that allowed implementation of that equation in CFD codes is QMOM: quadrature method of moments, that represents the particle size distribution (PSD) in a finite number of delta functions, corresponding to abscissas and weights of the quadrature, which are used to calculate the mean particle size or whatever moment of the PSD. Part (1) has been successfully validated experimentally by means of an acid-base neutralization
Modeling flow inside an anaerobic digester by CFD techniques
Directory of Open Access Journals (Sweden)
Alexandra Martínez Mendoza, Tatiana Montoya Martínez, Vicente Fajardo Montañana, P. Amparo López Jiménez
2011-11-01
Full Text Available Anaerobic processes are used to treat high strength organic wastewater as well as for the treatment of primary and secondary sludge from conventional wastewater treatment plants. In these processes, heterotrophic microorganisms convert biodegradable organic matter to methane and carbon dioxide in the absence of dissolved oxygen and nitrate. Some of the most important aspects of the design of anaerobic digesters are related to hydraulic considerations. In spite of its important role in performance, hydraulics of flow inside digesters has not been quantified or adequately characterized. In this contribution a three-dimensional steady-state computational fluid dynamics (CFD simulation has been performed for a particular anaerobic digester, in order to visualize the flow patterns. Flow and velocities profiles have been represented inside the digester to identify possible dead zones or stratifications. The geometry of a real digester installed in Valencia Waste Water Treatment Plant (located in Quart-Benager, Valencia, Spain has been used in order to consider the proposed methodology.
CFD Model of Water Droplet Transport for ISS Hygiene Activity
Son, Chang H.
2011-01-01
The goal of the study is to assess the impacts of free water propagation in the Waste and Hygiene Compartment (WHC). Free water can be generated inside the WHC in small quantities due to crew hygiene activity. To mitigate potential impact of free water in Node 3 cabin the WHC doorway is enclosed by a waterproof bump-out, Kabin, with openings at the top and bottom. At the overhead side of the rack, there is a screen that prevents large drops of water from exiting. However, as the avionics fan in the WHC causes airflow toward the deck side of the rack, small quantities of free water may exit at the bottom of the Kabin. A Computational Fluid Dynamics (CFD) analysis of Node 3 cabin airflow made possible to identify the paths of water transport. The Node 3 airflow was computed for several ventilation scenarios. To simulate the droplet transport the Lagrangian discrete phase approach was used. Various initial droplet distributions were considered in the study. The droplet diameter was varied in the range of 2-20 mm. The results of the computations showed that most of the drops fall to the rack surface not far from the WHC curtain. The probability of the droplet transport to the adjacent rack surface with electronic equipment was predicted.
Modelling die filling with charged particles using DEM/CFD
Institute of Scientific and Technical Information of China (English)
Emmanuel Nkem Nwose; Chunlei Pei; Chuan-Yu Wu
2012-01-01
The effects of electrostatic charge on powder flow behaviour during die filling in a vacuum and in air were analysed using a coupled discrete element method and computational fluid dynamics (DEM/CFD) code,in which long range electrostatic interactions were implemented.The present 2D simulations revealed that both electrostatic charge and the presence of air can affect the powder flow behaviour during die filling.It was found that the electrostatic charge inhibited the flow of powders into the die and induced a loose packing structure.At the same filling speed,increasing the electrostatic charge led to a decrease in the fill ratio which quantifies the volumetric occupancy of powder in the die.In addition,increasing the shoe speed caused a further decrease in the fill ratio,which was characterised using the concept of critical filling speed.When the electrostatic charge was low,the air/particle interaction was strong so that a lower critical filling speed was obtained for die filling in air than in a vacuum.With high electrostatic charge,the electrostatic interactions became dominant.Consequently,similar fill ratio and critical filling speed were obtained for die filling in air and in a vacuum.
Application Of CFD To Modeling Of Squeeze Mode Magnetorheological Dampers
Directory of Open Access Journals (Sweden)
Gołdasz Janusz
2015-09-01
Full Text Available The so-called squeeze flow involves a magnetorheological (MR fluid sandwiched between two planar surfaces setting up a flow channel. The height of the channel varies according to a prescribed displacement or force profile. When exposed to a magnetic field of sufficient strength MR fluids develop a yield stress. In squeeze-mode devices the yield stress varies with both the magnetic field magnitude and the channel height. In this paper an unsteady flow model of an MR fluid in squeeze mode is proposed. The model is developed in Ansys Fluent R16. The MR material flow model is based on the apparent viscosity approach. In order to investigate the material's behaviour the authors prepared a model of an idealized squeeze-mode damper in which the fluid flow is enforced by varying the height of the channel. Using mesh animation, the model plate is excited, and as the mesh moves, the fluid is squeezed out of the gap. In the simulations the model is subjected to a range of displacement inputs of frequencies from 10 to 20 Hz, and local yield stress levels up to 30 kPa. The results are presented in the form of time histories of the normal force on the squeezing plate and loops of force vs. displacement (velocity.
International Nuclear Information System (INIS)
Recent national and international emission legislations to reduce emissions of carbon dioxide are forcing power generation industries using coal to look at various alternatives, such as biomass and especially by co-firing techniques. Biomass is transported to the burners either mixed with the primary fuel, in general, coal, or used in dedicated pipelines. In both cases, transportation of biomass is difficult due to its composition, size, shape and physical behaviour in comparison to the transportation of coal. This study considers experimental measurements for biomass particle transportation in a pipeline with a transverse elbow and compares the results with those using computation fluid dynamic (CFD) techniques. Various materials: flour, willow, wood, bark and a mixture of flour and willow, have been considered in the present investigation. The experimental work was performed using the dynamic changes in the electrostatic charges of biomass particles in conjunction with correlation signal processing techniques. The CFD simulations were performed by considering the effects of gravity, non-spherical drag (based on estimated shape factor), detailed information of the particle distribution, particle wall collisions and particle–particle interactions. Good quantitative and qualitative agreement was obtained between the CFD simulations and the experimental data. It is concluded that particle–particle interactions are of less importance if the mass loading ratio of particles to air is less than 0.03. -- Highlights: ► Dispersed biomass particle transportation is studied using experiments and CFD. ► Inclusion of asphericity in the drag model clearly demonstrated the improvements. ► Gravity effects are found to be important for correct particle distribution in pipe lines. ► Inter-particle collisions were less important for mass loading ratios <0.05 kg/kg.
Mishra, Kirti Bhushan
2015-09-01
A volumetric source based CFD (Computational Fluid Dynamics) model for estimating the wind and gravity driven spread of an elevated released dense hazardous cloud on a flat terrain without and with obstacles is demonstrated. The model considers the development of a worst-case scenario similar to that occurred at Bhopal. Fully developed clouds of a dense gas having different densities, under ABL (Atmospheric Boundary Layer) with calm ground wind conditions are first obtained. These clouds are then allowed to spread under ABL with different ground wind speeds and gravity conditions. The developed model is validated by performing the grid independent study, the fluid dynamical evidences, post-disaster facts, the downwind MIC (Methyl Isocynate) concentrations estimated by earlier models and experiments on dense plume trajectories. It is shown that in case of an active dispersion under calm wind conditions the lateral spread would prevail over the downwind spread. The presence of a dense medium behaves like a weak porous media and initiates turbulence at much smaller downwind distances than that normally would occur without the dense medium. The safety distances from toxic exposures of MIC are predicted by specifying an isosurface of a minimum concentration above the ground surface. Discrepancies in near-field predictions still exist. However, the far-field predictions agree well with data published before.
Validation of 3-D CFD Model of Tritium Transport in the Atmosphere
International Nuclear Information System (INIS)
When solving 3-D problems for the atmospheric impurity transport in the bounded area, it is essential for the atmospheric dynamics to be correctly computed taking into account the actual terrain topography and environments specified by the boundary conditions. Such conditions as turbulence, convection, condensation and moisture evaporation processes, etc. are to be also taken into account as well as the interaction processes among impurities (gases, aerosols), atmosphere and the Earth's surface.3-D computational fluid dynamics model(CFD) developed on the basis of SRP hydrodynamic code was used to simulate tritium plume evolution and tritium transport in atmosphere under the area with relatively complex topography. SRP code is based on the continuum motion equations (Navier-Stockes equations) and thermodynamic relations taking into account specific features of atmospheric flows and complex topography and is designed to use on PC-type computers.The model has been validated using experimental release of tritium with specified source term and meteorology. Due to low release height above the underlying surface a fine grid was used in the vertical direction near the underlying surface. HT and HTO/H2O vertical fluxes were taken into account. Evolution of HT and HTO activities at 2 sampling locations along the plume axe were available for model-experiment inter-comparison. The modeling results of HT and HTO activities in the air during plume travel are in satisfactory agreement with observed values
Development and validation of the 3-D CFD model for CANDU-6 moderator temperature predictions
International Nuclear Information System (INIS)
A computational fluid dynamics model for predicting the moderator circulation inside the CANada Deuterium Uranium (CANDU) reactor vessel has been developed to estimate the local subcooling of the moderator in the vicinity of the Calandria tubes. The buoyancy effect induced by internal heating is accounted for by Boussinesq approximation. The standard κ-ε turbulence model associated with logarithmic wall treatment is applied to predict the turbulent jet flows from the inlet nozzles. The matrix of the Calandria tubes in the core region is simplified to porous media, in which an-isotropic hydraulic impedance is modeled using an empirical correlation of the frictional pressure loss. The governing equations are solved by CFX-4.4, a commercial CFD code developed by AEA technology. The CFD model has been successfully verified and validated against experimental data obtained in the Stern Laboratories Inc. (SLI) in Hamilton, Ontario
CFD modelling and validation of wall condensation in the presence of non-condensable gases
Energy Technology Data Exchange (ETDEWEB)
Zschaeck, G., E-mail: guillermo.zschaeck@ansys.com [ANSYS Germany GmbH, Staudenfeldweg 12, Otterfing 83624 (Germany); Frank, T. [ANSYS Germany GmbH, Staudenfeldweg 12, Otterfing 83624 (Germany); Burns, A.D. [ANSYS UK Ltd, 97 Milton Park, Abingdon, Oxfordshire OX14 4RY (United Kingdom)
2014-11-15
Highlights: • A wall condensation model was implemented and validated in ANSYS CFX. • Condensation rate is assumed to be controlled by the concentration boundary layer. • Validation was done using two laboratory scale experiments. • CFD calculations show good agreement with experimental data. - Abstract: The aim of this paper is to present and validate a mathematical model implemented in ANSYS CFD for the simulation of wall condensation in the presence of non-condensable substances. The model employs a mass sink at isothermal walls or conjugate heat transfer (CHT) domain interfaces where condensation takes place. The model was validated using the data reported by Ambrosini et al. (2008) and Kuhn et al. (1997)
CFD modelling and validation of wall condensation in the presence of non-condensable gases
International Nuclear Information System (INIS)
Highlights: • A wall condensation model was implemented and validated in ANSYS CFX. • Condensation rate is assumed to be controlled by the concentration boundary layer. • Validation was done using two laboratory scale experiments. • CFD calculations show good agreement with experimental data. - Abstract: The aim of this paper is to present and validate a mathematical model implemented in ANSYS CFD for the simulation of wall condensation in the presence of non-condensable substances. The model employs a mass sink at isothermal walls or conjugate heat transfer (CHT) domain interfaces where condensation takes place. The model was validated using the data reported by Ambrosini et al. (2008) and Kuhn et al. (1997)
A Simplified CFD Model for Simulation of the Suction Process Of Reciprocating Compressors
Pereira, Evandro L. L.; Santos, Claudio J.; Deschamps, Cesar J.; Kremer, Rodrigo
2012-01-01
The suction process in reciprocating compressors is strongly affected by the valve dynamics and the pulsating flow throughout the suction muffler. This paper describes a simplified computational fluid dynamics (CFD) model to simulate the flow through the muffler, suction valve and a small region inside the cylinder. The proposed method is applied to predict the suction process of a small reciprocating compressor and its adequacy is compared with a more time elaborate model in terms of accurac...
CFD Model of HDS Catalyst Tests in Trickle-Bed Reactor
Czech Academy of Sciences Publication Activity Database
Tukač, V.; Prokešová, A.; Hanika, Jiří; Zbuzek, M.; Kubička, D.
Prague : Orgit, 2014, s. 85. ISBN 978-80-02-02555-9. [International Congress of Chemical and Process Engineering /21./ - CHISA 2014 and Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction /17./ - PRES 2014. Prague (CZ), 23.08.2014-27.08.2014] Grant ostatní: GA MPO FR-TI3/084 Institutional support: RVO:67985858 Keywords : CFD model solution * reactor bed * catalyst activity tests Subject RIV: CI - Industrial Chemistry, Chemical Engineering
Energy Technology Data Exchange (ETDEWEB)
Soria, J. [Instituto Multidisciplinario de Investigación y Desarrollo de la Patagonia Norte (IDEPA, CONICET-UNCo) y Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén (Argentina); Laboratoire Procédés, Matériaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu (France); Gauthier, D., E-mail: Daniel.Gauthier@promes.cnrs.fr [Laboratoire Procédés, Matériaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu (France); Falcoz, Q.; Flamant, G. [Laboratoire Procédés, Matériaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu (France); Mazza, G. [Instituto Multidisciplinario de Investigación y Desarrollo de la Patagonia Norte (IDEPA, CONICET-UNCo) y Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén (Argentina)
2013-03-15
Highlights: ► A 2-D local CFD model for simulating the Cd vaporization process is presented. ► It includes a kinetic expression of Cd vaporization into the incineration process. ► Pyrolysis, volatiles’ combustion and residual carbon combustion are also taken into account. ► It fits very well the experimental results obtained on a lab-scale fluidized bed reported in literature. ► It also compares favorably with a model developed previously by the group. -- Abstract: The emissions of heavy metals during incineration of Municipal Solid Waste (MSW) are a major issue to health and the environment. It is then necessary to well quantify these emissions in order to accomplish an adequate control and prevent the heavy metals from leaving the stacks. In this study the kinetic behavior of Cadmium during Fluidized Bed Incineration (FBI) of artificial MSW pellets, for bed temperatures ranging from 923 to 1073 K, was modeled. FLUENT 12.1.4 was used as the modeling framework for the simulations and implemented together with a complete set of user-defined functions (UDFs). The CFD model combines the combustion of a single solid waste particle with heavy metal (HM) vaporization from the burning particle, and it takes also into account both pyrolysis and volatiles’ combustion. A kinetic rate law for the Cd release, derived from the CFD thermal analysis of the combusting particle, is proposed. The simulation results are compared with experimental data obtained in a lab-scale fluidized bed incinerator reported in literature, and with the predicted values from a particulate non-isothermal model, formerly developed by the authors. The comparison shows that the proposed CFD model represents very well the evolution of the HM release for the considered range of bed temperature.
International Nuclear Information System (INIS)
Highlights: ► A 2-D local CFD model for simulating the Cd vaporization process is presented. ► It includes a kinetic expression of Cd vaporization into the incineration process. ► Pyrolysis, volatiles’ combustion and residual carbon combustion are also taken into account. ► It fits very well the experimental results obtained on a lab-scale fluidized bed reported in literature. ► It also compares favorably with a model developed previously by the group. -- Abstract: The emissions of heavy metals during incineration of Municipal Solid Waste (MSW) are a major issue to health and the environment. It is then necessary to well quantify these emissions in order to accomplish an adequate control and prevent the heavy metals from leaving the stacks. In this study the kinetic behavior of Cadmium during Fluidized Bed Incineration (FBI) of artificial MSW pellets, for bed temperatures ranging from 923 to 1073 K, was modeled. FLUENT 12.1.4 was used as the modeling framework for the simulations and implemented together with a complete set of user-defined functions (UDFs). The CFD model combines the combustion of a single solid waste particle with heavy metal (HM) vaporization from the burning particle, and it takes also into account both pyrolysis and volatiles’ combustion. A kinetic rate law for the Cd release, derived from the CFD thermal analysis of the combusting particle, is proposed. The simulation results are compared with experimental data obtained in a lab-scale fluidized bed incinerator reported in literature, and with the predicted values from a particulate non-isothermal model, formerly developed by the authors. The comparison shows that the proposed CFD model represents very well the evolution of the HM release for the considered range of bed temperature
A CFD numerical model for the flow distribution in a MTR fuel element
International Nuclear Information System (INIS)
Previously, an instrumented dummy fuel element (DMPV-01), with the same geometric characteristics of a MTR fuel element, was designed and constructed for pressure drop and flow distribution measurement experiments at the IEA-R1 reactor core. This dummy element was also used to measure the flow distribution among the rectangular flow channels formed by element fuel plates. A CFD numerical model was developed to complement the studies. This work presents the proposed CFD model as well as a comparison between numerical and experimental results of flow rate distribution among the internal flow channels. Numerical results show that the model reproduces the experiments very well and can be used for the studies as a more convenient and complementary tool. (author)
A CFD numerical model for the flow distribution in a MTR fuel element
Energy Technology Data Exchange (ETDEWEB)
Andrade, Delvonei Alves de; Santos, Pedro Henrique Di Giovanni; Oliveira, Fabio Branco Vaz de; Torres, Walmir Maximo; Umbehaun, Pedro Ernesto; Souza, Jose Antonio Batista de; Belchior Junior, Antonio; Sabundjian, Gaiane; Prado, Adelk de Carvalho, E-mail: acprado@ipen.br, E-mail: delvonei@ipen.br, E-mail: dpedro_digiovanni_s@hotmail.com, E-mail: fabio@ipen.br, E-mail: wmtorres@ipen.br, E-mail: umbehaun@ipen.br, E-mail: jasouza@ipen.br, E-mail: abelchior@ipen.br, E-mail: gdjian@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear; Angelo, Edvaldo, E-mail: eangelo@mackenzie.br [Universidade Presbiteriana Mackenzie, Sao Paulo, SP (Brazil); Angelo, Gabriel, E-mail: gangelo@fei.edu.br [Fundacao Educacional Inaciana (FEI), Sao Bernardo do Campo, SP (Brazil)
2015-07-01
Previously, an instrumented dummy fuel element (DMPV-01), with the same geometric characteristics of a MTR fuel element, was designed and constructed for pressure drop and flow distribution measurement experiments at the IEA-R1 reactor core. This dummy element was also used to measure the flow distribution among the rectangular flow channels formed by element fuel plates. A CFD numerical model was developed to complement the studies. This work presents the proposed CFD model as well as a comparison between numerical and experimental results of flow rate distribution among the internal flow channels. Numerical results show that the model reproduces the experiments very well and can be used for the studies as a more convenient and complementary tool. (author)
Numerical estimation of wall friction ratio near the pseudo-critical point with CFD-models
International Nuclear Information System (INIS)
In this paper, the STAR-CCM+ CFD code is used in the attempt to reproduce the values of friction factor observed in experimental data at supercritical pressures at various operating conditions. A short survey of available data and correlations for smooth pipe friction in circular pipes puts the basis for the discussion, reporting observed trends of friction factor in the liquid-like and the gas-like regions and within the transitional region across the pseudo-critical temperature. For smooth pipes, a general decrease of the friction factor in the transitional region is reported, constituting one of the relevant effects to be predicted by the computational fluid-dynamic models. A limited number of low-Reynolds number models are adopted, making use of refined near-wall discretisation as required by the constraint y+ < 1 at the wall. In particular, the Lien k–ε and the SST k–ω models are considered. The values of the wall shear stress calculated by the code are then post-processed on the basis of bulk fluid properties to obtain the Fanning and then the Darcy–Weisbach friction factors, based on their classical definitions. The obtained values are compared with those provided by experimental tests and correlations, finding a reasonable qualitative agreement. Expectedly, the agreement is better in the gas-like and liquid-like regions, where fluid property changes are moderate, than in the transitional region, where the trends provided by available correlations are reproduced only in a qualitative way
Modeling and Simulation of Fixed Bed Adsorption Column using Integrated CFD Approach
Directory of Open Access Journals (Sweden)
A.M. Shariff
2010-01-01
Full Text Available The understanding of detailed fluid flow in the fixed bed adsorption column is substantially crucial since the mass and heat transfer in the bed is influenced by the column hydrodynamics. In this study, an integrated CFD model was developed to model and simulate the adsorption dynamics and hydrodynamics of gaseous fluid (CH4 and CO2 mixture in the fixed bed adsorption column. The developed integrated model was used to determine the CO2 concentration factor at the column (which indicating the CO2 adsorption capacity as a function of time, based on different operating conditions. The simulated results were compared with experimental data and found to give a good agreement with error less than 2.5%. The effect of various influencing parameters such as feed velocity, bed porosity and feed concentration were studied to investigate their influences on the CO2 adsorption capacity. Besides, the effect of inlet CO2 concentration on the bed temperature profile was also studied in the present study.
National Aeronautics and Space Administration — CFD-based design-oriented (DO) steady/unsteady aerodynamic analysis tools for Aeroelastic / Aeroservoelastic (AE/ASE) evaluation lag significantly behind other...
A CFD model for biomass combustion in a packed bed furnace
Karim, Md. Rezwanul; Ovi, Ifat Rabbil Qudrat; Naser, Jamal
2016-07-01
Climate change has now become an important issue which is affecting environment and people around the world. Global warming is the main reason of climate change which is increasing day by day due to the growing demand of energy in developed countries. Use of renewable energy is now an established technique to decrease the adverse effect of global warming. Biomass is a widely accessible renewable energy source which reduces CO2 emissions for producing thermal energy or electricity. But the combustion of biomass is complex due its large variations and physical structures. Packed bed or fixed bed combustion is the most common method for the energy conversion of biomass. Experimental investigation of packed bed biomass combustion is difficult as the data collection inside the bed is challenging. CFD simulation of these combustion systems can be helpful to investigate different operational conditions and to evaluate the local values inside the investigation area. Available CFD codes can model the gas phase combustion but it can't model the solid phase of biomass conversion. In this work, a complete three-dimensional CFD model is presented for numerical investigation of packed bed biomass combustion. The model describes the solid phase along with the interface between solid and gas phase. It also includes the bed shrinkage due to the continuous movement of the bed during solid fuel combustion. Several variables are employed to represent different parameters of solid mass. Packed bed is considered as a porous bed and User Defined Functions (UDFs) platform is used to introduce solid phase user defined variables in the CFD. Modified standard discrete transfer radiation method (DTRM) is applied to model the radiation heat transfer. Preliminary results of gas phase velocity and pressure drop over packed bed have been shown. The model can be useful for investigation of movement of the packed bed during solid fuel combustion.
Soria, J; Gauthier, D; Falcoz, Q; Flamant, G; Mazza, G
2013-03-15
The emissions of heavy metals during incineration of Municipal Solid Waste (MSW) are a major issue to health and the environment. It is then necessary to well quantify these emissions in order to accomplish an adequate control and prevent the heavy metals from leaving the stacks. In this study the kinetic behavior of Cadmium during Fluidized Bed Incineration (FBI) of artificial MSW pellets, for bed temperatures ranging from 923 to 1073 K, was modeled. FLUENT 12.1.4 was used as the modeling framework for the simulations and implemented together with a complete set of user-defined functions (UDFs). The CFD model combines the combustion of a single solid waste particle with heavy metal (HM) vaporization from the burning particle, and it takes also into account both pyrolysis and volatiles' combustion. A kinetic rate law for the Cd release, derived from the CFD thermal analysis of the combusting particle, is proposed. The simulation results are compared with experimental data obtained in a lab-scale fluidized bed incinerator reported in literature, and with the predicted values from a particulate non-isothermal model, formerly developed by the authors. The comparison shows that the proposed CFD model represents very well the evolution of the HM release for the considered range of bed temperature. PMID:23410804
Armenio, Vincenzo; Fakhari, Ahmad; Petronio, Andrea; Padovan, Roberta; Pittaluga, Chiara; Caprino, Giovanni
2015-11-01
Massive flow separation is ubiquitous in industrial applications, ruling drag and hydrodynamic noise. In spite of considerable efforts, its numerical prediction still represents a challenge for CFD models in use in engineering. Aside commercial software, over the latter years the opensource software OpenFOAMR (OF) has emerged as a valid tool for prediction of complex industrial flows. In the present work, we simulate two flows representative of a class of situations occurring in industrial problems: the flow around sphere and that around a wall-mounted square cylinder at Re = 10000 . We compare the performance two different tools, namely OF and ANSYS CFX 15.0 (CFX) using different unstructured grids and turbulence models. The grids have been generated using SNAPPYHEXMESH and ANSYS ICEM CFD 15.0 with different near wall resolutions. The codes have been run in a RANS mode using k - ɛ model (OF) and SST - k - ω (CFX) with and without wall-layer models. OF has been also used in LES, WMLES and DES mode. Regarding the sphere, RANS models were not able to catch separation, while good prediction of separation and distribution of stresses over the surface were obtained using LES, WMLES and DES. Results for the second test case are currently under analysis. Financial support from COSMO ``cfd open source per opera mortta'' PAR FSC 2007-2013, Friuli Venezia Giulia.
CFD to modeling molten core behavior simultaneously with chemical phenomena
International Nuclear Information System (INIS)
Full text of publication follows: This paper deals with the basic features of a computing procedure, which can be used for modeling of destruction and melting of a core with subsequent corium retaining into the reactor vessel. The destruction and melting of core mean the account of the following phenomena: a melting, draining (moving of the melt through a porous layer of core debris), freezing with release of an energy, change of geometry, formation of the molten pool, whose convective intermixing and distribution influence on a mechanism of borders destruction. It is necessary to take into account that during of heating molten pool and development in it of convective fluxes a stratification of a multi-component melt on two layers of metal light and of oxide heavy components is observed. These layers are in interaction, they can exchange by the separate components as result of diffusion or oxidizing reactions. It can have an effect considerably on compositions, on a specific weight, and on properties of molten interacting phases, and on a structure of the molten stratified pool. In turn, the retaining of the formed molten masses in reactor vessel requires the solution of a matched heat exchange problem, namely, of a natural convection in a heat generating fluid in partially or completely molten corium and of heat exchange problem with taking into account of a melting of the reactor vessel. In addition, it is necessary to take into account phase segregation, caused by influence of local and of global natural convective flows and thermal lag of heated up boundaries. The mathematical model for simulation of the specified phenomena is based on the Navier-Stokes equations with variable properties together with the heat transfer equation. For modeling of a corium moving through a porous layer of core debris, the special computing algorithm to take into account density jump on interface between a melt and a porous layer of core debris is designed. The model was
Energy Technology Data Exchange (ETDEWEB)
Rogel-Ramirez, A [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)]. E-mail: ARogelR@iingen.unam.mx
2008-10-15
This paper contains the description of a bidimensional Computational Fluid Dynamics (CFD), model Developer to simulate the flow and reaction in a stratified downdraft biomass gasifier, whereby Eulerian conservation equations are solved for particle and gas phase components, velocities and specific enthalpies. The model is based on the PHOENICS package and represents a tool which can be used in gasifier analysis and design. Contributions of chemical kinetics and the mixing rate using the EBU approach are considered in the gas phase global homogeneous reactions. The harmonic blending of chemical kinetics and mass transfer effects, determine the global heterogeneous reactions between char and O{sub 2}, CO{sub 2} and H{sub 2}O. The turbulence effect in the gas phase is accounted by the standard {kappa}-{epsilon} approach. The model provides information of the producer gas composition, velocities and temperature at the outlet, and allows different operating parameters and feed properties to be changed. Finally, a comparison with experimental data available in literature was done, which showed satisfactory agreement from a qualitative point of view, though further validation is required. [Spanish] Este estudio describe un modelo numerico bidimensional, basado en Dinamica de Fluidos Computacional (CFD), desarrollado para simular el flujo y las reacciones que ocurren en un gasificador estratificado de flujos paralelos, en el que se resuelven ecuaciones de conservacion Eulerianas para los componentes de la fase gaseosa, la fase solida, velocidades y entalpias especificas. El modelo esta basado en el codigo PHOENICS y representa una herramienta que puede ser utilizada en el analisis y diseno de gasificadores. En las reacciones globales homogeneas se consideran las contribuciones de la cinetica quimica y la rapidez de mezclado, usando el modelo Eddy Brake-UP (EBU). La medida harmonica de la cinetica quimica y la transferencia de masa, determinan las velocidades globales de
Computational Fluid Dynamics (CFD) simulations provide a number of unique opportunities for expanding and improving capabilities for modeling exposures to environmental pollutants. The US Environmental Protection Agency's National Exposure Research Laboratory (NERL) has been c...
Validation of Hydrodynamic Load Models Using CFD for the OC4-DeepCwind Semisubmersible: Preprint
Energy Technology Data Exchange (ETDEWEB)
Benitz, M. A.; Schmidt, D. P.; Lackner, M. A.; Stewart, G. M.; Jonkman, J.; Robertson, A.
2015-03-01
Computational fluid dynamics (CFD) simulations were carried out on the OC4-DeepCwind semi-submersible to obtain a better understanding of how to set hydrodynamic coefficients for the structure when using an engineering tool such as FAST to model the system. The focus here was on the drag behavior and the effects of the free-surface, free-ends and multi-member arrangement of the semi-submersible structure. These effects are investigated through code-to-code comparisons and flow visualizations. The implications on mean load predictions from engineering tools are addressed. The work presented here suggests that selection of drag coefficients should take into consideration a variety of geometric factors. Furthermore, CFD simulations demonstrate large time-varying loads due to vortex shedding, which FAST's hydrodynamic module, HydroDyn, does not model. The implications of these oscillatory loads on the fatigue life needs to be addressed.
Optimisation of pulverised coal combustion by means of CFD/CTA modelling
Energy Technology Data Exchange (ETDEWEB)
Risto V. Filkoski; Ilija J. Petrovski; Piotr Karas [University of Cyriul and Methodius, Skopje (Republic of Macedonia). Faculty of Mechanical Engineering
2006-07-01
A method was applied for handling two-phase reacting flow for prediction of pulverised coal combustion in large-scale boiler furnace and to assess the ability of the model to predict existing power plant data. The paper presents the principal steps and results of the numerical modelling of power boiler furnace with tangential disposition of the burners. The computational fluid dynamics/computational thermal analysis (CFD/CTA) approach is utilised for creation of a three-dimensional model of the boiler furnace, including the platen superheater in the upper part of the furnace. Standard k-{epsilon} model is employed for description of the turbulent flow. Coal combustion is modelled by the mixture fraction/probability density function approach for the reaction chemistry, with equilibrium assumption applied for description of the system chemistry. Radiation heat transfer is computed by means of the simplified P-N model, based on the expansion of the radiation intensity into an orthogonal series of spherical harmonics. Some distinctive results regarding the examined boiler performance in capacity range between 65 and 95 % are presented graphically. Comparing the simulation predictions and available site measurements concerning temperature, heat flux and combustion efficiency, the model produces realistic insight into the furnace processes. After the validation and verification of the model it was used to check the combustion efficiency as a function of coal dust sieve characteristics, as well as the impact of burners modification with introduction of OFA ports to the appearance of incomplete combustion, including CO concentration, as well as to the NOx concentration. 22 refs., 18 figs., 5 tabs.
Modeling and Simulation of Hamburger Cooking Process Using Finite Difference and CFD Methods
Directory of Open Access Journals (Sweden)
J. Sargolzaei
2011-01-01
Full Text Available Unsteady-state heat transfer in hamburger cooking process was modeled using one dimensional finite difference (FD and three dimensional computational fluid dynamic (CFD models. A double-sided cooking system was designed to study the effect of pressure and oven temperature on the cooking process. Three different oven temperatures (114, 152, 204°C and three different pressures (20, 332, 570 pa were selected and 9 experiments were performed. Applying pressure to hamburger increases the contact area of hamburger with heating plate and hence the heat transfer rate to the hamburger was increased and caused the weight loss due to water evaporation and decreasing cooking time, while increasing oven temperature led to increasing weight loss and decreasing cooking time. CFD predicted results were in good agreement with the experimental results than the finite difference (FD ones. But considering the long time needed for CFD model to simulate the cooking process (about 1 hour, using the finite difference model would be more economic.
Energy Technology Data Exchange (ETDEWEB)
Torano, J.; Torno, S.; Menendez, M.; Gent, M. [University of Oviedo, Asturias (Spain)
2010-01-15
The production of dust when driving mining roadways can affect workers health. In addition, there is a decrease in productivity since Mine Safety regulations establish a reduction in the working time depending on the quartz content and dust concentration in the atmosphere. One of the gate roadways of the longwall named E4-S, belonging to the underground coal mine Carbonar SA located in Northern Spain, is being driven by an AM50 roadheader machine. The mined coal has a high coal dust content. This paper presents a study of dust behaviour in two auxiliary ventilation systems by Computational Fluid Dynamics (CFD) models, taking into account the influence of time. The accuracy of these CFD models was assessed by airflow velocity and respirable dust concentration measurements taken in six points of six roadway cross-sections of the mentioned operating coal mine. It is concluded that these models predicted the airflow and dust behaviour at the working face, where the dust source is located, and in different roadways cross-sections behind the working face. As a result, CFD models allow optimization of the auxiliary ventilation system used, avoiding the important deficiencies when it is calculated by conventional methods.