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.
Validation and Analysis of Forward Osmosis CFD Model in Complex 3D Geometries
Directory of Open Access Journals (Sweden)
Lars Yde
2012-11-01
Full Text Available In forward osmosis (FO, an osmotic pressure gradient generated across a semi-permeable membrane is used to generate water transport from a dilute feed solution into a concentrated draw solution. This principle has shown great promise in the areas of water purification, wastewater treatment, seawater desalination and power generation. To ease optimization and increase understanding of membrane systems, it is desirable to have a comprehensive model that allows for easy investigation of all the major parameters in the separation process. Here we present experimental validation of a computational fluid dynamics (CFD model developed to simulate FO experiments with asymmetric membranes. Simulations are compared with experimental results obtained from using two distinctly different complex three-dimensional membrane chambers. It is found that the CFD model accurately describes the solute separation process and water permeation through membranes under various flow conditions. It is furthermore demonstrated how the CFD model can be used to optimize membrane geometry in such as way as to promote the mass transfer.
A workflow for patient-individualized virtual angiogram generation based on CFD simulation.
Endres, Jürgen; Kowarschik, Markus; Redel, Thomas; Sharma, Puneet; Mihalef, Viorel; Hornegger, Joachim; Dörfler, Arnd
2012-01-01
Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases. PMID:23193428
A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation
Directory of Open Access Journals (Sweden)
Jürgen Endres
2012-01-01
Full Text Available Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.
Hajati, Omid; Zarrabi, Khalil; Karimi, Reza; Hajati, Azadeh
2012-01-01
There is still controversy over the differences in the patency rates of the sequential and individual coronary artery bypass grafting (CABG) techniques. The purpose of this paper was to non-invasively evaluate hemodynamic parameters using complete 3D computational fluid dynamics (CFD) simulations of the sequential and the individual methods based on the patient-specific data extracted from computed tomography (CT) angiography. For CFD analysis, the geometric model of coronary arteries was reconstructed using an ECG-gated 64-detector row CT. Modeling the sequential and individual bypass grafting, this study simulates the flow from the aorta to the occluded posterior descending artery (PDA) and the posterior left ventricle (PLV) vessel with six coronary branches based on the physiologically measured inlet flow as the boundary condition. The maximum calculated wall shear stress (WSS) in the sequential and the individual models were estimated to be 35.1 N/m(2) and 36.5 N/m(2), respectively. Compared to the individual bypass method, the sequential graft has shown a higher velocity at the proximal segment and lower spatial wall shear stress gradient (SWSSG) due to the flow splitting caused by the side-to-side anastomosis. Simulated results combined with its surgical benefits including the requirement of shorter vein length and fewer anastomoses advocate the sequential method as a more favorable CABG method. PMID:23365974
International Nuclear Information System (INIS)
The purposes of containment spray system operation during a severe accident in a light water reactor (LWR) nuclear power plant (NPP) are to depressurize the containment by steam condensation on spray droplets, to reduce the risk of hydrogen burning by mixing the containment atmosphere, and to collect radioactive aerosols from the containment atmosphere. While the depressurization may be predicted fairly well using lumped-parameter codes, the prediction of mixing and collection of aerosols requires a local description of transport phenomena. In the present work, modelling of sprays on local instantenous scale is presented and the Design of Experiment (DOE) method is used to assess the influence of boundary conditions on the simulation results. Simulation results are compared to the TOSQAN 101 spray test, which was used for a benchmarking exercise in the European Severe accident research network of excellence (SARNET). The modelling approach is based on a Lagrangian description of the dispersed liquid phase (droplets), an Eulerian approach for the description of the continuous gas phase, and a two-way interaction between the phases. The simulations are performed using a combination of the computational fluid dynamics (CFD) code CFX4.4, which solves the gas transport equations, and of a newly proposed dedicated Lagrangian droplet-tracking code. (author)
Effect of longwall face advance rate on spontaneous heating process in the gob area - CFD modelling
Czech Academy of Sciences Publication Activity Database
Taraba, B.; Michalec, Zdeněk
2011-01-01
Roč. 90, č. 8 (2011), s. 2790-2797. ISSN 0016-2361 R&D Projects: GA ČR GA105/06/0630 Grant ostatní: GA ČR(CZ) GA105/08/1414 Institutional research plan: CEZ:AV0Z30860518 Keywords : coal oxidation * spontaneous heating * CFD modelling * Fluent Subject RIV: DH - Mining , incl. Coal Mining Impact factor: 3.248, year: 2011 http://www.sciencedirect.com/science/article/pii/S0016236111001724
Development of a Common Research Model for Applied CFD Validation Studies
Vassberg, John C.; Dehaan, Mark A.; Rivers, S. Melissa; Wahls, Richard A.
2008-01-01
The development of a wing/body/nacelle/pylon/horizontal-tail configuration for a common research model is presented, with focus on the aerodynamic design of the wing. Here, a contemporary transonic supercritical wing design is developed with aerodynamic characteristics that are well behaved and of high performance for configurations with and without the nacelle/pylon group. The horizontal tail is robustly designed for dive Mach number conditions and is suitably sized for typical stability and control requirements. The fuselage is representative of a wide/body commercial transport aircraft; it includes a wing-body fairing, as well as a scrubbing seal for the horizontal tail. The nacelle is a single-cowl, high by-pass-ratio, flow-through design with an exit area sized to achieve a natural unforced mass-flow-ratio typical of commercial aircraft engines at cruise. The simplicity of this un-bifurcated nacelle geometry will facilitate grid generation efforts of subsequent CFD validation exercises. Detailed aerodynamic performance data has been generated for this model; however, this information is presented in such a manner as to not bias CFD predictions planned for the fourth AIAA CFD Drag Prediction Workshop, which incorporates this common research model into its blind test cases. The CFD results presented include wing pressure distributions with and without the nacelle/pylon, ML/D trend lines, and drag-divergence curves; the design point for the wing/body configuration is within 1% of its max-ML/D. Plans to test the common research model in the National Transonic Facility and the Ames 11-ft wind tunnels are also discussed.
Dynamic analysis of the pump system based on MOC–CFD coupled method
International Nuclear Information System (INIS)
Highlights: • MOC–CFD coupled method was proposed to get the pump internal and external characteristics. • The coupled strategy and procedure were explained. • Some typical simulation cases were made for different factors. • The pump head deviation grows with the severity of the transient. • Valve closure law in linear and longer pipeline will cause higher pump head deviation. - Abstract: The dynamic characteristics of pump response to transient events were investigated by combining the Method of Characteristic (MOC) and Computational Fluid Dynamics (CFD) together. In a typical pump–pipeline–valve system, similar to the reactor system, the pump is treated as three-dimensional CFD model using Fluent code, whereas the rest is represented by one-dimensional components using MOC. A description of the coupling theory and procedure ensuring proper communication within the two codes is given. Several transient flow operations have been carried out. In the initial steady-state simulation, the coupled method could accurately find the operating condition of the pump when the valve is fully open. When the valve is closed rapidly, preliminary comparative calculations demonstrate that the coupled method is efficient in simulating the dynamic behavior of the pump and capable of getting detailed fluid field evolutions inside the pump. Deviation between the dynamic pump head and the value given by the steady-state curve at the same instantaneous flow-rate was established, and the cause of the deviation was further explained by the comparison of pump internal and external characteristics. Furthermore, it was found that the deviation grows with the severity of the transient. In addition, the effects of valve closure laws and pipe length on the pump dynamic performances were evaluated. All the results showed that MOC–CFD is an efficient and promising way for simulating the interaction between pump model and piping system
Energy Technology Data Exchange (ETDEWEB)
Bellivier, A.
2004-05-15
For 3D modelling of thermo-aeraulics in building using field codes, it is necessary to reduce the computing time in order to model increasingly larger volumes. The solution suggested in this study is to couple two modelling: a zonal approach and a CFD approach. The first part of the work that was carried out is the setting of a simplified CFD modelling. We propose rules for use of coarse grids, a constant effective viscosity law and adapted coefficients for heat exchange in the framework of building thermo-aeraulics. The second part of this work concerns the creation of fluid Macro-Elements and their coupling with a calculation of CFD finite volume type. Depending on the boundary conditions of the problem, a local description of the driving flow is proposed via the installation and use of semi-empirical evolution laws. The Macro-Elements is then inserted in CFD computation: the values of velocity calculated by the evolution laws are imposed on the CFD cells corresponding to the Macro-Element. We use these two approaches on five cases representative of thermo-aeraulics in buildings. The results are compared with experimental data and with traditional RANS simulations. We highlight the significant gain of time that our approach allows while preserving a good quality of numerical results. (author)
CFD Modeling of Water Flow through Sudden Contraction and Expansion in a Horizontal Pipe
Kaushik, V. V. R.; Ghosh, S.; Das, G.; Das, P. K.
2011-01-01
This paper deals with the use of commercial CFD software in teaching graduate level computational fluid dynamics. FLUENT 6.3.26 was chosen as the CFD software to teach students the entire CFD process in a single course. The course objective is to help students to learn CFD, use it in some practical problems and analyze as well as validate the…
Energy configuration optimization of submerged propeller in oxidation ditch based on CFD
International Nuclear Information System (INIS)
The submerged propeller is presented as an important dynamic source in oxidation ditch. In order to guarantee the activated sludge not deposit, it is necessary to own adequate drive power. Otherwise, it will cause many problems such as the awful mixed flow and the great consuming of energy. At present, carrying on the installation optimization of submerged propeller in oxidation ditch mostly depends on experience. So it is necessary to use modern design method to optimize the installation position and number of submerged propeller, and to research submerged propeller flow field characteristics. The submerged propeller internal flow is simulated by using CFD software FLUENT6.3. Based on Navier-Stokes equations and standard k − ε turbulence model, the flow was simulated by using a SIMPLE algorithm. The results indicate that the submerged propeller installation position change could avoid the condition of back mixing, which caused by the strong drive. Besides, the problem of sludge deposit and the low velocity in the bend which caused by the drive power attenuation could be solved. By adjusting the submerged propeller number, the least power density that the mixing drive needed could be determined and saving energy purpose could be achieved. The study can provide theoretical guidance for optimize the submerged propeller installation position and determine submerged propeller number.
Application of CFD techniques toward the validation of nonlinear aerodynamic models
Schiff, L. B.; Katz, J.
1985-01-01
Applications of computational fluid dynamics (CFD) methods to determine the regimes of applicability of nonlinear models describing the unsteady aerodynamic responses to aircraft flight motions are described. The potential advantages of computational methods over experimental methods are discussed and the concepts underlying mathematical modeling are reviewed. The economic and conceptual advantages of the modeling procedure over coupled, simultaneous solutions of the gas dynamic equations and the vehicle's kinematic equations of motion are discussed. The modeling approach, when valid, eliminates the need for costly repetitive computation of flow field solutions. For the test cases considered, the aerodynamic modeling approach is shown to be valid.
Giannuzzi, M.
2014-07-01
In electronic systems the presence of bluff bodies, sharp corners and bends are the cause of flow separation and large recirculation bubbles. Since the recirculation vortices develop they encapsulate the heat from an electronic component becoming one of the major contributors of malfunction. Going in depth in this, some numerical simulations of conjugate heat transfer for a heat wall-mounted cube have been performed using the commercial CFD code scSTREAM V11 by Software Cradle Co, Ltd. It is well known that the reliability of CFD analysis depends heavily on the turbulent model employed together with the wall functions implemented. The three low- Reynolds k - epsilon turbulent models developed by Abe-Nagano-Kondoh have been validated against experimental data consisting mainly of velocity profiles and surface temperature distributions provided in literature. The performed validation shows a satisfactory agreement between the measured and simulated data. The turbulent model chosen is then used for the CFD simulation of a complex electronic system.
International Nuclear Information System (INIS)
In electronic systems the presence of bluff bodies, sharp corners and bends are the cause of flow separation and large recirculation bubbles. Since the recirculation vortices develop they encapsulate the heat from an electronic component becoming one of the major contributors of malfunction. Going in depth in this, some numerical simulations of conjugate heat transfer for a heat wall-mounted cube have been performed using the commercial CFD code scSTREAM V11 by Software Cradle Co, Ltd. It is well known that the reliability of CFD analysis depends heavily on the turbulent model employed together with the wall functions implemented. The three low- Reynolds k – ε turbulent models developed by Abe-Nagano-Kondoh have been validated against experimental data consisting mainly of velocity profiles and surface temperature distributions provided in literature. The performed validation shows a satisfactory agreement between the measured and simulated data. The turbulent model chosen is then used for the CFD simulation of a complex electronic system.
CFD simulation of neutral ABL flows
Zhang, Xiaodong
2009-01-01
This work is to evaluate the CFD prediction of Atmospheric Boundary Layer flow field over different terrains employing Fluent 6.3 software. How accurate the simulation could achieve depend on following aspects: viscous model, wall functions, agreement of CFD model with inlet wind velocity profile and top boundary condition. Fluent employ wall function roughness modifications based on data from experiments with sand grain roughened pipes and channels, describe wall adjacent zone with Roughness...
DEFF Research Database (Denmark)
Li, Y.; Nielsen, Peter V.
2011-01-01
There has been a rapid growth of scientific literature on the application of computational fluid dynamics (CFD) in the research of ventilation and indoor air science. With a 1000–10,000 times increase in computer hardware capability in the past 20 years, CFD has become an integral part of...... scientific research and engineering development of complex air distribution and ventilation systems in buildings. This review discusses the major and specific challenges of CFD in terms of turbulence modelling, numerical approximation, and boundary conditions relevant to building ventilation. We emphasize...... the growing need for CFD verification and validation, suggest on-going needs for analytical and experimental methods to support the numerical solutions, and discuss the growing capacity of CFD in opening up new research areas. We suggest that CFD has not become a replacement for experiment and...
International Nuclear Information System (INIS)
The accurate prediction of particle transport is a primary safety issue. Tracking particles in Lagrangian fashion can naturally be performed with CFD tools which provide the right framework to follow the paths of particles in complex geometries. The presence of turbulent structures in the fluid complicates the particle tracking problem considerably, because particle trajectories are no longer deterministic and additional modeling of the velocity fluctuations is needed. In the present investigation, a Lagrangian continuous random walk (CRW) model is developed to predict turbulent particle dispersion in wall-bounded flows with prevailing inhomogeneous turbulence. The particle model uses 3D mean flow data from the Fluent CFD code, as well as Eulerian statistics from Direct Numerical Simulation (DNS) databases. The turbulent fluid velocities are based on the non-dimensional Langevin equation. The model predictions are compared to the DNS data by Marchioli et al. (2007) who produced detailed statistics of velocity and transfer rates for classes of particles having Stokes numbers between 0.2 and 125 and dispersed in a parallel channel flow with Ret=150. The model is in very good agreement with the DNS data for the various measures of particle dispersion. The predicted deposition rates are also in good agreement with the widely used experimental correlation of McCoy and Hanratty (1977) and Liu and Agarwal (1974). (authors)
International Nuclear Information System (INIS)
The electrical capacitance tomographic (ECT) approach is increasingly seen as attractive for measurement and control applications in the process industries. Recently, there is increased interest in using the tomographic details from ECT for comparing with and validating and tuning CFD models of multiphase flow. Collaboration with researchers working in the field of computational fluid dynamics (CFD) modeling of multiphase flows gives valuable information for both groups of researchers in the field of ECT and CFD. By studying the ECT tomograms of multiphase flows under carefully monitored inflow conditions of the different media and by obtaining the capacitance values, C(i, j, t) with i = 1…N, j = 1, 2,…N and i ≠ j obtained from ECT modules with N electrodes, it is shown how the interface heights in a pipe with stratified flow of oil and air can be fruitfully compared to the values of those obtained from ECT and gamma radiation meter (GRM) for improving CFD modeling. Monitored inflow conditions in this study are flow rates of air, water and oil into a pipe which can be positioned at varying inclinations to the horizontal, thus emulating the pipelines laid in subsea installations. It is found that ECT-based tomograms show most of the features seen in the GRM-based visualizations with nearly one-to-one correspondence to interface heights obtained from these two methods, albeit some anomalies at the pipe wall. However, there are some interesting features the ECT manages to capture: features which the GRM or the CFD modeling apparently do not show, possibly due to parameters not defined in the inputs to the CFD model or much slower response of the GRM. Results presented in this paper indicate that a combination of ECT and GRM and preferably with other modalities with enhanced data fusion and analysis combined with CFD modeling can help to improve the modeling, measurement and control of multiphase flow in the oil and gas industries and in the process industries
A New Single-blade Based Hybrid CFD Method for Hovering and Forward-flight Rotor Computation
Institute of Scientific and Technical Information of China (English)
SHI Yongjie; ZHAO Qijun; FAN Feng; XU Guohua
2011-01-01
A hybrid Euler/full potential/Lagrangian wake method, based on single-blade simulation, for predicting unsteady aerodynamic flow around helicopter rotors in hover and forward flight has been developed. In this method, an Euler solver is used to model the near wake evolution and transonic flow phenomena in the vicinity of the blade, and a full potential equation (FPE) is used to model the isentropic potential flow region far away from the rotor, while the wake effects of other blades and the far wake are incorporated into the flow solution as an induced inflow distribution using a Lagrangian based wake analysis. To further reduce the execution time, the computational fluid dynamics (CFD) solution and rotor wake analysis (including induced velocity update) are conducted parallelly, and a load balancing strategy is employed to account for the information exchange between two solvers. By the developed method, several hover and forward-flight cases on Caradonna-Tung and Helishape 7A rotors are performed. Good agreements of the loadings on blade surface with available measured data demonstrate the validation of the method. Also, the CPU time required for different computation runs is compared in the paper, and the results show that the present hybrid method is superior to conventional CFD method in time cost, and will be more efficient with the number of blades increasing.
Rockslide and Impulse Wave Modelling in the Vajont Reservoir by DEM-CFD Analyses
Zhao, T.; Utili, S.; Crosta, G. B.
2016-06-01
This paper investigates the generation of hydrodynamic water waves due to rockslides plunging into a water reservoir. Quasi-3D DEM analyses in plane strain by a coupled DEM-CFD code are adopted to simulate the rockslide from its onset to the impact with the still water and the subsequent generation of the wave. The employed numerical tools and upscaling of hydraulic properties allow predicting a physical response in broad agreement with the observations notwithstanding the assumptions and characteristics of the adopted methods. The results obtained by the DEM-CFD coupled approach are compared to those published in the literature and those presented by Crosta et al. (Landslide spreading, impulse waves and modelling of the Vajont rockslide. Rock mechanics, 2014) in a companion paper obtained through an ALE-FEM method. Analyses performed along two cross sections are representative of the limit conditions of the eastern and western slope sectors. The max rockslide average velocity and the water wave velocity reach ca. 22 and 20 m/s, respectively. The maximum computed run up amounts to ca. 120 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 and 190 m, respectively). Therefore, the overall study lays out a possible DEM-CFD framework for the modelling of the generation of the hydrodynamic wave due to the impact of a rapid moving rockslide or rock-debris avalanche.
Directory of Open Access Journals (Sweden)
A.H. Abdullah
2009-12-01
Full Text Available Computational Fluid Dynamics (CFD programs are powerful design tools that can predict detailed flow movement, temperature distribution, and contaminant dispersion. This paper reports the steady-state 3-D CFD modelling of air movement and temperature distribution due to thermal buoyancy within top-lit three-storey representative Malaysian atrium forms using the computer code PHOENICS. Details of temperature distribution, airflow patterns and other comfort parameters would provide a better picture of the resultant thermal performance within the atrium in response to the changes of design variables. The CFD modelling studies were to investigate quantitatively the effects of varying inlet to outlet opening area ratios and also the outlet’s arrangement on the atrium’s thermal environmental performance in relation to occupants’ thermal comfort. The simulation results have revealed that sufficiently higher inlet to outlet opening area ratio (i.e. n>1 can improve the thermal performance on the occupied levels; while with an equal inlet to outlet opening area ratio (i.e. n=1, changing the outlet’s arrangement (i.e. location and configuration has not significantly affected the atrium’s thermal performance.
CFD analysis and flow model reduction for surfactant production in helix reactor
Directory of Open Access Journals (Sweden)
Nikačević N.M.
2015-01-01
Full Text Available Flow pattern analysis in a spiral Helix reactor is conducted, for the application in the commercial surfactant production. Step change response curves (SCR were obtained from numerical tracer experiments by three-dimensional computational fluid dynamics (CFD simulations. Non-reactive flow is simulated, though viscosity is treated as variable in the direction of flow, as it increases during the reaction. The design and operating parameters (reactor diameter, number of coils and inlet velocity are varied in CFD simulations, in order to examine the effects on the flow pattern. Given that 3D simulations are not practical for fast computations needed for optimization, scale-up and control, CFD flow model is reduced to one-dimensional axial dispersion (AD model with spatially variable dispersion coefficient. Dimensionless dispersion coefficient (Pe is estimated under different conditions and results are analyzed. Finally, correlation which relates Pe number with Reynolds number and number of coils from the reactor entrance is proposed for the particular reactor application and conditions.
Chen, Lei; Chen, Youhua; Huang, Kai; Liu, Songlin
2015-12-01
Lithium ceramic pebble beds have been considered in the solid blanket design for fusion reactors. To characterize the fusion solid blanket thermal performance, studies of the effective thermal properties, i.e. the effective thermal conductivity and heat transfer coefficient, of the pebble beds are necessary. In this paper, a 3D computational fluid dynamics discrete element method (CFD-DEM) coupled numerical model was proposed to simulate heat transfer and thereby estimate the effective thermal properties. The DEM was applied to produce a geometric topology of a prototypical blanket pebble bed by directly simulating the contact state of each individual particle using basic interaction laws. Based on this geometric topology, a CFD model was built to analyze the temperature distribution and obtain the effective thermal properties. The current numerical model was shown to be in good agreement with the existing experimental data for effective thermal conductivity available in the literature. supported by National Special Project for Magnetic Confined Nuclear Fusion Energy of China (Nos. 2013GB108004, 2015GB108002, 2014GB122000 and 2014GB119000), and National Natural Science Foundation of China (No. 11175207)
Hadade, Ioan; di Mare, Luca
2016-08-01
Modern multicore and manycore processors exhibit multiple levels of parallelism through a wide range of architectural features such as SIMD for data parallel execution or threads for core parallelism. The exploitation of multi-level parallelism is therefore crucial for achieving superior performance on current and future processors. This paper presents the performance tuning of a multiblock CFD solver on Intel SandyBridge and Haswell multicore CPUs and the Intel Xeon Phi Knights Corner coprocessor. Code optimisations have been applied on two computational kernels exhibiting different computational patterns: the update of flow variables and the evaluation of the Roe numerical fluxes. We discuss at great length the code transformations required for achieving efficient SIMD computations for both kernels across the selected devices including SIMD shuffles and transpositions for flux stencil computations and global memory transformations. Core parallelism is expressed through threading based on a number of domain decomposition techniques together with optimisations pertaining to alleviating NUMA effects found in multi-socket compute nodes. Results are correlated with the Roofline performance model in order to assert their efficiency for each distinct architecture. We report significant speedups for single thread execution across both kernels: 2-5X on the multicore CPUs and 14-23X on the Xeon Phi coprocessor. Computations at full node and chip concurrency deliver a factor of three speedup on the multicore processors and up to 24X on the Xeon Phi manycore coprocessor.
Wu, Binxin
2011-02-01
This study evaluates six turbulence models for mechanical agitation of non-Newtonian fluids in a lab-scale anaerobic digestion tank with a pitched blade turbine (PBT) impeller. The models studied are: (1) the standard k-ɛ model, (2) the RNG k-ɛ model, (3) the realizable k-ɛ model, (4) the standard k-ω model, (5) the SST k-ω model, and (6) the Reynolds stress model. Through comparing power and flow numbers for the PBT impeller obtained from computational fluid dynamics (CFD) with those from the lab specifications, the realizable k-ɛ and the standard k-ω models are found to be more appropriate than the other turbulence models. An alternative method to calculate the Reynolds number for the moving zone that characterizes the impeller rotation is proposed to judge the flow regime. To check the effect of the model setup on the predictive accuracy, both discretization scheme and numerical approach are investigated. The model validation is conducted by comparing the simulated velocities with experimental data in a lab-scale digester from literature. Moreover, CFD simulation of mixing in a full-scale digester with two side-entry impellers is performed to optimize the installation. PMID:21216428
CFD Optimization on Network-Based Parallel Computer System
Cheung, Samson H.; VanDalsem, William (Technical Monitor)
1994-01-01
Combining multiple engineering workstations into a network-based heterogeneous parallel computer allows application of aerodynamic optimization with advance computational fluid dynamics codes, which is computationally expensive in mainframe supercomputer. This paper introduces a nonlinear quasi-Newton optimizer designed for this network-based heterogeneous parallel computer on a software called Parallel Virtual Machine. This paper will introduce the methodology behind coupling a Parabolized Navier-Stokes flow solver to the nonlinear optimizer. This parallel optimization package has been applied to reduce the wave drag of a body of revolution and a wing/body configuration with results of 5% to 6% drag reduction.
Parallel CFD design on network-based computer
Cheung, Samson
1995-01-01
Combining multiple engineering workstations into a network-based heterogeneous parallel computer allows application of aerodynamic optimization with advanced computational fluid dynamics codes, which can be computationally expensive on mainframe supercomputers. This paper introduces a nonlinear quasi-Newton optimizer designed for this network-based heterogeneous parallel computing environment utilizing a software called Parallel Virtual Machine. This paper will introduce the methodology behind coupling a Parabolized Navier-Stokes flow solver to the nonlinear optimizer. This parallel optimization package is applied to reduce the wave drag of a body of revolution and a wing/body configuration with results of 5% to 6% drag reduction.
Directory of Open Access Journals (Sweden)
Deimel Christian
2014-03-01
Full Text Available The most common method for simulating cavitating flows is using the governing flow equations in a form with a variable density and treats both phases as incompressible in combination with a transport equation for the vapour volume fraction. This approach is commonly referred to as volume of fluid method (VoF. To determine the transition of the liquid phase to vapour and vice versa, a relation for the mass transfer is needed. Several models exist, based on slightly differing physical assumptions, for example derivation from the dynamics of single bubbles or large bubble clusters. In our simulation, we use the model of Sauer and Schnerr which is based on the Rayleigh equation. One common problem of all mass transfer models is the use of model constants which often need to be tuned with regard to the examined problem. Furthermore, these models often overpredict the turbulent dynamic viscosity in the two-phase region which counteracts the development of transient shedding behaviour and is compensated by the modification proposed by Reboud. In the presented study, we vary the parameters of the Sauer-Schnerr model with Reboud modification that we implemented into an OpenFOAM solver to match numerical to experimental data.
Deimel, Christian; Günther, Markus; Skoda, Romuald
2014-03-01
The most common method for simulating cavitating flows is using the governing flow equations in a form with a variable density and treats both phases as incompressible in combination with a transport equation for the vapour volume fraction. This approach is commonly referred to as volume of fluid method (VoF). To determine the transition of the liquid phase to vapour and vice versa, a relation for the mass transfer is needed. Several models exist, based on slightly differing physical assumptions, for example derivation from the dynamics of single bubbles or large bubble clusters. In our simulation, we use the model of Sauer and Schnerr which is based on the Rayleigh equation. One common problem of all mass transfer models is the use of model constants which often need to be tuned with regard to the examined problem. Furthermore, these models often overpredict the turbulent dynamic viscosity in the two-phase region which counteracts the development of transient shedding behaviour and is compensated by the modification proposed by Reboud. In the presented study, we vary the parameters of the Sauer-Schnerr model with Reboud modification that we implemented into an OpenFOAM solver to match numerical to experimental data.
Modernization of vertical Pelton turbines with the help of CFD and model testing
International Nuclear Information System (INIS)
The modernization of water turbines bears a high potential of increasing the already installed hydropower capacity. In many projects the existing waterways allow a substantial increase of the available flow capacity and with it the energy output. But also the upgrading onto a state of the art hydraulic, mechanical and electrical design will increase the available power considerably after the rehabilitation. The two phase nature of the flow in Pelton turbines requires for the hydraulic refurbishment special care in the application of the available design methods. Where the flow in the high pressure section of the turbine is mainly of one phase nature, CFD has been used as a standard tool for many years. Also the jet quality, and with it the exploration of the source of flow disturbances that cause poor free surface quality can be investigated with CFD. The interaction of the jet with the buckets of the runner is also examined by means of CFD. However, its accuracy with respect to hydraulic efficiency is, because of the two phase flow and the transient flow process, in very few cases good enough for a reliable and accurate prediction of absolute numbers. The optimization of hydraulic bucket profiles is therefore always checked with measurements in homologous scaled model turbines. A similar situation exists for the housing flow after the water is discharged from the runner. Here also CFD techniques are available to explore the general mechanisms. However, due to the two phase flow nature, where only a very small space is filled with moving water, the experimental setup in a model turbine is always the final proof for optimizations of housing inserts and modifications. The hydraulic design of a modernization project for a power station equipped with vertical Pelton turbines of two different designs is described in the proposed paper. It will be shown, how CFD is applied to determine the losses in the high pressure section and how these results are combined with the
CFD Modeling of Airflow in a Livestock Building
DEFF Research Database (Denmark)
Rong, Li; Elhadidi, B.; Khalifa, H. E.;
2010-01-01
In this paper, a 2D simulation for a typical livestock building is performed to assess the ammonia emission removal rate to the atmosphere. Two geometry models are used and compared in order to represent the slatted floor. In the first model the floor is modeled as a slatted floor and in the second...... exploring the accuracy of the porous jump assumption by comparing the velocity, and ammonia concentration in a 2D simulation, heated solid bodies are added to represent the livestock in the following simulations. The results of simulations with heat source also indicate that modeling the slatted floor with...... livestock buildings....
RELIABLE VALIDATION BASED ON OPTICAL FLOW VISUALIZATION FOR CFD SIMULATIONS
Institute of Scientific and Technical Information of China (English)
姜宗林
2003-01-01
A reliable validation based on the optical flow visualization for numerical simulations of complex flowfields is addressed in this paper.Several test cases,including two-dimensional,axisymmetric and three-dimensional flowfields,were presented to demonstrate the effectiveness of the validation and gain credibility of numerical solutions of complex flowfields.In the validation,images of these flowfields were constructed from numerical results based on the principle of the optical flow visualization,and compared directly with experimental interferograms.Because both experimental and numerical results are of identical physical representation,the agreement between them can be evaluated effectively by examining flow structures as well as checking discrepancies in density.The study shows that the reliable validation can be achieved by using the direct comparison between numerical and experiment results without any loss of accuracy in either of them.
Efficient Functional-Based Adaptation for CFD Applications
Tyson, William C
2015-01-01
Adjoint methods have gained popularity in recent years for driving adaptation procedures which aim to reduce error in solution functionals. While adjoint methods have been proven effective for functional-based adaptation, the practical implementation of an adjoint method can be quite burdensome since code developers constantly need to ensure and maintain a dual consistent discretization as updates are made. Also, since most engineering problems consider multiple functionals, an adjoint solution must be obtained for each functional of interest which can increase the overall computational cost significantly. In this paper, an alternative to adjoints is presented which uses a sparse approximate inverse of the Jacobian of the residual to obtain approximate adjoint sensitivities for functional-based adaptation indicators. Since the approximate inverse need only be computed once, it can be recycled for any number of functionals making the new approach more efficient than a conventional adjoint method. This new meth...
CFD Approaches for Modelling Bubble Entrainment by an Impinging Jet
Directory of Open Access Journals (Sweden)
Martin Schmidtke
2009-01-01
Full Text Available This contribution presents different approaches for the modeling of gas entrainment under water by a plunging jet. Since the generation of bubbles happens on a scale which is smaller than the bubbles, this process cannot be resolved in meso-scale simulations, which include the full length of the jet and its environment. This is why the gas entrainment has to be modeled in meso-scale simulations. In the frame of a Euler-Euler simulation, the local morphology of the phases has to be considered in the drag model. For example, the gas is a continuous phase above the water level but bubbly below the water level. Various drag models are tested and their influence on the gas void fraction below the water level is discussed. The algebraic interface area density (AIAD model applies a drag coefficient for bubbles and a different drag coefficient for the free surface. If the AIAD model is used for the simulation of impinging jets, the gas entrainment depends on the free parameters included in this model. The calculated gas entrainment can be adapted via these parameters. Therefore, an advanced AIAD approach could be used in future for the implementation of models (e.g., correlations for the gas entrainment.
Modelling aerosol number distributions from a vehicle exhaust with an aerosol CFD model
Albriet, B.; Sartelet, K. N.; Lacour, S.; Carissimo, B.; Seigneur, C.
2010-03-01
Vehicular traffic contributes significantly to the aerosol number concentrations at the local scale by emitting primary soot particles and forming secondary nucleated nanoparticles. Because of their potential health effects, more attention is paid to the traffic induced aerosol number distributions. The aim of this work is to explain the phenomenology leading to the formation and the evolution of the aerosol number distributions in the vicinity of a vehicle exhaust using numerical modelling. The emissions are representative of those of a light-duty diesel truck without a diesel particle filter. The atmospheric flow is modelled with a computational fluid dynamics (CFD) code to describe the dispersion of pollutants at the local scale. The CFD code, coupled to a modal aerosol model (MAM) describing the aerosol dynamics, is used to model the tailpipe plume of a vehicle with emissions corresponding to urban driving conditions. On the basis of available measurements in Schauer et al. (1999), three surrogate species are chosen to treat the semi-volatile organic compounds in the emissions. The model simulates the formation of the aerosol distribution in the exhaust plume of a vehicle as follows. After emission to the atmosphere, particles are formed by nucleation of sulphuric acid and water vapour depending strongly on the thermodynamic state of the atmosphere and on the dilution conditions. The semi-volatile organic compounds are critical for the rapid growth of nanoparticles through condensation. The semi-volatile organic compounds are also important for the evolution of primary soot particles and can contribute substantially to their chemical composition. The most influential parameters for particle formation are the sulphur fuel content, the semi-volatile organic emissions and also the mass and initial diameter of the soot particles emitted. The model is able to take into account the complex competition between nucleation, condensation and dilution, as well as the
Validation of CFD models for microscale nanoprecipitation reactor using μ-PIV and confocal μ-LIF
Shi, Yanxiang; Olsen, Michael G.; Fox, Rodney O.
2011-11-01
Over the past a few decades, computational fluid dynamics (CFD) models have become more and more important in the process of reactor design in chemical engineering. Compared to experimental methods, they can provide comprehensive information on the flow field as well as other fields, such as concentration. However, they also need to be validated against experimental data to ensure the accuracy. In this work, the micro-scale particle image velocimetry (μ-PIV) is employed in conjunction with the confocal-base micro-scale laser induced fluorescence (μ-LIF) to specifically validate CFD models for use in microscale nanoprecipitation reactor. The former is for the velocity field measurement and the latter gives us the mixture fraction information. Both RANS and LES are used to simulate the field flow. For RANS, a DQMOM-IEM micromixing model is used to predict the mixture fraction field while only a scalar transport equation is solved in the LES simulations. Comparisons between simulation results and experimental data show that RANS might not be the right tool for such reactors. LES, on the other hand, gives reasonably satisfactory predictions.
International Nuclear Information System (INIS)
In this paper computational fluid dynamics (CFD) simulations are performed using ANSYS CFX to compare wake interaction results obtained from two rotor modelling methodologies: the standard actuator disc and the blade element momentum model (BEM). The unsteady simulations embed Coriolis forces and neutral stability conditions in the surface layer and stable conditions in the free stream. The BEM method is implemented in the CFD code through a pre-processing set of files that employs look-up tables. The control system for the wind turbines is considered through look-up tables that are constructed based on operational wind farm data. Simulations using the actuator disc and BEM methodologies have been performed using a number of different turbulence models in order to compare the wind turbine wake structure results. The use of URANS and LES numerical methods, coupled with the two different methodologies of representing the turbine, enables an assessment to be made of the details required for varying degrees of accuracy in computing the wake structures. The findings stress the importance of including the rotation of the wake and the non-uniform load on the rotor in LES simulations to account for more accurate turbulence intensity levels in the near wake
Lavaroni, Luca; Watson, Simon J.; Cook, Malcolm J.; Dubal, Mark R.
2014-06-01
In this paper computational fluid dynamics (CFD) simulations are performed using ANSYS CFX to compare wake interaction results obtained from two rotor modelling methodologies: the standard actuator disc and the blade element momentum model (BEM). The unsteady simulations embed Coriolis forces and neutral stability conditions in the surface layer and stable conditions in the free stream. The BEM method is implemented in the CFD code through a pre-processing set of files that employs look-up tables. The control system for the wind turbines is considered through look-up tables that are constructed based on operational wind farm data. Simulations using the actuator disc and BEM methodologies have been performed using a number of different turbulence models in order to compare the wind turbine wake structure results. The use of URANS and LES numerical methods, coupled with the two different methodologies of representing the turbine, enables an assessment to be made of the details required for varying degrees of accuracy in computing the wake structures. The findings stress the importance of including the rotation of the wake and the non-uniform load on the rotor in LES simulations to account for more accurate turbulence intensity levels in the near wake.
CFD Modeling of Non-Neutral Atmospheric Boundary Layer Conditions
DEFF Research Database (Denmark)
Koblitz, Tilman
For wind resource assessment, the wind industry is increasingly relying on Computational Fluid Dynamics models that focus on modeling the airflow in a neutrally stratified surface-layer. Physical processes like the Coriolis force, buoyancy forces and heat transport, that are important to the...... atmospheric boundary-layer, are mostly ignored so far. In order to decrease the uncertainty of wind resource assessment, the present work focuses on atmospheric flows that include atmospheric stability and the Coriolis effect. Within the present work a RANS model framework is developed and implemented into...
CFD simulation of neutral ABL flows
DEFF Research Database (Denmark)
Zhang, Xiaodong
This work is to evaluate the CFD prediction of Atmospheric Boundary Layer flow field over different terrains employing Fluent 6.3 software. How accurate the simulation could achieve depend on following aspects: viscous model, wall functions, agreement of CFD model with inlet wind velocity profile...... and top boundary condition. Fluent employ wall function roughness modifications based on data from experiments with sand grain roughened pipes and channels, describe wall adjacent zone with Roughness Height (Ks) instead of Roughness Length (z0). In a CFD simulation of ABL flow, the mean wind velocity...... ABL and the measurements are best documented until now. Comparison with measured data shows that the CFD model can well predict the velocity field and relative turbulence kinetic energy field. Furthermore, a series of artificial complex terrains are designed, and some of the main simulation results...
CFD Analyses for Water-Air Flow With the Euler-Euler Two-Phase Model in the Fluent4 CFD Code
International Nuclear Information System (INIS)
Framatome ANP develops a new boiling water reactor called SWR 1000. For the case of a hypothetical core melt accident it is designed in such a way that the core melt is retained in the Reactor Pressure Vessel (RPV) at low pressure owing to cooling of the RPV exterior and high reliable depressurization devices. Framatome ANP performs - in co-operation with VTT - tests to quantify the safety margins of the exterior cooling concept for the SWR 1000, for determining the limits to avoid the critical heat fluxes (CHFs). The three step procedure has been set up to investigate the phenomenon: 1. Water-air study for a 1:10 scaled global model, with the aim to investigate the global flow conditions 2. Water-air study for a 1:10 scaled, 10 % sector model, with the aim to find a flow sector with almost similar flow conditions as in the global model. 3. Final CHF experiments for a 1:1-scaled, 10 % sector., the boarders of this model have been selected based on the first two steps. The instrumentation for the water/air experiments included velocity profiles, the vertically averaged average void fraction and void fraction profiles in selected positions. The experimental results from the air-water experiments have been analyzed at VTT using the Fluent-4.5.2 code with its Eulerian multiphase flow modeling capability. The aim of the calculations was to learn how to model complex two-phase flow conditions. The structural mesh required by Fluent-4 is a strong limitation in the complex geometry, but modeling of the 1/4 sector from the facility was possible, when the GAMBIT pre-processor was used for the mesh generation. The experiments were analyzed with the 150 x 150 x 18 grid for the geometry. In the analysis the fluid viscosity was the main dials for adjusting the vertical liquid velocity profiles and the bubble diameter for adjusting the phase separation. The viscosity ranged between 1 to 10000 times the molecular viscosity, and bubble diameter between 3 to 100 mm, when the
Comparison of Engineering Wake Models with CFD Simulations
Andersen, S. J.; Sørensen, J. N.; Ivanell, S.; Mikkelsen, R. F.
2014-06-01
The engineering wake models by Jensen [1] and Frandsen et al. [2] are assessed for different scenarios simulated using Large Eddy Simulation and the Actuator Line method implemented in the Navier-Stokes equations. The scenarios include the far wake behind a single wind turbine, a long row of turbines in an atmospheric boundary layer, idealised cases of an infinitely long row of wind turbines and infinite wind farms with three different spacings. Both models include a wake expansion factor, which is calibrated to fit the simulated wake velocities. The analysis highlights physical deficiencies in the ability of the models to universally predict the wake velocities, as the expansion factor can be fitted for a given case, but with not apparent transition between the cases.
CFD Modelling of Flow and Solids Distribution in Carbon-in-Leach Tanks
Directory of Open Access Journals (Sweden)
Divyamaan Wadnerkar
2015-10-01
Full Text Available The Carbon-in-Leach (CIL circuit plays an important role in the economics of a gold refinery. The circuit uses multiphase stirred tanks in series, in which problems such as dead zones, short-circuiting, and presence of unsuspended solids are detrimental to its efficiency. Therefore, the hydrodynamics of such a system is critical for improving the performance. The hydrodynamics of stirred tanks can be resolved using computational fluid dynamics (CFD. While the flow generated by the impellers in the CIL tanks is complex and modelling it in the presence of high solid concentration is challenging, advances in CFD models, such as turbulence and particle-fluid interactions, have made modelling of such flows feasible. In the present study, the hydrodynamics of CIL tanks was investigated by modelling it using CFD. The models used in the simulations were validated using experimental data at high solid loading of 40 wt. % in a lab scale tank. The models were further used for examining the flow generated by pitched blade turbine and HA-715 Mixtec impellers in lab scale CIL tanks with 50 wt. % solids. The effect of design and operating parameters such as off-bottom clearance, impeller separation, impeller speed, scale-up, and multiple-impeller configuration on flow field and solid concentrations profiles was examined. For a given impeller speed, better solids suspension is observed with dual impeller and triple impeller configurations. The results presented in the paper are useful for understanding the hydrodynamics and influence of design and operating parameters on industrial CIL tanks.
Comparison of Engineering Wake Models with CFD Simulations
DEFF Research Database (Denmark)
Andersen, Søren Juhl; Sørensen, Jens Nørkær; Ivanell, S.;
2014-01-01
The engineering wake models by Jensen [1] and Frandsen et al. [2] are assessed for different scenarios simulated using Large Eddy Simulation and the Actuator Line method implemented in the Navier-Stokes equations. The scenarios include the far wake behind a single wind turbine, a long row of...... turbines in an atmospheric boundary layer, idealised cases of an infinitely long row of wind turbines and infinite wind farms with three different spacings. Both models include a wake expansion factor, which is calibrated to fit the simulated wake velocities. The analysis highlights physical deficiencies...
On the modelling of bubble entrainment by impinging jets in CFD-simulations
International Nuclear Information System (INIS)
This contribution presents different approaches for the modeling of air entrainment under water by plunging jets in CFD codes. In simulations which include the full length of the jet and its environment, the process of bubble generation cannot be resolved due to computational limitations. This is why the air entrainment has to be modeled in meso-scale simulations. In the frame of an Euler- Euler simulation, the local morphology of the phases has to be considered in the drag model. In the impinging jet configuration, the air is a continuous phase above the water level but bubbly below the water level. Various drag models are implemented in the CFD solver CFX11 and their influence on the gas void fraction below the water level is discussed. The algebraic interface area density (AIAD) model applies a drag coefficient for bubbles and a different drag coefficient for the free surface. If the AIAD model is used for the simulation of impinging jets, the gas entrainment depends on the free parameters included in this model. The calculated gas entrainment can be adapted via these parameters. Therefore, an advanced AIAD approach could be used in future for the implementation of models (e.g. correlations) for the gas entrainment. (authors)
Numerical estimation of wall friction ratio near the pseudo-critical point with CFD-models
Energy Technology Data Exchange (ETDEWEB)
Angelucci, M. [University of Pisa, Dipartimento di Ingegneria Meccanica Nucleare e della Produzione (Italy); Ambrosini, W., E-mail: w.ambrosini@ing.unipi.it [University of Pisa, Dipartimento di Ingegneria Meccanica Nucleare e della Produzione (Italy); Forgione, N. [University of Pisa, Dipartimento di Ingegneria Meccanica Nucleare e della Produzione (Italy)
2013-11-15
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{sup +} < 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.
Prediction of wall friction for fluids at supercritical pressure with CFD models
Energy Technology Data Exchange (ETDEWEB)
Angelucci, M.; Ambrosini, W.; Forgione, N., E-mail: w.ambrosini@ing.unipi.it, E-mail: n.forgione@ing.unipi.it [Univ. of Pisa, Dipartimento di Ingegneria Meccanica Nucleare e della Produzione (Italy)
2011-07-01
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 around 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 is adopted, making use of refined near-wall discretisations as required by the constraint y{sup +} < 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, basing 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. (author)
Prediction of wall friction for fluids at supercritical pressure 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 around 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 is adopted, making use of refined near-wall discretisations 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, basing 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. (author)
Krepper, E.; Rzehak, R.
2012-01-01
The paper presents CFD calculations of the void distribution tests of the PSBT benchmark using ANSYS CFX-12.1. First, relevant aspects of the implemented wall boiling model are reviewed highlighting the uncertainties in several model parameters. It is then shown that the measured cross-sectionally averaged values can be reproduced well with a single set of calibrated model parameters for different test cases. For the reproduction of patterns of void distribution cross-sections, attention has ...
CFD modelling of condensation of vapour in the pressurized PPOOLEX facility
International Nuclear Information System (INIS)
is performed by using the Euler-Euler two-phase model of FLUENT 6.3. In the model, the gas phase consists of air and vapour species components. In wall condensation, the condensing water forms a film layer on the wall surface, which is modelled by mass transfer of vapour to water phase in the near wall grid cell. The heat transfer from the gas phase through the water film to the wall is resolved. The direct-contact condensation in the wet well is modelled with simple correlations based on assumptions of the interfacial surface area. The wall condensation and direct-contact condensation models are implemented with user-defined functions of FLUENT. The results of the CFD simulation are compared to the PPOOLEX measurements, where the temperature and the pressure are measured in various locations of the facility. The calculated amount of condensate on the walls of the dry well is compared to the amount of condensate that is collected with an aqueduct system of PPOOLEX during the experiment. The applicability of the Euler-Euler model for this kind of simulations is assessed. The possibilities of following the Best Practise Guidelines in the simulation is discussed
CFD-modelling of natural convection in a groundwater-filled borehole heat exchanger
Gustafsson, A-M.; Westerlund, L.; Hellström, G.
2009-01-01
Abstract In design of ground-source energy systems the thermal erformance of the borehole heat exchangers is important. In Scandinavia, boreholes are usually not grouted but left with groundwater to fill the space between heat exchanger pipes and borehole wall. The common U-pipe arrangement in a groundwater-filled BHE has been studied by a three-dimensional, steady-state CFD model. The model consists of a three meter long borehole containing a single U-pipe with surrounding bedrock...
Validation and analysis of forward osmosis CFD model in complex 3D geometries
DEFF Research Database (Denmark)
Gruber, Mathias F.; Johnson, Carl J.; Tang, Chuyang;
2012-01-01
, seawater desalination and power generation. To ease optimization and increase understanding of membrane systems, it is desirable to have a comprehensive model that allows for easy investigation of all the major parameters in the separation process. Here we present experimental validation of a computational...... separation process and water permeation through membranes under various flow conditions. It is furthermore demonstrated how the CFD model can be used to optimize membrane geometry in such as way as to promote the mass transfer. © 2012 by the authors; licensee MDPI, Basel, Switzerland....
The difficult challenge of a two-phase CFD modelling for all flow regimes
International Nuclear Information System (INIS)
Highlights: • The theoretical difficulties for modelling all flow regimes at CFD scale are identified. • The choice of the number of fields and of the time and space averaging or filtering are discussed and clarified. • Closure issues related to an all flow regime CFD model are listed and the main difficulties are identified. - Abstract: System thermalhydraulic codes model all two-phase flow regimes but they are limited to a macroscopic description. Two-phase CFD tools predict two-phase flow with a much finer space resolution but the current modelling capabilities are limited to dispersed bubbly or droplet flow and separate-phase flow. Much less experience exists on more complex flow regimes which combine the existence of dispersed fields with the presence of large interfaces such as a free surface or a film surface. A list of possible reactor issues which might benefit from an “all flow regime CFD model” is given. The first difficulty is to identify the various types of local flow configuration. It is shown that a 4-field model has much better capabilities than a two-fluid approach to identify most complex regimes. Then the choice between time averaging, space averaging, or even ensemble averaging is discussed. It is shown that only the RANS-2-fluid and a space-filtered 4-field model may be reasonably envisaged. The latter has the capabilities to identify all types of interfaces and should be privileged if a good accuracy is expected or if time fluctuations in intermittent flow have to be predicted while the former may be used when a high accuracy is not necessary and if time fluctuations in intermittent flow are not of interest. Finally the closure issue is presented including wall transfers, interfacial transfers, mass transfers between dispersed and continuous fields, and turbulent transfers. An important effort is required to model all interactions between sub-filter phenomena and the transfers from the sub-filter domain to the simulated domain. The
Decompression wave speed in CO2 mixtures: CFD modelling with the GERG-2008 equation of state
International Nuclear Information System (INIS)
Highlights: • CFD models for decompression simulation of CO2 mixtures. • Incorporation of GERG-2008 EOS into CFD code for decompression modelling. • Predicted decompression wave speed validated by measurements. • Studies of effects of initial temperature and impurities on decompression wave speed. - Abstract: The development of CO2 pipelines for Carbon Capture and Storage (CCS) raises new questions regarding the control of ductile fracture propagation and fracture arrest toughness criteria. The decompression behaviour in the fluid must be determined accurately in order to estimate the proper pipe toughness. However, anthropogenic CO2 may contain impurities that can modify the fluid decompression characteristics quite significantly. To determine the decompression wave speed in CO2 mixtures, the thermodynamic properties of these mixtures must be determined by using an accurate equation of state. In this paper we present a new decompression model developed using the Computational Fluid Dynamics (CFD) package ANSYS Fluent. The GERG-2008 Equation of State (EOS) was implemented into this model through User Defined Functions (UDF) to predict the thermodynamic properties of CO2 mixtures. The model predictions were in good agreement with the experimental data of two ‘shock tube’ tests. A range of representative CO2 mixtures was examined in terms of the changes in fluid properties from the initial conditions, with time and distance, immediately after a sudden pipeline opening at one end. Phase changes that may occur within the fluid due to condensation of ‘impurities’ in the fluid were also investigated. Simulations were also conducted to examine how the initial temperature and impurities would affect the decompression wave speed
CFD Model Of A Planar Solid Oxide Electrolysis Cell For Hydrogen Production From Nuclear Energy
International Nuclear Information System (INIS)
A three-dimensional computational fluid dynamics (CFD) model has been created to model high temperature steam electrolysis in a planar solid oxide electrolysis cell (SOEC). The model represents a single cell as it would exist in an electrolysis stack. Details of the model geometry are specific to a stack that was fabricated by Ceramatec2, Inc. and tested at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT2. 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, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean model results are shown to compare favorably with experimental results obtained from an actual ten-cell stack tested at INL
THERMAL AND ELECTROCHEMICAL THREE DIMENSIONAL CFD MODEL OF A PLANAR SOLID OXIDE ELECTROLYSIS CELL
Energy Technology Data Exchange (ETDEWEB)
Grant Hawkes; Jim O& #39; Brien; Carl Stoots; Steve Herring; Mehrdad Shahnam
2005-07-01
A three-dimensional computational fluid dynamics (CFD) model has been created to model high-temperature steam electrolysis in a planar solid oxide electrolysis cell (SOEC). The model represents a single cell, as it would exist in an electrolysis stack. Details of the model geometry are specific to a stack that was fabricated by Ceramatec , Inc. and tested at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT2. 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, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean model results are shown to compare favorably with experimental results obtained from an actual ten-cell stack tested at INL.
Hong, Ban Zhen; Keong, Lau Kok; Shariff, Azmi Mohd
2016-05-01
The employment of different mathematical models to address specifically for the bubble nucleation rates of water vapour and dissolved air molecules is essential as the physics for them to form bubble nuclei is different. The available methods to calculate bubble nucleation rate in binary mixture such as density functional theory are complicated to be coupled along with computational fluid dynamics (CFD) approach. In addition, effect of dissolved gas concentration was neglected in most study for the prediction of bubble nucleation rates. The most probable bubble nucleation rate for the water vapour and dissolved air mixture in a 2D quasi-stable flow across a cavitating nozzle in current work was estimated via the statistical mean of all possible bubble nucleation rates of the mixture (different mole fractions of water vapour and dissolved air) and the corresponding number of molecules in critical cluster. Theoretically, the bubble nucleation rate is greatly dependent on components' mole fraction in a critical cluster. Hence, the dissolved gas concentration effect was included in current work. Besides, the possible bubble nucleation rates were predicted based on the calculated number of molecules required to form a critical cluster. The estimation of components' mole fraction in critical cluster for water vapour and dissolved air mixture was obtained by coupling the enhanced classical nucleation theory and CFD approach. In addition, the distribution of bubble nuclei of water vapour and dissolved air mixture could be predicted via the utilisation of population balance model.
Assessment of Nucleation Site Density Models for CFD Simulations of Subcooled Flow Boiling
Energy Technology Data Exchange (ETDEWEB)
Hoang, N. H.; Chu, I. C.; Euh, D. J.; Song, C. H. [KAERI, Daejeon (Korea, Republic of)
2015-05-15
The framework of a CFD simulation of subcooled flow boiling basically includes a block of wall boiling models communicating with governing equations of a two-phase flow via parameters like temperature, rate of phasic change, etc. In the block of wall boiling models, a heat flux partitioning model, which describes how the heat is taken away from a heated surface, is combined with models quantifying boiling parameters, i.e. nucleation site density, and bubble departure diameter and frequency. It is realized that the nucleation site density is an important parameter for predicting the subcooled flow boiling. The number of nucleation sites per unit area decides the influence region of each heat transfer mechanism. The variation of the nucleation site density will mutually change the dynamics of vapor bubbles formed at these sites. In addition, the nucleation site density is needed as one initial and boundary condition to solve the interfacial area transport equation. A lot of effort has been devoted to mathematically formulate the nucleation site density. As a consequence, numerous correlations of the nucleation site density are available in the literature. These correlations are commonly quite different in their mathematical form as well as application range. Some correlations of the nucleation site density have been applied successfully to CFD simulations of several specific subcooled boiling flows, but in combination with different correlations of the bubble departure diameter and frequency. In addition, the values of the nucleation site density, and bubble departure diameter and frequency obtained from simulations for a same problem are relatively different, depending on which models are used, even when global characteristics, e.g., void fraction and mean bubble diameter, agree well with experimental values. It is realized that having a good CFD simulations of the subcooled flow boiling requires a detailed validations of all the models used. Owing to the importance
Assessment of Nucleation Site Density Models for CFD Simulations of Subcooled Flow Boiling
International Nuclear Information System (INIS)
The framework of a CFD simulation of subcooled flow boiling basically includes a block of wall boiling models communicating with governing equations of a two-phase flow via parameters like temperature, rate of phasic change, etc. In the block of wall boiling models, a heat flux partitioning model, which describes how the heat is taken away from a heated surface, is combined with models quantifying boiling parameters, i.e. nucleation site density, and bubble departure diameter and frequency. It is realized that the nucleation site density is an important parameter for predicting the subcooled flow boiling. The number of nucleation sites per unit area decides the influence region of each heat transfer mechanism. The variation of the nucleation site density will mutually change the dynamics of vapor bubbles formed at these sites. In addition, the nucleation site density is needed as one initial and boundary condition to solve the interfacial area transport equation. A lot of effort has been devoted to mathematically formulate the nucleation site density. As a consequence, numerous correlations of the nucleation site density are available in the literature. These correlations are commonly quite different in their mathematical form as well as application range. Some correlations of the nucleation site density have been applied successfully to CFD simulations of several specific subcooled boiling flows, but in combination with different correlations of the bubble departure diameter and frequency. In addition, the values of the nucleation site density, and bubble departure diameter and frequency obtained from simulations for a same problem are relatively different, depending on which models are used, even when global characteristics, e.g., void fraction and mean bubble diameter, agree well with experimental values. It is realized that having a good CFD simulations of the subcooled flow boiling requires a detailed validations of all the models used. Owing to the importance
Modeling strategies to compute natural circulation using CFD in a VHTR after a LOFA
International Nuclear Information System (INIS)
Highlights: • CFD analysis was performed of natural circulation in a block VHTR after a loss of flow accident. • Multiple strategies were investigated to perform CFD analysis to estimate strength of natural circulation. • Symmetry considerations allowed fine mesh application of CFD to reactor core. • Results extrapolated to whole core to estimate heat loss due to natural circulation. • CFD shows promise for use in nuclear reactor design and analysis. - Abstract: A prismatic gas-cooled very high temperature reactor (VHTR) is being developed under the next generation nuclear plant program (NGNP) of the U.S. Department of Energy, Office of Nuclear Energy. In the design of the prismatic VHTR, hexagonal shaped graphite blocks are drilled to allow insertion of fuel pins, made of compacted tristructural-isotropic (TRISO) fuel particles, and coolant channels for the helium coolant. One of the concerns for the reactor design is the effects of a loss of flow accident (LOFA) where the coolant circulators are lost for some reason, causing a loss of forced coolant flow through the core. In such an event, it is desired to know what happens to the (reduced) heat still being generated in the core and if it represents a problem for the fuel compacts, the graphite core or the reactor vessel (RV) walls. One of the mechanisms for the transport of heat out of the core is by the natural circulation of the coolant, which is still present. It is desired to know how much heat may be transported by natural circulation through the core and upwards to the top of the upper plenum. It is beyond current capability for a computational fluid dynamics (CFD) analysis to perform a calculation on the whole RV with a sufficiently refined mesh to examine the full potential of natural circulation in the vessel. The present paper reports the investigation of several strategies to model the flow and heat transfer in the RV. It is found that it is necessary to employ representative geometries of
Base Flow Model Validation Project
National Aeronautics and Space Administration — The innovation is the systematic "building-block" validation of CFD/turbulence models employing a GUI driven CFD code (RPFM) and existing as well as new data sets...
Canton, Gador; Chiu, Bernard; Hatsukami, Tom; Kerwin, William; Yuan, Chun
2010-11-01
The aim of this study was to explore the hypothesis that intra-plaque hemorrhage, a feature associated with adverse outcomes and atherosclerotic plaque progression and destabilization, is more likely to occur in plaques with elevated levels of wall shear stress (WSS). We used multi-sequence in-vivo magnetic resonance imaging (MRI) to characterize ten human carotid atherosclerotic plaques and an MRI-based computational fluid dynamics (CFD) model to solve the equations governing the blood flow. Hemorrhage was detected within the necrotic core (intra-plaque hemorrhage) in five of these ten cases. WSS data were extracted from the results of the CFD simulations to compare patterns between the cases with and without hemorrhage. We computed the mean value of the WSS (for each time point of the cardiac cycle) at the region where a necrotic core was detected. The results from this pilot study indicate a possible link between the presence of hemorrhage within a lipid-rich necrotic core in human carotid atherosclerotic plaques and elevated levels of shear stress force acting on the luminal surface. Thus, elevated wall shear stress may be used as a high risk feature in advanced carotid atherosclerotic plaques.
QM-400 CFD 自然对流模型研究及验证%Research and Validation on CFD Natural Convection Model of QM-400
Institute of Scientific and Technical Information of China (English)
左巧林; 干富军; 朱丽兵
2016-01-01
The spent fuel dry storage facility named QM-400 module for Third Qinshan Nuclear Power Co.Ltd.(TQNPC)is the first commercial dry storage facility in opera-tion in China.The heat transfer in QM-400 mainly consists of natural convention,con-duction,conjugate heat transfer and radiation,etc.The decay heat of each fuel basket was calculated accurately at typical surrounding temperature.Mesh sensitivity analysis was performed using commercial computational fluid dynamics (CFD)code FLUENT 14.0. A set of CFD simulation models on natural convection of QM-400 were developed.The results show that the distributions of the pressure and temperature on the cylinder sur-face meet the rules of natural convection.Good agreements are achieved between the simulated temperature and the measured temperature at the measured points and the simulated temperature trend varying with surrounding temperature agree well with the measured trend,which demonstrates the correctness of the calculation method of natural convection in this paper.This work can be the reference of the further CFD simulation on temperature distributions of dry storage facility without thermal insulation panels.%秦山第三核电厂乏燃料干式贮存模块 QM-400是我国第一座投入商业运行的干式贮存设施，模块内的热量交换主要包括自然对流、热传导、耦合传热和辐射换热等。本文精确计算了典型环境温度下每个燃料篮的衰变热，运用商用计算流体动力学(CFD)软件 FLUENT 14.0开展了网格敏感性分析，并建立了 QM-400存储模块的自然对流 CFD 分析模型。结果表明，模块顶面、侧面以及贮存筒表面压力和温度分布符合自然对流规律，计算的测点温度与现场的实测温度符合良好，测点温度随环境温度的变化趋势也与实测趋势符合良好，证明了建立的 CFD 自然对流计算方法的正确性。本文结果为后续采用CFD 方法进行取消绝热板后的温度场计算奠定了基础。
CFD modelling approach for dam break flow studies
Directory of Open Access Journals (Sweden)
C. Biscarini
2010-04-01
Full Text Available This paper presents numerical simulations of free surface flows induced by a dam break comparing the shallow water approach to fully three-dimensional simulations. The latter are based on the solution of the complete set of Reynolds-Averaged Navier-Stokes (RANS equations coupled to the Volume of Fluid (VOF method.
The methods assessment and comparison are carried out on a dam break over a flat bed without friction, a dam break over a triangular bottom sill and a dam break flow over a 90° bend. Experimental and numerical literature data are compared to present results.
The results demonstrate that the shallow water approach, even if able to sufficiently reproduce the main aspects of the fluid flows, loses some three-dimensional phenomena, due to the incorrect shallow water idealization that neglects the three-dimensional aspects related to the gravity force.
Darby, S. E.; Rinaldi, M.; Rossi Romanelli, L.; Spyropoulos, E.
2003-12-01
River bank erosion often significantly contributes to the catchment sediment yield. Knowledge of the rates & controls on bank erosion events is therefore important in understanding sediment flux. In recent years progress has been made in understanding processes controlling large-scale mass failure (MF) of stream banks, but less attention has been paid to the role that direct fluvial erosion (FE) plays in bank retreat. This is an important omission, not only because FE is a significant process in its own right, but because FE also often triggers mass failure. FE models are typically of the form: E = k(τ - τ c)b where E is the bank erosion rate, τ is the applied fluid shear stress, τ c is the critical stress for entrainment of the bank material, k is an empirically-derived erodibility parameter, and b is an empirically-derived exponent, often assumed to be close to unity. To apply this model, accurate observations of applied fluid stresses, FE rates & bank erodibility are required. Recent developments in bank erosion monitoring technology [e.g. Lawler, 1993], and in the quantification of the bank erodibility parameters k and τ c using jet-testing devices [e.g. Hanson and Simon, 2001; Dapporto, 2001], offer the means of determining FE rates and bank erodibility. Nevertheless, the problem of collecting the high-resolution spatially-distributed data needed to characterise near-bank fluid stresses remains. One possible solution is to use Computational Fluid Dynamics (CFD) models as a substitute for empirical data. CFD simulations potentially offer a means of acquiring near-bank, distributed, boundary shear stress data at very high spatial resolution. In contrast, empirical data sets of comparable spatial extent and resolution are very difficult to obtain, particularly during the large (competent) flows of interest here. The critical question is therefore whether CFD-derived data are sufficiently accurate for this purpose. Herein we evaluate a series of 3-dimensional
Bonneville Powerhouse 2 Fish Guidance Efficiency Studies: CFD Model of the Forebay
Energy Technology Data Exchange (ETDEWEB)
Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.
2012-07-01
In ongoing work, U.S. Army Corps of Engineers, Portland District (CENWP) is seeking to better understand and improve the conditions within the Bonneville Powerhouse 2 (B2) turbine intakes to improve survival of downstream migrant salmonid smolt. In this study, the existing B2 forebay computational fluid dynamics (CFD) model was modified to include a more detailed representation of all B2 turbine intakes. The modified model was validated to existing field-measured forebay ADCP velocities. The initial CFD model scenarios tested a single project operation and the impact of adding the Behavior Guidance System (BGS) or Corner Collector. These structures had impacts on forebay flows. Most notable was that the addition of the BGS and Corner Collector reduced the lateral extent of the recirculation areas on the Washington shore and Cascade Island and reduced the flow velocity parallel to the powerhouse in front of Units 11 and 12. For these same cases, at the turbine intakes across the powerhouse, there was very little difference in the flow volume into the gatewell for the clean forebay, and the forebay with the BGS in place and/or the Corner Collector operating. The largest differences were at Units 11 to 13. The CFD model cases testing the impact of the gatewell slot fillers showed no impact to the forebay flows, but large differences within the gatewells. With the slot fillers, the flow above the standard traveling screen and into the gatewell increased (about 100 cfs at each turbine intake) and the gap flow decreased across the powerhouse for all cases. The increased flow up the gatewell was further enhanced with only half the units operating. The flow into the gatewell slot was increased about 35 cfs for each bay of each intake across the powerhouse; this change was uniform across the powerhouse. The flows in the gatewell of Unit 12, the most impacted unit for the scenarios, was evaluated. In front of the vertical barrier screen, the CFD model with slot fillers
CFD modelling approach for dam break flow studies
Directory of Open Access Journals (Sweden)
C. Biscarini
2009-11-01
Full Text Available This paper presents numerical simulations of free surface flows induced by a dam break comparing the shallow water approach to fully three-dimensional simulations. The latter are based on the solution of the complete set of Reynolds-Averaged Navier-Stokes (RANS equations coupled to the Volume of Fluid (VOF method.
The methods assessment and comparison are carried out on a dam break over a flat bed without friction and a dam break over a triangular bottom sill. Experimental and numerical literature data are compared to present results.
The results demonstrate that the shallow water approach loses some three-dimensional phenomena, which may have a great impact when evaluating the downstream wave propagation. In particular, water wave celerity and water depth profiles could be underestimated due to the incorrect shallow water idealization that neglects the three-dimensional aspects due to the gravity force, especially during the first time steps of the motion.
Wang, Xu; Ding, Jie; Guo, Wan-Qian; Ren, Nan-Qi
2010-12-01
Investigating how a bioreactor functions is a necessary precursor for successful reactor design and operation. Traditional methods used to investigate flow-field cannot meet this challenge accurately and economically. Hydrodynamics model can solve this problem, but to understand a bioreactor in sufficient depth, it is often insufficient. In this paper, a coupled hydrodynamics-reaction kinetics model was formulated from computational fluid dynamics (CFD) code to simulate a gas-liquid-solid three-phase biotreatment system for the first time. The hydrodynamics model is used to formulate prediction of the flow field and the reaction kinetics model then portrays the reaction conversion process. The coupled model is verified and used to simulate the behavior of an expanded granular sludge bed (EGSB) reactor for biohydrogen production. The flow patterns were visualized and analyzed. The coupled model also demonstrates a qualitative relationship between hydrodynamics and biohydrogen production. The advantages and limitations of applying this coupled model are discussed. PMID:20727741
Prototype coupling of the CFD code ANSYS CFX with the 3D neutron kinetic core model DYN3D
International Nuclear Information System (INIS)
Analyses of postulated reactivity initiated accidents in nuclear reactors are carried out using 3D neutron kinetic core models. The feedback is usually calculated using 1D thermal hydraulic models for channel flow, partly with the possibility of cross flow between these channels. A different possibility is the use of subchannel codes for the determination of the feedback. The code DYN3D developed at Forschungszentrum Dresden-Rossendorf is an example for a 3D neutron kinetic core model. In its basic version, the code contains models for the solution of the 3D neutron diffusion equation in two energy groups for fuel assemblies with rectangular and hexagonal cross section. Recently the code was extended to an arbitrary number of energy groups. Further, a simplified transport approximation for the flux calculation was implemented for fuel assemblies with quadratic cross section. The CFD code ANSYS CFX is the reference CFD code of the German CFD Network in Nuclear Reactor Safety. One of the goals of the co-operation inside this network is the development of CFD software for the simulation of multi-dimensional flows in reactor cooling systems. This includes the coupling of the CFD code ANSYS CFX with the 3D neutron kinetic core model DYN3D. (orig.)
Kim, C. G.; Kim, B. H.; Bang, B. H.; Lee, Y. H.
2015-01-01
Sump model testing is mainly used to check flow conditions around the intake structure. In present paper, numerical simulation with SST turbulence model for a scaled sump model was carried out with air entrainment and two phases for prediction of locations of vortex generation. The sump model used for the CFD and experimental analysis was scaled down by a ratio of 1:10. The experiment was performed in Korea Maritime and Ocean University (KMOU) and the flow conditions around pump's intake structure were investigated. In this study, uniformity of flow distribution in the pump intake channel was examined to find out the specific causes of vortex occurrence. Furthermore, the effectiveness of an Anti Vortex Device (AVD) to suppress the vortex occurrence in a single intake pump sump model was examined. CFD and experimental analysis carried out with and without AVDs produced very similar results. Without the AVDs, the maximum swirl angle obtained for experimental and CFD analysis were 10.9 and 11.3 degree respectively. Similarly, with AVDs, the maximum swirl angle obtained for experimental and CFD analysis was 2.7 and 0.2 degree respectively. So, with reference to the ANSI/HI 98 standard that permits a maximum swirl angle of 5 degree, the use of AVDs in experimental and CFD analysis produced very desirable results which is well within the limit.
CFD model of multiphase flow in the abrasive water jet tool
Czech Academy of Sciences Publication Activity Database
Říha, Zdeněk
Ostrava: Ústav geoniky AV ČR, v.v.i, 2015 - (Sitek, L.; Klichová, D.), s. 157-163 ISBN 978-80-86407-56-2. [Vodní paprsek 2015 - výzkum, vývoj, aplikace. Velké Losiny (CZ), 06.10.2015-08.10.2015] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : abrasive water jet * multiphase flow * CFD model Subject RIV: JQ - Machines ; Tools
Galerkin CFD solvers for use in a multi-disciplinary suite for modeling advanced flight vehicles
Moffitt, Nicholas J.
This work extends existing Galerkin CFD solvers for use in a multi-disciplinary suite. The suite is proposed as a means of modeling advanced flight vehicles, which exhibit strong coupling between aerodynamics, structural dynamics, controls, rigid body motion, propulsion, and heat transfer. Such applications include aeroelastics, aeroacoustics, stability and control, and other highly coupled applications. The suite uses NASA STARS for modeling structural dynamics and heat transfer. Aerodynamics, propulsion, and rigid body dynamics are modeled in one of the five CFD solvers below. Euler2D and Euler3D are Galerkin CFD solvers created at OSU by Cowan (2003). These solvers are capable of modeling compressible inviscid aerodynamics with modal elastics and rigid body motion. This work reorganized these solvers to improve efficiency during editing and at run time. Simple and efficient propulsion models were added, including rocket, turbojet, and scramjet engines. Viscous terms were added to the previous solvers to create NS2D and NS3D. The viscous contributions were demonstrated in the inertial and non-inertial frames. Variable viscosity (Sutherland's equation) and heat transfer boundary conditions were added to both solvers but not verified in this work. Two turbulence models were implemented in NS2D and NS3D: Spalart-Allmarus (SA) model of Deck, et al. (2002) and Menter's SST model (1994). A rotation correction term (Shur, et al., 2000) was added to the production of turbulence. Local time stepping and artificial dissipation were adapted to each model. CFDsol is a Taylor-Galerkin solver with an SA turbulence model. This work improved the time accuracy, far field stability, viscous terms, Sutherland?s equation, and SA model with NS3D as a guideline and added the propulsion models from Euler3D to CFDsol. Simple geometries were demonstrated to utilize current meshing and processing capabilities. Air-breathing hypersonic flight vehicles (AHFVs) represent the ultimate
CFD modeling using PDF approach for investigating the flame length in rotary kilns
Elattar, H. F.; Specht, E.; Fouda, A.; Bin-Mahfouz, Abdullah S.
2016-02-01
Numerical simulations using computational fluid dynamics (CFD) are performed to investigate the flame length characteristics in rotary kilns using probability density function (PDF) approach. A commercial CFD package (ANSYS-Fluent) is employed for this objective. A 2-D axisymmetric model is applied to study the effect of both operating and geometric parameters of rotary kiln on the characteristics of the flame length. Three types of gaseous fuel are used in the present work; methane (CH4), carbon monoxide (CO) and biogas (50 % CH4 + 50 % CO2). Preliminary comparison study of 2-D modeling outputs of free jet flames with available experimental data is carried out to choose and validate the proper turbulence model for the present numerical simulations. The results showed that the excess air number, diameter of kiln air entrance, radiation modeling consideration and fuel type have remarkable effects on the flame length characteristics. Numerical correlations for the rotary kiln flame length are presented in terms of the studied kiln operating and geometric parameters within acceptable error.
Agarwal, T K; Sahoo, B K; Gaware, J J; Joshi, M; Sapra, B K
2014-10-01
The release of (220)Rn gas (conventionally referred to as thoron) is an issue of concern from the radiological point of view for occupational environments pertaining to the thorium fuel cycle. Studies for understanding its release and developing systems to control it are crucial for exposure control research. A thorough study of the "Delay Volume Technique" for mitigation of (220)Rn has been carried out. Experiments have been carried out with (220)Rn source and associated measurement system in a cubical chamber (delay chamber) of 0.5 m(3) volume. For different flow conditions and inlet-outlet positions, (220)Rn transmission factor has been obtained. Computational Fluid Dynamics (CFD) technique has been employed for these experimental conditions and the simulated transmission factors have been compared. The results show that the flow and the position of the inlet and outlet play an imperative role in the transportation, mixing and subsequent mitigation of thoron inside the chamber. Predictive capability of CFD technique for such delay volume experiments has been validated in this work. A comparison has been made with uniform mixing model and it is found that the results of simulation differ appreciably from that of uniform mixing model at the tested flow regime. PMID:24860913
The 3-D CFD modeling of gas turbine combustor-integral bleed flow interaction
Chen, D. Y.; Reynolds, R. S.
1993-01-01
An advanced 3-D Computational Fluid Dynamics (CFD) model was developed to analyze the flow interaction between a gas turbine combustor and an integral bleed plenum. In this model, the elliptic governing equations of continuity, momentum and the k-e turbulence model were solved on a boundary-fitted, curvilinear, orthogonal grid system. The model was first validated against test data from public literature and then applied to a gas turbine combustor with integral bleed. The model predictions agreed well with data from combustor rig testing. The model predictions also indicated strong flow interaction between the combustor and the integral bleed. Integral bleed flow distribution was found to have a great effect on the pressure distribution around the gas turbine combustor.
International Nuclear Information System (INIS)
A detailed analysis of two-phase flow boiling characteristics inside high pressure systems is presented focusing on non-uniform axial heating profiles. For this purpose, a detailed numerical model has been developed after presenting the current status of the use of CFD techniques in flow boiling predictions. User defined functions written in C++ were compiled and hooked to the software in order to account for mass interaction between phases using the Eulerian multiphase flow model. The modeled domain is a 2 m long stainless steel pipe with inside and outside diameters of 15.4 mm, 25.4 mm, respectively. The base imposed uniform heat flux was 345.6 kW/m2, for mass flow rate of water of 0.161 kg/s and at a temperature of 200 °C. The model was validated against range of experimental data and the results are very promising for the use of CFD in flow boiling characterization. Effects of increasing uniform heat flux were considered for different increments of 30, 50 and 75% as reference to the basic applied heat flux. The influences of heat flux profile in the axial direction were investigated while maintaining the same total power. Different heat flux profiles of linearly increasing, linearly decreasing, sine, and cosine shapes were considered. - Highlights: • Current status of CHF predictions using CFD modeling technique. • State of the art, flow boiling 2D-model for the applications of high pressure systems. • Validation of the model using the available experimental data in the literature. • Investigation of flow boiling in real systems for non-uniform heating profile. • Analysis of keeping the system away from the CHF conditions for non-uniform heating
Validation of a FLUENT CFD model for hydrogen distribution in a containment
International Nuclear Information System (INIS)
Highlights: ► NRG developed a CFD model to simulate the hydrogen distribution in the containment during a severe accident. ► The containment model is validated for the formation and break-up of a stable hydrogen-rich layer. ► Guidelines are obtained on mesh resolution, near-wall treatment and turbulence modeling. - Abstract: Hydrogen may be released into the containment atmosphere of a nuclear power plant during a severe accident. Locally, high hydrogen concentrations may be reached that can possibly cause fast deflagration or even detonation and put the integrity of the containment at risk. The distribution and mixing of hydrogen is, therefore, an important safety issue for nuclear power plants. Computational fluid dynamics (CFD) codes can be applied to predict the hydrogen distribution in the containment within the course of a hypothetical severe accident and get an estimate of the local hydrogen concentration in the various zones of the containment. In this way the risk associated with the hydrogen safety issue can be determined, and safety related measurements and procedures could be assessed. In order to further validate the CFD containment model of NRG in the context of hydrogen distribution in the containment of a nuclear power plant, the HM-2 test performed in the German THAI (thermal-hydraulics, hydrogen, aerosols and iodine) facility is selected. In the first phase of the HM-2 test a stratified hydrogen-rich light gas layer was established in the upper part of the THAI containment. In the second phase steam was injected at a lower position. This induced a rising plume that gradually dissolved the stratified hydrogen-rich layer from below. Phenomena that are expected in severe accidents, like natural convection, turbulent mixing, condensation, heat transfer and distribution in different compartments, are simulated in this hypothetical severe accident scenario. The hydrogen distribution and associated physical phenomena monitored during the HM-2 test
Energy Technology Data Exchange (ETDEWEB)
Fazeli, Ali; Behnam, Mohsen [Gas Research Division, Research Institute of Petroleum Industry (RIPI), P.O. Box 14665-137, Tehran (Iran)
2010-09-15
Hydrogen production from steam reforming of methanol for fuel cell application was modeled in a wall coated micro channel reactor by CFD approach. Heat of steam reforming (SR) was supplied from catalytic total oxidation (TOX) of methanol on Cu/ZnO/Al{sub 2}O{sub 3} catalyst and Heat conducts from TOX to SR zone through Steel divider wall between two channels. Heat integration was compared in zigzag and straight geometry of microreactor by CFD modeling. The model is two dimensional, steady state and containing five zones: TOX fluid, TOX catalyst layer, steel wall of the channel, SR catalyst layer and SR fluid. Set of partial differential equations (PDEs) including x and y momentum balance, continuity, partial mass balances and energy balance was solved by finite volume method. Stiff reaction rates were considered for methanol total oxidation (TOX), methanol steam reforming (SR), water gas shift (WGS) and methanol decomposition (MD) reactions. The results show that zigzag geometry is better than straight one because heat and mass transfer in zigzag reactor are more than straight. Conversion of methanol in zigzag geometry is greater than straight one. In the outlet of zigzag micro channels, carbon monoxide selectivity is less and hydrogen mole fraction is more than straight one. (author)
Propulsion Simulations Using Advanced Turbulence Models with the Unstructured Grid CFD Tool, TetrUSS
Abdol-Hamid, Khaled S.; Frink, Neal T.; Deere, Karen A.; Pandya, Mohangna J.
2004-01-01
A computational investigation has been completed to assess the capability of TetrUSS for exhaust nozzle flows. Three configurations were chosen for this study (1) an axisymmetric supersonic jet, (2) a transonic axisymmetric boattail with solid sting operated at different Reynolds number and Mach number, and (3) an isolated non-axisymmetric nacelle with a supersonic cruise nozzle. These configurations were chosen because existing experimental data provided a means for measuring the ability of TetrUSS for simulating complex nozzle flows. The main objective of this paper is to validate the implementation of advanced two-equation turbulence models in the unstructured-grid CFD code USM3D for propulsion flow cases. USM3D is the flow solver of the TetrUSS system. Three different turbulence models, namely, Menter Shear Stress Transport (SST), basic k epsilon, and the Spalart-Allmaras (SA) are used in the present study. The results are generally in agreement with other implementations of these models in structured-grid CFD codes. Results indicate that USM3D provides accurate simulations for complex aerodynamic configurations with propulsion integration.
Validating CFD Models of Multiphase Mixing in the Waste Treatment Plant at the Hanford Site
International Nuclear Information System (INIS)
The Columbia River in Washington State is threatened by the radioactive legacy of the cold war. Two hundred thousand cubic meters (fifty-three million US gallons) of radioactive waste is stored in 177 underground tanks (60% of the Nation's radioactive waste). A vast complex of waste treatment facilities is being built to convert this waste into stable glass (vitrification). The waste in these underground tanks is a combination of sludge, slurry, and liquid. The waste will be transported to a pre-treatment facility where it will be processed before vitrification. It is necessary to keep the solids in suspension during processing. The mixing devices selected for this task are known as pulse-jet mixers (PJMs). PJMs cyclically empty and refill with the contents of the vessel to keep it mixed. The transient operation of the PJMs has been proven successful in a number of applications, but needs additional evaluation to be proven effective for the slurries and requirements at the Waste Treatment Plant (WTP). Computational fluid dynamic (CFD) models of mixing vessels have been developed to demonstrate the ability of the PJMs to meet mixing criteria. Experimental studies have been performed to validate these models. These tests show good agreement with the transient multiphase CFD models developed for this engineering challenge. (authors)
Experiments and CFD-modelling of insulation debris transport phenomena in water flow
International Nuclear Information System (INIS)
The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core cooling systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems. Open questions of generic interest are the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow and the particle load on strainers and corresponding pressure drop. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Goerlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Goerlitz, the theoretical modeling efforts are concentrated at Forschungszentrum Dresden-Rossendorf. In the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented. (authors)
A model for the evolution of pyrolysis products in a fluidized bed has been developed. In this study the unsteady constitutive transport equations for inert gas flow and decomposition kinetics were modeled using the commercial computational fluid dynamics (CFD) software FLUENT-12. The model system d...
Towards a CFD Model for Prediction of Wind Turbine Power Losses due to Icing in Cold Climate
DEFF Research Database (Denmark)
Pedersen, Marie Cecilie; Sørensen, Henrik
Icing induced power losses is an important issue when operating wind turbines in cold climate. This paper presents a concept of modelling ice accretion on wind turbines using Computational Fluid Dynamics (CFD). The modelling concept works towards unifying the processes of modelling ice accretion...
Salim, S M; Viswanathan, Shekar; Ray, Madhumita Bhowmick
2006-12-01
Dispersion of airborne contaminants in indoor air was evaluated employing physical measurement, empirical models, and computer simulation methods. Field data collected from a tray of evaporating solvent in the laboratory were compared with computational fluid dynamics (CFD) simulations coupled with evaporation models. The results indicated that mathematical models of evaporation can be coupled with CFD simulations to produce reasonable qualitative predictions of airborne contaminant levels. The airflow pattern within a room is primarily determined by the room layout and the position of the air supply diffusers. Variations in ventilation rate did not alter the airflow pattern, thus generating a characteristic concentration profile of the airborne contaminants. PMID:17050350
Energy Technology Data Exchange (ETDEWEB)
Grant Hawkes; James E. O' Brien
2008-10-01
A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in a new novel integrated planar porous-tube supported solid oxide electrolysis cell (SOEC). The model is of several integrated planar cells attached to a ceramic support tube. This design is being evaluated with modeling at the Idaho National Laboratory. 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, Nernst potential, operating potential, activation over-potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean per-cell area-specific-resistance (ASR) values decrease with increasing current density. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, cathode and anode exchange current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicated 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 efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.
Feng, Yuqing; Schwarz, M. Philip; Yang, William; Cooksey, Mark
2015-08-01
A two-phase computational fluid dynamics (CFD) model has been developed to simulate the time-averaged flow in the molten electrolyte layer of a Hall -Héroult aluminum cell. The flow is driven by the rise of carbon dioxide bubbles formed on the base of the anodes. The CFD model has been validated against detailed measurements of velocity and turbulence taken in a full-scale air-water physical model containing three anodes in four different configurations, with varying inter-anode gap and the option of slots. The model predictions agree with the measurements of velocity and turbulence energy for all configurations within the likely measurement repeatability, and therefore can be used to understand the overall electrolyte circulation patterns and mixing. For example, the model predicts that the bubble holdup under an anode is approximately halved by the presence of a slot aligned transverse to the cell long axis. The flow patterns do not appear to be significantly altered by halving the inter-anode gap width from 40 to 20 mm. The CFD model predicts that the relative widths of center, side, and end channels have a major influence on several critical aspects of the cell flow field.
CFD Modelling of Biomass Combustion in Small-Scale Boilers. Final Report
Energy Technology Data Exchange (ETDEWEB)
Xue-Song Bai; Griselin, Niklas; Klason, Torbern; Nilsson, Johan [Lund Inst. of Tech. (Sweden). Dept. of Heat and Power Engineering
2002-10-01
This project deals with CFD modeling of combustion of wood in fixed bed boilers. A flamelet model for the interaction between turbulence and chemical reactions is developed and applied to study small-scale boiler. The flamelet chemistry employs 43 reactive species and 174 elementary reactions. It gives detailed distributions of important species such as CO and NO{sub x} in the flow field and flue gas. Simulation of a small-scale wood fired boiler measured at SP Boraas (50 KW) shows that the current flamelet model yields results agreeable to the available experimental data. A detailed chemical kinetic model is developed to study the bed combustion process. This model gives boundary conditions for the CFD analysis of gas phase volatile oxidation in the combustion chambers. The model combines a Functional Group submodel with a Depolymerisation, Vaporisation and Crosslinking submodel. The FG submodel simulates how functional groups decompose and form light gas species. The DVC submodell predicts depolymerisation and vaporisation of the macromolecular network and this includes bridge breaking and crosslinking processes, where the wood structure breaks down to fragments. The light fragments form tar and the heavy ones form metaplast. Two boilers firing wood log/chips are studied using the FG-DVC model, one is the SP Boraas small-scale boiler (50 KW) and the other is the Sydkraft Malmoe Vaerme AB's Flintraennan large-scale boiler (55 MW). The fix bed is assumed to be two zones, a partial equilibrium drying/devolatilisation zone and an equilibrium zone. Three typical biomass conversion modes are simulated, a lean fuel combustion mode, a near-stoichiometric combustion and a fuel rich gasification mode. Detailed chemical species and temperatures at different modes are obtained. Physical interpretation is provided. Comparison of the computational results with experimental data shows that the model can reasonably simulate the fixed bed biomass conversion process. CFD
Development of a GUI Based Front End for Open Source CFD Program, OpenFOAM
Energy Technology Data Exchange (ETDEWEB)
Han, Samhee; Lee, Youngjin; Kim, Hyongchol; Park, Sunbyung; Kim, Hyunjik [Nuclear Safety Evaluation, Daejeon (Korea, Republic of)
2013-05-15
OpenFOAM is sorely lacking in user friendliness as it runs in console mode under Li nux. Run{sub F}OAM was developed to greatly simplify the task of running an OpenFOAM calculation under Windows OS. Run{sub F}OAM was written using Delphi object pascal language, and GLScene package was used for the 3D graphics. Verification of Run{sub F}OAM was carried out by performing some OpenFOAM CFD calculations provided in OpenFOAM package, and these showed that the use of Run{sub F}OAM is simple whilst providing sufficient allowances in user modifications. Run{sub F}oam, a GUI based front end program to simplify running Open Foam CFD cases, has been developed. By incorporating numerous GUI in the program, Run{sub F}oam has demonstrated that running an Open Foam case can be easily accomplished. There is a potential for further development as the Open Foam has the great advantage of being free to develop and to use. There is also a potential to couple or interface the Open Foam with the systems analysis code such as Relap5.
Development of a GUI Based Front End for Open Source CFD Program, OpenFOAM
International Nuclear Information System (INIS)
OpenFOAM is sorely lacking in user friendliness as it runs in console mode under Li nux. RunFOAM was developed to greatly simplify the task of running an OpenFOAM calculation under Windows OS. RunFOAM was written using Delphi object pascal language, and GLScene package was used for the 3D graphics. Verification of RunFOAM was carried out by performing some OpenFOAM CFD calculations provided in OpenFOAM package, and these showed that the use of RunFOAM is simple whilst providing sufficient allowances in user modifications. RunFoam, a GUI based front end program to simplify running Open Foam CFD cases, has been developed. By incorporating numerous GUI in the program, RunFoam has demonstrated that running an Open Foam case can be easily accomplished. There is a potential for further development as the Open Foam has the great advantage of being free to develop and to use. There is also a potential to couple or interface the Open Foam with the systems analysis code such as Relap5
Clearance Analysis and Leakage Flow CFD Model of a Two-Lobe Multi-Recompression Heater
Directory of Open Access Journals (Sweden)
Joseph C. Mollendorf
2006-10-01
Full Text Available This paper reports the results of a study on multi-recompression heating. This process employs a Roots-type mechanism to heat gases to very high temperatures by compressive gas heating. A CFD model predicting the leakage flows in the machine was developed, and an excellent comparison with experimental data taken on a two-lobe Roots blower was obtained. A Ã¢Â€Âœclearance analysisÃ¢Â€Â was performed to show that the clearance between the impellers remains constant for 96% of the angles of rotation. Assuming a quasi-steady state, the CFD simulation was performed for a single angle of rotation. A three-dimensional analysis showed that the flow field is identical along the rotor length, except for the leakage through the end plates. Hence, the model was further simplified to a two-dimensional analysis. This research may provide guidance in predicting the leakage flows in other blowers of the same kind with a different geometry.
CFD Analysis for Optimum Thermal Design of Carbon Nanotube Based Micro-Channel Heatsink
Directory of Open Access Journals (Sweden)
M. Mahbub
2011-10-01
Full Text Available Carbon nanotube (CNT is considered as an ideal material for thermal management in electronic packaging because of its extraordinary high thermal conductivity. Fabricated onto a silicon substrate to form micro-channels, the CNT based cooling fins show high heat dissipation efficiency. A series of 2D and 3D CFD simulations have been carried out for CNT based micro-channel cooling architectures based on one and two dimensional fin array in this paper using COMSOL 4.0a software. Micro-channels are generally regarded as an effective method for the heat transfer in electronic products. The influence of various fluids, micro-fin structures, fluid velocity and heating powers on cooling effects have been simulated and compared in this study. Steady-state thermal stress analyses for the forced convection heat transfer are also performed to determine maximum allowable stress and deflections for the different types of cooling assembly.
DEFF Research Database (Denmark)
Yin, Chungen; Johansen, Lars Christian Riis; Rosendahl, Lasse; Kær, Søren Knudsen
2010-01-01
Radiation is the principal mode of heat transfer in furnaces. Models for gaseous radiative properties have been well established for air combustion. However, there is uncertainty regarding their applicability to oxy-fuel conditions. In this paper, a new and complete set of weighted sum of gray...... gases model (WSGGM) is derived, which is applicable to computational fluid dynamics (CFD) modeling of both air-fuel and oxy-fuel combustion. First, a computer code is developed to evaluate the emissivity of any gas mixture at any condition by using the exponential wide band model (EWBM), and the...... guidelines on oxy-fuel modeling are recommended....
Zanino, R.; Giors, S.
2008-03-01
Computational Fluid Dynamics (CFD) techniques have been proposed and applied in a series of papers to analyze cable-in-conduit conductors (CICC) for the International Thermonuclear Experimental Reactor (ITER). Previous work on the pressure drop in the central channel of ITER CICC is extended here to the problem of combined heat and momentum transfer. The CFD model, solved by the FLUENT commercial code, is first validated against 2D and 3D data from compact heat exchangers, showing good agreement. The Colburn analogy between the friction factor f and the Nusselt number Nu is not verified in the considered 2D geometries, as shown by both experiment and simulation. The validated CFD model is finally applied to the 3D analysis of central channel-like geometries relevant for ITER CICC. It is shown that the heat transfer coefficient on the central channel side stays relatively close to the smooth-pipe (Dittus-Boelter) value.
Actuator forces in CFD: RANS and LES modeling in OpenFOAM
International Nuclear Information System (INIS)
Wind turbine wakes are a very challenging topic for scientific computations, but modern CFD frameworks and latest HPC centers allow setting up numerical computations on the wake induced by the wind turbine. The main issues is that the correct modeling of the wake is related to the correct modeling of the interaction between the blade and the incoming flow. The aim of the proposed work is to estimate the aerodynamic forces acting on the blades in order to correctly generate the rotor wake applying equivalent aerodynamic force source on the flow. The definition of a blade forces is done developing a model able to correctly estimate this aerodynamic forces as a function of the local flow seen by the blade during its revolution
Derivation of airfoil characteristics for the LM 19.1 blade based on 3D CFD rotor calculations
Energy Technology Data Exchange (ETDEWEB)
Bak, C.; Soerensen, N.N.; Madsen, H.A. [Risoe National Lab., Roskilde (Denmark)
1999-03-01
Airfoil characteristics for the LM 19.1 blade are derived from 3D CFD computations on a full-scale 41-m rotor. Based on 3D CFD the force distributions on the blades are determined, from which airfoil characteristics are derived using the momentum theory. The final airfoil characteristics are constructed using both wind tunnel measurements and 3D CFD. Compared to 2D wind tunnel measurements they show a low lift in stall for the airfoil sections at the tip. At the airfoil sections at the inner part of the blade, they show a high lift in stall. At about 60% radius the lift agrees well to 2D wind tunnel measurements. Aero-elastic calculations using the final airfoil characteristics show good agreement to measured power and flap moments. Furthermore, a fatigue load analysis shows a reduction of up to 15% of the load compared to commonly used data. (au)
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Both parallel and staggered plate fin arrays have shown promise for use in high performance heatsinks regard of its individual manufacturing costs. The geometrical and operational parameters are very important to their cooling performance as heatsinks in practical applications. Fluent 5.0 commercial CFD (computational fluid dynamic) code is used to simulate the flow and heat transfer of those heatsinks of different realistic parameters. Based on those simulations, two correlations, concerning Nusselt number and friction factor as the functions of geometrical and operational parameters, FB (fin-base area ratio), PR (ratio of spanwise pitch to lengthwise pitch) and Re, were developed. From the both, the performance comparisons for optimizing geometrical and operational parameters of a fixed dimension heatsink are shown at constant pumping power and constant thermal resistance. Several optimized parameters were obtained with the discussion to various goals in real application. It demonstrates that in some particular situations, the parallel plate fin heatsinks can out perform the staggered ones.
The CFD Investigation of Two Non-Aligned Turbines Using Actuator Disk Model and Overset Grids
International Nuclear Information System (INIS)
In this study flow over two axially non-aligned wind turbines is investigated via 3-D CFD analysis by solving Navier-Stokes equations. This setting is the test case geometry for the NTNU's ''Blind-Test'' Workshop 3 (BT3) and it aims to predict the performance of the wind turbines and their wake development under asymmetrical flow conditions. The performance of the turbine in the wake of the other turbine is numerically studied for different tip speed ratios. The measurements of velocity profile which is severely disturbed by both turbines are also carried out at the several locations of the wind tunnel. The computational results for NTNU wind turbine test case were obtained by 3-D CFD simulations with two different approaches. The first approach is to employ the actuator disk model, which is used in order to approximate the pressure jump across the rotor disk to simulate the impact of the wind turbines. At the second approach, the actual geometry of the turbine rotor was used, and the rotor blades were rotated using an overset grid methodology over the background grids. The thrust coefficients and the velocity profiles are calculated with two different approaches and the results are compared to experimental data presented in BT3
International Nuclear Information System (INIS)
Highlights: ► We study thermal hydraulic design of main vessel cooling system of fast reactors. ► A CFD based approach is proposed for determination of coolant flow rate. ► Effect of cooling system ovality on temperature asymmetry is quantified. ► Suitable flow distribution device is identified to achieve acceptable flow field. ► To compare efficacy of various devices, a flow mal-distribution index is defined. - Abstract: A computational fluid dynamics (CFDs) based approach is proposed for the thermal hydraulic design of the main vessel cooling system for pool type sodium cooled reactors. Usage of the proposed method is demonstrated by applying it to a future Indian commercial fast breeder reactor. Towards quantifying the amount of sodium flow rate for the main vessel cooling system, two-dimensional CFD investigations have been performed. The conjugate conduction–convection models adopted for this purpose are validated against sodium experiments available in literature. The required flow fraction has been determined to be 2.6% of core flow, which is 175.6 kg/s at full power conditions. The heat loss from the hot pool to the cold pool through the main vessel cooling system is estimated to be 10.6 MW at full power and 3.7 MW at 20% power conditions. By detailed three-dimensional CFD studies, the effect of ovality in the main vessel cooling annuli due to manufacturing tolerances has been assessed and the associated circumferential temperature difference in the main vessel is determined to be 14 °C, which is less than the permissible upper limit of 30 °C. The uniformity of sodium flow in the cooling annulus has been investigated by a three-dimensional hydraulic analysis with a view to identify a suitable passive device that can render a uniform velocity distribution. To compare the effectiveness of various devices, a flow mal-distribution index is defined. Detailed parametric studies have been carried out to identify an appropriate porous jet breaker
International Nuclear Information System (INIS)
This paper presents an unstructured mesh based multi-physics interface implemented in the Serpent 2 Monte Carlo code, for the purpose of coupling the neutronics solution to component-scale thermal hydraulics calculations, such as computational fluid dynamics (CFD). The work continues the development of a multi-physics coupling scheme, which relies on the separation of state-point information from the geometry input, and the capability to handle temperature and density distributions by a rejection sampling algorithm. The new interface type is demonstrated by a simplified molten-salt reactor test case, using a thermal hydraulics solution provided by the CFD solver in OpenFOAM. (author)
Tracer experimental techniques for CFD model verification and validation in sugar crystallizer
International Nuclear Information System (INIS)
In the framework of the CRP improvement of the experimental design for RTD tests at a pilot crystallizer was performed. A new approach for RTD studies in non-Newtonian fluids for flow patterns characterization at the pilot crystallizer was carried out. Batch mixing process was tested and the homogenization time for massecuite fluid close to seven hours proved that the crystallizers with relative low residence time that the Cuban sugar industry is trying to develop will achieve low exhaustion efficiency with significant sugar losses. The flow simulation was carried out by CFD Flotran in ANSYS 5.4 package. The possibility of RTD prediction on the basis of numerical solution of transport equations for fluid dynamics in a more simplified geometry of the crystallizer and molasses as fluid using transient analysis of temperature pulse spreading is discussed. Finally, taking in account that in complex flow structure, the most general Stimulus Response Method (SRM) based in point source response (PSR) is more suitable for CFD verification than the ambiguous, in some cases, RTD function, the design and preparation of a multipurpose relative long live 99Mo/99mTc point source device has been developed and special PC-program has been prepared for the interpolation of detector responses function. (author)
International Nuclear Information System (INIS)
Yucca Mountain, Nevada has been designated as the nation's high-level radioactive waste repository and the U.S. Department of Energy has been approved to apply to the U.S. Nuclear Regulatory Commission for a license to construct a repository. Heat transfer in the Yucca Mountain Project (YMP) drift enclosures is an important aspect of repository waste emplacement. Canisters containing radioactive waste are to be emplaced in tunnels drilled 500 m below the ground surface. After repository closure, decaying heat is transferred from waste packages to the host rock by a combination of thermal radiation, natural convection and conduction heat transfer mechanism?. Current YMP mountain-scale and drift-scale numerical models often use a simplified porous medium code to model fluid and heat flow in the drift openings. To account for natural convection heat transfer, the thermal conductivity of the air was increased in the porous medium model. The equivalent thermal conductivity, defined as the ratio of total heat flow to conductive heat flow, used in the porous media models was based on horizontal concentric cylinders. Such modeling does not effectively capture turbulent natural convection in the open spaces as discussed by Webb et al. (2003) yet the approach is still widely used on the YMP project. In order to mechanistically model natural convection conditions in YMP drifts, the computational fluid dynamics (CFD) code FLUENT (Fluent, Incorporated, 2001) has been used to model natural convection heat transfer in the YMP emplacement drifts. A two-dimensional (2D) model representative of YMP geometry (e.g., includes waste package, drip shield, invert and drift wall) has been developed and numerical simulations made (Francis et al., 2003). Using CFD simulation results for both natural convection and conduction-only heat transfer in a single phase, single component fluid, equivalent thermal conductivities have been calculated for different Rayleigh numbers. Correlation
Numerical analysis on noise of rotor with unconventional blade tips based on CFD/Kirchhoff method
Institute of Scientific and Technical Information of China (English)
Wang Bo; Zhao Qijun; Xu Guohua; Ye Liang; Wang Junyi
2013-01-01
A solver is developed aiming at efficiently predicting rotor noise in hover and forward flight.In this solver,the nonlinear near-field solutions are calculated by a hybrid approach which includes the Navier-Stokes and Euler equations based on a moving-embedded grid system and adaptive grid methodology.A combination of the third-order upwind scheme and flux-difference splitting scheme,instead of the second-order center-difference scheme which may cause larger wake dissipation,has been employed in the present computational fluid dynamics (CFD) method.The sound pressure data in the near field can be calculated directly by solving the Navier-Stokes equations,and the sound propagation can be predicted by the Kirchhoffmethod.A harmonic expansion approach is presented for rotor far-field noise prediction,which gives an analytical expression for the integral function in the Kirchhoff formula.As a result,the interpolation process is simplified and the efficiency and accuracy of the interpolation are improved.Then,the high-speed impulsive (HIS) noise of a helicopter rotor at different tip Mach numbers and on different observers is calculated and analyzed in hover and forward flight,which shows a highly directional characteristic of the rotor HIS noise with a maximum value in the rotor plane,and the HSI noise weakens rapidly with the increasing of the directivity angle.In order to investigate the effects of the rotor blade-tip shape on its aeroacoustic characteristics,four kinds of blade tips are designed and their noise characteristics have been simulated.At last,a new unconventional CLOR-Ⅱ blade tip has been designed,and the noise characteristics of the presented CLOR-Ⅱ model rotor have been simulated and measured compared to the reference rotors with a rectangular or swept-back platform blade tip.The results demonstrate that the unconventional CLOR-Ⅱblade tip can significantly reduce the HSI noise of a rotor.
CFD model of thermal and velocity conditions in a particular indoor environment
Energy Technology Data Exchange (ETDEWEB)
Mora Perez, Miguel; Lopez Patino, Gonzalo; Lopez Jimenez, P. Amparo [Hydraulic and Environmental Engineering Department, Universitat Politecnica de Valencia (Spain); Guillen Guillamon, Ignacio [Applied Physics Department, Universitat Politecnica de Valencia (Spain)
2013-07-01
The demand for maintaining high indoor environmental quality (IEQ) with the minimum energy consumption is rapidly increasing. In the recent years, several studies have been completed to investigate the impact of indoor environment factors on human comfort, health and energy efficiency. Therefore, the design of the thermal environment in any sort of room, specially offices, has huge economic consequences. In this paper, a particular analysis on the air temperature in a multi-task room environment is modeled, in order to represent the velocities and temperatures inside the room by using Computational Fluid Dynamics (CFD) techniques. This model will help to designers to analyze the thermal comfort regions inside the studied air volume and to visualize the whole temperatures inside the room, determining the effect of the fresh external incoming air in the internal air temperature.
Skřínský, Jan; Vereš, Ján; Peer, Václav; Friedel, Pavel
2016-06-01
The effect of initial concentration on the explosion behavior of a stoichiometric CH4/O2/N2 mixture under air-combustion conditions was studied. Two mathematical models were used with the aim at simulating the gas explosion in the middle scale explosion vessel, and the associated effects of the temperature for different gas/air concentrations. Peak pressure, maximum rate of pressure rise and laminar burning velocity were measured from pressure time records of explosions occurring in a 1 m3 closed cylindrical vessel. The results of the models were validated considering a set of data (pressure time histories and root mean square velocity). The obtained results are relevant to the practice of gas explosion testing and the interpretation of test results and, they should be taken as the input data for CFD simulation to improve the conditions for standard tests.
Energy Technology Data Exchange (ETDEWEB)
Soria, José, E-mail: jose.soria@probien.gob.ar [Institute for Research and Development in Process Engineering, Biotechnology and Alternative Energies (PROBIEN, CONICET – UNCo), 1400 Buenos Aires St., 8300 Neuquén (Argentina); Gauthier, Daniel; Flamant, Gilles [Processes, Materials and Solar Energy Laboratory (PROMES-CNRS, UPR 8521), 7 Four Solaire Street, Odeillo, 66120 Font-Romeu (France); Rodriguez, Rosa [Chemical Engineering Institute, National University of San Juan, 1109 Libertador (O) Avenue, 5400 San Juan (Argentina); Mazza, Germán [Institute for Research and Development in Process Engineering, Biotechnology and Alternative Energies (PROBIEN, CONICET – UNCo), 1400 Buenos Aires St., 8300 Neuquén (Argentina)
2015-09-15
Highlights: • A CFD two-scale model is formulated to simulate heavy metal vaporization from waste incineration in fluidized beds. • MSW particle is modelled with the macroscopic particle model. • Influence of bed dynamics on HM vaporization is included. • CFD predicted results agree well with experimental data reported in literature. • This approach may be helpful for fluidized bed reactor modelling purposes. - Abstract: Municipal Solid Waste Incineration (MSWI) in fluidized bed is a very interesting technology mainly due to high combustion efficiency, great flexibility for treating several types of waste fuels and reduction in pollutants emitted with the flue gas. However, there is a great concern with respect to the fate of heavy metals (HM) contained in MSW and their environmental impact. In this study, a coupled two-scale CFD model was developed for MSWI in a bubbling fluidized bed. It presents an original scheme that combines a single particle model and a global fluidized bed model in order to represent the HM vaporization during MSW combustion. Two of the most representative HM (Cd and Pb) with bed temperatures ranging between 923 and 1073 K have been considered. This new approach uses ANSYS FLUENT 14.0 as the modelling platform for the simulations along with a complete set of self-developed user-defined functions (UDFs). The simulation results are compared to the experimental data obtained previously by the research group in a lab-scale fluid bed incinerator. The comparison indicates that the proposed CFD model predicts well the evolution of the HM release for the bed temperatures analyzed. It shows that both bed temperature and bed dynamics have influence on the HM vaporization rate. It can be concluded that CFD is a rigorous tool that provides valuable information about HM vaporization and that the original two-scale simulation scheme adopted allows to better represent the actual particle behavior in a fluid bed incinerator.
International Nuclear Information System (INIS)
Highlights: • A CFD two-scale model is formulated to simulate heavy metal vaporization from waste incineration in fluidized beds. • MSW particle is modelled with the macroscopic particle model. • Influence of bed dynamics on HM vaporization is included. • CFD predicted results agree well with experimental data reported in literature. • This approach may be helpful for fluidized bed reactor modelling purposes. - Abstract: Municipal Solid Waste Incineration (MSWI) in fluidized bed is a very interesting technology mainly due to high combustion efficiency, great flexibility for treating several types of waste fuels and reduction in pollutants emitted with the flue gas. However, there is a great concern with respect to the fate of heavy metals (HM) contained in MSW and their environmental impact. In this study, a coupled two-scale CFD model was developed for MSWI in a bubbling fluidized bed. It presents an original scheme that combines a single particle model and a global fluidized bed model in order to represent the HM vaporization during MSW combustion. Two of the most representative HM (Cd and Pb) with bed temperatures ranging between 923 and 1073 K have been considered. This new approach uses ANSYS FLUENT 14.0 as the modelling platform for the simulations along with a complete set of self-developed user-defined functions (UDFs). The simulation results are compared to the experimental data obtained previously by the research group in a lab-scale fluid bed incinerator. The comparison indicates that the proposed CFD model predicts well the evolution of the HM release for the bed temperatures analyzed. It shows that both bed temperature and bed dynamics have influence on the HM vaporization rate. It can be concluded that CFD is a rigorous tool that provides valuable information about HM vaporization and that the original two-scale simulation scheme adopted allows to better represent the actual particle behavior in a fluid bed incinerator
Enlarging the operation range of a centrifugal compressor by cutting vanes based on CFD
International Nuclear Information System (INIS)
Many centrifugal compressors are liable to insufficient operation range. The purpose of this paper is to enlarge the operation range of a centrifugal compressor used in turbocharger by cutting vanes. Some numerical works have been done based on CFD. The comparison of the calculated and measured results shows good agreement. The overall performance characteristics of the centrifugal compressor with different cutted vanes are observed and analyzed. The performance characteristic curves show that cutting vanes can increase the operation range by more than 50% with the loss of the highest efficiency limited in 1%. The flow fields are also shown in this paper and related explanations about the change of the performance characteristics curves are given. Shock wave is also detected in the simulation, and some related characteristics are summed up
Enlarging the operation range of a centrifugal compressor by cutting vanes based on CFD
Mo, J. T.; Gu, C. H.; Pan, X. H.; Y Zheng, S.
2013-12-01
Many centrifugal compressors are liable to insufficient operation range. The purpose of this paper is to enlarge the operation range of a centrifugal compressor used in turbocharger by cutting vanes. Some numerical works have been done based on CFD. The comparison of the calculated and measured results shows good agreement. The overall performance characteristics of the centrifugal compressor with different cutted vanes are observed and analyzed. The performance characteristic curves show that cutting vanes can increase the operation range by more than 50% with the loss of the highest efficiency limited in 1%. The flow fields are also shown in this paper and related explanations about the change of the performance characteristics curves are given. Shock wave is also detected in the simulation, and some related characteristics are summed up.
Institute of Scientific and Technical Information of China (English)
李大美; 王祥三; 赖永根
2001-01-01
Schistosomiasis is a parasitic disease. They propagate in the Yangtze River valley of Chi-na. The spread of the disease is solely through a middle-agent named oncomelania, so the spread ofschistosomiasis by oncomelania can be controlled by properly designing water intakes which preventoncomelania from entering the farming land or residential areas. In this paper, a successful design pro-cess is reported and a new oncomelania-free intake device is demonstrated in the laboratory. The de-sign of the new intake is based on a sound research program in which an extensive experimental stud-ies have been carried out to gain knowledge of oncomelania eco-hydraulic behaviors and a detailed flowfield information is obtained through CFD simulation.
CFD analysis of a cask for spent fuel dry storage: Model fundamentals and sensitivity studies
International Nuclear Information System (INIS)
Highlights: • A dry storage cask has been evaluated by a CFD code, FLUENT 14. • An alternative methodology for thermal-fluid dynamic modeling has been performed. • Fuel maximum temperature obtained is around 50 K below the regulation limit (673 K). • Even in the most unfavorable heat load distribution temperature increase is smaller than 4%. - Abstract: Dry storage technology must ensure spent fuel cooling under any conditions. This turns thermo-fluid dynamics within dry storage casks a key aspect to investigate, as it would heavily affect fuel rod temperatures. This paper introduces a Computational Fluid Dynamic (CFD) model and analyses of a HI-STORM 100S cask with FLUENT 14.0. Fuel assemblies have been modeled as a porous medium characterized by a thermal conductivity and pressure drop that have been derived from specific approximations, algorithms and methods. This approach has been verified by comparing its results to those published by Holtec International for the HI-STORM cask. The application of the 3D model to HI-STORM 100S cask type under normal conditions, confirms that fuel maximum temperatures more than about 50 K below the regulation limit (673 K) should be expected. In addition, the effect on these results of aspects such as cask design (inlet/outlet orientation), heat load (regionalization) and local climate (external temperature), have been explored. The results indicate that the most relevant factor is heat load distribution and that, even in the most unfavorable regionalization feasible, temperature increase is smaller than 4%. Nonetheless, it should be highlighted that thermal margin to regulatory setting might be reduced down to around 40%
CFD of mixing of multi-phase flow in a bioreactor using population balance model.
Sarkar, Jayati; Shekhawat, Lalita Kanwar; Loomba, Varun; Rathore, Anurag S
2016-05-01
Mixing in bioreactors is known to be crucial for achieving efficient mass and heat transfer, both of which thereby impact not only growth of cells but also product quality. In a typical bioreactor, the rate of transport of oxygen from air is the limiting factor. While higher impeller speeds can enhance mixing, they can also cause severe cell damage. Hence, it is crucial to understand the hydrodynamics in a bioreactor to achieve optimal performance. This article presents a novel approach involving use of computational fluid dynamics (CFD) to model the hydrodynamics of an aerated stirred bioreactor for production of a monoclonal antibody therapeutic via mammalian cell culture. This is achieved by estimating the volume averaged mass transfer coefficient (kL a) under varying conditions of the process parameters. The process parameters that have been examined include the impeller rotational speed and the flow rate of the incoming gas through the sparger inlet. To undermine the two-phase flow and turbulence, an Eulerian-Eulerian multiphase model and k-ε turbulence model have been used, respectively. These have further been coupled with population balance model to incorporate the various interphase interactions that lead to coalescence and breakage of bubbles. We have successfully demonstrated the utility of CFD as a tool to predict size distribution of bubbles as a function of process parameters and an efficient approach for obtaining optimized mixing conditions in the reactor. The proposed approach is significantly time and resource efficient when compared to the hit and trial, all experimental approach that is presently used. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:613-628, 2016. PMID:26850863
Bai, YuGuang; Yang, Kai; Sun, DongKe; Zhang, YuGuang; Kennedy, David; Williams, Fred; Gao, XiaoWei
2013-02-01
This paper focuses on numerical simulations of bluff body aerodynamics with three-dimensional CFD (computational fluid dynamics) modeling, where a computational scheme for fluid-structure interactions is implemented. The choice of an appropriate turbulence model for the computational modeling of bluff body aerodynamics using both two-dimensional and three-dimensional CFD numerical simulations is also considered. An efficient mesh control method which employs the mesh deformation technique is proposed to achieve better simulation results. Several long-span deck sections are chosen as examples which were stationary and pitching at a high Reynolds number. With the proposed CFD method and turbulence models, the force coefficients and flutter derivatives thus obtained are compared with the experimental measurement results and computed values completely from commercial software. Finally, a discussion on the effects of oscillation amplitude on the flutter instability of a bluff body is carried out with extended numerical simulations. These numerical analysis results demonstrate that the proposed three-dimensional CFD method, with proper turbulence modeling, has good accuracy and significant benefits for aerodynamic analysis and computational FSI studies of bluff bodies.
Launer, M; Lyko, S; Fahlenkamp, H; Jagemann, P; Ehrhard, P
2013-01-01
Since November 2009, Germany's first full-scale ozonation plant for tertiary treatment of secondary effluent is in continuous operation. A kinetic model was developed and combined with the commercial computational fluid dynamics (CFD) software ANSYS(®) CFX(®) to simulate the removal of micropollutants from secondary effluents. Input data like reaction rate constants and initial concentrations of bulk components of the effluent organic matter (EfOM) were derived from experimental batch tests. Additionally, well-known correlations for the mass transfer were implemented into the simulation model. The CFD model was calibrated and validated by full-scale process data and by analytical measurements for micropollutants. The results show a good consistency of simulated values and measured data. Therewith, the validated CFD model described in this study proved to be suited for the application of secondary effluent ozonation. By implementing site-specific ozone exposition and the given reactor geometry the described CFD model can be easily adopted for similar applications. PMID:24056432
Issues in the validation of CFD modelling of semi-solid metal forming
International Nuclear Information System (INIS)
Modelling of die filling during semi-solid metal processing (thixoforming) places particular demands on the CFD package being used. Not only are the velocities of the metal slurry in the die very high, the viscosity is too. Furthermore, the viscosity changes with shear rate (i.e. with changes in cross sectional area of the region the slurry travels through) and with time, as the injected material is thixotropic. The CFD software therefore requires good free surface tracking, accurate implicit solutions of the flow equations (as the CPU times for explicit solutions at high viscosities are impractical) and a model that adequately describes the slurry thixotropy. Finally, reliable, experimentally determined viscosity data are required. This paper describes the experiments on tin-lead and aluminium alloy slurries using compressive tests and rotating cylinder viscometry, followed by modelling using FLOW-3D. This package is known for its ability to track free surfaces accurately. Compressive tests allow rapid changes in shear rate to be imparted to the slurry, without wall slip, while the simple geometry of the viscometer makes it possible to compare analytical and numerical solutions. It is shown that the implicit viscous solver in its original form can reproduce the general trends found in the compressive and viscometry tests. However, sharp changes in shear rate lead to overestimation of pressure gradients in the slurry, making it difficult to separate these effects from those due to thixotropic breakdown. In order to achieve this separation, it is necessary to implement a more accurate implicit solver, which is currently under development. (author)
DEFF Research Database (Denmark)
Aage, Christian
1998-01-01
-scale measurements have been carried out as well. The CFD method also offers the possibility of a computational estimate of scale effects related to wind tunnel model testing. An example of such an estimate on the ferry is discussed. This work has been published in more details in Proceedings of BOSS'97, Aage et al...
Ma, Baoshun; Ruwet, Vincent; Corieri, Patricia; Theunissen, Raf; Riethmuller, Michel; Darquenne, Chantal
2009-05-01
Accurate modeling of air flow and aerosol transport in the alveolated airways is essential for quantitative predictions of pulmonary aerosol deposition. However, experimental validation of such modeling studies has been scarce. The objective of this study is to validate CFD predictions of flow field and particle trajectory with experiments within a scaled-up model of alveolated airways. Steady flow (Re = 0.13) of silicone oil was captured by particle image velocimetry (PIV), and the trajectories of 0.5 mm and 1.2 mm spherical iron beads (representing 0.7 to 14.6 mum aerosol in vivo) were obtained by particle tracking velocimetry (PTV). At twelve selected cross sections, the velocity profiles obtained by CFD matched well with those by PIV (within 1.7% on average). The CFD predicted trajectories also matched well with PTV experiments. These results showed that air flow and aerosol transport in models of human alveolated airways can be simulated by CFD techniques with reasonable accuracy. PMID:20161301
CFD modeling of two phase flow in asymmetric rotating disc contactor
International Nuclear Information System (INIS)
The present work includes CFD modeling of ARDC to generate data related to hydrodynamics in different regions and to understand phase interaction for two phase flow. The system fluids were phosphoric acid as continuous phase and Organo-phosphorus solvent as dispersed phase for uranium extraction from phosphoric acid. Plots of parameters related to hydrodynamics and mass transfer like axial velocity, radial velocity, velocity magnitude, and pressure and volume fraction of phases are generated which are important for design and to understand the contacting phenomenon in multistage agitated column. Time dependent analysis of two phase interaction has been done to simulate actual phenomenon. Special emphasis is given to the critical design and operation parameters. Resultant to the above work, for a typical case of 250 rpm, light phase volume friction is displayed and results of simulation are summarized
Ferreira, E.; Alves, E.; Ferreira, R. M. L.
2012-04-01
Sediment deposition by continuous turbidity currents may affect eco-environmental river dynamics in natural reservoirs and hinder the maneuverability of bottom discharge gates in dam reservoirs. In recent years, innovative techniques have been proposed to enforce the deposition of turbidity further upstream in the reservoir (and away from the dam), namely, the use of solid and permeable obstacles such as water jet screens , geotextile screens, etc.. The main objective of this study is to validate a computational fluid dynamics (CFD) code applied to the simulation of the interaction between a turbidity current and a passive retention system, designed to induce sediment deposition. To accomplish the proposed objective, laboratory tests were conducted where a simple obstacle configuration was subjected to the passage of currents with different initial sediment concentrations. The experimental data was used to build benchmark cases to validate the 3D CFD software ANSYS-CFX. Sensitivity tests of mesh design, turbulence models and discretization requirements were performed. The validation consisted in comparing experimental and numerical results, involving instantaneous and time-averaged sediment concentrations and velocities. In general, a good agreement between the numerical and the experimental values is achieved when: i) realistic outlet conditions are specified, ii) channel roughness is properly calibrated, iii) two equation k - ɛ models are employed iv) a fine mesh is employed near the bottom boundary. Acknowledgements This study was funded by the Portuguese Foundation for Science and Technology through the project PTDC/ECM/099485/2008. The first author thanks the assistance of Professor Moitinho de Almeida from ICIST and to all members of the project and of the Fluvial Hydraulics group of CEHIDRO.
The application of CFD modelling to support the reduction of CO2 emissions in cement industry
International Nuclear Information System (INIS)
The cement industry is one of the leading producers of anthropogenic greenhouse gases, of which CO2 is the most significant. Recently, researchers have invested a considerable amount of time studying ways to improve energy consumption and pollutant formation in the overall cement manufacturing process. One idea involves dividing the calcination and clinkering processes into two separate furnaces. The calcination process is performed in a calciner while the clinkering process takes place in a rotary kiln. As this is new technology in the cement manufacturing process, calciners are still in the research and development phase. The purpose of this paper is to demonstrate the potential of CFD to support the design and optimization of calciners, whose use appears to be essential in reduction of CO2 emission during cement production. The mathematical model of the calcination process was developed, validated and implemented into a commercial CFD code, which was then used for the analysis. From the results obtained by these simulations, researchers will gain an in-depth understanding of all thermo-chemical reactions in a calciner. This understanding can be used to optimize the calciner's geometry, to make production more efficient, to lower pollutant formation and to subsequently reduce greenhouse gas emissions. -- Highlights: ► The potential of CO2 emissions reduction, by using a cement calciner was presented. ► When a cement calciner is used, CO2 emissions reduction of 3–4% can be achieved. ► The calcination model was developed, validated, and then used for the analysis. ► Shown method can be applied for investigation and optimization of cement calciners.
International Nuclear Information System (INIS)
Convective heat transfer at exterior building surfaces has an impact on the design and performance of building components such as double-skin facades, solar collectors, solar chimneys and ventilated photovoltaic arrays, and also affects the thermal climate and cooling load in urban areas. In this study, an overview is given of existing correlations of the exterior convective heat transfer coefficient (CHTC) with the wind speed, indicating significant differences between these correlations. As an alternative to using existing correlations, the applicability of CFD to obtain forced CHTC correlations is evaluated, by considering a cubic building in an atmospheric boundary layer. Steady Reynolds-averaged Navier-Stokes simulations are performed and, instead of the commonly used wall functions, low-Reynolds number modelling (LRNM) is used to model the boundary-layer region for reasons of improved accuracy. The flow field is found to become quasi independent of the Reynolds number at Reynolds numbers of about 105. This allows limiting the wind speed at which the CHTC is evaluated and thus the grid resolution in the near-wall region, which significantly reduces the computational expense. The distribution of the power-law CHTC-U10 correlation over the windward and leeward surfaces is presented (U10 = reference wind speed at 10 m height). It is shown that these correlations can be accurately determined by simulations with relatively low wind speed values, which avoids the use of excessively fine grids for LRNM, and by using only two or three discrete wind speed values, which limits the required number of CFD simulations.
CFD Modelling of Bore Erosion in Two-Stage Light Gas Guns
Bogdanoff, D. W.
1998-01-01
A well-validated quasi-one-dimensional computational fluid dynamics (CFD) code for the analysis of the internal ballistics of two-stage light gas guns is modified to explicitly calculate the ablation of steel from the gun bore and the incorporation of the ablated wall material into the hydrogen working cas. The modified code is used to model 45 shots made with the NASA Ames 0.5 inch light gas gun over an extremely wide variety of gun operating conditions. Good agreement is found between the experimental and theoretical piston velocities (maximum errors of +/-2% to +/-6%) and maximum powder pressures (maximum errors of +/-10% with good igniters). Overall, the agreement between the experimental and numerically calculated gun erosion values (within a factor of 2) was judged to be reasonably good, considering the complexity of the processes modelled. Experimental muzzle velocities agree very well (maximum errors of 0.5-0.7 km/sec) with theoretical muzzle velocities calculated with loading of the hydrogen gas with the ablated barrel wall material. Comparison of results for pump tube volumes of 100%, 60% and 40% of an initial benchmark value show that, at the higher muzzle velocities, operation at 40% pump tube volume produces much lower hydrogen loading and gun erosion and substantially lower maximum pressures in the gun. Large muzzle velocity gains (2.4-5.4 km/sec) are predicted upon driving the gun harder (that is, upon using, higher powder loads and/or lower hydrogen fill pressures) when hydrogen loading is neglected; much smaller muzzle velocity gains (1.1-2.2 km/sec) are predicted when hydrogen loading is taken into account. These smaller predicted velocity gains agree well with those achieved in practice. CFD snapshots of the hydrogen mass fraction, density and pressure of the in-bore medium are presented for a very erosive shot.
MODELING OF MESO-SCALE STRUCTURES IN PARTICLE-FLUID SYSTEMS: THE EMMS/CFD APPROACH
Institute of Scientific and Technical Information of China (English)
Ning; Yang; Wei; Wang; Wei; Ge; Jinghai; Li
2005-01-01
Meso-scale structures existing in the form of particle-rich clusters, streamers or strands in circulating fluidized beds, and of ascending bubble plumes and descending liquid-rich vortices in bubble columns and slurry-bed reactors, as commonly observed, have played an important role in the macro-scale behavior of particle-fluid systems. These meso-scale structures span a wide range of length and time scales, and their origin, evolution and influence are still far from being well understood.Recent decades have witnessed the emergence of computer simulation of particle-fluid systems based on computational fluid dynamic (CFD) models. However, strictly speaking these models are far from mature and the complex nature of particle-fluid systems arising from the meso-scale structures has been posing great challenges to investigators. The reason may be that the current two-fluid models (TFM) are derived either from continuum mechanics by using different kinds of averaging techniques for the conservation equations of single-phase flow, or from the kinetic theory of gases in which the assumption of molecular chaos is employed, thereby losing sight of the meso-scale heterogeneity at the scale of computational cells and leading to inaccurate calculation of the interaction force between particles and fluids. For example, the overall drag force for particles in a cell is usually calculated from the empirical Wen & Yu/Ergun correlations,which should be suspected since these correlations were originally derived from homogeneous systems.Schemes to solve this problem for gas-particles systems may be classified into four categories. First, one could capture the detailed meso-scale structure information at the cell scale by employing the so-called direct numerical simulation (DNS) (Hu, 1996), the pseudo-particle modeling (PPM) (Ge & Li, 2003), or the Lattice-Boltzmann method (LBM) to track the interface between gas and particles. Second, refinement of the computational meshes may
International Nuclear Information System (INIS)
A methodology to estimate the spatial representativeness of air pollution monitoring sites is applied to two urban districts. This methodology is based on high resolution maps of air pollution computed by using Computational Fluid Dynamics (CFD) modelling tools. Traffic-emitted NO2 dispersion is simulated for several meteorological conditions taking into account the effect of the buildings on air flow and pollutant dispersion and using a steady state CFD-RANS approach. From these results, maps of average pollutant concentrations for January -May 2011 are computed as a combination of the simulated scenarios. Two urban districts of Madrid City were simulated. Spatial representativeness areas for 32 different sites within the same district (including the site of the operative air quality stations) have been estimated by computing the portion of the domains with average NO2 concentration differing less than a 20% of the concentration at each candidate monitoring site. New parameters such as the ratio AR between the representativeness area and the whole domain area or the representativeness index (IR) has been proposed to discuss and compare the representativeness areas. Significant differences between the spatial representativeness of the candidate sites of both studied districts have been found. The sites of the Escuelas Aguirre district have generally smaller representativeness areas than those of the Plaza de Castilla. More stations are needed to cover the Escuelas Aguirre district than for the Plaza de Castilla one. The operative air quality station of the Escuelas Aguirre district is less representative than the station of the Plaza de Castilla district. The cause of these differences seems to be the differences in urban structure of both districts prompting different ventilation. (Author)
Suatean, Bogdan; Colidiuc, Alexandra; Galetuse, Slelian
2012-11-01
The purpose of this paper is to present different CFD models used to determine the aerodynamic performance of horizontal axis wind turbine (HAWT). The models presented have various levels of complexity to calculate the aerodynamic performances of HAWT, starting with a simple model, the actuator line method, and ending with a CFD approach.
International Nuclear Information System (INIS)
Safety analysis is an important tool for justifying the safety of nuclear reactors. The traditional method for nuclear reactor safety analysis is performed by means of system codes, which use one-dimensional lumped-parameter method to model real reactor systems. However, there are many multi-dimensional thermal-hydraulic phenomena cannot be predicated using traditional one-dimensional system codes. This problem is extremely important for pool-type nuclear systems. Computational fluid dynamics (CFD) codes are powerful numerical simulation tools to solve multi-dimensional thermal-hydraulics problems, which are widely used in industrial applications for single phase flows. In order to use general CFD codes to solve nuclear reactor transient problems, some additional models beyond general ones are required. Neutron kinetics model for power calculation and fuel pin model for fuel pin temperature calculation are two important models of these additional models. The motivation of this work is to develop an advance numerical simulation method for nuclear reactor safety analysis by implementing neutron kinetics model and fuel pin model into general CFD codes. In this paper, the Point Kinetics Model (PKM) and Fuel Pin Model (FPM) are implemented into a general CFD code FLUENT. The improved FLUENT was called as FLUENT/PK. The mathematical models and implementary method of FLUENT/PK are descripted and two demonstration application cases, e.g. the unprotected transient overpower (UTOP) accident of a Liquid Metal cooled Fast Reactor (LMFR) and the unprotected beam overpower (UBOP) accident of an Accelerator Driven System (ADS), are presented. (author)
Energy Technology Data Exchange (ETDEWEB)
Ge, Y.T.; Tassou, S.A.; Hadawey, A. [Mechanical Engineering, School of Engineering and Design, Brunel University, Uxbridge, Middlesex, UB8 3PH (United Kingdom)
2010-10-15
In this paper, the model for the multi-deck medium temperature display cabinets is developed with the integration of CFD and cooling coil sub-models. The distributed method is used to develop the cooling coil model with the airside inputs from the outputs of the CFD model. Inversely, the airside outputs from the cooling coil model are used to update the boundary conditions of the CFD model. To validate this cabinet model, a multi-deck medium temperature display cabinet refrigerated with a secondary refrigerant cooling coil was selected as a prototype and mounted in an air conditioned chamber. Extensive tests were conducted at constant space air temperature and varied relative humilities. The cabinet model has been validated by comparing with the test results for the parameters of air at different locations of the flow path, and temperatures of refrigerant and food product, etc. The validated model is therefore used to explore and analyse the cabinet performance and control strategies at various operating and design conditions. (author)
Cavitation performance prediction of mixed-flow pump based on CFD
International Nuclear Information System (INIS)
The computational fluid dynamics (CFD) method is used to investigate the three-dimensional cavitation flow fields in a mixed-flow pump with high specific speed. In the numerical modeling, the homogeneous mixture model and Navier-Stokes equation with RNG k−ε turbulence model are employed. At the best efficiency condition, the cavitation location on the impeller blades and the distribution situation of vapor volume fraction were analyzed, as well as the performance curve between the pump's NPSHA and efficiency were predicted. The results show that, the cavitation directly affects the pressure distribution on impeller blade surfaces, and also results in change of the pump external characteristic. Under the primary cavitation condition, Water vapors first accumulate on the suction surface of blade's leading edge, which is close to the tip. With the decrease of inlet total pressure, the cavitation region extended towards the trailing edge and water vapor fraction volume become larger gradually. When cavitation is serious, water vapors mainly accumulate on the suction surface of blade's trailing edge. The prediction curve has the same trend as the practical curve, which can reveal the mixed-flow pump cavitation within the static characteristics.
A CFD model for particle dispersion in turbulent boundary layer flows
International Nuclear Information System (INIS)
In Lagrangian particle dispersion modeling, the assumption that turbulence is isotropic everywhere yields erroneous predictions of particle deposition rates on walls, even in simple geometries. In this investigation, the stochastic particle tracking model in Fluent 6.2 is modified to include a better treatment of particle-turbulence interactions close to walls where anisotropic effects are significant. The fluid rms velocities in the boundary layer are computed using fits of DNS data obtained in channel flow. The new model is tested against correlations for particle removal rates in turbulent pipe flow and 90o bends. Comparison with experimental data is much better than with the default model. The model is also assessed against data of particle removal in the human mouth-throat geometry where the flow is decidedly three-dimensional. Here, the agreement with the data is reasonable, especially in view of the fact that the DNS fits used are those of channel flows, for lack of better alternatives. The CFD Best Practice Guidelines are followed to a large extent, in particular by using multiple grid resolutions and at least second order discretization schemes
Directory of Open Access Journals (Sweden)
Jan Skočilas
2015-08-01
Full Text Available This paper deals with a computational fluid dynamics (CFD simulation of the heat transfer process during turbulent hot water flow between two chevron plates in a plate heat exchanger. A three-dimensional model with the simplified geometry of two cross-corrugated channels provided by chevron plates, taking into account the inlet and outlet ports, has been designed for the numerical study. The numerical model was based on the shear-stress transport (SST k-! model. The basic characteristics of the heat exchanger, as values of heat transfer coefficient and pressure drop, have been investigated. A comparative analysis of analytical calculation results, based on experimental data obtained from literature, and of the results obtained by numerical simulation, has been carried out. The coefficients and the exponents in the design equations for the considered plates have been arranged by using simulation results. The influence on the main flow parameters of the corrugation inclination angle relative to the flow direction has been taken into account. An analysis of the temperature distribution across the plates has been carried out, and it has shown the presence of zones with higher heat losses and low fluid flow intensity.
Wachowicz, Jan; Łączny, Jacek Marian; Iwaszenko, Sebastian; Janoszek, Tomasz; Cempa-Balewicz, Magdalena
2015-09-01
The results of model studies involving numerical simulation of underground coal gasification process are presented. For the purpose of the study, the software of computational fluid dynamics (CFD) was selected for simulation of underground coal gasification. Based on the review of the literature, it was decided that ANSYS-Fluent will be used as software for the performance of model studies. The ANSYS- -Fluent software was used for numerical calculations in order to identify the distribution of changes in the concentration of syngas components as a function of duration of coal gasification process. The nature of the calculations was predictive. A geometric model has been developed based on construction data of the georeactor used during the researches in Experimental Mine "Barbara" and Coal Mine "Wieczorek" and it was prepared by generating a numerical grid. Data concerning the georeactor power supply method and the parameters maintained during the process used to define the numerical model. Some part of data was supplemented based on the literature sources. The main assumption was to base the simulation of the georeactor operation on a mathematical models describing reactive fluid flow. Components of the process gas and the gasification agent move along the gasification channel and simulate physicochemical phenomena associated with the transfer of mass and energy as well as chemical reactions (together with the energy effect). Chemical reactions of the gasification process are based on a kinetic equation which determines the course of a particular type of equation of chemical coal gasification. The interaction of gas with the surrounding coal layer has also been described as a part of the model. The description concerned the transport of thermal energy. The coal seam and the mass rock are treated as a homogeneous body. Modelling studies assumed the coal gasification process is carried out with the participation of separately oxygen and air as a gasification agent
Energy Technology Data Exchange (ETDEWEB)
Donna Post Guillen; Daniel S. Wendt
2007-11-01
The purpose of this paper is to document the review of several open-literature sources of both experimental capabilities and published hydrodynamic data to aid in the validation of a Computational Fluid Dynamics (CFD) based model of a slurry bubble column (SBC). The review included searching the Web of Science, ISI Proceedings, and Inspec databases, internet searches as well as other open literature sources. The goal of this study was to identify available experimental facilities and relevant data. Integral (i.e., pertaining to the SBC system), as well as fundamental (i.e., separate effects are considered), data are included in the scope of this effort. The fundamental data is needed to validate the individual mechanistic models or closure laws used in a Computational Multiphase Fluid Dynamics (CMFD) simulation of a SBC. The fundamental data is generally focused on simple geometries (i.e., flow between parallel plates or cylindrical pipes) or custom-designed tests to focus on selected interfacial phenomena. Integral data covers the operation of a SBC as a system with coupled effects. This work highlights selected experimental capabilities and data for the purpose of SBC model validation, and is not meant to be an exhaustive summary.
Energy Technology Data Exchange (ETDEWEB)
Donna Post Guillen; Daniel S. Wendt; Steven P. Antal; Michael Z. Podowski
2007-11-01
The purpose of this paper is to document the review of several open-literature sources of both experimental capabilities and published hydrodynamic data to aid in the validation of a Computational Fluid Dynamics (CFD) based model of a slurry bubble column (SBC). The review included searching the Web of Science, ISI Proceedings, and Inspec databases, internet searches as well as other open literature sources. The goal of this study was to identify available experimental facilities and relevant data. Integral (i.e., pertaining to the SBC system), as well as fundamental (i.e., separate effects are considered), data are included in the scope of this effort. The fundamental data is needed to validate the individual mechanistic models or closure laws used in a Computational Multiphase Fluid Dynamics (CMFD) simulation of a SBC. The fundamental data is generally focused on simple geometries (i.e., flow between parallel plates or cylindrical pipes) or custom-designed tests to focus on selected interfacial phenomena. Integral data covers the operation of a SBC as a system with coupled effects. This work highlights selected experimental capabilities and data for the purpose of SBC model validation, and is not meant to be an exhaustive summary.
CFD Applications in Energy and Environment Sectors: Volume 1
Directory of Open Access Journals (Sweden)
Maher A.R. Sadiq Al-Baghdadi and Hashim R. Abdol Hamid
2012-01-01
Full Text Available Chapter 1: Simulation and Modelling of Oxygen Coal Combustion with Flue Gas Recirculation. Chaouki Ghenai Chapter 2: The Choice of the Best Air Distribution Concept in Air-Conditioned Auditorium by Means of CFD Numerical Prediction. Barbara Lipska, Piotr Koper Chapter 3: CFD Applications in Natural Ventilation of Buildings and Air Quality Dispersion. N. Nikolopoulos, A. Nikolopoulos, I. Papadakis, K.-S. P. Nikas Chapter 4: CFD Modeling of Air Pollutant Transport and Dispersion. Labovský Juraj, Jelemenský Ľudovít Chapter 5: CFD Modeling of Multiphase Flow in Environmental Engineering. Masroor Mohajerani, Mehrab Mehrvar, Farhad Ein-Mozaffari Chapter 6: CFD Study on the Roles of Trees on Airflow and Pollutant Dispersion within Urban Street Canyons. Salim Mohamed Salim, Andrew Chan, Riccardo Buccolieri, Silvana Di Sabatino Chapter 7: Energy Efficiency and Air Quality in Hospitals Design. Essam E. Khalil Chapter 8: Application of CFD in Pulverized Fuel Combustion. M. Tayyeb Javed, Tahira Sultana Chapter 9: A Heat Transfer Model For Fluids Based on Cellular Automaton Application to an Air Conditioning of A Building. Andrés Saiz Martínez Chapter 10: CFD Application in Power Plants. Essam E. Khalil Chapter 11: Analysis and Computation of the Heat Charge/Discharge Behavior in Packed Bed Thermal Storage Systems. Pei-Wen Li, Jon Van Lew, Wafaa Karaki, Cho Lik Chan, Jake Stephens
Validation of CFD Simulations of Cerebral Aneurysms With Implication of Geometric Variations
Hoi, Yiemeng; Woodward, Scott H.; Kim, Minsuok; Taulbee, Dale B.; Meng, Hui
2006-01-01
Computational fluid dynamics (CFD) simulations using medical-image-based anatomical vascular geometry are now gaining clinical relevance. This study aimed at validating the CFD methodology for studying cerebral aneurysms by using particle image velocimetry (PIV) measurements, with a focus on the effects of small geometric variations in aneurysm models on the flow dynamics obtained with CFD. Method of Approach. An experimental phantom was fabricated out of silicone elastomer to best mimic a sp...
Pollutant Emission Validation of a Heavy-Duty Gas Turbine Burner by CFD Modeling
Directory of Open Access Journals (Sweden)
Roberto Meloni
2013-10-01
Full Text Available 3D numerical combustion simulation in a can burner fed with methane was carried out in order to evaluate pollutant emissions and the temperature field. As a case study, the General Electric Frame 6001B system was considered. The numerical investigation has been performed using the CFD code named ACE+ Multiphysics (by Esi-Group. The model was validated against the experimental data provided by Cofely GDF SUEZ and related to a real power plant. To completely investigate the stability of the model, several operating conditions were taken into account, at both nominal and partial load. In particular, the influence on emissions of some important parameters, such as air temperature at compressor intake and steam to fuel mass ratio, have been evaluated. The flamelet model and Zeldovich’s mechanism were employed for combustion modeling and NOx emissions, respectively. With regard to CO estimation, an innovative approach was used to compute the Rizk and Mongia relationship through a user-defined function. Numerical results showed good agreement with experimental data in most of the cases: the best results were obtained in the NOx prediction, while unburned fuel was slightly overestimated.
Numerical simulation of the pulsing air separation field based on CFD
Institute of Scientific and Technical Information of China (English)
He Jingfeng; He Yaqun; Zhao Yuemin; Duan Chenlong; Ye Cuiling
2012-01-01
The flow field of pulsing air separation is normally in an unsteady turbulence state.With the application of the basic principles of multiphase turbulent flows,we established the dynamical computational model,which shows a remarkable variation of the unstable pulsing air flow field.CFD (computational fluid dynamics) was used to conduct the numerical simulation of the actual geometric model of the classifier.The inside velocity of the flowing fields was analyzed later.The simulation results indicate that the designed structure of the active pulsing air classifier provided a favorable environment for the separation of the particles with different physical characters by density.We shot the movement behaviors of the typical tracer grains in the active pulsing flow field using a high speed dynamic camera.The displacement and velocity curves of the particles in the continuous impulse periods were then analyzed.The experimental results indicate that the effective separation by density of the particles with the same settling velocity and different ranges of the density and particle size can be achieved in the active pulsing airflow field.The experimental results provide an agreement with the simulation results.
Investigation on the Use of a Multiphase Eulerian CFD solver to simulate breaking waves
DEFF Research Database (Denmark)
Tomaselli, Pietro D.; Christensen, Erik Damgaard
2015-01-01
investigation on a CFD model capable of handling this problem. The model is based on a solver, available in the open-source CFD toolkit OpenFOAM, which combines the Eulerian multi-fluid approach for dispersed flows with a numerical interface sharpening method. The solver, enhanced with additional formulations...
CFD Analysis on the Main-Rotor Blade ofa Scale Helicopter Model using Overset Meshing
Rodriguez, Christian
2012-01-01
In this paper, an analysis in computational uid dynamics (CFD) is presented on a helicopter scale model with focus on the main-rotor blades.The helicopter model is encapsulated in a background region and the ow eld is solved using Star CCM+. A surface and volume mesh continuum was generated that contained approximately seven million polyhedral cells, where the Finite Volume Method (FVM) was chosen as a discretization technique. Each blade was assigned to an overset region making it possible t...
Simulation on Tire Hydroplaning Based on CFD%轮胎滑水特性的CFD分析
Institute of Scientific and Technical Information of China (English)
王国林; 邓元; 金梁; 梁晨
2013-01-01
以205/50R16子午线轮胎为研究对象,建立带有纵向花纹沟的轮胎有限元模型(FEM)和计算流体动力学(CFD)模型.基于流固耦合的FEM模拟轮胎滑水产生的过程,采用重整规化群和流体体积组分方法的CFD模型得到轮胎接地区域内的水膜流场分布.两种模型计算结果对比表明,CFD模型能够用来分析胎面微花纹沟内流体流动特性.随着水膜厚度的增大,轮胎受到的流体压力也变大,容易出现滑水现象.%The finite element model(FEM) and the computational fluid dynamics(CFD) model of 205/50R16 radial tire with longitudinal tread groove pattern were developed.The process of hydroplaning was simulated by fluid-solid coupled FEM,and the fluid flow field in tire contact region was obtained by using CFD model with RNG(renormalization group) and VOF(volume of fluid) methods.The comparison results of two models showed that the CFD model could be used to effectively analyze the fluid flow characteristics in micro grooves,and as the thickness of water film increased,the fluid pressure increased,which would most likely cause dynamic hydroplaning.
The presentation summarizes developments of ongoing applications of fine-scale (geometry specific) CFD simulations to urban areas within atmospheric boundary layers. Enabling technology today and challenges for the future are discussed. There is a challenging need to develop a ...
CFD modeling of liquid-solid fluidization: Effect of drag correlation and added mass force
Institute of Scientific and Technical Information of China (English)
Xiao yan Huang
2011-01-01
Computational fluid dynamics (CFD) has been widely used to study the hydrodynamics of gas-solid fluidization; however,its applications in liquid-solid fluidization are relatively rare.In this study,CFD simulations of a liquid-solid fluidized bed are carried out,focusing on the effect of drag correlation and added mass force on the hydrodynamics of liquid-solid fluidization.It is shown that drag correlation has a significant effect on the simulation results and the correlation proposed by Beetstra et al.(2007) gives the best agreement with experimental data.We further show that the added mass force does play an important role in CFD simulation of liquid-solid fluidization,and therefore should not be ignored in CFD simulations.
Coupling of FVCOM and CFD Model for Simulation of Multiscale Coastal Flows
Tang, H.; Qu, K.
2013-12-01
In correspondence with the need to simulate many emerging problems, especially those in nearshore regions such as deepwater oil spill, it is necessary to develop capabilities to predict small-scale, fully 3D phenomena in coastal ocean flows. A feasible as well as effective approach for the development is a hybrid method that couples different models designed for physics at different scales. We have developed a two-way coupling between a fully 3D CFD model and the FVCOM, in which the former captures small-scale 3D flows and the latter predicts large-scale background currents. In this presentation, a few new applications of such approach will be illustrated. The following figures show a result on tidal flow in a bay and past bridge peers. Tests and analysis are made on solution accuracy and computation efficiency, and discussions are presented on how to achieve seamless solution transition at the model interfaces. Computed large-scale background flow Simulated flow past a brigde
Coupling of the 3D neutron kinetic core model DYN3D with the CFD software ANSYS-CFX
International Nuclear Information System (INIS)
Highlights: • Improved thermal hydraulic description of nuclear reactor cores. • Possibility of three-dimensional flow phenomena in the core, such as cross flow, flow reversal, flow around obstacles. • Simulation at higher spatial resolution as compared to system codes. - Abstract: This article presents the implementation of a coupling between the 3D neutron kinetic core model DYN3D and the commercial, general purpose computational fluid dynamics (CFD) software ANSYS-CFX. In the coupling approach, parts of the thermal hydraulic calculation are transferred to CFX for its better ability to simulate the three-dimensional coolant redistribution in the reactor core region. The calculation of the heat transfer from the fuel into the coolant remains with DYN3D, which incorporates well tested and validated heat transfer models for rod-type fuel elements. On the CFX side, the core region is modeled based on the porous body approach. The implementation of the code coupling is verified by comparing test case results with reference solutions of the DYN3D standalone version. Test cases cover mini and full core geometries, control rod movement and partial overcooling transients
Hydraulic performance improvement of the bidirectional pit pump installation based on CFD
Chen, H. X.; Zhou, D. Q.
2013-12-01
At present, the efficiency of bidirectional pit pump installation with lift under 2m is still low because of lack of research on it in the past. In the paper, the CFD numerical method and experimental test were applied to study flow characteristic of bidirectional pit pump installation under positive and reverse condition. Through changing airfoil type and position of blade and stay vane, the comprehensive performance of improved model were obtained by calculating many different models. The results showed that when improved model is obtained with type A runner with 4 blades that is 0.7D away from pit exit and unsymmetrical guide vane 0.25dh which away from the impeller outlet, and the flow pattern of the improved solution is steady with high efficiency. Compared with the original scheme, the efficiency of positive and reverse design condition reach to 67.23% and 58.32% respectively, which is increased 6% more than original model on the design condition and 5% on the optimum operating condition, and it achieved the purpose of improvement. According to the runner blade angle of the optimization solution, model synthetic characteristic curve was drawn and internal flow field characteristics was analyzed under optimal positive and reverse conditions. The numerical calculation shows that owing to the lack of stay vane to recycle the energy in outlet runner chamber, the water flow regime is not steady enough in the outlet passage, and that is the main reason for lower efficiency at reverse condition than that at positive condition.
Institute of Scientific and Technical Information of China (English)
Charles HIRSCH
2006-01-01
QNET-CFD is a thematic network on quality and trust for the industrial applications of Computational Fluid Dynamics (CFD), developed under the European Union R&D program. The main objectives of QNET-CFD were to collect CFD and experimental data in a systematic and quality controlled way and to set the basis for a consistent Knowledge Base in support of CFD guidance and validation. The QNET-CFD activity was organized around six Thematic Areas (TAs) covering the following industry sectors: external aerodynamics; combustion & heat transfer; chemical process, thermal hydraulics and nuclear safety; civil construction & HVAC; environment; turbomachinery internal flows. The main outcome of the QNET-CFD actions is the Knowledge Base (KB) with contains in a user oriented interface, extensive experimental and CFD data for a large number of test cases subdivided into 53 Application Challenges (AC) and 43 Underlying Flow Regimes (UFR). The KB contains, in addition to state-of-the-art reviews for each of the six thematic areas, Best Practice Advice (BPA) in the use of CFD for most of AC. This is considered as a significant contribution form the QNET-CFD activities and it is expected that the level of the thrust and quality in CFD will hereby be improved.%QNET-CFD是欧盟R&D项目开发的一个主题网络,该网络讨论了计算流体力学(CFD)供工业应用应具有的品质和可信度,其主要目的是以系统和质量控制的方式收集CFD和实验数据,建立两者相容的知识库(KB),以此为基础,支持对CFD进行指导和评估.QNET-CFD围绕覆盖下述工业部门的6个主题(TA)组成:外流空气动力学; 燃烧和传热; 化学过程、热水力学和核安全; 土木建筑和HVAC; 环境; 涡轮机内流.其主要成果是建立了具有面向用户界面及丰富的实验和CFD数据的知识库,这些数据来自于大量实验数据,分为53种应用挑战(AC)和43种基本流动状态(UFR).除对上述6个主题领域中每一个的科学发
A self-standing two-fluid CFD model for vertical upward two-phase annular flow
Energy Technology Data Exchange (ETDEWEB)
Liu, Y., E-mail: yang_liu@mail.dlut.edu.c [Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning Province (China); Li, W.Z.; Quan, S.L. [Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning Province (China)
2011-05-15
Research highlights: A mathematic model for two-phase annular flow is established in this paper. Pressure loss and wall shear stress increase with inlet gas and liquid flow velocities. Droplet mass fraction distribution exhibits a concave profile radially. - Abstract: In this paper, a new two-fluid CFD (computational fluid dynamics) model is proposed to simulate the vertical upward two-phase annular flow. This model solves the basic mass and momentum equations for the gas core region flow and the liquid film flow, where the basic governing equations are accounted for by the commercial CFD package Fluent6.3.26. The liquid droplet flow and the interfacial inter-phase effects are accounted for by the programmable interface of Fluent, UDF (user defined function). Unlike previous models, the present model includes the effect of liquid roll waves directly determined from the CFD code. It is able to provide more detailed and, the most important, self-standing information for both the gas core flow and the film flow as well as the inner tube wall situations.
Reynolds Number Effects Investigation of Supercritical Airfoil Based on EFD and CFD
Directory of Open Access Journals (Sweden)
Da-Wei Liu
2013-12-01
Full Text Available This study aimed to investigate the transonic Reynolds number effects of supercritical airfoil by EFD and CFD method. An experiment was conducted in NF-6 wind tunnel, to obtain the pressure distribution and aerodynamic coefficients of a typical supercritical airfoil through pressure measuring, with Reynolds numbers varied from 3.5×106 to 1.0×107 per airfoil chord, Mach numbers from 0.6 to 0.8, angles of attack from 0° to 8°. Also, flows over the supercritical airfoil were numerically studied; the two-dimensional Navier-Stokes equations were solved with structure grids by utilizing the Spalart-Allmaras (S-A turbulence model, with Reynolds numbers varied from 2.0×106 to 50×10 6 per airfoil chord and Mach numbers from 0.6 to 0.8. Computational results compared well with experimental results. It is shown that the upper surface pressure distribution of supercritical airfoil including the location and intensity of shock wave and trailing-edge pressure coefficient, changed apparently with variable Reynolds numbers, when shock-induced trailing-edge separation existed. It is also noticed that the lift coefficient increased, drag and pitching moment coefficient decreased as Reynolds number increasing. Results implied that Reynolds number effects should be considered during the early designing stage and optimization of large aircrafts applied supercritical airfoil.
Rocket-Based Combined Cycle Engine Technology Development: Inlet CFD Validation and Application
DeBonis, J. R.; Yungster, S.
1996-01-01
A CFD methodology has been developed for inlet analyses of Rocket-Based Combined Cycle (RBCC) Engines. A full Navier-Stokes analysis code, NPARC, was used in conjunction with pre- and post-processing tools to obtain a complete description of the flow field and integrated inlet performance. This methodology was developed and validated using results from a subscale test of the inlet to a RBCC 'Strut-Jet' engine performed in the NASA Lewis 1 x 1 ft. supersonic wind tunnel. Results obtained from this study include analyses at flight Mach numbers of 5 and 6 for super-critical operating conditions. These results showed excellent agreement with experimental data. The analysis tools were also used to obtain pre-test performance and operability predictions for the RBCC demonstrator engine planned for testing in the NASA Lewis Hypersonic Test Facility. This analysis calculated the baseline fuel-off internal force of the engine which is needed to determine the net thrust with fuel on.
Modeling and simulation of PEM fuel cell's flow channels using CFD techniques
Energy Technology Data Exchange (ETDEWEB)
Cunha, Edgar F.; Andrade, Alexandre B.; Robalinho, Eric; Bejarano, Martha L.M.; Linardi, Marcelo [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mails: efcunha@ipen.br; abodart@ipen.br; eric@ipen.br; mmora@ipen.br; mlinardi@ipen.br; Cekinski, Efraim [Instituto de Pesquisas Tecnologicas (IPT-SP), Sao Paulo, SP (Brazil)]. E-mail: cekinski@ipt.br
2007-07-01
Fuel cells are one of the most important devices to obtain electrical energy from hydrogen. The Proton Exchange Membrane Fuel Cell (PEMFC) consists of two important parts: the Membrane Electrode Assembly (MEA), where the reactions occur, and the flow field plates. The plates have many functions in a fuel cell: distribute reactant gases (hydrogen and air or oxygen), conduct electrical current, remove heat and water from the electrodes and make the cell robust. The cost of the bipolar plates corresponds up to 45% of the total stack costs. The Computational Fluid Dynamic (CFD) is a very useful tool to simulate hydrogen and oxygen gases flow channels, to reduce the costs of bipolar plates production and to optimize mass transport. Two types of flow channels were studied. The first type was a commercial plate by ELECTROCELL and the other was entirely projected at Programa de Celula a Combustivel (IPEN/CNEN-SP) and the experimental data were compared with modelling results. Optimum values for each set of variables were obtained and the models verification was carried out in order to show the feasibility of this technique to improve fuel cell efficiency. (author)
Comparative Study for Modeling Reactor Internal Geometry in CFD Simulation of PHWR Internal Flow
Energy Technology Data Exchange (ETDEWEB)
Lee, Gong Hee; Woo, Sweng Woong; Cheong, Ae Ju [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)
2013-10-15
The main objective of the present study is to compare the results predicted by using either the real geometry of tubes or porous medium assumption and to assess the prediction performance of both methods. Estimating the local subcooling of the moderator in a CANDU calandria under transient conditions is one of the major concerns in the CANDU safety analysis. Therefore extensive CFD analyses have been performed for predicting the moderator temperature in a CANDU calandria or its similar shape. However most of previous studies used a porous medium assumption instead of considering the real geometry of calandria tube. A porous medium assumption has some possible weaknesses; The increased production of turbulence due to vortex shedding in the wake of the individual tubes is not considered in the turbulence model. It is difficult to identify the true effects of the outer ring of calandria tubes on the generation of the highly non-uniform flows in the reflector region. It is not clear how well the pressure loss models quantitatively represent the three-dimensional effects of the turbulent flows through the calandria tubes.
CFD analysis of municipal solid waste combustion using detailed chemical kinetic modelling.
Frank, Alex; Castaldi, Marco J
2014-08-01
Nitrogen oxides (NO x ) emissions from the combustion of municipal solid waste (MSW) in waste-to-energy (WtE) facilities are receiving renewed attention to reduce their output further. While NO x emissions are currently 60% below allowed limits, further reductions will decrease the air pollution control (APC) system burden and reduce consumption of NH3. This work combines the incorporation of the GRI 3.0 mechanism as a detailed chemical kinetic model (DCKM) into a custom three-dimensional (3D) computational fluid dynamics (CFD) model fully to understand the NO x chemistry in the above-bed burnout zones. Specifically, thermal, prompt and fuel NO formation mechanisms were evaluated for the system and a parametric study was utilized to determine the effect of varying fuel nitrogen conversion intermediates between HCN, NH3 and NO directly. Simulation results indicate that the fuel nitrogen mechanism accounts for 92% of the total NO produced in the system with thermal and prompt mechanisms accounting for the remaining 8%. Results also show a 5% variation in final NO concentration between HCN and NH3 inlet conditions, demonstrating that the fuel nitrogen intermediate assumed is not significant. Furthermore, the conversion ratio of fuel nitrogen to NO was 0.33, revealing that the majority of fuel nitrogen forms N2. PMID:25005043
Implementation of a pressure drop model for the CFD simulation of clogged containment sump strainers
International Nuclear Information System (INIS)
The investigation of insulation debris generation and transport during LOCA events as well as the short and long term behaviour of the ECCS must be considered with regard to the safety of pressure and boiling water reactors under such conditions [1-3]. The mineral wool blankets that are used to insulate the components of nuclear reactors can be destroyed by jetting steam during LOCA. A portion of the mineral wool fiber debris can then be transported into the containment sump, which collects the cooling water for use in the ECCS in the late phase of LOCA. Mineral wool fibers that accumulate at the ECCS pump suction strainers lead to increased pressure drops which could reduce the pumps capability to recirculate the cooling water. Hazards associated with such an incident were emphasized by an incident at the Barsebaeck-2 nuclear power plant in Sweden in 1992 when a steam valve inadvertently opened [4]. The debris quickly blocked the ECCS pump strainers, resulting in a potential compromise in the defense-in-depth concept for the reactor. The present paper reports on our efforts in modelling the pressure drop buildup at strainers obstructed by fibrous materials and the implementation of the strainer model into the commercial, general-purpose CFD code ANSYS-CFX [5]. Special attention is drawn to the compressibility of the fibrous cake. (orig.)
Modeling and simulation of PEM fuel cell's flow channels using CFD techniques
International Nuclear Information System (INIS)
Fuel cells are one of the most important devices to obtain electrical energy from hydrogen. The Proton Exchange Membrane Fuel Cell (PEMFC) consists of two important parts: the Membrane Electrode Assembly (MEA), where the reactions occur, and the flow field plates. The plates have many functions in a fuel cell: distribute reactant gases (hydrogen and air or oxygen), conduct electrical current, remove heat and water from the electrodes and make the cell robust. The cost of the bipolar plates corresponds up to 45% of the total stack costs. The Computational Fluid Dynamic (CFD) is a very useful tool to simulate hydrogen and oxygen gases flow channels, to reduce the costs of bipolar plates production and to optimize mass transport. Two types of flow channels were studied. The first type was a commercial plate by ELECTROCELL and the other was entirely projected at Programa de Celula a Combustivel (IPEN/CNEN-SP) and the experimental data were compared with modelling results. Optimum values for each set of variables were obtained and the models verification was carried out in order to show the feasibility of this technique to improve fuel cell efficiency. (author)
Nkengue Tsobguin, Bienvenue
2008-01-01
A three‐dimensional CFD study of the two‐phase flow field in a Gas‐Liquid Cylindrical Cyclone (GLCC) using the finite volume‐based finite element method is presented. The numerical analysis was made for air‐water mixtures at near atmospheric conditions, while both liquid and gas flow rates were changed. The two‐phase flow behavior is modeled using an Eulerian‐Eulerian approach, considering both phases as an interpenetrating continuum. This method computed the inter‐phase phenom...
International Nuclear Information System (INIS)
In this paper, sensitivity study on a CFD model for the accurate analysis of moderator fluid flow and heat transfer inside calandria is conducted. Two main items, i.e. porous medium assumption and turbulence model, are considered for in-line tube bank and Sheridan Park Engineering Laboratory (SPEL) experiment. Using the commercial flow solver, FLUENT, the prediction to consider the real geometry of fuel channels is compared to previous results conducted with the porous medium assumption using the isotropic pressure loss model. Also, the prediction performance of various turbulence models (e.g. k-ε model, Reynolds stress model, etc.) is assessed. (author)
Validation of impinging jet models to be used in CANDU calandria vessel CFD simulations
International Nuclear Information System (INIS)
The knowledge of the external wall temperature distributions on calandria tubes is of major concern in nuclear safety analysis. One of the models used by the Canadian industry consists in replacing the calandria by an equivalent porous media with appropriate anisotropic hydraulic resistances. This technique has the advantage to treat a non-connected domain as an equivalent quasi-continuous media; however, it cannot provide information about local velocity variations. Within the framework of the present study, a full-scale modeling of the moderator using a Computational Fluid Dynamic code (FLUENT) is underway. The use of a 2D model have shown that the geometry of calandria nozzles have a strong effect on the flow distribution. Some authors suggest to model the flow at the entrance of the calandria as successive flow circulation through a portion of a straight pipe, a curved pipe, and a circular nozzle placed in front of an impinging plate, and to use the results as input data in full-scale calculations. Obtaining these data requires large computational resources before performing complete flow simulations, while they do necessarily represent neither the real geometry nor the actual flow conditions. Therefore, the present study is aimed to find appropriate water-jet modeling approaches that can help in improving moderator circulation simulations. In particular, the principal interest consists in finding a semi-analytical nozzle model that can be used as a constitutive relationship in a CFD code. This approach will contribute both to increase the number of meshes in the calandria vessel as well as to decrease the computational time. (author)
cfd modelling and experimental study on the fluid flow and heat transfer in copper heat sink design
Karimpourian, Bijan
2007-01-01
Abstract This thesis is studying the heatsinks new designs for copper heatsinks which utilizes modelling and simulation by CFD, construction of prototypes and experimental works. Challenges and complications in manufacturing of copper heatsinks are expressed and finding the solutions to these hindrances involve in this work. Numerical efforts supported by fluent are made to promote investigation and approaching the goal in which serves the new opportunities for wider application of copper mat...
International Nuclear Information System (INIS)
Centralized environmental regulations require the use of efficient detoxification technologies for the secure disposal of hazardous wastewaters. Guided by federal directives, existing plants need reengineering activities and careful analysis to improve their overall effectiveness and to become environmentally friendly. Here, we illustrate the application of an integrated methodology which encompasses the experimental investigation of catalytic wet air oxidation and CFD simulation of trickle-bed reactors. As long as trickle-bed reactors are determined by the flow environment coupled with chemical kinetics, first, on the optimization of prominent numerical solution parameters, the CFD model was validated with experimental data taken from a trickle bed pilot plant specifically designed for the catalytic wet oxidation of phenolic wastewaters. Second, several experimental and computational runs were carried out under unsteady-state operation to evaluate the dynamic performance addressing the TOC concentration and temperature profiles. CFD computations of total organic carbon conversion were found to agree better with experimental data at lower temperatures. Finally, the comparison of test data with simulation results demonstrated that this integrated framework was able to describe the mineralization of organic matter in trickle beds and the validated consequence model can be exploited to promote cleaner remediation technologies of contaminated waters.
Energy Technology Data Exchange (ETDEWEB)
Lopes, Rodrigo J.G., E-mail: rodrigo@eq.uc.pt [Centro de Investigacao em Engenharia dos Processos Quimicos e Produtos da Floresta (CIEPQPF), GERSE - Group on Environmental, Reaction and Separation Engineering, Department of Chemical Engineering, University of Coimbra, Rua Silvio Lima, Polo II - Pinhal de Marrocos, 3030-790 Coimbra (Portugal); Almeida, Teresa S.A.; Quinta-Ferreira, Rosa M. [Centro de Investigacao em Engenharia dos Processos Quimicos e Produtos da Floresta (CIEPQPF), GERSE - Group on Environmental, Reaction and Separation Engineering, Department of Chemical Engineering, University of Coimbra, Rua Silvio Lima, Polo II - Pinhal de Marrocos, 3030-790 Coimbra (Portugal)
2011-05-15
Centralized environmental regulations require the use of efficient detoxification technologies for the secure disposal of hazardous wastewaters. Guided by federal directives, existing plants need reengineering activities and careful analysis to improve their overall effectiveness and to become environmentally friendly. Here, we illustrate the application of an integrated methodology which encompasses the experimental investigation of catalytic wet air oxidation and CFD simulation of trickle-bed reactors. As long as trickle-bed reactors are determined by the flow environment coupled with chemical kinetics, first, on the optimization of prominent numerical solution parameters, the CFD model was validated with experimental data taken from a trickle bed pilot plant specifically designed for the catalytic wet oxidation of phenolic wastewaters. Second, several experimental and computational runs were carried out under unsteady-state operation to evaluate the dynamic performance addressing the TOC concentration and temperature profiles. CFD computations of total organic carbon conversion were found to agree better with experimental data at lower temperatures. Finally, the comparison of test data with simulation results demonstrated that this integrated framework was able to describe the mineralization of organic matter in trickle beds and the validated consequence model can be exploited to promote cleaner remediation technologies of contaminated waters.
Lopes, Rodrigo J G; Almeida, Teresa S A; Quinta-Ferreira, Rosa M
2011-05-15
Centralized environmental regulations require the use of efficient detoxification technologies for the secure disposal of hazardous wastewaters. Guided by federal directives, existing plants need reengineering activities and careful analysis to improve their overall effectiveness and to become environmentally friendly. Here, we illustrate the application of an integrated methodology which encompasses the experimental investigation of catalytic wet air oxidation and CFD simulation of trickle-bed reactors. As long as trickle-bed reactors are determined by the flow environment coupled with chemical kinetics, first, on the optimization of prominent numerical solution parameters, the CFD model was validated with experimental data taken from a trickle bed pilot plant specifically designed for the catalytic wet oxidation of phenolic wastewaters. Second, several experimental and computational runs were carried out under unsteady-state operation to evaluate the dynamic performance addressing the TOC concentration and temperature profiles. CFD computations of total organic carbon conversion were found to agree better with experimental data at lower temperatures. Finally, the comparison of test data with simulation results demonstrated that this integrated framework was able to describe the mineralization of organic matter in trickle beds and the validated consequence model can be exploited to promote cleaner remediation technologies of contaminated waters. PMID:21377790
Zhu, Dongming; Sakowski, Barbara A.; Fisher, Caleb
2014-01-01
SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. However, the environmental stability of Si-based ceramics in high pressure, high velocity turbine engine combustion environment is of major concern. The water vapor containing combustion gas leads to accelerated oxidation and corrosion of the SiC based ceramics due to the water vapor reactions with silica (SiO2) scales forming non-protective volatile hydroxide species, resulting in recession of the ceramic components. Although environmental barrier coatings are being developed to help protect the CMC components, there is a need to better understand the fundamental recession behavior of in more realistic cooled engine component environments.In this paper, we describe a comprehensive film cooled high pressure burner rig based testing approach, by using standardized film cooled SiCSiC disc test specimen configurations. The SiCSiC specimens were designed for implementing the burner rig testing in turbine engine relevant combustion environments, obtaining generic film cooled recession rate data under the combustion water vapor conditions, and helping developing the Computational Fluid Dynamics (CFD) film cooled models and performing model validation. Factors affecting the film cooled recession such as temperature, water vapor concentration, combustion gas velocity, and pressure are particularly investigated and modeled, and compared with impingement cooling only recession data in similar combustion flow environments. The experimental and modeling work will help predict the SiCSiC CMC recession behavior, and developing durable CMC systems in complex turbine engine operating conditions.
CFD Study of NOx Emissions in a Model Commercial Aircraft Engine Combustor
Institute of Scientific and Technical Information of China (English)
ZHANG Man; FU Zhenbo; LIN Yuzhen; LI Jibao
2012-01-01
Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design.With the motivation to design high performance and clean combustor,computational fluid dynamics (CFD) is utilized as the powerful design approach.In this paper,Reynolds averaged Navier-Stokes (RANS) equations of reactive two-phase flow in an experimental low emission combustor is performed.The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction.The NOx formation is modeled by the concept of post-processing,which resolves the NOx transport equation with the assumption of frozen temperature distribution.Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection (LDI) combustor.The test rig studied in this paper is called low emission stirred swirl (LESS) combustor,which is a two-stage model combustor,fueled with liquid kerosene (RP-3) and designed by Beihang University (BUAA).The main stage of LESS combustor employs the principle of lean prevaporized and premixed (LPP) concept to reduce pollutant,and the pilot stage depends on a diffusion flame for flame stabilization.Detailed numerical results including species distribution,turbulence performance and burning performance are qualitatively and quantitatively evaluated.Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor.Preliminary results of the flame structure are shown in this paper.The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.
Simulation of hydrogen mitigation in catalytic recombiner. Part-II: Formulation of a CFD model
Energy Technology Data Exchange (ETDEWEB)
Prabhudharwadkar, Deoras M. [Department of Mechanical Engineering, Indian Institute of Technology-Bombay, Powai, Mumbai 400076 (India); Iyer, Kannan N., E-mail: kiyer@me.iitb.ac.i [Department of Mechanical Engineering, Indian Institute of Technology-Bombay, Powai, Mumbai 400076 (India)
2011-05-15
Research highlights: Hydrogen transport in containment with recombiners is a multi-scale problem. A novel methodology worked out to lump the recombiner characteristics. Results obtained using commercial code FLUENT are cast in the form of correlations. Hence, coarse grids can obtain accurate distribution of H{sub 2} in containment. Satisfactory working of the methodology is clearly demonstrated. - Abstract: This paper aims at formulation of a model compatible with CFD code to simulate hydrogen distribution and mitigation using a Passive Catalytic Recombiner in the Nuclear power plant containments. The catalytic recombiner is much smaller in size compared to the containment compartments. In order to fully resolve the recombination processes during the containment simulations, it requires the geometric details of the recombiner to be modelled and a very fine mesh size inside the recombiner channels. This component when integrated with containment mixing calculations would result in a large number of mesh elements which may take large computational times to solve the problem. This paper describes a method to resolve this simulation difficulty. In this exercise, the catalytic recombiner alone was first modelled in detail using the best suited option to describe the reaction rate. A detailed parametric study was conducted, from which correlations for the heat of reaction (hence the rate of reaction) and the heat transfer coefficient were obtained. These correlations were then used to model the recombiner channels as single computational cells providing necessary volumetric sources/sinks to the energy and species transport equations. This avoids full resolution of these channels, thereby allowing larger mesh size in the recombiners. The above mentioned method was successfully validated using both steady state and transient test problems and the results indicate very satisfactory modelling of the component.
International Nuclear Information System (INIS)
Highlights: • A DES of a turbocharger compressor working at peak pressure point is performed. • In-duct pressure signals are measured in a steady flow rig with 3-sensor arrays. • Pressure spectra comparison is performed as a validation for the numerical model. • A suitable comparison methodology is developed, relying on pressure decomposition. • Whoosh noise at outlet duct is detected in experimental and numerical spectra. - Abstract: Centrifugal compressors working in the surge side of the map generate a broadband noise in the range of 1–3 kHz, named as whoosh noise. This noise is perceived at strongly downsized engines operating at particular conditions (full load, tip-in and tip-out maneuvers). A 3-dimensional CFD model of a centrifugal compressor is built to analyze fluid phenomena related to whoosh noise. A detached eddy simulation is performed with the compressor operating at the peak pressure point of 160 krpm. A steady flow rig mounted on an anechoic chamber is used to obtain experimental measurements as a means of validation for the numerical model. In-duct pressure signals are obtained in addition to standard averaged global variables. The numerical simulation provides global variables showing excellent agreement with experimental measurements. Pressure spectra comparison is performed to assess noise prediction capability of numerical model. The influence of the type and position of the virtual pressure probes is evaluated. Pressure decomposition is required by the simulations to obtain meaningful spectra. Different techniques for obtaining pressure components are analyzed. At the simulated conditions, a broadband noise in 1–3 kHz frequency band is detected in the experimental measurements. This whoosh noise is also captured by the numerical model
Cagin, Stéphanie; Bourabaa, Nachida; Delacourt, Eric; Morin, Céline; Fischer, Xavier; Coutellier, Daniel; Carré, Bertrand; Loumé, Sylvain
2015-01-01
International audience This paper presents a method to improve cylinder design of 2-stroke auto-ignition engine based on a CFD (Computational Fluid Dynamics) study of internal flows in the chamber and an unsteady global 0D parametric approach. In 2-stroke engine, scavenging process plays an important role regarding engine efficiency and pollutant emissions. Several geometrical and environmental parameters (like piston velocity and inlet/outlet thermofluid conditions) impact the scavenging ...
CFD Modeling of Sodium-Oxide Deposition in Sodium-Cooled Fast Reactor Compact Heat Exchangers
Energy Technology Data Exchange (ETDEWEB)
Tatli, Emre; Ferroni, Paolo; Mazzoccoli, Jason
2015-09-02
The possible use of compact heat exchangers (HXs) in sodium-cooled fast reactors (SFR) employing a Brayton cycle is promising due to their high power density and resulting small volume in comparison with conventional shell-and-tube HXs. However, the small diameter of their channels makes them more susceptible to plugging due to Na2O deposition during accident conditions. Although cold traps are designed to reduce oxygen impurity levels in the sodium coolant, their failure, in conjunction with accidental air ingress into the sodium boundary, could result in coolant oxygen levels that are above the saturation limit in the cooler parts of the HX channels. This can result in Na2O crystallization and the formation of solid deposits on cooled channel surfaces, limiting or even blocking coolant flow. The development of analysis tools capable of modeling the formation of these deposits in the presence of sodium flow will allow designers of SFRs to properly size the HX channels so that, in the scenario mentioned above, the reactor operator has sufficient time to detect and react to the affected HX. Until now, analytical methodologies to predict the formation of these deposits have been developed, but never implemented in a high-fidelity computational tool suited to modern reactor design techniques. This paper summarizes the challenges and the current status in the development of a Computational Fluid Dynamics (CFD) methodology to predict deposit formation, with particular emphasis on sensitivity studies on some parameters affecting deposition.
Investigation of mucus transport in an idealized lung airway model using multiphase CFD analysis
Rajendran, Rahul; Banerjee, Arindam
2015-11-01
Mucus, a Bingham fluid is transported in the pulmonary airways by consistent beating of the cilia and exhibits a wide range of physical properties in response to the core air flow and various pathological conditions. A better understanding of the interfacial instability is required as it plays a crucial role in gas transport, mixing, mucus clearance and drug delivery. In the current study, mucus is modelled as a Newtonian fluid and the two phase gas-liquid flow in the airways is investigated using an inhomogeneous Eulerian-Eulerian approach. The complex interface between the phases is tracked using the conventional VOF (Volume of Fluid) method. Results from our CFD simulations which are performed in idealized single and double bifurcation geometries will be presented and the influence of airflow rate, mucus layer thickness, mucus viscosity, airway geometry (branching & diameter) and surface tension on mucus flow behavior will be discussed. Mean mucus layer thickness, pressure drop due to momentum transfer & increased airway resistance, mucus transport speed and the flow morphology will be compared to existing experimental and theoretical data.
Validation of CFD-models for natural convection, heat transfer and turbulence phenomena
International Nuclear Information System (INIS)
Natural convection, heat transfer and turbulence phenomena play an important role for the distribution of steam and hydrogen in a reactor containment in the case of a severe accident. These phenomena have influence on all important aspects of an accident scenario, on transport processes, mixing of steam, hydrogen and air, the flammability and combustibility of the air/H2/steam-mixture, the temperature distribution and on the containment pressure. In cooperation with other institutions the GRS adapts and validates the CFX code developed by ANSYS for containment applications. To simulate convection and turbulence phenomena in an accident scenario in a reactor containment the simulation tools and models have to be validated with experimental data. For the validation of CFX two experiments performed at the THAI test facility were simulated (TH-18 and TH-21). THAI is a down-scaled containment facility operated at Becker Technologies, Eschborn, Germany, which was designed to investigate thermal hydraulic processes. The main component is a steel vessel with a height of 9.2 m and a cross-section of 3.2 m. The THAI facility could be divided into different subsections by an inner cylinder and different steel plates. The TH-18 experiment was designed for the validation of CFD models for mass transfer and turbulence. In the inner cylinder a fan was installed which produces a circular flow field in the THAI vessel. At different positions in the THAI vessel the velocity of the flow field was measured by PIV (Particle Image Velocimetry) and LDA (Laser Doppler Anemometer). The TH-21 experiment was designed for the investigation of heat transfer and natural convection phenomena. For this purpose the walls of the THAI vessel were heated differentially. The lower vessel wall was heated up to 120 deg.C and the upper vessel wall was cooled down to 46 deg.C. This differential heating induced a natural convection process in the THAI vessel. Pressure, temperature and flow velocity were
International Nuclear Information System (INIS)
Highlights: • A multiphase CFD model was combined with RSM. • Gasification optimal operating conditions were found in a pilot scale reactor. • Syngas quality indices were optimized in a biomass gasification process. • Propagation of error methodology was combined with a CFD model and RSM. - Abstract: This paper presents a study to evaluate the potential of Portuguese biomasses (coffee husks, forest residues and vine pruning residues) to produce syngas for different applications. By using a 2-D Eulerian–Eulerian approach within the CFD framework, a design of several computer experiments was developed and were used as analysis tools the response surface method (RSM) and the propagation of error (POE) approach. The CFD model was validated under experimental results collected at a semi-industrial reactor. For design purposes, temperature, steam to biomass ratio (SBR) and the type of biomass were selected as input factors. The responses were the H2 generation, the H2/CO ratio, the CH4/H2 ratio, the carbon conversion and the cold gas efficiency. It was concluded that after an optimization procedure to determine the operating conditions, vine pruning residues could show very promising results considering some of the typical syngas indice standards for commercial purposes. From the optimization procedure, it was also concluded that forest residues are preferable for domestic natural gas applications and vine pruning residues for fuel cells and integrated gasification systems application. By using the RSM combined with POE, it was verified that the operating conditions to get higher performances do not always coincide with those necessary to obtain a stable syngas composition
A validated CFD model to predict O₂ and CO₂ transfer within hollow fiber membrane oxygenators.
Hormes, Marcus; Borchardt, Ralf; Mager, Ilona; Rode, Thomas Schmitz; Behr, Marek; Steinseifer, Ulrich
2011-03-01
Hollow fiber oxygenators provide gas exchange to and from the blood during heart surgery or lung recovery. Minimal fiber surface area and optimal gas exchange rate may be achieved by optimization of hollow fiber shape and orientation (1). In this study, a modified CFD model is developed and validated with a specially developed micro membrane oxygenator (MicroMox). The MicroMox was designed in such a way that fiber arrangement and bundle geometry are highly reproducible and potential flow channeling is avoided, which is important for the validation. Its small size (V(Fluid)=0.04 mL) allows the simulation of the entire bundle of 120 fibers. A non-Newtonian blood model was used as simulation fluid. Physical solubility and chemical bond of O₂ and CO₂ in blood was represented by the numerical model. Constant oxygen partial pressure at the pores of the fibers and a steady state flow field was used to calculate the mass transport. In order to resolve the entire MicroMox fiber bundle, the mass transport was simulated for symmetric geometry sections in flow direction. In vitro validation was achieved by measurements of the gas transfer rates of the MicroMox. All measurements were performed according to DIN EN 12022 (2) using porcine blood. The numerical simulation of the mass transfer showed good agreement with the experimental data for different mass flows and constant inlet partial pressures. Good agreement could be achieved for two different fiber configurations. Thus, it was possible to establish a validated model for the prediction of gas exchange in hollow fiber oxygenators. PMID:21462147
Nawaz AHMAD
2009-01-01
The thesis work aims at devising analytical thermodynamic model and numerical modeling of the compressor of a small gas turbine to be operated on producer gas with lower heating contents. The turbine will serve as a component of “EXPLORE-Biomass Based Polygeneration” project to meet the internal electrical power requirements of 2-5 KW. The gas turbine engine is of radial type (one stage radial compressor, one stage radial turbine). Small gas turbines give less electrical efficiencies especial...
On the wind-induced undercatch in rainfall measurement using CFD-based simulations
Colli, Matteo; Lanza, Luca
2016-04-01
The reliability of liquid atmospheric precipitation measurements is a basic requirement since rainfall data represent the fundamental input variables of many scientific applications (hydrologic models, weather forecasting data assimilation, climate change studies, calibration of weather radar, etc.). The scientific community and the National Meteorological Services worldwide are facing the issue of improving the accuracy of precipitation measurements, with an increased focus on retrieving the information at a high temporal resolution. The rainfall intensity is indeed fundamental information for the precise quantification of the markedly time-varying behavior of precipitation events. Environmental conditions have a relevant impact on the rain collection/sensing efficiency. Among other effects, wind is recognized as a major source of underestimation since it reduces the collection efficiency of the catching-type gauges (Nespor and Sevruk, 1999), the most common type of instruments used worldwide in the national observation networks. The collection efficiency is usually obtained by comparing the rainfall amounts measured by the gauge with the reference, which was defined by EN-13798 standard (CEN, 2002) as a gauge placed below the ground level inside a pit. A lot of scatter can be observed for a given wind speed, which is mainly caused by comparability issues among the tested gauges. An additional source of uncertainty is the drops size distribution (DSD) of the rain, which varies on an event-by-event basis. The goal of this study is to understand the role of the physical characteristics of precipitation particles on the wind-induced rainfall underestimation observed for catching-type gauges. To address this issue, a detailed analysis of the flow field in the vicinity of the gauge is conducted using time-averaged computational fluid dynamics (CFD) simulations (Colli et al., 2015). Using a Lagrangian model, which accounts for the hydrodynamic behavior of liquid
VR-based interactive CFD data comparison of flow fields in a human nasal cavity
Gerndt, Andreas; Kuhlen, Torsten; van Reimersdahl, Thomas; Haack, Matthias; Bischof, Christian
2004-05-01
The Virtual Reality Center Aachen is developing a Virtual Reality based operation planning system in cooperation with aerodynamics scientists and physicians of several clinical centers. This system is meant to help the preparation of nose surgeries aimed at the elimination of respiratory diseases. A core part is the interactive comparison of experimental data and simulation data in the area of fluid dynamics. In a first step, data comparison is to depict the differences between healthy noses and diseased noses. Later on, data comparison should supply evidence for successful virtual surgeries, which finally results in guidance on the real operation. During virtual surgery sessions, scientists can interactively explore, analyze, annotate, and compare various medical and aerodynamics data sets. Image-based methods are used to extract several features in one image and between compared data sets. The determination of linked features between different data sets is a particular challenge because of their different time frames, scales, and distortions. An optimized human computer interface enables the user to interact intuitively within a virtual environment in order to select and deal with these data sets. Additionally to this interactive exploration, the system also allows automatic searches for cut plane and key frame candidates corresponding to given feature patterns. The comparison system makes use of an already implemented parallelized Computational Fluid Dynamics (CFD) postprocessing, which also extracts enhanced flow features that allow automatic detection of relevant flow regions. Beside vortex detection, the computation of critical points including flow field segmentation is a current research activity. These flow features are favored characteristics for the comparison and help considerably to classify different nose geometries and operation recommendations.
Stabilizing a CFD model of an unstable system through model reduction
Directory of Open Access Journals (Sweden)
Svein Hovland
2006-07-01
Full Text Available We demonstate stabilization of a computational fluid dynamics model of an unstable system. The unstable heating of a two-dimensional plate is used as a case study. Active control is introduced by cooling parts of the boundaries of the plate. The high order of the original model is reduced by proper orthogonal decomposition, giving an unstable reduced order model with a state space structure convenient for controller design. A stabilizing controller based on pole placement is designed for the reduced order model and integral action is included to enhance performance. The controller is then applied to the full model, where it is shown through simulations to stabilize the system. The demonstrated procedure makes it possible to analyze stability properties and design control systems for a class of systems that would otherwise be very computationally demanding.
Keye, Stefan; Togiti, Vamish; Eisfeld, Bernhard; Brodersen, Olaf P.; Rivers, Melissa B.
2013-01-01
The accurate calculation of aerodynamic forces and moments is of significant importance during the design phase of an aircraft. Reynolds-averaged Navier-Stokes (RANS) based Computational Fluid Dynamics (CFD) has been strongly developed over the last two decades regarding robustness, efficiency, and capabilities for aerodynamically complex configurations. Incremental aerodynamic coefficients of different designs can be calculated with an acceptable reliability at the cruise design point of transonic aircraft for non-separated flows. But regarding absolute values as well as increments at off-design significant challenges still exist to compute aerodynamic data and the underlying flow physics with the accuracy required. In addition to drag, pitching moments are difficult to predict because small deviations of the pressure distributions, e.g. due to neglecting wing bending and twisting caused by the aerodynamic loads can result in large discrepancies compared to experimental data. Flow separations that start to develop at off-design conditions, e.g. in corner-flows, at trailing edges, or shock induced, can have a strong impact on the predictions of aerodynamic coefficients too. Based on these challenges faced by the CFD community a working group of the AIAA Applied Aerodynamics Technical Committee initiated in 2001 the CFD Drag Prediction Workshop (DPW) series resulting in five international workshops. The results of the participants and the committee are summarized in more than 120 papers. The latest, fifth workshop took place in June 2012 in conjunction with the 30th AIAA Applied Aerodynamics Conference. The results in this paper will evaluate the influence of static aeroelastic wing deformations onto pressure distributions and overall aerodynamic coefficients based on the NASA finite element structural model and the common grids.
Effect of longwall face advance rate on spontaneous heating process in the gob area - CFD modelling
Energy Technology Data Exchange (ETDEWEB)
Boleslav Taraba; Zdenek Michalec [University of Ostrava, Ostrava (Czech Republic). Dept. of Chemistry
2011-08-15
A commercial CFD software programme, FLUENT, was used to study the oxidation process of coal in the mined-out longwall (gob) area. A three-dimensional, single-phase model with a continuously advancing longwall face has been developed. For the model, the gob longwall area was designed on the basis of the actual longwall panel operating in the Ostrava-Karvina Coal Mines (OKD, Czech Republic). The behaviour of the coal to oxygen was modelled using the results arising mainly from the former laboratory-scale experiments with Czech bituminous coals. Basically, the technique of pulse flow calorimetry and measurements at a continuous airflow reactor were applied during the laboratory investigations. In the contribution, the main focus was to understand the effect of the longwall face advancing speed on the oxidation heat production as well as evolution of the gases in the gob area. Simultaneously, the effect of coal crushing in the mined-out area on the spontaneous heating process was examined. Numerical simulations confirmed the existence of a 'favourable' zone for the onset and development of the spontaneous heating process in the gob area. The location and the maximal temperature reached in the 'favourable' zone were found to be significantly affected by the advancing rate of the coalface. The slower the advancing rate is, the higher the maximal temperature and smaller the depth of the 'favourable' zone in the gob area are. When the rate drops to a certain 'critical' value, spontaneous heating turns to flammable combustion of the coal. The value of the 'critical' advancing rate was confirmed to increase if the grain size of the coal left in the gob decreases. Numerical examinations of carbon monoxide concentrations then proved that small incidents of spontaneous heating could occur in the gob area that need not be detected in the airflow of the longwall tail gate. 46 refs., 8 figs., 2 tabs.
Multi-scale Model Coupling for CFD Simulations of Discharge Dispersion in the Sea
Robinson, D.; Wood, M.; Piggott, M. D.; Gorman, G.
2014-12-01
The processes that influence the dispersion of effluent discharges in the sea occur over a wide range of length and time scales. The distance that effluent can travel before it is considered mixed can be several kilometres, whereas the turbulent eddies that affect the near-field mixing of a discharge can be as small as a few centimetres. The range of scales that are involved mean that it is not generally practical to include all influencing physical phenomena within one model. Typically, the modelling of effluent dispersion is performed using two separate numerical models: a local model of the outlet(s), including the near-field effects of momentum, buoyancy and turbulence; and a larger scale model that can include the far-field effects of tidal-, wind- and wave-driven-currents, water depth variations, atmospheric fluxes, and Coriolis forces. The boundary between the two models is often not strictly defined, but is usually placed at the transition from where the behaviour of the effluent is dominated by the ambient environment, rather than the discharge characteristics and outfall configuration. In most real applications, this transition line varies considerably in time and space. This paper presents the findings of collaborative research between the Applied Modelling and Computation Group (AMCG) at Imperial College London, UK, and HR Wallingford Ltd. Results are presented using a range of coupling methods to link the near- and far-field mixing regions. An idealised domain and tidal conditions are used, with the outfall and ambient conditions typical of those found at small coastal desalination plants. Open-source CFD code Fluidity is used for both the near-field and far-field modelling. Fluidity scales well when run in parallel on large numbers of cores. It also has an anisotropic adaptive mesh capability which allows local control over solution accuracy throughout the domain. This combination means that accuracy can be achieved without excessive time costs, with
A texture-based framework for improving CFD data visualization in a virtual environment
Energy Technology Data Exchange (ETDEWEB)
Gerrick O' Ron Bivins
2005-05-05
In the field of computational fluid dynamics (CFD) accurate representations of fluid phenomena can be simulated hut require large amounts of data to represent the flow domain. Most datasets generated from a CFD simulation can be coarse, {approx}10,000 nodes or cells, or very fine with node counts on the order of 1,000,000. A typical dataset solution can also contain multiple solutions for each node, pertaining to various properties of the flow at a particular node. Scalar properties such as density, temperature, pressure, and velocity magnitude are properties that are typically calculated and stored in a dataset solution. Solutions are not limited to just scalar properties. Vector quantities, such as velocity, are also often calculated and stored for a CFD simulation. Accessing all of this data efficiently during runtime is a key problem for visualization in an interactive application. Understanding simulation solutions requires a post-processing tool to convert the data into something more meaningful. Ideally, the application would present an interactive visual representation of the numerical data for any dataset that was simulated while maintaining the accuracy of the calculated solution. Most CFD applications currently sacrifice interactivity for accuracy, yielding highly detailed flow descriptions hut limiting interaction for investigating the field.
A texture-based frameowrk for improving CFD data visualization in a virtual environment
Energy Technology Data Exchange (ETDEWEB)
Biveins, Gerrick O' Ron
2005-05-01
In the field of computational fluid dynamics (CFD) accurate representations of fluid phenomena can be simulated but require large amounts of data to represent the flow domain. Most datasets generated from a CFD simulation can be coarse, {approx} 10,000 nodes or cells, or very fine with node counts on the order of 1,000,000. A typical dataset solution can also contain multiple solutions for each node, pertaining to various properties of the flow at a particular node. Scalar properties such as density, temperature, pressure, and velocity magnitude are properties that are typically calculated and stored in a dataset solution. Solutions are not limited to just scalar properties. Vector quantities, such as velocity, are also often calculated and stored for a CFD simulation. Accessing all of this data efficiently during runtime is a key problem for visualization in an interactive application. Understanding simulation solutions requires a post-processing tool to convert the data into something more meaningful. Ideally, the application would present an interactive visual representation of the numerical data for any dataset that was simulated while maintaining the accuracy of the calculated solution. Most CFD applications currently sacrifice interactivity for accuracy, yielding highly detailed flow descriptions but limiting interaction for investigating the field.
Czech Academy of Sciences Publication Activity Database
Vlaev, S. D.; Staykov, P.; Fialová, Marie
2009-01-01
Roč. 23, č. 4 (2009), s. 513-518. ISSN 0352-9568 R&D Projects: GA ČR GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column bioreactor * gas holdup * cfd Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.387, year: 2009
Janiga, Gábor; Daróczy, László; Berg, Philipp; Thévenin, Dominique; Skalej, Martin; Beuing, Oliver
2015-11-01
The optimal treatment of intracranial aneurysms using flow diverting devices is a fundamental issue for neuroradiologists as well as neurosurgeons. Due to highly irregular manifold aneurysm shapes and locations, the choice of the stent and the patient-specific deployment strategy can be a very difficult decision. To support the therapy planning, a new method is introduced that combines a three-dimensional CFD-based optimization with a realistic deployment of a virtual flow diverting stent for a given aneurysm. To demonstrate the feasibility of this method, it was applied to a patient-specific intracranial giant aneurysm that was successfully treated using a commercial flow diverter. Eight treatment scenarios with different local compressions were considered in a fully automated simulation loop. The impact on the corresponding blood flow behavior was evaluated qualitatively as well as quantitatively, and the optimal configuration for this specific case was identified. The virtual deployment of an uncompressed flow diverter reduced the inflow into the aneurysm by 24.4% compared to the untreated case. Depending on the positioning of the local stent compression below the ostium, blood flow reduction could vary between 27.3% and 33.4%. Therefore, a broad range of potential treatment outcomes was identified, illustrating the variability of a given flow diverter deployment in general. This method represents a proof of concept to automatically identify the optimal treatment for a patient in a virtual study under certain assumptions. Hence, it contributes to the improvement of virtual stenting for intracranial aneurysms and can support physicians during therapy planning in the future. PMID:26472308
CFD MODELING AND ANALYSIS FOR A-AREA AND H-AREA COOLING TOWERS
Energy Technology Data Exchange (ETDEWEB)
Lee, S.; Garrett, A.; Bollinger, J.
2009-09-02
Mechanical draft cooling towers are designed to cool process water via sensible and latent heat transfer to air. Heat and mass transfer take place simultaneously. Heat is transferred as sensible heat due to the temperature difference between liquid and gas phases, and as the latent heat of the water as it evaporates. Mass of water vapor is transferred due to the difference between the vapor pressure at the air-liquid interface and the partial pressure of water vapor in the bulk of the air. Equations to govern these phenomena are discussed here. The governing equations are solved by taking a computational fluid dynamics (CFD) approach. The purpose of the work is to develop a three-dimensional CFD model to evaluate the flow patterns inside the cooling tower cell driven by cooling fan and wind, considering the cooling fans to be on or off. Two types of the cooling towers are considered here. One is cross-flow type cooling tower located in A-Area, and the other is counterflow type cooling tower located in H-Area. The cooling tower located in A-Area is mechanical draft cooling tower (MDCT) consisting of four compartment cells as shown in Fig. 1. It is 13.7m wide, 36.8m long, and 9.4m high. Each cell has its own cooling fan and shroud without any flow communications between two adjacent cells. There are water distribution decks on both sides of the fan shroud. The deck floor has an array of about 25mm size holes through which water droplet falls into the cell region cooled by the ambient air driven by fan and wind, and it is eventually collected in basin area. As shown in Fig. 1, about 0.15-m thick drift eliminator allows ambient air to be humidified through the evaporative cooling process without entrainment of water droplets into the shroud exit. The H-Area cooling tower is about 7.3 m wide, 29.3 m long, and 9.0 m high. Each cell has its own cooling fan and shroud, but each of two corner cells has two panels to shield wind at the bottom of the cells. There is some
CFD Experiments for Wind-Turbine-Platform Seakeeping Models and Flow Physics
Dunbar, Alexander; Paterson, Eric; Craven, Brent; Brasseur, James
2013-11-01
As part of the Penn State ``Cyber Wind Facility,'' we describe the development and application of a tightly-coupled CFD/6-DOF solver in OpenFOAM for the simulation of offshore floating wind turbine platforms. We highlight the tightly-coupled computational framework and validation of the solver via a comparison with benchmark experimental measurements. The validated CFD/6-DOF solver is then applied to the OC4 DeepCwind semisubmersible for the prediction of platform motion due to wind and wave loading. Supported by the US Department of Energy.
International Nuclear Information System (INIS)
The efficiency of pesticide application to agricultural fields and the resulting environmental contamination highly depend on atmospheric airflow. A computational fluid dynamics (CFD) modelling of airflow within plant canopies using 3D canopy architecture was developed to understand the effect of the canopy to airflow. The model average air velocity was validated using experimental results in a wind tunnel with two artificial model trees of 24 cm height. Mean air velocities and their root mean square (RMS) values were measured on a vertical plane upstream and downstream sides of the trees in the tunnel using 2D hotwire anemometer after imposing a uniform air velocity of 10 m s-1 at the inlet. 3D virtual canopy geometries of the artificial trees were modelled and introduced into a computational fluid domain whereby airflow through the trees was simulated using Reynolds-Averaged Navier-Stokes (RANS) equations and k-ε turbulence model. There was good agreement of the average longitudinal velocity, U between the measurements and the simulation results with relative errors less than 2% for upstream and 8% for downstream sides of the trees. The accuracy of the model prediction for turbulence kinetic energy k and turbulence intensity I was acceptable within the tree height when using a roughness length (y0 = 0.02 mm) for the surface roughness of the tree branches and by applying a source model in a porous sub-domain created around the trees. The approach was applied for full scale orchard trees in the atmospheric boundary layer (ABL) and was compared with previous approaches and works. The simulation in the ABL was made using two groups of full scale orchard trees; short (h = 3 m) with wider branching and long (h = 4 m) with narrow branching. This comparison showed good qualitative agreements on the vertical profiles of U with small local differences as expected due to the spatial disparities in tree architecture. This work was able to show airflow within and above the
Integration of Engine, Plume, and CFD Analyses in Conceptual Design of Low-Boom Supersonic Aircraft
Li, Wu; Campbell, Richard; Geiselhart, Karl; Shields, Elwood; Nayani, Sudheer; Shenoy, Rajiv
2009-01-01
This paper documents an integration of engine, plume, and computational fluid dynamics (CFD) analyses in the conceptual design of low-boom supersonic aircraft, using a variable fidelity approach. In particular, the Numerical Propulsion Simulation System (NPSS) is used for propulsion system cycle analysis and nacelle outer mold line definition, and a low-fidelity plume model is developed for plume shape prediction based on NPSS engine data and nacelle geometry. This model provides a capability for the conceptual design of low-boom supersonic aircraft that accounts for plume effects. Then a newly developed process for automated CFD analysis is presented for CFD-based plume and boom analyses of the conceptual geometry. Five test cases are used to demonstrate the integrated engine, plume, and CFD analysis process based on a variable fidelity approach, as well as the feasibility of the automated CFD plume and boom analysis capability.
Nikačević, N.M.; Thielen, L.; Twerda, A.; Hof, P.M.J. van den
2015-01-01
Flow pattern analysis in a spiral Helix reactor is conducted, for the application in commercial surfactant production. Step change response curves (SCR) were obtained from numerical tracer experiments by three-dimensional computational fluid dynamics (CFD) simulations. Non-reactive flow is simulated
Directory of Open Access Journals (Sweden)
Behzad Shahizare
2016-03-01
Full Text Available With soaring energy demands, the desire to explore alternate and renewable energy resources has become the focal point of various active research fronts. Therefore, the scientific community is revisiting the notion to tap wind resources in more rigorous and novel ways. In this study, a two-dimensional computational investigation of the vertical axis wind turbine (VAWT with omni-direction-guide-vane (ODGV is proposed to determine the effects of this guide vane. In addition, the mesh and time step (dt size dependency test, as well as the effect of the different turbulence models on results accuracy are investigated. Eight different shape ratios (R of the omni-direction-guide-vane were also examined in this study. Further, the CFD model is validated by comparing the numerical results with the experimental data. Validation results show a good agreement in terms of shape and trend in CFD simulation. Based on these results, all the shape ratios, except two ratios including 0.3 and 0.4 at TSR of 1.3 to 3, have a positive effect on the power and torque coefficient improvement. Moreover, results show that the best case has a shape ratio of 0.55, which improves the power coefficient by 48% and the torque coefficient up to 58%.
CFD simulation of highly transient flows
Denton, G. S.
2009-01-01
This thesis describes the fundamental extension and extensive testing of a robust CFD model for predicting outflow following the failure of pressurised hydrocarbon pipelines. The main thrust of the study involves the extension of the basic outflow model to account for complex pipeline systems, improvements of the theoretical basis and numerical stability. The basic model, based on the numerical solution of conservation equations using the method of characteristics, incorporates a suitabl...
International Nuclear Information System (INIS)
An efficient hydraulic optimization procedure, suitable for industrial use, requires an advanced optimization tool (EASY software), a fast solver (block coupled CFD) and a flexible geometry generation tool. EASY optimization software is a PCA-driven metamodel-assisted Evolutionary Algorithm (MAEA (PCA)) that can be used in both single- (SOO) and multiobjective optimization (MOO) problems. In MAEAs, low cost surrogate evaluation models are used to screen out non-promising individuals during the evolution and exclude them from the expensive, problem specific evaluation, here the solution of Navier-Stokes equations. For additional reduction of the optimization CPU cost, the PCA technique is used to identify dependences among the design variables and to exploit them in order to efficiently drive the application of the evolution operators. To further enhance the hydraulic optimization procedure, a very robust and fast Navier-Stokes solver has been developed. This incompressible CFD solver employs a pressure-based block-coupled approach, solving the governing equations simultaneously. This method, apart from being robust and fast, also provides a big gain in terms of computational cost. In order to optimize the geometry of hydraulic machines, an automatic geometry and mesh generation tool is necessary. The geometry generation tool used in this work is entirely based on b-spline curves and surfaces. In what follows, the components of the tool chain are outlined in some detail and the optimization results of hydraulic machine components are shown in order to demonstrate the performance of the presented optimization procedure
CFD analysis and flow model reduction for surfactant production in helix reactor
Nikačević, N.M.; Thielen, L.; Twerda, A.; Hof, P.M.J. van den
2014-01-01
Flow pattern analysis in a spiral Helix reactor is conducted, for the application in the commercial surfactant production. Step change response curves (SCR) were obtained from numerical tracer experiments by three-dimensional computational fluid dynamics (CFD) simulations. Non-reactive flow is simul
DEFF Research Database (Denmark)
Rosendahl, Lasse; Yin, Chungen; Kær, Søren Knudsen;
2007-01-01
shapes. The sample is subdivided by straw type, and coherent size, type and mass distribution parameters are reported for the entire sample. This type of data is necessary in order to use CFD reliably as a design and retrofit tool for co-firing biomass with fossil fuels, as the combustion processes of...
CFD activities in support of thermal-hydraulic modeling of SFR fuel bundles
International Nuclear Information System (INIS)
Extensive testing and validation work is being performed to assess and validate Computational Fluid Dynamics (CFD) applicability to the simulation of SFR fuel assemblies. The demonstrated robustness of the method allows extending the CFD analysis to distorted fuel configurations, which will inevitably occur during extended fuel operation. The subchannel code COBRA-IV-I-MIT is adopted to evaluate the range of applicability of lumped parameter methods. Comparisons of mixing simulations show some intrinsic limitation in the subchannel methods, but allow confirming its overall applicability to nominal and mildly deformed assembly configurations. For significantly deformed geometries CFD is the recommend approach and is applied in this work. Deformed geometries considered include duct swelling, rod swelling, rod bowing, rod twisting, and various combinations of the simple deformations. While not derived from the realistic analysis of the in-core fuel behavior, the distorted geometries have been designed to embrace all conceptual worst case scenarios. The work focuses on the evaluation of the influence of the deformation on the fuel behavior, rather than on the actual fuel performance. Such approach is driven by the objective of deriving general understanding, and evaluating the applicability of subchannel analysis codes to long life fuel design, possibly in combination with distorted-channel factors derived from the CFD analyses. (author)
CFD for Better Understanding of Wind Tunnel Tests
Qin, N.
2003-01-01
In this paper, we discuss how CFD may be used for better understanding of wind tunnel tests. Three examples are used to illustrate the potential use of CFD to help the understanding of phenomena observed in the wind tunnel tests, to extend/derive simple aerodynamic criteria based on CFD, and to use CFD to improve the accuracy of wind tunnel measurements.
Institute of Scientific and Technical Information of China (English)
李永乐; 朱佳琪; 唐浩俊
2015-01-01
Taking advantage of the software FLUENT and using the numerical solution of differential equation and the dynamic mesh model,a CFD/CSD coupling solution based on loose coupling was realized by embedding the Newmark method into FLUNT with the help of UDF function.A 2D-square cylinder model was established to investigate the change of Strouhal number and the maximum vertical vortex-excited amplitude of the square cylinder under different wind speed. The lock-in phenomenon of vortex-excited resonance was observed in the process of simulation and it was compared with the result of static square cylinder.A 2D flat plate model with vertical and torsional degrees of freedom was established to identify the flutter derivatives of the flat plate and to determine the flutter critical wind speed of flutter.The simulation result agrees well with the critical wind speeds of flutter calculated by using the Scanlan's formula and Selberg's formula.%以 FLUENT 为研究工具，利用微分方程的数值解法和动网格技术，基于松耦合方法将 Newmark 算法通过UDF 嵌入 Fluent 软件中，实现了 CFD 和 CSD 耦合的分析方法。通过建立二维方柱绕流模型，计算了竖向单自由度振动方柱在不同风速下的斯托罗哈数和最大振幅的变化情况，模拟了涡激共振锁定现象，并与静态绕流的结果进行了对比。建立了具有竖向振动和扭转振动二自由度的薄平板模型，并识别了该平板的颤振导数，进一步对其弯扭耦合颤振临界风速进行了逼近计算，本方法得到的颤振临界风速与 Scanlan 理论公式和 Selberg 理论公式吻合较好。
Soria, José; Gauthier, Daniel; Flamant, Gilles; Rodriguez, Rosa; Mazza, Germán
2015-09-01
Municipal Solid Waste Incineration (MSWI) in fluidized bed is a very interesting technology mainly due to high combustion efficiency, great flexibility for treating several types of waste fuels and reduction in pollutants emitted with the flue gas. However, there is a great concern with respect to the fate of heavy metals (HM) contained in MSW and their environmental impact. In this study, a coupled two-scale CFD model was developed for MSWI in a bubbling fluidized bed. It presents an original scheme that combines a single particle model and a global fluidized bed model in order to represent the HM vaporization during MSW combustion. Two of the most representative HM (Cd and Pb) with bed temperatures ranging between 923 and 1073K have been considered. This new approach uses ANSYS FLUENT 14.0 as the modelling platform for the simulations along with a complete set of self-developed user-defined functions (UDFs). The simulation results are compared to the experimental data obtained previously by the research group in a lab-scale fluid bed incinerator. The comparison indicates that the proposed CFD model predicts well the evolution of the HM release for the bed temperatures analyzed. It shows that both bed temperature and bed dynamics have influence on the HM vaporization rate. It can be concluded that CFD is a rigorous tool that provides valuable information about HM vaporization and that the original two-scale simulation scheme adopted allows to better represent the actual particle behavior in a fluid bed incinerator. PMID:26050934
Influence of operation parameters on flash smelting furnace based on CFD
Institute of Scientific and Technical Information of China (English)
Xinfeng Li; Shiheng Peng; Xiangli Han; Chi Mei; Tianyuan Xiao
2004-01-01
The influence of three important operation parameters in Jinlong flash smelting furnace, including the distributing blast speed, the oxygen enrichment rate of process air and the ratio of central oxygen to overall oxygen (Oc/Oo), has been investigated using a virtual simulation system on copper flash smelting furnace. The core of this virtual simulation system is a numerical simulation of CFD (computational fluid dynamics), and this system incorporates coupling momentum transport, heat transport, mass transport,reaction kinetics between gas and particles and chemical reactions between gas and gas. A set of numerical predicted data were obtained. The CFD simulation shows that there is a sensitive zone of the distributing blast speed, and the dust content ascends when the speed exceeds 180 m-s-1. Increasing the oxygen concentration of processing air benefits the efficient production of the flash smelting furnace.
Arbitrary Shape Deformation in CFD Design
Landon, Mark; Perry, Ernest
2014-01-01
Sculptor(R) is a commercially available software tool, based on an Arbitrary Shape Design (ASD), which allows the user to perform shape optimization for computational fluid dynamics (CFD) design. The developed software tool provides important advances in the state-of-the-art of automatic CFD shape deformations and optimization software. CFD is an analysis tool that is used by engineering designers to help gain a greater understanding of the fluid flow phenomena involved in the components being designed. The next step in the engineering design process is to then modify, the design to improve the components' performance. This step has traditionally been performed manually via trial and error. Two major problems that have, in the past, hindered the development of an automated CFD shape optimization are (1) inadequate shape parameterization algorithms, and (2) inadequate algorithms for CFD grid modification. The ASD that has been developed as part of the Sculptor(R) software tool is a major advancement in solving these two issues. First, the ASD allows the CFD designer to freely create his own shape parameters, thereby eliminating the restriction of only being able to use the CAD model parameters. Then, the software performs a smooth volumetric deformation, which eliminates the extremely costly process of having to remesh the grid for every shape change (which is how this process had previously been achieved). Sculptor(R) can be used to optimize shapes for aerodynamic and structural design of spacecraft, aircraft, watercraft, ducts, and other objects that affect and are affected by flows of fluids and heat. Sculptor(R) makes it possible to perform, in real time, a design change that would manually take hours or days if remeshing were needed.
Comprehensive Aerodynamic Analysis of a 10 MW Wind Turbine Rotor Using 3D CFD
DEFF Research Database (Denmark)
Zahle, Frederik; Bak, Christian; Sørensen, Niels N.;
2014-01-01
This article describes a comprehensive aerodynamic analysis carried out on the DTU 10 MW Reference Wind Turbine (DTU 10MW RWT), in which 3D CFD simulations were used to analyse the rotor performance and derive airfoil aerodynamic characteristics for use in aero-elastic simulation tools. The 3D CFD...... airfoil data derived using the Azimuthal Averaging Technique (AAT) was compared to airfoil data based on 2D CFD simulations on airfoil sections in combination with an array of 3D-correction engineering models, which indicated that the model by Chaviaropoulos and Hansen was in best agreement with the 3D...... CFD predictions. BEM simulations on the DTU 10MW RWT using the AAT-based airfoil data were carried out and compared to BEM simulations using the original airfoil data and the 3D CFD results, which showed clear improvements, particularly on the inner part of the rotor. Finally, 3D unsteady Detached...
Directory of Open Access Journals (Sweden)
K. Alawadhi
2014-12-01
Full Text Available Computational Fluid Dynamics (CFD analysis was carried out for the convergent-divergent fins arranged inline and staggered on the base plate as per the experimental setup provided in the technical paper [1]. This paper reports on the validation of results of modeling and simulation in CFD. The simulation was carried out using the ANSYS 12.0 as the CFD modeling software. The main objective of the CFD analysis was to calculate the temperature distribution on the surface of the base plate and surface of the convergent-divergent fins for the given inline and staggered arrangement of fins due to the effect of natural convection heat transfer for different heat power inputs, and also to compare the CFD results with the experimental results.
Development and application of computational fluid dynamics (CFD) simulations are being advanced through case studies for simulating air pollutant concentrations from sources within open fields and within complex urban building environments. CFD applications have been under deve...
International Nuclear Information System (INIS)
Highlights: • Validated CFD models for decompression and dispersion of CO2 releases from pipelines. • Incorporation of real gas EOS into CFD code for source strength estimation. • Demonstration of better performance of SST k–ω turbulence model for jet flow. • Demonstration of better performance of real gas EOS compared to ideal gas EOS. • Demonstration of superiority of CFD models over a commercial risk assessment package. - Abstract: Transportation of CO2 in high-pressure pipelines forms a crucial link in the ever-increasing application of Carbon Capture and Storage (CCS) technologies. An unplanned release of CO2 from a pipeline presents a risk to human and animal populations and the environment. Therefore it is very important to develop a deeper understanding of the atmospheric dispersion of CO2 before the deployment of CO2 pipelines, to allow the appropriate safety precautions to be taken. This paper presents a two-stage Computational Fluid Dynamics (CFD) study developed (1) to estimate the source strength, and (2) to simulate the subsequent dispersion of CO2 in the atmosphere, using the source strength estimated in stage (1). The Peng–Robinson (PR) EOS was incorporated into the CFD code. This enabled accurate modelling of the CO2 jet to achieve more precise source strength estimates. The two-stage simulation approach also resulted in a reduction in the overall computing time. The CFD models were validated against experimental results from the British Petroleum (BP) CO2 dispersion trials, and also against results produced by the risk management package Phast. Compared with the measurements, the CFD simulation results showed good agreement in both source strength and dispersion profile predictions. Furthermore, the effect of release direction on the dispersion was studied. The presented research provides a viable method for the assessment of risks associated with CCS
轴流式血泵流体特性 CFD 研究%Research on fluid properties of the anxial flow blood pump based on CFD
Institute of Scientific and Technical Information of China (English)
谢雄; 谭建平; 刘云龙
2014-01-01
在轴流式血泵的研发中，通常将血液当作牛顿流体来处理，考虑到当动脉存在局部狭窄等几何突变情况时，动脉局部流场中可能产生流动剪切率非常低的区域，因此有必要考虑血液的非牛顿特性。建立了轴流式血泵模型，通过C FD仿真分析得到血泵转速和流量的变化对血泵出入口流场的影响，以及血泵导叶对泵体内流场的影响规律，并通过对设计的血泵进行泵水实验，测量了轴流式血泵输出流量和压力参数。结果表明所设计的血泵在驱动性能上和仿真是相符的。%In the development of the axial flow blood pump ,the blood was usually taken as a New-tonian fluid .When taking into account of the existence of local artery stenosis and other geomet-ric mutation occurs ,an area with very low flow shear rate meight be produced in the arterial par-tial flow field .So the non-New tonian characteristics of blood should be considered .A model of the axial flow blood pump was established ,and the impaction of the flow and the rotate speed on the inlet and outlet of the flow field in the blood pump was analyzed through CFD as well as the influence of the guide vane on the flow field .By the drive experiment of the designed blood pump ,the output flow and pressure were measured .The results showed that the designed blood pump was consistent on the drive performance of the simulation .
Institute of Scientific and Technical Information of China (English)
Majid Ebrahimzadeh Gheshlaghi; Ataallah Soltani Goharrizi; Alireza Aghajani Shahrivar; Hadi Abdollahi
2013-01-01
Separation of particles from liquid in the large gravitational tanks is widely used in mining and industrial wastewater treatment process. Thickener is key unit in the operational processes of hydrometallurgy and is used to separate solid from liquid. In this study, population balance models were combined with com-putational fluid dynamics (CFD) for modeling the tailing thickener. Parameters such as feed flow rate, flocculant dosage, inlet solid percent and feedwell were investigated. CFD was used to simulate the industrial tailing thickener with settled bed of 120 m diameter which is located in the Sarcheshmeh cop-per mine. Important factor of drag force that defines the rake torque of rotating paddles on the bed was also determined. Two phases turbulence model of Eulerian/Eulerian in accordance with turbulence model of k-e was used in the steady-state. Also population balance model consists of 15 groups of particle sizes with Luo and Lehr kernel was used for aggregation/breakage kernel. The simulation results showed good agreement with the operational data.
Van Wassenbergh, Sam
2015-07-01
The gill cover of fish and pre-metamorphic salamanders has a key role in suction feeding by acting as a one-way valve. It initially closes and avoids an inflow of water through the gill slits, after which it opens to allow outflow of the water that was sucked through the mouth into the expanded buccopharyngeal cavity. However, due to the inability of analytical models (relying on the continuity principle) to calculate the flow of fluid through a cavity with two openings and that was changing in shape and size, stringent boundary conditions had to be used in previously developed mathematical models after the moment of the valve's opening. By solving additionally for the conservation of momentum, computational fluid dynamics (CFD) has the capacity to dynamically simulate these flows, but this technique also faces complications in modeling a transition from closed to open valves. Here, I present a relatively simple solution strategy to incorporate the opening of the valves, exemplified in an axisymmetrical model of a suction-feeding sunfish in ANSYS Fluent software. By controlling viscosity of a separately defined fluid entity in the region of the opercular cavity, early inflow can be blocked (high viscosity assigned) and later outflow can be allowed (changing viscosity to that of water). Finally, by analyzing the CFD solution obtained for the sunfish model, a few new insights into the biomechanics of suction feeding are gained. PMID:25936359
International Nuclear Information System (INIS)
Highlights: • A CFD model of a ventilated active façade with PCM was developed. • Results were validated against real-scale experimental data. • Convection effects within PCM can be neglected in for the façade under study. • DO radiation model and RNG k–ε showed accurate results for air turbulent flow regime. • k–ω models showed better accuracy than the RNG k–ε model for transitional air flows. - Abstract: This article describes the development of a CFD 2D model of a new type of ventilated active façade which includes a PCM (Phase Change Material) in its outer layer. The model was carried out using the software Fluent. The numerical results were compared against experimental data obtained by means of a real-scale PASLINK test facility. Two different approaches were tested to model the PCM. To model the radiation, S2S and DO sub-models were tested. RNG k–ε, Standard k–ω and SST k–ω turbulence models were compared to model the air flow inside the ventilated layer. The results showed that for the geometry under consideration it was suitable to consider the PCM to be a solid material with variable Cp. The DO model accurately reproduced the radiation phenomena. For an air flow rate that resulted in a turbulent regime inside the air chamber, the RNG k–ε model showed good agreement between the experimental data and the simulated results. The developed model can be considered suitable for the simulation and optimization of the fa ade under turbulent flow conditions. Further research should be conducted to improve the accuracy of the model for low-Reynolds-number turbulence conditions
Beyer, Friedemann; Choisnet, Thomas; Kretschmer, Matthias; Cheng, Po Wen
2015-01-01
A two MW floating offshore wind turbine is currently developed within the EU-FP7 project FLOATGEN. A wave tank test of the floater model at 1/32th scale has been performed in extreme wave conditions. In the present study numerical calculations of the floating foundation with regular waves using coupled MBS-CFD methods are compared to experimental data enabling a validation. Results of the wave elevation, floater motion and mooring line tension show a very good correlation. Flow phenomena like...
CFD Application and OpenFOAM on the 2-D Model for the Moderator System of Heavy-Water Reactors
International Nuclear Information System (INIS)
The flow in the complex pipeline system in a calandria tank of CANDU reactor is transported through the distribution of heat sources, which also exerts the pressure drop to the coolant flow. So the phenomena should be considered as multi-physics both in the viewpoints of heat transfer and fluid dynamics. In this study, we have modeled the calandria tank system as two-dimensional simplified one preliminarily that is yet far from the real objects, but to see the essential physics and to test the possibility of the present CFD(computational fluid dynamics) methods for the thermo-hydraulic problem in the moderator system of heavy-water reactors
CFD modelling of flow mal-distribution in an industrial ammonia oxidation reactor: A case study
International Nuclear Information System (INIS)
Ammonia oxidation reactor is widely used in nitric acid plant to cause the catalytic reaction between air and ammonia to produce nitrous gases. In this work, the flow distribution inside the ammonia oxidation reactor at Shiraz Petrochemical Complex (SPC) has been simulated using Computational Fluid Dynamics (CFD) code. The CFD results showed that the flow is non-uniformly distributed inside the reactor due to improper header design of the reactor. Measuring of the temperature distribution around the skin of the reactor has been carried out using thermograph. The thermograph experiment showed a considerable temperature difference between the left and right side of the reactor. It was found that the mal-distribution of the gas flow inside the reactor can directly affect the performance of the reactor. - Highlights: •A failure has been observed in an industrial ammonia oxidation reactor. •CFD code helps to simulate the flow inside the reactor. •The flow becomes non-uniformly distributed due to the reactor header mal-design. •The flow mal-distribution results in some drawbacks
Energy Technology Data Exchange (ETDEWEB)
Castro, Landy Y.; Rojas, Leorlen Y.; Gamez, Abel; Rosales, Jesus; Gonzalez, Daniel; Garcia, Carlos, E-mail: lcastro@instec.cu, E-mail: leored1984@gmail.com, E-mail: agamezgmf@gmail.com, E-mail: jrosales@instec.cu, E-mail: danielgonro@gmail.com, E-mail: cgh@instec.cu [Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), La Habana (Cuba); Oliveira, Carlos Brayner de, E-mail: cabol@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil); Dominguez, Dany S., E-mail: dsdominguez@gmail.com [Universidade Estadual de Santa Cruz (UESC), Ilheus, BA (Brazil). Pos-Graduacao em Modelagem Computacional
2015-07-01
Chosen as one of six Generation‒IV nuclear-reactor concepts, Supercritical Water-cooled Reactors (SCWRs) are expected to have high thermal efficiencies within the range of 45 - 50% owing to the reactor's high pressures and outlet temperatures. In this reactor, the primary water enters the core under supercritical-pressure condition (25 MPa) at a temperature of 280 deg C and leaves it at a temperature of up to 510 deg C. Due to the significant changes in the physical properties of water at supercritical-pressure, the system is susceptible to local temperature, density and power oscillations. The behavior of supercritical water into the core of the SCWR, need to be sufficiently studied. Most of the methods available to predict the effects of the heat transfer phenomena within the pseudocritical region are based on empirical one-directional correlations, which do not capture the multidimensional effects and do not provide accurate results in regions such as the deteriorated heat transfer regime. In this paper, computational fluid dynamics (CFD) analysis was carried out to study the thermal-hydraulic behavior of supercritical water flows in sub-channels of a typical European High Performance Light Water Reactor (HPLWR) fuel assembly using commercial CFD code CFX-14. It was determined the steady-state equilibrium parameters and calculated the temperature and density distributions. A comparative study for different turbulence models were carried out and the obtained results are discussed. (author)
International Nuclear Information System (INIS)
Chosen as one of six Generation‒IV nuclear-reactor concepts, Supercritical Water-cooled Reactors (SCWRs) are expected to have high thermal efficiencies within the range of 45 - 50% owing to the reactor's high pressures and outlet temperatures. In this reactor, the primary water enters the core under supercritical-pressure condition (25 MPa) at a temperature of 280 deg C and leaves it at a temperature of up to 510 deg C. Due to the significant changes in the physical properties of water at supercritical-pressure, the system is susceptible to local temperature, density and power oscillations. The behavior of supercritical water into the core of the SCWR, need to be sufficiently studied. Most of the methods available to predict the effects of the heat transfer phenomena within the pseudocritical region are based on empirical one-directional correlations, which do not capture the multidimensional effects and do not provide accurate results in regions such as the deteriorated heat transfer regime. In this paper, computational fluid dynamics (CFD) analysis was carried out to study the thermal-hydraulic behavior of supercritical water flows in sub-channels of a typical European High Performance Light Water Reactor (HPLWR) fuel assembly using commercial CFD code CFX-14. It was determined the steady-state equilibrium parameters and calculated the temperature and density distributions. A comparative study for different turbulence models were carried out and the obtained results are discussed. (author)
3D CFD modeling of subsonic and transonic flowing-gas DPALs with different pumping geometries
Yacoby, Eyal; Sadot, Oren; Barmashenko, Boris D.; Rosenwaks, Salman
2015-10-01
Three-dimensional computational fluid dynamics (3D CFD) modeling of subsonic (Mach number M ~ 0.2) and transonic (M ~ 0.9) diode pumped alkali lasers (DPALs), taking into account fluid dynamics and kinetic processes in the lasing medium is reported. The performance of these lasers is compared with that of supersonic (M ~ 2.7 for Cs and M ~ 2.4 for K) DPALs. The motivation for this study stems from the fact that subsonic and transonic DPALs require much simpler hardware than supersonic ones where supersonic nozzle, diffuser and high power mechanical pump (due to a drop in the gas total pressure in the nozzle) are required for continuous closed cycle operation. For Cs DPALs with 5 x 5 cm2 flow cross section pumped by large cross section (5 x 2 cm2) beam the maximum achievable power of supersonic devices is higher than that of the transonic and subsonic devices by only ~ 3% and ~ 10%, respectively. Thus in this case the supersonic operation mode has no substantial advantage over the transonic one. The main processes limiting the power of Cs supersonic DPALs are saturation of the D2 transition and large ~ 60% losses of alkali atoms due to ionization, whereas the influence of gas heating is negligible. For K transonic DPALs both the gas heating and ionization effects are shown to be unimportant. The maximum values of the power are higher than those in Cs transonic laser by ~ 11%. The power achieved in the supersonic and transonic K DPAL is higher than for the subsonic version, with the same resonator and K density at the inlet, by ~ 84% and ~ 27%, respectively, showing a considerable advantaged of the supersonic device over the transonic one. For pumping by rectangular beams of the same (5 x 2 cm2) cross section, comparison between end-pumping - where the laser beam and pump beam both propagate at along the same axis, and transverse-pumping - where they propagate perpendicularly to each other, shows that the output power and optical-to-optical efficiency are not
Estimation of Radius Ratio in a Fin Using Inverse CFD Model
Directory of Open Access Journals (Sweden)
Ranjan Das
2011-03-01
Full Text Available
This article deals with the retrieval of parameters such as the radius-ratio in a rectangular fin using an inverse CFD model involving a mixed boundary condition. At first, the temperature field is obtained from a forward problem using the finite difference method (FDM in which the inner and outer radii or the radius-ratio is assumed to be known. Next, by an inverse approach using the FDM in conjunction with the genetic algorithm (GA, the inner and outer radii or the radius-ratio is retrieved. To accomplish the task, an objective function represented by the sum of square of the error between the guessed and the exact/measured temperature fields is minimized. Apart from demonstrating the suitability of the FDM
International Nuclear Information System (INIS)
The interfacial area transport equation for the subcooled boiling flow was developed with a mechanistic model for the wall boiling source term. It included the bubble lift-off diameter model and lift-off frequency reduction factor model. To implement the model, the two-phase flow CFD code was developed, which was named as EAGLE (Elaborated Analysis of Gas-Liquid Evolution). The developed model and EAGLE code was validated the experimental data of SUBO and SNU facilities. The computational analysis revealed that the interfacial area transport equation with the bubble lift-off diameter model agreed well with the experimental results. It presents that the source term for the wall nucleation enhanced the prediction capability for a multi-dimensional behavior of void fraction or interfacial area concentration
Verification of a CFD model for indoor airflow and heat transfer
Energy Technology Data Exchange (ETDEWEB)
Stamou, A.; Katsiris, I. [School of Civil Engineering, National Technical University of Athens (NTUA), Heroon Polytechniou 5, 15780 Athens (Greece)
2006-09-15
The SST k-{omega} based model is applied to calculate air-flow velocities and temperatures in a model office room. Calculations are compared with experiments and with the results of the standard k-{epsilon}, the RNG k-{epsilon} model and the laminar model. It is concluded that (a) all the three tested turbulent models predict satisfactorily the main qualitative features of the flow and the layered type of temperature fields and (b) computations with the SST k-{omega} based model show the best agreement with measurements. The use of this model is proposed combined with a suitable grid. (author)
A comparison of turbulence models in airship steady-state CFD simulations
Voloshin, Vitaly; Chen, Yong K.; Calay, Rajnish K.
2012-01-01
The accuracy and resource consumption of the four different turbulence models based on the eddy viscosity assumption, namely, $k-\\varepsilon$, two $k-\\omega$ and Spallart-Allmaram models, in modeling airships are investigated. The test airship shape is a conventional shape. Three different angles of attack are considered. The results are checked against the wind tunnel experimental data. The resource consumption study is based on the benchmark of 1500 iterations. Based on all data obtained it...
Anusonti-Inthra, Phuriwat
2010-01-01
A novel Computational Fluid Dynamics (CFD) coupling framework using a conventional Reynolds-Averaged Navier-Stokes (BANS) solver to resolve the near-body flow field and a Particle-based Vorticity Transport Method (PVTM) to predict the evolution of the far field wake is developed, refined, and evaluated for fixed and rotary wing cases. For the rotary wing case, the RANS/PVTM modules are loosely coupled to a Computational Structural Dynamics (CSD) module that provides blade motion and vehicle trim information. The PVTM module is refined by the addition of vortex diffusion, stretching, and reorientation models as well as an efficient memory model. Results from the coupled framework are compared with several experimental data sets (a fixed-wing wind tunnel test and a rotary-wing hover test).
Real-Time Visualization of an HPF-based CFD Simulation
Kremenetsky, Mark; Vaziri, Arsi; Haimes, Robert; Chancellor, Marisa K. (Technical Monitor)
1996-01-01
Current time-dependent CFD simulations produce very large multi-dimensional data sets at each time step. The visual analysis of computational results are traditionally performed by post processing the static data on graphics workstations. We present results from an alternate approach in which we analyze the simulation data in situ on each processing node at the time of simulation. The locally analyzed results, usually more economical and in a reduced form, are then combined and sent back for visualization on a graphics workstation.
Comprehensive Aerodynamic Analysis of a 10 MW Wind Turbine Rotor Using 3D CFD
DEFF Research Database (Denmark)
Zahle, Frederik; Bak, Christian; Sørensen, Niels N.; Guntur, Srinivas; Troldborg, Niels
2014-01-01
airfoil data derived using the Azimuthal Averaging Technique (AAT) was compared to airfoil data based on 2D CFD simulations on airfoil sections in combination with an array of 3D-correction engineering models, which indicated that the model by Chaviaropoulos and Hansen was in best agreement with the 3D...... CFD predictions. BEM simulations on the DTU 10MW RWT using the AAT-based airfoil data were carried out and compared to BEM simulations using the original airfoil data and the 3D CFD results, which showed clear improvements, particularly on the inner part of the rotor. Finally, 3D unsteady Detached...
Simulating Flow and Dispersion by Using WRF-CFD Coupled Model in a Built-Up Area of Shenyang, China
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Yijia Zheng
2015-01-01
Full Text Available Results are presented from a series of numerical studies designed to investigate the atmospheric boundary layer structure, ambient wind, and pollutant source location and their impacts on the wind field and pollutant distribution within the built-up areas of Shenyang, China. Two models, namely, Open Source Field Operation and Manipulation (OpenFOAM software package and Weather Research and Forecasting (WRF model, are used in the present study. Then the high resolution computational fluid dynamics (CFD numerical experiments were performed under the typical simulated atmospheric boundary conditions. It was found that the atmospheric boundary structure played a crucial role in the pollution within the building cluster, which determined the potential turbulent diffusion ability of the atmospheric surface layer; the change of the ambient wind direction can significantly affect the dispersion pattern of pollutants, which was a more sensitive factor than the ambient wind speed; under a given atmospheric state, the location of the pollution sources would dramatically determine the pollution patterns within built-up areas. The WRF-CFD numerical evaluation is a reliable method to understand the complicated flow and dispersion within built-up areas.
On Further Enhancement of CFD Predictive Algorithms Based on Evidence Theory
Poroseva, Svetlana; Yousuff Hussaini, M.
2006-11-01
The Dempster-Shafer theory of evidence provides two basic tools -- i) belief functions that represent the degree of belief (confidence) in a given proposition on the basis of given evidence, and ii) Dempster's rule for combining the belief functions generated by different sources in relation to the same proposition. Previously, we have shown that these tools can be used effectively in application to various CFD problems (subsonic flow around the RAE 2822 airfoil and hurricane/typhoon track forecasts). The current study focuses on further enhancement of the predictive algorithms employing Dempster's rule. Specifically, we analyze one of the requirements of Dempster's rule that belief functions corresponding to different sources should be constructed using independent evidence. In CFD problems, evidence is experimental/observational data, which can be quite limited in number and barely sufficient to construct a single belief function. Application of Dempster's rule requires a minimum of two belief functions. We examine the origin of the requirement that independent data be used to construct belief functions and consider a strategy to overcome this constraint and its implications.
A comparison of turbulence models in airship steady-state CFD simulations
Voloshin, Vitaly; Calay, Rajnish K
2012-01-01
The accuracy and resource consumption of the four different turbulence models based on the eddy viscosity assumption, namely, $k-\\varepsilon$, two $k-\\omega$ and Spallart-Allmaram models, in modeling airships are investigated. The test airship shape is a conventional shape. Three different angles of attack are considered. The results are checked against the wind tunnel experimental data. The resource consumption study is based on the benchmark of 1500 iterations. Based on all data obtained it is evident that Spallart-Allmaras model is the most optimal one in the majority of cases.
Coarse-Grid-CFD for pressure loss evaluation in rod bundles
International Nuclear Information System (INIS)
CFD simulation of the complete reactor core of a nuclear power plant requires exceedingly huge computational resources so that this crude power approach has not been pursued yet. The traditional approach is the use of one dimensional sub channel analysis, employing calibrated transport models. Coarse-Grid-CFD is an attractive alternative technique based on strongly under-resolved CFD and the inviscid Euler equations. Obviously, using inviscid equations and coarse grids does not resolve all the relevant physics. The neglected physics is restored by additional volumetric source terms modeling viscosity and other sub-grid effects. The source terms are implemented via correlations derived from fully resolved representative simulations. The new simulation technique is demonstrated for a rod bundle experiment performed at the KALLA experiment of the Karlsruhe Institute of Technology (KIT) which includes three spacer grids. In this paper a 3D CFD study of the rod bundle is presented. A representative computational domain of the bundle is selected for the Coarse-Grid-CFD study. Comparison of the 3D CFD results to experimental results shows that a good agreement is obtained by an adequate selection of the computational grid. Coarse-Grid- CFD study results in good agreement with 3D CFD results. Careful selection of the representative coarse grid in geometrically complex regions like spacers is recommended. (authors)
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The aim of the project was the qualification of CFD codes for steam-water flows with phase transfer. While CFD methods for single-phase flows are already widely used for industrial applications, a corresponding use for two-phase flows is only at the beginning due to the complex structure of the interface and the related interactions between the phases. For the further development and validation of appropriate closure models, experimental data with high spatial and temporal resolution are required. Such data were obtained at the TOPFLOW test facility of HZDR by combination of experiments at realistic parameters for the nuclear reactor safety (large scales, high pressures and temperatures) with innovative measuring techniques. The wire-mesh sensor technology, which provides detailed information on the structure of the interface, was applied in adiabatic air-water experiments as well as in condensation and pressure relief experiments in a large DN200 pipe. As the result of the project, extensive databases with high quality are available. The technology for the fast X-ray tomography, which allows measurements without influencing the flow, was further developed and successfully applied in a first test series. High-resolution data were also obtained from experiments in a model of the hot leg of a pressurized water reactor for different flow situations, including counter-current flow limitation. For the corresponding steam-water experiments conducted at pressures of up to 5 MPa, the newly developed pressure tank technology was successfully used for the first time. For the qualification of CFD codes for two-phase flows the Inhomogeneous MUSIG model was extended in co.operation with ANSYS to consider phase transfer and validated on the basis of the above mentioned TOPFLOW experiments. In addition, improvements were achieved e.g. for turbulence modelling in bubbly flows and simulations were done to validate models for bubble forces and bubble coalescence and breakup. A
CFD for Nuclear Reactor Safety Applications (CFD4NRS-4) - Workshop Proceedings
International Nuclear Information System (INIS)
Following the CFD4NRS workshops held in Garching, Germany (Sept. 2006), Grenoble, France (Sep. 2008) and Washington D.C., USA (Sept. 2010), this Workshop is intended to extend the forum created for numerical analysts and experimentalists to exchange information in the application of CFD and CMFD to NRS issues and in guiding nuclear reactor design thinking. The workshop includes single-phase and multi-phase CFD applications, and offers the opportunity to present new experimental data for CFD validation. More emphasis has been given to the experiments, especially on two-phase flow, for advanced CMFD modelling for which sophisticated measurement techniques are required. Understanding of the physics has been depen before starting numerical analysis. Single-phase and multi-phase CFD simulations with a focus on validation were performed in areas such as: single-phase heat transfer, boiling flows, free-surface flows, direct contact condensation and turbulent mixing. These relate to NRS-relevant issues, such as pressurised thermal shock, critical heat flux, pool heat exchangers, boron dilution, hydrogen distribution in containments, thermal striping, etc. The use of systematic error quantification and the application of BPGs were strongly encouraged. Experiments providing data suitable for CFD or CMFD validation were also presented. These included local measurements using multi-sensor probes, laser-based techniques (LDV, PIV or LIF), hot-film/wire anemometry, imaging, or other advanced measuring techniques. There were over 150 registered participants at the CFD4NRS-4 workshop. The programme consisted of 48 technical papers. Of these, 44 were presented orally and 4 as posters. An additional 8 posters related to the OECD/NEA-KAERI sponsored CFD benchmark exercise on turbulent mixing in a rod bundle with spacers (MATiS-H) were presented and a special session was allocated for 6 video presentations. In addition, five keynote lectures were given by distinguished experts. The
CFD Simulation on Ethylene Furnace Reactor Tubes
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics (CFD) technique was presented. This approach took the flow, heat transfer, mass transfer and thermal cracking reactions in the reactor tubes into consideration. The coupled reactor model was solved with the SIMPLE algorithm. Some detailed information about the flow field, temperature field and concentration distribution in the reactor tubes was obtained, revealing the basic characteristics of the hydrodynamic phenomena and reaction behavior in the reactor tubes. The CFD approach provides the necessary information for conclusive decisions regarding the production optimization, the design and improvement of reactor tubes, and the new techniques implementation.
Dmitriev, S. M.; Dobrov, A. A.; Legchanov, M. A.; Khrobostov, A. E.
2015-09-01
Results of computer modeling of coolant flow in the fuel assembly of the reactor of a floating nuclear power plant using the LOGOS CFD programs have been given. The possibility of using the obtained results to improve models built into the engineering programs of thermohydraulic calculation of nuclear-reactor cores has been considered.
Nuclear Energy CFD Application Management System
International Nuclear Information System (INIS)
In modeling and simulation (M and S), it is virtually impossible to separately evaluate the effectiveness of the model from the data used because the results produced rely heavily on the interaction between the two. Both the data and the simulation are responsible for achieving the ultimate goal of providing defensible research and development (R and D) products and decisions. It is therefore vital that data verification and validation (V and V) activities, along with stringent configuration management, be considered part of the overall M and S accreditation process. In support of these goals is the Nuclear Energy CFD Application Management System (NE-CAMS) for nuclear system design and safety analysis. Working with Bettis Laboratory and Utah State University, a plan of action is being developed by the Idaho National Laboratory (INL) that will address the highest and most immediate needs to track and manage computational fluid dynamics (CFD) models and experimental data in an electronic database. The database will intrinsically incorporate the Nuclear Regulatory Commission (NRC) approved policies and procedures for quality. The quality requirements will be such that the model and data must conform to the quality specifications outlined by the NRC before they can be entered into the database. The primary focus of this database is CFD V and V for nuclear industry needs and will, in practice, serve as the best practice guideline that will accommodate NRC regulations. Such a database, along with a prescriptive methodology for how to utilize it, will provide the NRC with accepted CFD results that could potentially be used for licensing. Input from major organizations in government and industry have shown the need to develop a coordinated strategy at a national level to effectively accelerate the use of CFD for nuclear systems design and safety analysis. The growth of CFD for nuclear applications is evident from publications, both in journals and conferences, where CFD
International Nuclear Information System (INIS)
Highlights: • OECD/KAERI international CFD benchmark exercise was operated by KAERI. • The purpose is to validate relevant CFD codes based on the MATiS-H experiments. • Blind calculation results were synthesized in terms of mean velocity and RMS. • Quality of control volume rather than the number of it was emphasized. • Major findings were followed OECD/NEA CSNI report. - Abstract: The second international CFD benchmark exercise on turbulent mixing in a rod bundle has been launched by OECD/NEA, to validate relevant CFD (Computational Fluid Dynamics) codes and develop problem-specific Best Practice Guidelines (BPG) based on the KAERI (Korea Atomic Energy Research Institute) MATiS-H experiments on the turbulent mixing in a 5 × 5 rod array having two different types of vaned spacer grids: split and swirl types. For this 2nd international benchmark exercise (IBE-2), the MATiS-H testing provided a unique set of experimental data such as axial and lateral velocity components, turbulent intensity, and vorticity information. Blind CFD calculation results were submitted by twenty-five (25) participants to KAERI, who is the host organization of the IBE-2, and then analyzed and synthesized by comparing them with the MATiS-H data. Based on the synthesis of the results from both the experiments and blind CFD calculations for the IBE-2, and also by comparing with the IBE-1 benchmark exercise on the mixing in a T-junction, useful information for simulating this kind of complicated physical problem in a rod bundle was obtained. And some additional Best Practice Guidelines (BPG) are newly proposed. A summary of the synthesis results obtained in the IBE-2 is presented in this paper
Iannetti, Aldo; Stickland, Matthew T.; Dempster, William M.
2015-09-01
An advanced transient CFD model of a positive displacement reciprocating pump was created to study its behavior and performance in cavitating condition during the inlet stroke. The "full" cavitation model developed by Singhal et al. was utilized, and a sensitivity analysis test on two air mass fraction amounts (1.5 and 15 parts per million) was carried out to study the influence of the dissolved air content in water on the cavitation phenomenon. The model was equipped with user defined functions to introduce the liquid compressibility, which stabilizes the simulation, and to handle the two-way coupling between the pressure field and the inlet valve lift history. Estimation of the performance is also presented in both cases.
Directory of Open Access Journals (Sweden)
Iannetti Aldo
2015-09-01
Full Text Available An advanced transient CFD model of a positive displacement reciprocating pump was created to study its behavior and performance in cavitating condition during the inlet stroke. The “full” cavitation model developed by Singhal et al. was utilized, and a sensitivity analysis test on two air mass fraction amounts (1.5 and 15 parts per million was carried out to study the influence of the dissolved air content in water on the cavitation phenomenon. The model was equipped with user defined functions to introduce the liquid compressibility, which stabilizes the simulation, and to handle the two-way coupling between the pressure field and the inlet valve lift history. Estimation of the performance is also presented in both cases.
International Nuclear Information System (INIS)
This study relies on computational fluid dynamics (CFD) tools to analyse a possible method for creating a stable quadrupole vortex within a simulated, circular-port, cylindrical rocket chamber. A model of the vortex generator is created in a SolidWorks CAD program and then the grid is generated using the Pointwise mesh generation software. The non-reactive flowfield is simulated using an open source computational program, Stanford University Unstructured (SU2). Subsequent analysis and visualization are performed using ParaView. The vortex generation approach that we employ consists of four tangentially injected monopole vortex generators that are arranged symmetrically with respect to the center of the chamber in such a way to produce a quadrupole vortex with a common downwash. The present investigation focuses on characterizing the flow dynamics so that future investigations can be undertaken with increasing levels of complexity. Our CFD simulations help to elucidate the onset of vortex filaments within the monopole tubes, and the evolution of quadrupole vortices downstream of the injection faceplate. Our results indicate that the quadrupole vortices produced using the present injection pattern can become quickly unstable to the extent of dissipating soon after being introduced into simulated rocket chamber. We conclude that a change in the geometrical configuration will be necessary to produce more stable quadrupoles
International Nuclear Information System (INIS)
Highlights: ► New drag law in AIAD model was implemented in a CFD code to simulate the flows in nuclear reactor. ► The problems include the CCFL, hydraulic jump and pressurized thermal shock (PTS). ► The model is able to distinguish the local flow morphologies in frame of the Euler–Euler. ► CFD calculations agree well with the experimental data. - Abstract: This paper presents different CFD-simulations on flows which are relevant for nuclear reactor safety using a new modeling approach for the interfacial drag at free surfaces. The developed drag coefficient model was implemented together with the Algebraic Interfacial Area Density (AIAD) model () into the three-dimensional (3-D) computational fluid dynamics (CFD) code ANSYS-CFX. The applications considered include the prediction of counter-current flow limitations (CCFL) in a PWR hot leg, the development of hydraulic jump during the air–water co-current flow in a horizontal channel, and pressurized thermal shock (PTS) phenomena in a PWR cold leg and downcomer. For the modeling of these tasks, an Euler–Euler approach was used. This approach allows the use of different models depending on the local morphology. In the frame of an Euler–Euler simulation, the local morphology of the phases has to be considered in the drag model. To demonstrate the feasibility of the present approach, the computed main parameters of each case were compared with experimental data. It is shown that the CFD calculations agree well with the experimental data. This indicates that the AIAD model combined with new drag force modeling is a promising way to simulate the phenomena in frame of the Euler–Euler approach. Moreover the further validation of the model by including mass transfer effects should be carried out.
Institute of Scientific and Technical Information of China (English)
WEI Ying-san; WANG Yong-sheng; CHANG Shu-ping; FU Jian
2012-01-01
A mesh-less Refined Integral Algorithm (RIA) of Boundary Element Method (BEM) is proposed to accurately solve the Helmholtz Integral Equation (HIE).The convergence behavior and the practicability of the method are validated.Computational Fluid Dynamics (CFD),Finite Element Method (FEM) and RIA are used to predict the propeller excited underwater noise of the submarine hull structure.Firstly the propeller and submarine's flows are independently validated,then the self propulsion of the “submarine+propeller” system is simulated via CFD and the balanced point of the system is determined as well as the self propulsion factors.Secondly,the transient response of the “submarine + propeller” system is analyzed at the balanced point,and the propeller thrust and torque excitations are calculated.Thirdly the thrust and the torque excitations of the propeller are loaded on the submarine,respectively,to calculate the acoustic response,and the sound pover and the main peak frequencies are obtained.Results show that:(1) the thrust mainly excites the submarine axial mode and the high frequency area appears at the two conical-type ends,while the torque mainly excites the circumferential mode and the high frequency area appears at the broadside of the cylindrical section,but with rather smaller sound power and radiation efficiency than the former,(2) the main sound source appears at BPF and 2BPF and comes from the harmonic propeller excitations.So,the main attention should be paid on the thrust excitation control for the sound reduction of the propeller excited submarine structure.
International Nuclear Information System (INIS)
To gain reliable data for the development of an empirical model for the prediction of the local high temperature corrosion potential in biomass fired boilers, online corrosion probe measurements have been carried out. The measurements have been performed in a specially designed fixed bed/drop tube reactor in order to simulate a superheater boiler tube under well-controlled conditions. The investigated boiler steel 13CrMo4-5 is commonly used as steel for superheater tube bundles in biomass fired boilers. Within the test runs the flue gas temperature at the corrosion probe has been varied between 625 °C and 880 °C, while the steel temperature has been varied between 450 °C and 550 °C to simulate typical current and future live steam temperatures of biomass fired steam boilers. To investigate the dependence on the flue gas velocity, variations from 2 m·s−1 to 8 m·s−1 have been considered. The empirical model developed fits the measured data sufficiently well. Therefore, the model has been applied within a Computational Fluid Dynamics (CFD) simulation of flue gas flow and heat transfer to estimate the local corrosion potential of a wood chips fired 38 MW steam boiler. Additionally to the actual state analysis two further simulations have been carried out to investigate the influence of enhanced steam temperatures and a change of the flow direction of the final superheater tube bundle from parallel to counter-flow on the local corrosion potential. - Highlights: • Online corrosion probe measurements in a fixed bed/drop tube reactor. • Development of an empirical corrosion model. • Application of the model in a CFD simulation of flow and heat transfer. • Variation of boundary conditions and their effects on the corrosion potential
CFD Script for Rapid TPS Damage Assessment
McCloud, Peter
2013-01-01
This grid generation script creates unstructured CFD grids for rapid thermal protection system (TPS) damage aeroheating assessments. The existing manual solution is cumbersome, open to errors, and slow. The invention takes a large-scale geometry grid and its large-scale CFD solution, and creates a unstructured patch grid that models the TPS damage. The flow field boundary condition for the patch grid is then interpolated from the large-scale CFD solution. It speeds up the generation of CFD grids and solutions in the modeling of TPS damages and their aeroheating assessment. This process was successfully utilized during STS-134.
Energy Technology Data Exchange (ETDEWEB)
Finlayson, Elizabeth U.; Gadgil, Ashok J.; Thatcher, Tracy L.; Sextro, Richard G.
2002-10-01
This paper reports on an investigation of the adequacy of Computational fluid dynamics (CFD), using a standard Reynolds Averaged Navier Stokes (RANS) model, for predicting dispersion of neutrally buoyant gas in a large indoor space. We used CFD to predict pollutant (dye) concentration profiles in a water filled scale model of an atrium with a continuous pollutant source. Predictions from the RANS formulation are comparable to an ensemble average of independent identical experiments. Model results were compared to pollutant concentration data in a horizontal plane from experiments in a scale model atrium. Predictions were made for steady-state (fully developed) and transient (developing) pollutant concentrations. Agreement between CFD predictions and ensemble averaged experimental measurements is quantified using the ratios of CFD-predicted and experimentally measured dye concentration at a large number of points in the measurement plane. Agreement is considered good if these ratios fall between 0.5 and 2.0 at all points in the plane. The standard k-epsilon two equation turbulence model obtains this level of agreement and predicts pollutant arrival time to the measurement plane within a few seconds. These results suggest that this modeling approach is adequate for predicting isothermal pollutant transport in a large room with simple geometry.
Extending the capabilities of CFD codes to assess ash related problems
DEFF Research Database (Denmark)
Kær, Søren Knudsen; Rosendahl, Lasse Aistrup; Baxter, B. B.
2004-01-01
This paper discusses the application of FLUENT? in theanalysis of grate-fired biomass boilers. A short description of theconcept used to model fuel conversion on the grate and the couplingto the CFD code is offered. The development and implementation ofa CFD-based deposition model is presented in...... the reminder of thepaper. The growth of deposits on furnace walls and super heatertubes is treated including the impact on heat transfer rates determinedby the CFD code. Based on the commercial CFD code FLUENT?,the overall model is fully implemented through the User DefinedFunctions. The model is...... configured entirely through a graphical userinterface integrated in the standard FLUENT? interface. The modelconsiders fine and coarse mode ash deposition and stickingmechanisms for the complete deposit growth, as well as an influenceon the local boundary conditions for heat transfer due to thermalresistance...
V&V Of CFD Modeling Of The Argonne Bubble Experiment: FY15 Summary Report
Energy Technology Data Exchange (ETDEWEB)
Hoyt, Nathaniel C. [Argonne National Lab. (ANL), Argonne, IL (United States); Wardle, Kent E. [Argonne National Lab. (ANL), Argonne, IL (United States); Bailey, James L. [Argonne National Lab. (ANL), Argonne, IL (United States); Basavarajappa, Manjunath [Univ. of Utah, Salt Lake City, UT (United States)
2015-09-30
In support of the development of accelerator-driven production of the fission product Mo 99, computational fluid dynamics (CFD) simulations of an electron-beam irradiated, experimental-scale bubble chamber have been conducted in order to aid in interpretation of existing experimental results, provide additional insights into the physical phenomena, and develop predictive thermal hydraulic capabilities that can be applied to full-scale target solution vessels. Toward that end, a custom hybrid Eulerian-Eulerian-Lagrangian multiphase solver was developed, and simulations have been performed on high-resolution meshes. Good agreement between experiments and simulations has been achieved, especially with respect to the prediction of the maximum temperature of the uranyl sulfate solution in the experimental vessel. These positive results suggest that the simulation methodology that has been developed will prove to be suitable to assist in the development of full-scale production hardware.
Parallel CFD simulation of flow in a 3D model of vibrating human vocal folds
Czech Academy of Sciences Publication Activity Database
Šidlof, Petr; Horáček, Jaromír; Řidký, V.
2013-01-01
Roč. 80, č. 1 (2013), s. 290-300. ISSN 0045-7930 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional research plan: CEZ:AV0Z20760514 Keywords : numerical simulation * vocal folds * glottal airflow * inite volume method * parallel CFD Subject RIV: BI - Acoustics Impact factor: 1.532, year: 2013 http://www.sciencedirect.com/science?_ob=ArticleListURL&_method=list&_ArticleListID=-268060849&_sort=r&_st=13&view=c&_acct=C000034318&_version=1&_urlVersion=0&_userid=640952&md5=7c5b5539857ee9a02af5e690585b3126&searchtype=a
V&V Of CFD Modeling Of The Argonne Bubble Experiment: FY15 Summary Report
International Nuclear Information System (INIS)
In support of the development of accelerator-driven production of the fission product Mo 99, computational fluid dynamics (CFD) simulations of an electron-beam irradiated, experimental-scale bubble chamber have been conducted in order to aid in interpretation of existing experimental results, provide additional insights into the physical phenomena, and develop predictive thermal hydraulic capabilities that can be applied to full-scale target solution vessels. Toward that end, a custom hybrid Eulerian-Eulerian-Lagrangian multiphase solver was developed, and simulations have been performed on high-resolution meshes. Good agreement between experiments and simulations has been achieved, especially with respect to the prediction of the maximum temperature of the uranyl sulfate solution in the experimental vessel. These positive results suggest that the simulation methodology that has been developed will prove to be suitable to assist in the development of full-scale production hardware.
Colli, Matteo; Lanza, Luca; Rasmussen, Roy; Thériault, Julie
2016-04-01
Despite its importance, accurate measurements of precipitation remains a challenge. Measurement errors for solid precipitation, which are often ignored for automated systems, frequently range from 20% to 70% due to undercatch in windy conditions. While solid precipitation measurements have been the subject of many studies, there have been only a limited number of numerical modeling efforts to estimate the collection efficiency of solid precipitation gauges when exposed to the wind, in both shielded and unshielded configurations. The available models use CFD simulations of the airflow pattern generated by the aerodynamic response of the gauge/shield geometry to perform the Lagrangian tracking of solid precipitation particles (Thériault et al., 2012; Colli et al. 2016a and 2016b). Validation of the results against field observations yields similarities in the overall behavior, but the model output only approximately reproduces the dependence of the experimental collection efficiency on wind speed. We present recent developments of such a modelling approach including various gauge/shield configurations, the influence of the drag coefficient calculation on the model performance, and the role of the particle size distribution in explaining the scatter of the collection efficiency observed at any particular wind speed (Colli et al. 2015). Comparison with observations at the Marshall (CO) field test site is used to validate results of the various modelling schemes and to support the analysis of the microphysical characteristics of ice crystals. References: Colli, M., Rasmussen, R.M., Thèriault, J.M., Lanza, L.G., Baker, B.C. and J. Kochendorfer (2015). An improved trajectory model to evaluate the collection performance of snow gauges. J.Appl.Meteor.Climatol., 54(8), pages 1826-1836. Colli, M., Lanza, L.G., Rasmussen, R.M. and J.M. Thèriault (2016a). The collection efficiency of shielded and unshielded precipitation gauges. Part I: CFD airflow modelling. J. of
Tracer dispersion - experiment and CFD
International Nuclear Information System (INIS)
Description of tracer distribution by means of dispersion models is a method successfully used in process engineering for fifty years. Application of dispersion models in reactor engineering for characterization of flows in column apparatus, heat exchangers, etc. is summarized and experimental tracer techniques as well as CFD methods for dispersion coefficients evaluation are discussed. Possible extensions of thermal axial dispersion model (ADM) and a core-wall ADM model suitable for description of tracer dispersion in laminar flows are suggested as well as CFD implementation as 1D finite elements. (author)
International Nuclear Information System (INIS)
Research highlights: → The COOLOD/N2 and PARET/ANL codes were used for a steady-state thermal-hydraulic and safety analysis of the 2 MW TRIGA MARK II reactor located at the Nuclear Studies Center of Maamora (CENM), Morocco. → The main objective of this study is to ensure the safety margins of different safety related parameters by steady-state calculations at full power level (2 MW). → The most important conclusion is that all obtained values of DNBR, fuel center and surface temperature, cladding surface temperature and coolant temperature across the hottest channel are largely far to compromise safety of the reactor. - Abstract: In this study, a pool-typed design similar to sodium-cooled fast reactor (SFR) of the fourth generation reactors has been modeled using CFD simulations to investigate the characteristics of a passive mechanism of Shutdown Heat Removal System (SHRS). The main aim is to refine the reactor pool design in terms of temperature safety margin of the sodium pool. Thus, an appropriate protection mechanism is maintained in order to ensure the safety and integrity of the reactor system during a shutdown mode without using any active heat removal system. The impacts on the pool temperature are evaluated based on the following considerations: (1) the aspect ratio of pool diameter to depth, (2) the values of thermal emissivity of the surface materials of reactor and guard vessels, and (3) innerpool liner and core periphery structures. The computational results show that an optimal pool design in geometry can reduce the maximum pool temperature down to ∼551 oC which is substantially lower than ∼627 oC as calculated for the reference case. It is also concluded that the passive Reactor Air Cooling System (RACS) is effective in removing decay heat after shutdown. Furthermore, thermal radiation from the surface of the reactor vessel is found to be important; and thus, the selection of the vessel surface materials with a high emissivity would be a
Energy Technology Data Exchange (ETDEWEB)
Hung, T.C., E-mail: tchung@ntut.edu.t [Department of Mechanical Engineering, National Taipei University of Technology, 1, Sec. 3, Chung-hsiao E. Rd., Taipei 10608, Taiwan (China); Dhir, V.K. [Department of Mechanical and Aerospace Engineering, UCLA, CA (United States); Chang, J.C. [Graduate Institute of Mechanical and Electrical Engineering, National Taipei University of Technology, Taiwan (China); Wang, S.K. [Department of Mechanical and Automation Engineering, I-Shou University, Taiwan (China)
2011-01-15
Research highlights: The COOLOD/N2 and PARET/ANL codes were used for a steady-state thermal-hydraulic and safety analysis of the 2 MW TRIGA MARK II reactor located at the Nuclear Studies Center of Maamora (CENM), Morocco. The main objective of this study is to ensure the safety margins of different safety related parameters by steady-state calculations at full power level (2 MW) The most important conclusion is that all obtained values of DNBR, fuel center and surface temperature, cladding surface temperature and coolant temperature across the hottest channel are largely far to compromise safety of the reactor. - Abstract: In this study, a pool-typed design similar to sodium-cooled fast reactor (SFR) of the fourth generation reactors has been modeled using CFD simulations to investigate the characteristics of a passive mechanism of Shutdown Heat Removal System (SHRS). The main aim is to refine the reactor pool design in terms of temperature safety margin of the sodium pool. Thus, an appropriate protection mechanism is maintained in order to ensure the safety and integrity of the reactor system during a shutdown mode without using any active heat removal system. The impacts on the pool temperature are evaluated based on the following considerations: (1) the aspect ratio of pool diameter to depth, (2) the values of thermal emissivity of the surface materials of reactor and guard vessels, and (3) innerpool liner and core periphery structures. The computational results show that an optimal pool design in geometry can reduce the maximum pool temperature down to {approx}551 {sup o}C which is substantially lower than {approx}627 {sup o}C as calculated for the reference case. It is also concluded that the passive Reactor Air Cooling System (RACS) is effective in removing decay heat after shutdown. Furthermore, thermal radiation from the surface of the reactor vessel is found to be important; and thus, the selection of the vessel surface materials with a high emissivity
Overview 2004 of NASA Stirling-Convertor CFD-Model Development and Regenerator R&D Efforts
Tew, Roy C.; Dyson, Rodger W.; Wilson, Scott D.; Demko, Rikako
2005-01-01
This paper reports on accomplishments in 2004 in development of Stirling-convertor CFD model at NASA GRC and via a NASA grant, a Stirling regenerator-research effort being conducted via a NASA grant (a follow-on effort to an earlier DOE contract), and a regenerator-microfabrication contract for development of a "next-generation Stirling regenerator." Cleveland State University is the lead organization for all three grant/contractual efforts, with the University of Minnesota and Gedeor Associates as subcontractors. Also, the Stirling Technology Co. and Sunpower, Inc. are both involved in all three efforts, either as funded or unfunded participants. International Mezzo Technologies of Baton Rouge, LA is the regenerator fabricator for the regenerator-microfabrication contract. Results of the efforts in these three areas are summarized.
CFD analysis for spacer grid mixing vane design
International Nuclear Information System (INIS)
A computational fluid dynamics (CFD) analysis for a rod bundle with the larger scale model (6x6 array model) has been performed to develop the base shape of mixing vane in accordance with the hydraulic and thermal performance. Explanatory parameters are span pressure drop and span average heat transfer coefficient. The concern related to hot spot is also considered as a subsidiary criterion. Of the several candidates, the final candidate was determined by using the CFD analysis code, STAR-CD. And then, the optimization for it was performed using the response surface method (RSM) that the proper tolerance was considered under the two acceptance criteria such as lower span pressure drop while maintaining the span average heat transfer coefficient with respect to the current shape. The optimized mixing vane shape was verified by the CFD analysis including the effects of allowable tolerance. (author)
Numerical analysis of the internal flow field in screw centrifugal blood pump based on CFD
Han, W.; Han, B. X.; Y Wang, H.; Shen, Z. J.
2013-12-01
As to the impeller blood pump, the high speed of the impeller, the local high shear force of the flow field and the flow dead region are the main reasons for blood damage. The screw centrifugal pump can effectively alleviate the problems of the high speed and the high shear stress for the impeller. The softness and non-destructiveness during the transfer process can effectively reduce the extent of the damage. By using CFD software, the characteristics of internal flow are analyzed in the screw centrifugal pump by exploring the distribution rules of the velocity, pressure and shear deformation rate of the blood when it flows through the impeller and the destructive effects of spiral blades on blood. The results show that: the design of magnetic levitation solves the sealing problems; the design of regurgitation holes solves the problem of the flow dead zone; the magnetic levitated microcirculation screw centrifugal pump can effectively avoid the vortex, turbulence and high shear forces generated while the blood is flowing through the pump. Since the distribution rules in the velocity field, pressure field and shear deformation rate of the blood in the blood pump are comparatively uniform and the gradient change is comparatively small, the blood damage is effectively reduced.
CFD modeling of two immiscible fluids mixing in a commercial scale static mixer
Directory of Open Access Journals (Sweden)
V. Abdolkarimi
2014-12-01
Full Text Available A Computational Fluid Dynamics model based on the Eulerian formulation for multiphase flow was developed to model the mixing hydrodynamics of two immiscible fluids in a commercial scale static mixer. The two immiscible liquids were condensate and caustic solutions and were considered as two phases that are interpenetrating each other. The aim of this study was to develop a comprehensive Computational Fluid Dynamics model for predicting the impact of hydrodynamic parameters such as length, diameter and the arrangement of the corrugated plates of a static mixer on the degree of mixing and the pressure drop of the mixture. The model has been evaluated by comparing predictions of the degree of mixing and the mixture pressure drop with the same data available for the static mixer of the desulfurization plant of the Kharg petrochemical company. It has been shown that the predictions of the developed model are well adapted to the experimental data.