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Journal articles on the topic 'K-epsilon turbulence modeling'
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1
Mansour, N. N., J. Kim, and P. Moin. "Near-wall k-epsilon turbulence modeling." AIAA Journal 27, no. 8 (1989): 1068–73. http://dx.doi.org/10.2514/3.10222.
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YAMAKAWA, Masanori, and Shinichi INAGE. "Modeling of k-.EPSILON. Turbulence Model by Statistical Turbulence Theory and its Applications." Transactions of the Japan Society of Mechanical Engineers Series B 57, no. 544 (1991): 4072–79. http://dx.doi.org/10.1299/kikaib.57.4072.
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LEE, Young Jae, and Yoshiaki ONUMA. "Modeling of turbulent jet diffusion flames. 1st Report, modification of k-.EPSILON. turbulence model with isothermal hot air jets." Transactions of the Japan Society of Mechanical Engineers Series B 56, no. 532 (1990): 3921–27. http://dx.doi.org/10.1299/kikaib.56.3921.
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Menni, Younes, Ahmed Azzi, and A. Chamkha. "Modeling and analysis of solar air channels with attachments of different shapes." International Journal of Numerical Methods for Heat & Fluid Flow 29, no. 5 (2019): 1815–45. http://dx.doi.org/10.1108/hff-08-2018-0435.
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Purpose This paper aims to report the results of numerical analysis of turbulent fluid flow and forced-convection heat transfer in solar air channels with baffle-type attachments of various shapes. The effect of reconfiguring baffle geometry on the local and average heat transfer coefficients and pressure drop measurements in the whole domain investigated at constant surface temperature condition along the top and bottom channels’ walls is studied by comparing 15 forms of the baffle, which are simple (flat rectangular), triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, double V (or W), Z, T, G and epsilon (or e)-shaped, with the Reynolds number changing from 12,000 to 32,000. Design/methodology/approach The baffled channel flow model is controlled by the Reynolds-averaged Navier–Stokes equations, besides the k-epsilon (or k-e) turbulence model and the energy equation. The finite volume method, by means of commercial computational fluid dynamics software FLUENT is used in this research work. Findings Over the range investigated, the Z-shaped baffle gives a higher thermal enhancement factor than with simple, triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, W, T, G and e-shaped baffles by about 3.569-20.809; 3.696-20.127; 3.916-20.498; 1.834-12.154; 1.758-12.107; 7.272-23.333; 6.509-22.965; 8.917-26.463; 8.257-23.759; 5.513-18.960; 8.331-27.016; 7.520-26.592; 6.452-24.324; and 0.637-17.139 per cent, respectively. Thus, the baffle of Z-geometry is considered as the best modern model of obstacles to significantly improve the dynamic and thermal performance of the turbulent airflow within the solar channel. Originality/value This analysis reports an interesting strategy to enhance thermal transfer in solar air channels by use of attachments with various shapes
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Korpus, R. A., and J. M. Falzarano. "Prediction of Viscous Ship Roll Damping by Unsteady Navier-Stokes Techniques." Journal of Offshore Mechanics and Arctic Engineering 119, no. 2 (1997): 108–13. http://dx.doi.org/10.1115/1.2829050.
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This paper describes a numerical technique for analyzing the viscous unsteady flow around oscillating ship hulls. The technique is based on a general Reynolds-averaged Navier-Stokes (RANS) capability, and is intended to generate viscous roll moment data for the incorporation of real-flow effects into potential flow ship motions programs. The approach utilizes the finite analytic technique for discretizing the unsteady RANS equations, and a variety of advanced turbulence models for closure. The calculations presented herein focus on viscous and vortical effects without free-surface, and utilize k-epsilon turbulence modeling. Series variations are presented to study the effects of frequency, amplitude, Reynolds number, and the presence of bilge keels. Moment component breakdown studies are performed in each case to isolate the effects of viscosity, vorticity, and potential flow pressures.
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Han, Fenglei, Jingzheng Yao, Chunhui Wang, and Haitao Zhu. "Bow Flare Water Entry Impact Prediction and Simulation Based on Moving Particle Semi-Implicit Turbulence Method." Shock and Vibration 2018 (2018): 1–16. http://dx.doi.org/10.1155/2018/7890892.
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Prandtl’s mixing length method and the k-epsilon method are introduced into the Moving Particle Semi-Implicit (MPS) method for the purpose of modeling turbulence effects associated with water entries of two-dimensional (2D) bow flare section. The presented numerical method is validated by comparing its numerical prediction with experimental data and other numerical results obtained from the Boundary Element Method (BEM). The time histories of the pressure and the vertical slamming force acting on the dropping ship section subjected to various conditions with different dropping velocity and inclined angles are analyzed. The results show that both the pressure and the vertical slamming force are in good agreement with the experimental data.
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López, Juan A., Marco A. Ramírez-Argáez, Adrián M. Amaro-Villeda, and Carlos González. "Mathematical and Physical Modeling of Three-Phase Gas-Stirred Ladles." MRS Proceedings 1812 (2016): 29–34. http://dx.doi.org/10.1557/opl.2016.14.
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ABSTRACTA very realistic 1:17 scale physical model of a 140-ton gas-stirred industrial steel ladle was used to evaluate flow patterns measured by Particle Image Velocimetry (PIV), considering a three-phase system (air-water-oil) to simulate the argon-steel-slag system and to quantify the effect of the slag layer on the flow patterns. The flow patterns were evaluated for a single injector located at the center of the ladle bottom with a gas flow rate of 2.85 l/min, with the presence of a slag phase with a thickness of 0.0066 m. The experimental results obtained in this work are in excellent agreement with the trends reported in the literature for these gas-stirred ladles. Additionally, a mathematical model was developed in a 2D gas-stirred ladle considering the three-phase system built in the physical model. The model was based on the Eulerian approach in which the continuity and the Navier Stokes equations are solved for each phase. Therefore, there were three continuity and six Navier-Stokes equations in the system. Additionally, turbulence in the ladle was computed by using the standard k-epsilon turbulent model. The agreement between numerical simulations and experiments was excellent with respect to velocity fields and turbulent structure, which sets the basis for future works on process analysis with the developed mathematical model, since there are only a few three-phase models reported so far in the literature to predict fluid dynamics in gas-stirred steel ladles.
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Guevara-Luna, Marco Andrés, and Luis Carlos Belalcázar-Cerón. "NGL supersonic separator: modeling, improvement, and validation and adjustment of k-epsilon RNG modified for swirl flow turbulence model." Revista Facultad de Ingeniería Universidad de Antioquia, no. 82 (March 2017): 82–93. http://dx.doi.org/10.17533/udea.redin.n82a11.
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Sedej, Owen, and Eric Mbonimpa. "CFD Modeling of a Lab-Scale Microwave Plasma Reactor for Waste-to-Energy Applications: A Review." Gases 1, no. 3 (2021): 133–47. http://dx.doi.org/10.3390/gases1030011.
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Rapidly increasing solid waste generation and energy demand are two critical issues of the current century. Plasma gasification, a type of waste-to-energy (WtE) technology, has the potential to produce clean energy from waste and safely destroy hazardous waste. Among plasma gasification technologies, microwave (MW)-driven plasma offers numerous potential advantages to be scaled as a leading WtE technology if its processes are well understood and optimized. This paper reviews studies on modeling experimental microwave-induced plasma gasification systems. The system characterization requires developing mathematical models to describe the multiphysics phenomena within the reactor. The injection of plasma-forming gases and carrier gases, the rate of the waste stream, and the operational power heavily influence the initiation of various chemical reactions that produce syngas. The type and kinetics of the chemical reactions taking place are primarily influenced by either the turbulence or temperature. Navier–Stokes equations are used to describe the mass, momentum, and energy transfer, and the k-epsilon model is often used to describe the turbulence within the reactor. Computational fluid dynamics software offers the ability to solve these multiphysics mathematical models efficiently and accurately.
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Alvarado, Yolitzin, Rosenberg Romero, Juan Carlos García, Adrian del Pozo, Roberto Zenit, and Sergio Alonso Serna. "Using CFD and PIV to investigate rotating cage-related hydrodynamics for CO2 corrosion studies analyzing 2-, 4- and 8-coupons setups." Anti-Corrosion Methods and Materials 66, no. 6 (2019): 802–11. http://dx.doi.org/10.1108/acmm-09-2017-1836.
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Purpose The purpose of this study is to evaluate the corrosion in CO2 using Rotating cage (RC) and Computational fluid dynamics (CFD) software. RC experiments were carried out in a CO2 environment, to evaluate corrosion in a C-Mn Steel. CFD software was used to simulate RC flow conditions during the corrosion process, to evaluate wall shear stress. Design/methodology/approach The RC is used as a laboratory tool for studies of accelerated corrosion, according to standard ASTM G184-06. Steel corrosion was studied by means of the RC methodology. The hydrodynamics are solved numerically using CFD. Numerical calculations were performed on a 2D geometry of 8 coupons JG, for speeds of 460 and 230 rpm. The flow was analyzed with vector graphics and velocity profiles. The numerical calculations were validated with experimental measurements of the velocity field obtained with the technique of Particle Image Velocimetry (PIV). Findings Different turbulence models were used, in which CFD simulations were compared with data obtained from PIV. According to this comparison, the best turbulence model was determined. Originality/value It was found that experimental flow speeds have closer values with Spalart–Allmaras modeling than K-epsilon and K-kl-omega.
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Delgado-Álvarez, J. A., J. G. Perea-Zurita, A. Antonio-Morales, C. González-Rivera, and M. A. Ramírez-Argáez. "Mathematical modeling of the fluid flow in a mixing device for melting/dissolving solid particles in a liquid alloy." MRS Proceedings 1611 (2014): 19–24. http://dx.doi.org/10.1557/opl.2014.752.
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ABSTRACTA study of the fluid flow in a mixing device proposed to dissolve alloying elements in iron baths is performed through a mathematical model in order to predict the best operating conditions for a proper melting/dissolution of solid alloying particles. The mathematical model consists in the mass and momentum conservation equations (continuity and Turbulent Navier-Stokes equations), and the standard two k-epsilon turbulence model. The model is numerically solved in transient regime with the Volume of Fluid algorithm (VOF) to calculate the vortex shape. VOF is built-in the CFD (Computational Fluid Dynamics) software ANSYS FLUENT 14. A flow of metal enters tangentially in the mixing chamber of the proposed mixing device (taken from an open patent) to generate a vortex. The shape and height of the vortex reached in this chamber depends on several design variables, but in this work only the presence or absence of a barrier in the device is analyzed. Results are obtained on the vortex sizes and shapes, liquid flow patterns, turbulent structure, residence times of the particles of alloying elements added to the melt and mixing times (Residence time distribution curves) of two devices: one with a barrier and the other without this barrier. It is found that the presence of the barrier in the device increases turbulence, destroys the vortex, decreases the residence time of the particles, and decreases the volume of fluid in the device. Most of the features of the barrier are detrimental for mixing and inhibits melting/dissolution of the alloying elements. Then, it is suggested a device without the presence of barrier for better performance.
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Bennaya, Mohamed, Jing Feng Gong, Moutaz M. Hegaze, and Wen Ping Zhang. "Numerical Simulation of Marine Propeller Hydrodynamic Performance in Uniform Inflow with Different Turbulence Models." Applied Mechanics and Materials 389 (August 2013): 1019–25. http://dx.doi.org/10.4028/www.scientific.net/amm.389.1019.
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In general, marine propellers have complicated geometries and as a consequence complicated flow around propeller. The aim of this work is to find an appropriate method and assess the turbulence model to approach the open water hydrodynamic characteristics of the marine propellers. In this work, a numerical modeling using a finite volume commercial code (FVM) for different turbulence models has been applied on the well known conventional screw propeller DTRC P4119. The 3-D solid model of P4119 is established using pro/E software and for the mesh generation ANSYS-ICEM has been used. Steady Reynolds-Averaged Navier Stokes (RANS) simulations are accomplished using FLUENT software with unstructured mesh in the rotating computational domain and structured mesh for the rest of the domain. The open water performance coefficients, thrust (KT), torque (KQ) and efficiency (η) have been calculated and compared with available experimental data to assess the applicability of different turbulence models for the open water study of propeller. This paper shows that, the accuracy of the CFD based on RANS equations is dependent on the used turbulence model and the RNG K-epsilon turbulence model yields to provide the most accurate results. Also, all the turbulence models via FLUENT software behave the same behavior for the total span of the advance coefficient (J) with two types of result accuracy. All the turbulence models shows high accuracy at low advance coefficient and this accuracy decreases but with an acceptable error till it decreases suddenly at the maximum advance coefficient.
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Henaoui, Mustapha, and Khaled Aliane. "Air Behavior Inside Duct of Air Solar Collector with Three Models of Baffles." Algerian Journal of Renewable Energy and Sustainable Development 2, no. 01 (2020): 28–33. http://dx.doi.org/10.46657/ajresd.2020.2.1.4.
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The objective of this work is to study numerically the effect of the geometry of the baffles on the heat exchange in a solar air collector. Three models of collector were used in this study, fitted with simple baffles and perforated baffles. Fluid dynamics calculation (CFD) tool has been used to simulate the geometries of the solar collectors. Its three models involving air intake, are modeled by the FLUENT6.3 software and the grids were created with the Gambit software. The shape of the perforations is in the forms strips perforated in the baffles. The numerical resolution uses the finite volume method and the turbulence modeling K-Epsilon. The results have been validated by previous work and the simulation results are in terms of the evolution of the axial velocity and temperature distribution for the three models.
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Lvov, Vladislav, and Leonid Chitalov. "Semi-Autogenous Wet Grinding Modeling with CFD-DEM." Minerals 11, no. 5 (2021): 485. http://dx.doi.org/10.3390/min11050485.
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The paper highlights the features of constructing a model of a wet semi-autogenous grinding mill based on the discrete element method and computational fluid dynamics. The model was built using Rocky DEM (v. 4.4.2, ESSS, Brazil) and Ansys Fluent (v. 2020 R2, Ansys, Inc., United States) software. A list of assumptions and boundary conditions necessary for modeling the process of wet semi-autogenous grinding by the finite element method is presented. The created model makes it possible to determine the energy-coarseness ratios of the semi-autogenous grinding (SAG) process under given conditions. To create the model in Rocky DEM the following models were used: The Linear Spring Rolling Limit rolling model, the Hysteretic Linear Spring model of the normal interaction forces and the Linear Spring Coulomb Limit for tangential forces. When constructing multiphase in Ansys Fluent, the Euler model was used with the primary phase in the form of a pulp with a given viscosity and density, and secondary phases in the form of air, crushing bodies and ore particles. The resistance of the solid phase to air and water was described by the Schiller–Naumann model, and viscosity by the realizable k-epsilon model with a dispersed multiphase turbulence model. The results of the work methods for material interaction coefficients determination were developed. A method for calculating the efficiency of the semi-autogenous grinding process based on the results of numerical simulation by the discrete element method is proposed.
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Larbi, Ahmed Amine, Abdelhamid Bounif, and Mohamed Bouzit. "Modeling and numerical study of H2/N2 jet flame in vitiated co-flow using Eulerian PDF transport approach." Mechanics & Industry 19, no. 5 (2018): 504. http://dx.doi.org/10.1051/meca/2018029.
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The multi-environment Eulerian approach (MEPDF) is the eulerian method to solve the PDF transport equations; it is considered a product of the delta function. Its advantages are the prediction of extinction and ignition of the flame, also the kinetic control of the species as CO and NOX. Even though the MEPDF approach has been improved in recent years, most improvements have been achieved with parametric study in order to investigate the impact of the model accuracy. The main objective of this work is to improve further the model accuracy, the prediction of the lift off height by a parametric study of the mixing constant and Schmidt number and to understand its impact in flame stabilization. The numerical investigation of H2/N2 jet flame in vitiated co-flow is presented using MEPDF approach. The study was applied with K-epsilon modified model of turbulence. The chosen mixture model is the IEM (Interaction by Exchange with the Mean). The number of environment in the multi-environment Eulerian approach MEPDF is (2.0). The model was solved in this work by the commercial CFD code, ANSYS fluent and the chemical reaction mechanism injected is GRI mech 2.1. The results are validated with experimental data and discussed.
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Ramji, V., Raju Mukesh, and Inamul Hasan. "Design and Numerical Simulation of Convergent Divergent Nozzle." Applied Mechanics and Materials 852 (September 2016): 617–24. http://dx.doi.org/10.4028/www.scientific.net/amm.852.617.
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This works centers on the design of a De Laval (convergent - Divergent) nozzle to accelerate the flow to supersonic or hypersonic speeds and computational analysis of the same. An initial design of the nozzle is made from the method of characteristics. The coding was done in Matlab to obtain the contour of the divergent section for seven different exit Mach numbers viz. 2.5,3,3.5,4,4.5,5 and 5.5.To quantify variation in the minimum length of the nozzle divergent section with respect to the exit mach number, a throat of constant height (0.005m) and width (0.05m) was chosen for all the design. The area exit required for each mach no varying from 1 to 5.5 was plotted using isentropic relations and was also used to verify the exit area of the nozzle for each of those mach numbers. An estimate of the exit pressure ratio is obtained by using isentropic and normal shock relations. With this exit pressure ratio, a more refined verification is done by computational analysis using ANSYS Fluent software for a contour nozzle with exit Mach number 5.5. The spalart Allmaras and k-epsilon model were used for turbulence modeling.
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Hodapp, Maximilian J., Jhon J. Ramirez-Behainne, Milton Mori, and Leonardo Goldstein. "Numerical Studies of the Gas-Solid Hydrodynamics at High Temperature in the Riser of a Bench-Scale Circulating Fluidized Bed." International Journal of Chemical Engineering 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/786982.
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The hydrodynamics of circulating fluidized beds (CFBs) is a complex phenomenon that can drastically vary depending on operational setup and geometrical configuration. A research of the literature shows that studies for the prediction of key variables in CFB systems operating at high temperature still need to be implemented aiming at applications in energy conversion, such as combustion, gasification, or fast pyrolysis of solid fuels. In this work the computational fluid dynamics (CFD) technique was used for modeling and simulation of the hydrodynamics of a preheating gas-solid flow in a cylindrical bed section. For the CFD simulations, the two-fluid approach was used to represent the gas-solid flow with the k-epsilon turbulence model being applied for the gas phase and the kinetic theory of granular flow (KTGF) for the properties of the dispersed phase. The information obtained from a semiempirical model was used to implement the initial condition of the simulation. The CFD results were in accordance with experimental data obtained from a bench-scale CFB system and from predictions of the semiempirical model. The initial condition applied in this work was shown to be a viable alternative to a more common constant solid mass flux boundary condition.
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Toapanta-Ramos, Fernando, Luis González-Rojas, Elmo Calero, Bryan Calderón, and William Quitiaquez. "Numerical Study of a Helical Heat Exchanger for Wort Cooling in the Artisanal Beer Production Process." Revista Facultad de Ingeniería 29, no. 54 (2020): e11632. http://dx.doi.org/10.19053/01211129.v29.n54.2020.11632.
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The objective of the present work is to study the behavior of a helical tube and shell heat exchanger, for the cooling of the wort in the process of making craft beer with cold water, through the methodology of computational fluid dynamics (CFD) by finite volume models for heat exchanger modeling. This by using the ANSYS Fluent software, which allows to understand the behavior of the fluid through equations that describe their movement and behavior, using numerical methods and computational techniques. In the mesh convergence, two methods were used, orthogonality and obliquity, with which it was confirmed that the meshing is ideal in the simulations that were carried out. For the simulation, the k-epsilon turbulence model and the energy model were used. Through various simulations, it was obtained that by varying the mass flow, better results are reducing the outlet temperature, with a variation of 15.16 °C, while varying the inlet temperature of the water, there is just a variation from 2.71 °C to 0.01 °C. Therefore, a significant improvement in the performance of the heat exchanger was found. In the same way, it was confirmed that the number of spikes in the heat exchanger is adequate, since the outlet temperature would not be reached with less spikes.
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OKAMURA, Kiyoshi, and Toshihiro KITADA. "Modeling Study on the Parameterization of Sub-grid Scale Land Use Distribution for the Development of Atmospheric Boundary Layer. Expression of Urban Canopy in the k-.EPSILON. Turbulence Model." ENVIRONMENTAL SYSTEMS RESEARCH 25 (1997): 593–97. http://dx.doi.org/10.2208/proer1988.25.593.
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Karimpour, Farid, and Subhas K. Venayagamoorthy. "A revisit of the equilibrium assumption for predicting near-wall turbulence." Journal of Fluid Mechanics 760 (November 7, 2014): 304–12. http://dx.doi.org/10.1017/jfm.2014.532.
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AbstractIn this study, we revisit the consequence of assuming equilibrium between the rates of production ($P$) and dissipation $({\it\epsilon})$ of the turbulent kinetic energy $(k)$ in the highly anisotropic and inhomogeneous near-wall region. Analytical and dimensional arguments are made to determine the relevant scales inherent in the turbulent viscosity (${\it\nu}_{t}$) formulation of the standard $k{-}{\it\epsilon}$ model, which is one of the most widely used turbulence closure schemes. This turbulent viscosity formulation is developed by assuming equilibrium and use of the turbulent kinetic energy $(k)$ to infer the relevant velocity scale. We show that such turbulent viscosity formulations are not suitable for modelling near-wall turbulence. Furthermore, we use the turbulent viscosity $({\it\nu}_{t})$ formulation suggested by Durbin (Theor. Comput. Fluid Dyn., vol. 3, 1991, pp. 1–13) to highlight the appropriate scales that correctly capture the characteristic scales and behaviour of $P/{\it\epsilon}$ in the near-wall region. We also show that the anisotropic Reynolds stress ($\overline{u^{\prime }v^{\prime }}$) is correlated with the wall-normal, isotropic Reynolds stress ($\overline{v^{\prime 2}}$) as $-\overline{u^{\prime }v^{\prime }}=c_{{\it\mu}}^{\prime }(ST_{L})(\overline{v^{\prime 2}})$, where $S$ is the mean shear rate, $T_{L}=k/{\it\epsilon}$ is the turbulence (decay) time scale and $c_{{\it\mu}}^{\prime }$ is a universal constant. ‘A priori’ tests are performed to assess the validity of the propositions using the direct numerical simulation (DNS) data of unstratified channel flow of Hoyas & Jiménez (Phys. Fluids, vol. 18, 2006, 011702). The comparisons with the data are excellent and confirm our findings.
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Karimpour, Farid, and Subhas K. Venayagamoorthy. "Some insights for the prediction of near-wall turbulence." Journal of Fluid Mechanics 723 (April 16, 2013): 126–39. http://dx.doi.org/10.1017/jfm.2013.117.
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AbstractIn this paper, we revisit the eddy viscosity formulation to highlight a number of important issues that have direct implications for the prediction of near-wall turbulence. For steady wall-bounded turbulent flows, we make the equilibrium assumption between rates of production ($P$) and dissipation ($\epsilon $) of turbulent kinetic energy ($k$) in the near-wall region to propose that the eddy viscosity should be given by ${\nu }_{t} \approx \epsilon / {S}^{2} $, where $S$ is the mean shear rate. We then argue that the appropriate velocity scale is given by $\mathop{(S{T}_{L} )}\nolimits ^{- 1/ 2} {k}^{1/ 2} $ where ${T}_{L} = k/ \epsilon $ is the turbulence (decay) time scale. The difference between this velocity scale and the commonly assumed velocity scale of ${k}^{1/ 2} $ is subtle but the consequences are significant for near-wall effects. We then extend our discussion to show that the fundamental length and time scales that capture the near-wall behaviour in wall-bounded shear flows are the shear mixing length scale ${L}_{S} = \mathop{(\epsilon / {S}^{3} )}\nolimits ^{1/ 2} $ and the mean shear time scale $1/ S$, respectively. With these appropriate length and time scales (or equivalently velocity and time scales), the eddy viscosity can be rewritten in the familiar form of the $k$–$\epsilon $ model as ${\nu }_{t} = \mathop{(1/ S{T}_{L} )}\nolimits ^{2} {k}^{2} / \epsilon $. We use the direct numerical simulation (DNS) data of turbulent channel flow of Hoyas & Jiménez (Phys. Fluids, vol. 18, 2006, 011702) and the turbulent boundary layer flow of Jiménez et al. (J. Fluid Mech. vol. 657, 2010, pp. 335–360) to perform ‘a priori’ tests to check the validity of the revised eddy viscosity formulation. The comparisons with the exact computations from the DNS data are remarkable and highlight how well the equilibrium assumption holds in the near-wall region. These findings could prove to be useful in near-wall modelling of turbulent flows.
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Viollet, P. L., and O. Simonin. "Modelling Dispersed Two-Phase Flows: Closure, Validation and Software Development." Applied Mechanics Reviews 47, no. 6S (1994): S80—S84. http://dx.doi.org/10.1115/1.3124445.
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Closure for the Eulerian modelling of two-phase flows have been developed, based upon extensions of the theory of Tchen of the dispersion of particles in homogeneous turbulence. This model has been validated using large-eddy simulation of homogeneous turbulence, jets loaded with particles, and bubbly flows. In addition with k-epsilon model for the continuous phase, and closures for the Reynolds stresses of the dispersed phase, this theory has been implemented in 2D and 3D software solving the Eulerian two-phase equations (Me´lodif in 2D, as a research code, and ESTET-ASTRID in 3D). These softwares have been applied to complex situations of industrial interest.
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Hodapp, Maximilian Joachim, Eduardo de Paula Kirinus, Wiliam Correa Marques, Phelype Haron Oleinik, and Osmar Olinto Moller. "Investigation of persistent coherent structures along the Southern Brazilian Shelf." Brazilian Journal of Oceanography 66, no. 2 (2018): 199–209. http://dx.doi.org/10.1590/s1679-87592018005906602.
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Abstract The freshwater-influenced region of the Patos Lagoon discharge to the Southern Brazilian Shelf (SBS) is a region of complex fluid dynamics. Seasoning and synoptic variable winds and coastal current conditions create an alternating flow pattern. The aim of this paper was to investigate the occurrence of persistent coherent structures in this environment. A numerical approach was chosen to describe the main hydrodynamic features of the region during a climatological year. The open-source finite-element code Telemac-Mascaret was applied to the three-dimensional domain. In addition the two-equation k-epsilon model described the turbulence mechanisms. The presence of persistent high-turbulent structures was identified within the study area. These occur as a strong curvilinear disturbance characterized by higher turbulent production and dissipation rates, which increase local mixture. As a result, upward circulation flow was observed, which may be due to irregularities in bottom topography associated with wind-induced stress forces. These results increase the information about the circulation structures of the study area by means of numerical modelling analysis.
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Sundararaj, Aldin Justin, B. C. Pillai, Austin Lord Tennyson, Allison Edward, and Bhaskar Gupta. "Numerical Investigation of Convective Heat Transfer of Refined Kerosene-Alumina Nanofluid Under Laminar and Turbulent Regime." Advanced Science Letters 24, no. 8 (2018): 5543–47. http://dx.doi.org/10.1166/asl.2018.12145.
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The study reports Computational Fluid Dynamics (CFD) investigations of the convective heat transfer coefficient of Al2O3/refined kerosene nanofluids. The study was carried out under laminar and turbulent regime in a circular tube under uniform and constant heat flux on the wall. The study was carried out for Re 500 to 5500 for base refined kerosene and with alumina added with 0.01% and 0.05% volume concentration in the base refined kerosene. The size of the alumina nanoparticle was 35 nm. Different computational models of Ansys-Fluent were used for the study. For laminar flows, laminar viscous models and K-Epsilon model for turbulence modelling was used. Energy model was used to define convective heat transfer and a discrete phase model to study particle behaviour and flow pattern in the tube. Multi-phase model with two phase refined kerosene suspended with alumina nano particles were used for the study. Experimental and simulation results showed that as the Reynolds number and the particle concentration increased there was an enhancement in the thermal performance of nanofluids which was found to be higher than that of the base fluid. The convective heat transfer increased by 14% for volume concentration of 0.05% and Reynolds number of 5500.
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Pan, Qing Qing, Stein Tore Johansen, Mark Reed, and Lars Roar Satran. "CFD MODELING OF PNEUMATIC OIL BARRIER." International Oil Spill Conference Proceedings 2014, no. 1 (2014): 300087. http://dx.doi.org/10.7901/2169-3358-2014-1-300087.1.
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Pneumatic oil barriers (so called “bubble oil boom (BOB)”) are based on the rise of air bubbles which are injected from the submerged parallel line spargers (McClimans et al., 2012). Local outward flows are formed when the bubbles and entrained water reach the sea surface, and thereby could counterbalance the opposing sea current to retain the spilled oil. It could function alone or work together with a traditional oil boom to improve the recovery effectiveness. A multiphase Computational Fluid Dynamic model, which couples volume of fluid (VOF) and discrete phase model (DPM) approach together with an enhanced k-epsilon model, is developed. Trajectories of bubbles are computed in the Lagrangian frame of reference, exchanging momentum and turbulent energy with water and oil slick, represented in the Eulerian frame of reference. The interface between atmosphere, water and oil slick is captured by the VOF model. The model is applied to meso-scale experiments in McClimans et al. (2012) for validation. The validated numerical model can provide improved basis for the further design of BOB system.
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Lopez, G., A. C. Bennis, Y. Barbin, A. Sentchev, L. Benoit, and L. Marié. "Surface currents in the Alderney Race from high-frequency radar measurements and three-dimensional modelling." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2178 (2020): 20190494. http://dx.doi.org/10.1098/rsta.2019.0494.
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Two weeks of high-frequency radar measurements collected at the Alderney Race are compared with the results of a three-dimensional fully coupled wave–current model. Spatial current measurements are rare in this site, otherwise well investigated through modelling. Thus, the radar measurements offer a unique opportunity to examine the spatial reliability of numerical results, and can help to improve our understanding of the complex currents in the area. Comparison of observed and modelled surface current velocities showed a good agreement between the methods, represented by root mean squared errors ranging from 14 to 40 cm s −1 and from 18 to 60 cm s −1 during neap and spring tides, respectively. Maximum errors were found in shallow regions with consistently high current velocities, represented by mean neap and spring magnitudes of 1.25 m s −1 and 2.7 m s −1 , respectively. Part of the differences between modelled and observed surface currents in these areas are thought to derive from limitations in the k-epsilon turbulence model used to simulate vertical mixing, when the horizontal turbulent transport is high. In addition, radar radial currents showed increased variance over the same regions, and might also be contributing to the discrepancies found. Correlation analyses yielded magnitudes above 0.95 over the entire study area, with better agreement during spring than during neap tides, probably because of an increase in the phase lag between radar and model velocities during the latter. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.
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Agarwal, Abhishek. "Modelling & Numerical Investigation of the Effectiveness of Plate Heat Exchanger for Cooling Engine Oil Using ANSYS CFX." International Journal of Heat and Technology 39, no. 2 (2021): 653–58. http://dx.doi.org/10.18280/ijht.390237.
Full textAbstract:
Heat exchangers are used for various industrial application for transfer of enthalpy from hot fluid to cold. One of them is Plate Heat Exchanger which finds its application in evaporating systems. The compactness, high effectiveness and easy maintenance of Plate Heat Exchanger makes it best choice for process industries. The current research investigates the application of Plate Heat Exchanger in cooling of engine oil using techniques of Computational Fluid Dynamics for low, medium and high Reynolds number using ANSYS CFX software. The CAD model is developed using Creo design software and turbulence model used for analysis is RNG k-epsilon which gives good predictions for complex flows involving swirls. The CFD analysis is conducted for different values of Reynolds number. The temperature distribution, effectiveness and overall heat transfer coefficient is determined for different values of Reynolds number.
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Tyack, J. N., and R. A. Fenner. "Computational fluid dynamics modelling of velocity profiles within a hydrodynamic separator." Water Science and Technology 39, no. 9 (1999): 169–76. http://dx.doi.org/10.2166/wst.1999.0469.
Full textAbstract:
To help improve the understanding of the process of hydrodynamic separation, a computational fluid dynamic model of a 1600 mm diameter prototype hydrodynamic separator has been developed. The separator was modelled without a baseflow and configured for grit removal in a manner typical of operation within a wastewater treatment works. Some simplifications were made to the complex geometry to reduce the number of elements in the mesh and the results discussed are based on a renormalisation group k-epsilon (RNG) turbulence model. Experimental 3-components velocity measurements were made in a physical prototype separator operating under similar conditions, and these were found to be of a similar order to those predicted in the CFD model thus giving confidence in the results. The CFD model showed that the flow pattern in the separator is helical with secondary recirculation patterns. There is an asymmetrical flow pattern within the device due to the high velocities at the inlet causing skewing of the flow around the central shaft and cone. The paper illustrates that the high vertical velocities within the device permit only particles with a high settling velocity to be removed, with the fine suspended solids (mostly organic) being passed forward for treatment in the wastewater treatment works.
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Hillebrand, G., I. Klassen, and N. R. B. Olsen. "3D CFD modelling of velocities and sediment transport in the Iffezheim hydropower reservoir." Hydrology Research 48, no. 1 (2016): 147–59. http://dx.doi.org/10.2166/nh.2016.197.
Full textAbstract:
The simulation of sediment transport by three-dimensional (3D) modelling is linked with the question of how accurate such models are. The current paper provides a test where detailed field measurements of velocities and bed elevation changes over a 3-month period from a prototype reservoir are compared with simulation results. The SSIIM software was used to compute water flow and sediment transport in the Iffezheim reservoir. The numerical model solved the Navier–Stokes equations on a 3D unstructured grid with dominantly hexahedral cells. The k-epsilon turbulence model was used, together with the SIMPLE method to find the pressure. The 3D convection–diffusion equation for suspended sediments was solved for nine sediment fractions. The computed velocity pattern showed good correspondence with the measurements. Grid sensitivity tests showed that the main flow features were computed in different grid sizes, but more accurately so with the finest grid. The sediment deposits were reasonably well computed in location and magnitude. A sensitivity test revealed that the computed bed elevation changes were most sensitive to the fall velocities of the finest cohesive sediment particles and sediment cohesion. The sediment deposition computations were also to some degree sensitive to the sediment discharge formula, bed roughness, discretization scheme and the grid resolution.
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Kumar, Aishvarya, Ali Ghobadian, and Jamshid M. Nouri. "Assessment of Cavitation Models for Compressible Flows Inside a Nozzle." Fluids 5, no. 3 (2020): 134. http://dx.doi.org/10.3390/fluids5030134.
Full textAbstract:
This study assessed two cavitation models for compressible cavitating flows within a single hole nozzle. The models evaluated were SS (Schnerr and Sauer) and ZGB (Zwart-Gerber-Belamri) using realizable k-epsilon turbulent model, which was found to be the most appropriate model to use for this flow. The liquid compressibility was modeled using the Tait equation, and the vapor compressibility was modeled using the ideal gas law. Compressible flow simulation results showed that the SS model failed to capture the flow physics with a weak agreement with experimental data, while the ZGB model predicted the flow much better. Modeling vapor compressibility improved the distribution of the cavitating vapor across the nozzle with an increase in vapor volume compared to that of the incompressible assumption, particularly in the core region which resulted in a much better quantitative and qualitative agreement with the experimental data. The results also showed the prediction of a normal shockwave downstream of the cavitation region where the local flow transforms from supersonic to subsonic because of an increase in the local pressure.
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Mustafa, Adnan Ghulam, Mohd Fadhil Majnis, and Nor Azyati Abdul Muttalib. "CFD Study on Impeller Effect on Mixing in Miniature Stirred Tank Reactor." CFD Letters 12, no. 10 (2020): 15–26. http://dx.doi.org/10.37934/cfdl.12.10.1526.
Full textAbstract:
Mixing of fluid can happen in existence or absence of impeller which will affect the mixing performance. The hydrodynamics behavior of fluid has a strong effect on the mixing. The design of mixing systems and operation using the agitated tanks is complicated because it is difficult to obtain accurate information for turbulence’s impeller induced. Computational Fluid Dynamics can be used to provide a detailed comprehension of those systems. This paper describes the effect of various designs of impeller in miniature stirred tank reactor towards the mixing of the calcium alginate beads with the milk using Computational Fluid Dynamics (CFD) software, ANSYS Fluent 19.2. The four different type of impellers are edge beater, 5-turbine blade, t-shape, and paddle. The impeller was simulated at different speeds of 150 rpm, 250 rpm, and 300 rpm. K-epsilon turbulence model was employed to simulate the flow distribution pattern of calcium alginate beads and the Multiple Reference Frame approach was used for the impeller rotation’s simulation. The simulation results obtained have a good agreement with the experimental results in term of vortex formation. The simulation results obtained for contour plots were fitted well with the experimental results as well as with pattern of impeller flow which was also studied. As a result, an optimal design of the impeller that is able to produce good mixing can be achieved using CFD analysis. The results obtained after performing the simulation proved that edge beater blade outperformed the other impellers and took the least time to fully distribute the calcium alginate beads in the tank at 250 rpm compared to 150 and 300 rpm. It can also be concluded that the edge beater blade is the best for the mixing of two-phase fluid and also produces mixed pattern flow. The obtained results from CFD can also be used to scale up the mixing process in larger systems.
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Reinhardt, Yvonne, and Leonhard Kleiser. "Validation of Particle-Laden Turbulent Flow Simulations Including Turbulence Modulation." Journal of Fluids Engineering 137, no. 7 (2015). http://dx.doi.org/10.1115/1.4029838.
Full textAbstract:
The objective of the present numerical study is the validation of wall-bounded, turbulent particle-laden air flow simulations for a wide range of flow and particle parameters (i.e., flow and particle Reynolds numbers, Stokes number, particle-to-fluid density ratio, ratio of particle diameter to turbulent length scale) covering the one-, two- and four-way coupling regimes. The applied computational fluid dynamics (CFD) model follows the Eulerian two-fluid approach in a Reynolds-Averaged Navier–Stokes (RANS) context and is based on the kinetic theory of granular flow (KTGF) for closures concerning the particulate phase. The fluid turbulence is modeled applying a low-Reynolds-number k–epsilon turbulence model. The main focus is put on the modeling of turbulence coupling between the fluid and the particle phase. Different from common practice, the choice of a model accounting for turbulence modulation is made dependent on the prevailing coupling regime. For the case of four-way coupling, a new modulation model is suggested that well predicts turbulence augmentation and attenuation. The predictive capabilities of the present approach are evaluated by comparing simulation results to experimental benchmark data of various pipe and channel flows. Very good agreement with reference data is obtained for the mean flow and turbulence profiles of both phases.
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"Modeling the effect of vegetation on river floodplain hydraulics." Issue 3 14, no. 3 (2013): 371–77. http://dx.doi.org/10.30955/gnj.000883.
Full textAbstract:
Vegetation in river floodplains has significant influence on the flood hydraulics and fate of suspended
 sediments, nutrients and contaminants. In the present, work preliminary 3-D calculations were
 performed to examine the effect of vegetation on the mean flow in open channels using the CFD
 model CFX-12.1, employing the RANS k-epsilon turbulence model. Calculated flow velocity
 distributions were compared against an experiment of free surface uniform flow in a vegetated
 experimental channel, filled with cylindrical submerged elements representing vegetation; these
 elements were rigid and arranged in a staggered pattern.
 Four unstructured numerical grids were employed, ranging from approximately 9.5 to 27.5 millions of
 tetrahedral elements. The main characteristics of the flow were (a) the formation of small recirculation
 regions in the wakes of the cylinders and (b) the relative uniform flow conditions
 throughout the length of the channel. Low flow velocities were observed in the vegetated region,
 implying the resistance due to vegetation, and higher velocities close to the free surface. The best
 agreement with experimental data was achieved for the finest grid that also included grid refinement
 at the top of the cylinders. Grid independence behaviour using relatively very fine grids was rather
 surprising and requires further detailed investigation.
 
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Zalesny, V. B., S. N. Moshonkin, V. L. Perov, and A. V. Gusev. "Ocean Circulation Modeling with K-Omega and K-Epsilon Parameterizations of Vertical Turbulent Exchange." Morskoy gidrofizicheskiy zhurnal 35, no. 6 (2019). http://dx.doi.org/10.22449/0233-7584-2019-6-517-529.
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Tieghi, Lorenzo, Alessandro Corsini, Giovanni Delibra, and Gino Angelini. "Assessment of a Machine-Learnt Adaptive Wall-Function in a Compressor Cascade With Sinusoidal Leading Edge." Journal of Engineering for Gas Turbines and Power 142, no. 12 (2020). http://dx.doi.org/10.1115/1.4048568.
Full textAbstract:
Abstract Near-wall modeling is one of the most challenging aspects of computational fluid dynamic computations. In fact, integration-to-the-wall with low-Reynolds approach strongly affects accuracy of results, but strongly increases the computational resources required by the simulation. A compromise between accuracy and speed to solution is usually obtained through the use of wall functions (WFs), especially in Reynolds averaged Navier–Stokes computations, which normally require that the first cell of the grid to fall inside the log-layer (50 < y+ < 200) (Wilcox, D. C., 1998, Turbulence Modeling for CFD, Vol. 2, DCW Industries, La Cañada, CA). This approach can be generally considered as robust, however the derivation of wall functions from attached flow boundary layers can mislead to nonphysical results in presence of specific flow topologies, e.g., recirculation, or whenever a detailed boundary layer representation is required (e.g., aeroacoustics studies) (Craft, T., Gant, S., Gerasimov, A., Lacovides, H., and Launder, B., 2002, “Wall – Function Strategies for Use in Turbulent Flow CFD,” Proceedings to 12th International Heat Transfer Conference, Grenoble, France, Aug. 18–23). In this work, a preliminary attempt to create an alternative data-driven wall function is performed, exploiting artificial neural networks (ANNs). Whenever enough training examples are provided, ANNs have proven to be extremely powerful in solving complex nonlinear problems (Goodfellow, I., Bengio, Y., Courville, A., and Bengio, Y., 2016, Deep Learning, Vol. 1, MIT Press, Cambridge, MA). The learner that is derived from the multilayer perceptron ANN, is here used to obtain two-dimensional, turbulent production and dissipation values near the walls. Training examples of the dataset have been initially collected either from large eddy simulation (LES) simulations of significant 2D test cases or have been found in open databases. Assessments on the morphology and the ANN training can be found in the paper. The ANN has been implemented in a Python environment, using scikit-learn and tensorflow libraries (Scikit-Learn Developers, 2019, “Scikit-learn v0.20.0 User Guide,” Software, Scikit-Learn Developers; Abadi, M., Barham, P., Chen, J., Chen, Z., Davis, A., Dean, J., Devin, M., Ghemawat, S., Irving, G., Isard, M., Kudlur, M., Levenberg, J., Monga, R., Moore, S., Murray, D. G., Steiner, B., Tucker, P., Vasudevan, V., Warden, P., Wicke, M., Yu, Y., and Zheng, X., 2016, “TensorFlow: A System for Large-Scale Machine Learning,” 12th Symposium on Operating Systems Design and Implementation, Savannah, GA, Nov. 2–4, pp. 265–283). The derived wall function is implemented in openfoam v-17.12 (CFD Direct, 2020, “OpenFoam User Guide v5,” CFD Direct, Caversham, UK), embedding the forwarding algorithm in run-time computations exploiting Python3.6m C_Api library. The data-driven wall function is here applied to k-epsilon simulations of a 2D periodic hill with different computational grids and to a modified compressor cascade NACA aerofoil with sinusoidal leading edge. A comparison between ANN enhanced simulations, available data and standard modelization is here performed and reported.
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Zalesny, V. B., S. N. Moshonkin, V. L. Perov, and A. V. Gusev. "Ocean Circulation Modeling with K-Omega and K-Epsilon Parameterizations of Vertical Turbulent Exchange." Physical Oceanography 26, no. 6 (2019). http://dx.doi.org/10.22449/1573-160x-2019-6-455-466.
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Amedorme, Sherry Kwabla, and Joseph Apodi. "Computational Fluid Dynamics (CFD) Modelling of Mixture Formation in Gasoline Direct Injection (GDI) Engine." Journal of Engineering Research and Reports, September 28, 2019, 1–13. http://dx.doi.org/10.9734/jerr/2019/v7i216968.
Full textAbstract:
Automotive engine faces stringent regulations on emission with improved fuel consumption. As such, the Gasoline Direct Injection (GDI) engines which have the potential to meet these requirements are being improved on especially the mixture formation to the burning of the mixture. In GDI, late injection compared with early injection scheme generates charge stratification which contributes to the optimised fuel consumption and combustion. As a result, this strategy in GDI engines is considered to be promising with increasing research focus. This paper aims at evaluating the computational fluids dynamics (CFD) modelling of two-phase transient injection process in generic GDI engines with the late injection to study the features of fuel atomisation process, injection velocity and its influence on turbulence. The commercial CFD code Star CCM+ was used to perform this simulation due to its advanced polyhedral mesh technology and the user-friendly interface. Transient liquid and gas flow inside the combustion chamber was simulated using the Eulerian multiphase segregated flow model with k-epsilon turbulence. The contour plots show that during the injection period turbulence for each phase was independent of the spray shape predicted to be asymmetric under non-vaporisation conditions. In addition, increasing injection velocity of liquid fuel causes stronger turbulence for the liquid phase. The results also show that the variation of turbulence for gas-phase is mainly centred in the region of the inlet during the injection process and non-homogenous turbulent characteristics were observed for the late injection with the volume fraction of the liquid phase also seen to be asymmetric.