CFD Code FLUENT Research Articles

Modeling Thermal Oxidation of Coal Mine Methane in a Non-Catalytic Reverse-Flow Reactor

Inspired by detailed designs of industrial porous burners, the combustion of methane–air mixtures in a non-catalytic reverse-flow reactor was studied numerically. The governing equations are the unsteady state equations of conservation of mass and chemical species, with separate energy equations for the solid and gas phases. These equations were solved using the commercial CFD code Fluent. In order to reveal the actual thermal oxidation in porous media, the user defined function (UDF) is used to extend the ability of FLUENT. The model has been used to investigate the effects of operating conditions such as the mixture inlet approach velocity (0.15 to 0.8 m/s) and methane concentration (0.3 to 0.7%) on the oxidation of methane within non-catalytic reactors packed with ceramic monolith blocks under adiabatic conditions. The calculated values of methane conversion showed good agreement with the corresponding available experimental data. Moreover temperature distribution characteristics in the oxidation bed were studied in order to maintain the autothermicity of TFRR with a high enough temperature in the hot zone.

Thermal energy storages analysis for high temperature in air solar systems

In this paper a high temperature thermal storage in a honeycomb solid matrix is numerically investigated and a parametric analysis is accomplished. In the formulation of the model it is assumed that the system geometry is cylindrical, the fluid and the solid thermo physical properties are temperature independent and radiative heat transfer is taken into account whereas the effect of gravity is neglected. Air is employed as working fluid and the solid material is cordierite. The evaluation of the fluid dynamic and thermal behaviors is accomplished assuming the honeycomb as a porous medium. The Brinkman–Forchheimer–extended Darcy model is used in the governing equations and the local thermal non equilibrium is assumed. The commercial CFD Fluent code is used to solve the governing equations in transient regime. Numerical simulations are carried out with storage medium for different mass flow rates of the working fluid and different porosity values. Results in terms of temperature profiles, temperatures fields and stored thermal energy as function of time are presented. The effects of storage medium, different porosity values and mass flow rate on stored thermal energy and storage time are shown.

Modeling service life of pleated filters exposed to poly-dispersed aerosols

In this work, we present a fast and flexible 3-D macroscale simulation method for modeling the instantaneous pressure drop and collection efficiency of pleated fibrous filters when exposed to poly-dispersed aerosols in both surface and depth filtration regimes. The simulations are conducted using the Fluent CFD code enhanced with a series of in-house subroutines. A cluster-injection method is developed to accelerate the formation and growth of dust-cake both inside and outside the filter media. Once calibrated with experiment or more accurate microscale simulations, the cluster-injection method can be used to simulate the service life of a pleated filter with reasonable accuracy and CPU time. The simulation methodology developed in this work can be used to design and develop pleated filters for different applications. In particular, it allows one to study the effects of pleat shape, pleat count, filter porosity, fiber diameter(s), flow velocity, aerosol concentration, and particle diameter, as well as the aerodynamic parameters of the flow on the evolution of a filter's pressure drop and collection efficiency over time. For demonstration purposes, performance of an arbitrary filter with 2 and 4 pleats per inch is simulated when challenged with poly-dispersed particles of 1 to 10μm in diameter. For the filter simulated here, it was found that exposure to the above poly-dispersed aerosols results in a shorter service life in comparison to when the filter is exposure to mono-dispersed aerosols with a diameter of 1 or 10μm having the same mass flux.

Numerical investigation of hydrodynamics behaviour of melt layer during laser cutting of steel

Understanding of the melt layer hydrodynamic behaviour during laser-cutting process under gas jet assistance is of high importance for cut quality control. In the present work, a numerical model is developed to calculate the three-dimensional behaviour of the melt flow on the kerf front, while an inert gas jet interacts with the melt film. Fluent CFD code is used to solve the governing hydrodynamic equations by finite volume method. The results show that the melt flow on the kerf front reveals a strong instability, which depends on the cutting speed and on the gas jet velocity. Global flow behaviour (gas and molten metal flows) computed using a laminar model, reveals oscillations of the gas–metal liquid interface, which is assimilated to Kelvin–Helmholtz instability. The origin of this instability is discussed in terms of instabilities in thermal dynamics and hydrodynamics. Instability in thermal dynamics is related to the localized melting, while the instability in hydrodynamics is governed by forces balance between gas and resistant surface tension.

CFD modeling and analysis of the fish-hook effect on the rotor separator's efficiency

This paper presents a three-dimensional numerical simulation of the gas–solid flow in the third generation dynamic separator. The industrial CFD code (Fluent) is used to model the high turbulent fluid flow and the separation efficiency inside this separator. The Reynolds Stress Model (RSM) and the Discrete Phase Model (DPM) are used respectively to predict the velocity field and pressure drop and to estimate the selectivity curve inside the high efficiency separator. While the DPM model is used to estimate the selectivity curve. Some factors which affect the performance of dynamic separator were identified. The fish-hook effect is the most marked mechanism for selecting finer cement powder. The CFD simulation results are analyzed in order to understand the fish-hook effect and the separation mechanism in the dynamic separator. It is found that the RSM model better captures the phenomenon in the dynamic separator when compared with industrial results made by the Enfidha Cement plant “CE” and that the fish-hook effect was a result of the bubble-type vortex breakdown in the separating chamber. But much difficulty has been reached to achieve convergence.

Modeling of Free-Burning Arc and Effects of Boundary Conditions on the Anode Temperature Field

A two dimensional numerical model of the free-burning arc and its interaction with anode are given. The commercial CFD code FLUENT is used to model the plasma and the solid anode part. The anode sheath is considered, as well as the heat transfer mechanism of the anode surface. The second boundary condition of heat conduction is introduced to give a more reasonable cooling boundary, so that the temperature distribution in the anode plate is more realistic. Through iteration calculation of steady MHD equations, the temperature field, pressure field and velocity field profiles are given. The result is of significant use to analysis thermal and control the electric power in the arc industrial applications.

Numerical Simulation of Natural Convection in a Vertical Conical Cylinder Partially Annular Space

The present paper is dedicated to the numerical simulation of thermal convection in a two dimensional vertical conical cylinder partially annular space. The governing equations of mass, momentum and energy are solved using the CFD FLUENT code. The results of streamlines and the isotherms of the fluid are discussed for different annuli with various boundary conditions and Rayleigh numbers. Emphasis was put on the height of the inner vertical cylinder influence on the flow and the temperature distribution. More, the effects on the heat transfer are analyzed for different values of the fluid’s physical parameters in the annulus geometry. The heat transfer on the hot wall of the annulus is also computed in order to make comparisons the cylinder annulus for boundary conditions and several Rayleigh numbers. The obtained results in terms of Nusselt number has been found between the present previsions and available data from the published literature data.

System–CFD coupled simulations of flow instability in steam generator U tubes

The transient behavior of flow instability in SG U tubes is simulated numerically by performing system–CFD coupled simulations. The system analysis code RELAP5 is used to simulate the overall system behavior in the test facility, which consists of the heating loop and the model SG, and the commercial CFD code FLUENT is used to simulate detailed flow phenomena in the model SG. The flow conditions obtained by RELAP5 are used as the boundary conditions for FLUENT, and the calculated results by FLUENT are used for RELAP5. The flow instability with temperature fluctuation observed experimentally in the long U tube is simulated well, and the downward flow is shown to occur simultaneously with the upward flow in one U tube.

CFD simulation of air–steam flow with condensation

This article presents a custom condensation model for commercial CFD code Fluent. The condensation model was developed for the species transport model in Fluent code and it is suitable for both compressible and incompressible flow of air–steam mixture with additional non-condensable gases. The condensation model consists of two parts: condensation in volume and condensation on the wall. Condensation in volume is modeled by “return to saturation in constant time scale” method. Condensation on the wall is calculated from diffusion of steam through a layer of non-condensable gases near the wall.The performance of the condensation model was tested on the CONAN experiments. In these experiments, air–steam mixture flows downwards through a vertical channel with square cross section. One vertical wall of the channel is cooled and the steam condenses on it. The same model was then applied in simulation of PANDA Test 9bis experiment with condensation. In this test, two vessels connected with a pipe were filled with air; and steam was released into the first vessel. As the steam concentration increased in the vessels, the steam started condensing on the walls. The results of CFD simulations of both CONAN and PANDA experiments compared well with the measured data.

Coupling CFD code with system code and neutron kinetic code

The aim of this work was to develop the coupling interface between CFD code Fluent and system code Athlet internally coupled with neutron kinetic code Dyn3D. The coupling interface is intended for simulation of complex transients such as Main Steam Line Break scenarios, which cannot be modeled separately first by system and neutron kinetic code and then by CFD code, because of the feedback between the codes. In the first part of this article, the coupling method is described. Explicit coupling of overlapped computational domains is used in this work. The second part of the article presents a demonstration simulation performed by the coupled system of Athlet/Dyn3D and Fluent. The “Opening a Steam Dump to the Atmosphere” test carried out at the Temelin NPP (VVER-1000) was simulated by the coupled system. In this simulation, the primary and secondary circuits were modeled by Athlet, mixing in downcomer and lower plenum was simulated by Fluent and heat generation in the core was calculated by Dyn3D. The results of the simulation with Athlet/Dyn3D+Fluent were compared with the experimental data and the results from a calculation performed with Athlet/Dyn3D without Fluent.

CFD code benchmark against the air/helium tests performed in the MISTRA facility

The behaviour of hydrogen mixing and distribution has always been an important safety issue and the hydrogen distribution studies gained importance especially after Fukushima accident. The hydrogen generated due to metal water reaction releases into the containment and may get stratified locally under accident conditions. The stratification of hydrogen may be eroded by diffusion or by other means. CFD codes are increasingly being used for hydrogen distribution analysis and need to be validated before applying it to full scale containment simulations. In this context, the CFD code FLUENT is validated against the experiment conducted in the MISTRA facility on stratification and erosion behaviour. This paper deals with the validation of the CFD code FLUENT against the experiment conducted in MISTRA facility to study the stratification behaviour. Turbulence model sensitivity was carried out to identify the best suited turbulence model.

Transient Simulations of Spouted Fluidized Bed for Coal-Direct Chemical Looping Combustion

Chemical-looping combustion holds significant promise as one of the next generation combustion technology for high-efficiency low-cost carbon capture from fossil fuel power plants. For thorough understanding of the chemical-looping combustion process and its successful implementation in CLC based industrial scale power plants, the development of high-fidelity modeling and simulation tools becomes essential for analysis and evaluation of efficient and cost-effective designs. In this paper, multiphase flow simulations of coal-direct chemical-looping combustion process are performed using ANSYS Fluent CFD code. The details of solid–gas two-phase hydrodynamics in the CLC process are investigated by employing the Lagrangian particle-tracking approach called the discrete element method (DEM) for the movement and interaction of solid coal particles moving inside the gaseous medium created due to the combustion of coal particles with an oxidizer. The CFD/DEM simulations show excellent agreement with the experimental results obtained in a laboratory scale fuel reactor in cold flow conditions. More importantly, simulations provide important insights for making changes in fuel reactor configuration design that have resulted in significantly enhanced performance.

Implementation and validation of the condensation model for containment hydrogen distribution studies

This paper aims at the implementation details of a condensation model in the CFD code FLUENT and its validation so that it can be used in performing the containment hydrogen distribution studies. In such studies, computational fluid dynamics simulations are necessary for obtaining accurate predictions. While steam condensation plays an important role, commercial CFD codes such as FLUENT do not have an in-built condensation model. Therefore, a condensation model was developed and implemented in the FLUENT code through user defined functions (UDFs) for the sink terms in the mass, momentum, energy and species balance equations together with associated turbulence quantities viz., kinetic energy and dissipation rate. The implemented model was validated against the ISP-47 test of TOSQAN facility using the standard wall functions and enhanced wall treatment approaches. The best suitable grid size and the turbulence model for the low density gas (He) distribution studies are brought out in this paper.

The Optimal Hydraulic Design of Centrifugal Impeller Using Genetic Algorithm with BVF

Derived from idea of combining the advantages of two-dimensional hydraulic design theory, genetic algorithm, and boundary vorticity flux diagnosis, an optimal hydraulic design method of centrifugal pump impeller was developed. Given design parameters, the desired optimal centrifugal impeller can be obtained after several iterations by this method. Another 5 impellers with the same parameters were also designed by using single arc, double arcs, triple arcs, logarithmic spiral, and linear-variable angle spiral as blade profiles to make comparisons. Using Reynolds averaged N-S equations with a RNGk-εtwo-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the flow channel between blades of 6 designed impellers by CFD code FLUENT, the investigation on velocity distributions, pressure distributions, boundary vorticity flux distributions on blade surfaces, and hydraulic performance of impellers was presented and the comparisons of impellers by different design methods were demonstrated. The results showed that the hydraulic performance of impeller designed by this method is much better than the other 5 impellers under design operation condition with almost the same head, higher efficiency, and lower rotating torque, which implied less hydraulic loss and energy consumption.

Performance Enhancement of the In-Line Fan Equipped with the Guiding Vane and the Tail Body

This integrated numerical and experimental study intends to enhance the performance of an in-line fan with the implement of the guiding vane and the tail body. At first the flow flied associated with the original in-line fan is simulated and analyzed within the framework of CFD code Fluent, in which the finite volume method is applied. Next, the guiding vane is constructed based on the calculated flow characteristics, and attached in the downstream of rotor to smoothen the flow pattern. An appropriate guiding vane with high-performance and low-noise features can be achieved after several design iterations. In addition, the tail body connected to the motor is introduced for further enhancing the fan performance by reducing the sizes of wake and reversed flow behind the hub. Thereafter, to manufacture the mockup for experimental verification, the modified fan with guiding vane is plotted in the CAD/CAM format for mockup fabrication via the rapid-prototype technique. Moreover, a set of relations correlating the performance and noise of this fan prototype are executed inside AMCA test chamber and semianechoic chamber, respectively. Consequently, the feasibility of design scheme and numerical system can be verified according to these experimental results. In summary, this work provides a systematic scheme for designing and analyzing the in-line fan.

Analysis of Turbulent Flow over a 90° Bend of Duct Using In Centralized A. C. Plant by CFD Code

*Corresponding Author: mukeshdidwania4u@gmail.com Abstract: This test case was calculated using a commercial finite volume CFD computer code ANSYS 12.0 Fluent. The geometry of Model is a three-dimensional turbulent flow over a 90° bend. Experimental setup comprising an open-circuit suction wind tunnel system for the 90° bend which is used in ducting of centralized A. C. plant in various buildings or Malls. This test case focuses on the use of approximate models such as the turbulence models to predict the physical characteristics of the turbulent flow around a 90° bend. The results from the more sophisticated Reynolds stress model are shown to better capture the anisotropy behavior of the flow in contrast to the standard k-e model that assumes isotropy in its original model formulation and also k-w SST model use to comparison. Finite Volume Discretization (FVM) is employed to approximate the governing equation. Velocity and pressure distribution at bend show by simulation of fluent CFD Code. By increasing the bend length in duct, losses can be reduce.

철도 방음벽의 형상에 따른 태양복사 에너지 흡수 특성 연구

The present study aims to determine the optimized shape for the maximum electric energy production of building integrated photovoltaic system (BIPV) noise barrier through numerical analysis. The shape of BIPV noise barrier is one of the important factors in determining angle difference between direction vector of the sun and normal vector of the sound barrier surface. This study simulated numerically the flow and thermal fields for different angles in the range from <TEX>$90^{\circ}$</TEX> to <TEX>$180^{\circ}$</TEX>, and from the results, the amount of isolation onto noise barrier surface was estimated along the angle between ground and top side of noise barrier. The commercial CFD code (Fluent V. 13.0) was used for calculation. It was found that the maximum amount of insolation per unit area was 19.6 MJ for <TEX>$105^{\circ}$</TEX> case during a day in summer and was estimated 12.4 MJ in <TEX>$150^{\circ}$</TEX> case during a day in winter. The results of the summer and winter cases showed the different tendency and this result would be useful in determining the appropriate shape of noise barrier which can be mounted under various circumstances.

Numerical prediction of air flow within street canyons based on different two-equation k-ε models

Numerical simulations on airflow within street canyons were performed to investigate the effect of the street aspect ratio and wind speed on velocity profiles inside a street canyon. Three-dimensional Standard, Renormalization Group (RNG) and Realizable k-ε turbulence model are employed using the commercial CFD code FLUENT to solve the Reynolds-averaged Navier-Stokes (RANS) equations. A comparison of the results from the presently adopted models with those previously published demonstrated that the k-e model is most reliable when simulating wind flow. The model is then employed to predict the flow structures in a street canyon for a range of aspect ratios (building height to street width ratio) between 0.5 – 2 at Reynolds number of 9000, 19200 and 30700 corresponding to the ambient wind speeds of 0.68m/s, 1.46m/s and 2.32m/s respectively. It is observed that the flow structure in the street canyon is influenced by the buildings aspect ratios and prevailing wind speeds. As the street aspect ratio increases, the air ventilation within the canyon reduces.

An Integrated CFD and Experimental Study of the In-Line Fan

This study analyzes the flow flied and the guide vane associated with an in-line fan by an integrated numerical and experimental investigation. At first, the flow field associated with the fan is simulated by using a commercial CFD code Fluent with the finite volume method. In addition, the guiding vane profile is imposed and modified by examining characteristics of flow field. An appropriate guiding vane with high-performance and low-noise feature can be achieved after several design iterations. To manufacture the mock-up for experimental verification, the designed fan is expressed in the CAD/CAM format for the rapid-prototype technique. Moreover, a set of relations correlating the performance and noise of this fan prototype are executed with the aids of AMCA test chamber and semi-anechoic chamber, respectively. Consequently, the feasibility of design scheme and numerical system can be verified according to these experimental results. In summary, this work provides a systematic scheme for designing and analyzing the in-line fan.

Effect of Pressure Ratio on Film Cooling of Turbine Aerofoil Using CFD

Gas turbine blades are cooled internally and externally and one widely used blade cooling technique is film cooling. In this type of cooling, relatively cool air is injected from the inside of the blade to the outside surface which forms a protective layer between the blade surface and hot gas streams. The present study is an attempt to establish the effect of blowing ratio and pressure ratio numerically on film cooling effectiveness in a typical nozzle guide vane with single hole on both pressure and suction surface of the vane. The commercially available CFD code FLUENT has been used after validating it against the experimental results reported in literature. Pressure ratio was varied from 1.1 to 1.2 with density ratio 2.0. Results obtained from the numerical investigation show that with increase in pressure ratio at constant blowing ratio, there was an increase in film cooling effectiveness. It is found that film spread is more on the pressure side as compared to suction side.