Articoli di riviste: "Gas dynamics computer simulation"

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Borman, V. D., S. V. Bogovalov, V. D. Borisevich, I. V. Tronin e V. N. Tronin. "The computer simulation of 3d gas dynamics in a gas centrifuge". Journal of Physics: Conference Series 751 (settembre 2016): 012017. http://dx.doi.org/10.1088/1742-6596/751/1/012017.

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Rakkapao, Natthida. "Molecular Dynamics Simulation of Gas Transport in Polyisoprene Matrix". Advanced Materials Research 844 (novembre 2013): 209–13. http://dx.doi.org/10.4028/www.scientific.net/amr.844.209.

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Molecular Dynamics (MD) simulation was employed to study the diffusivity of biogas in a PI matrix with the aim to verify simulations as a useful tool to predict PI membrane properties for biogas treatment. The simulation model of PI numerical was reliable and accurate in predicting both the material properties and the diffusivity of gases in PI matrix. The diffusion coefficients (D) of the major components in biogas, namely CH4, CO2, H2O, O2, and N2, were computed by simulating trajectories of each gas in PI matrix at 300 K. The simulations gave DCO2 that was 6 times larger than DCH4, and this agrees well with permeabilities reported in the literature. This suggests that PI membranes could be used to treat biogas by separating CO2 and CH4. However, the diffusivities of N2, H2O, and CH4 are closely similar, so PI membranes are not capable of separating these. The potential application of PI membrane to CO2/CH4 separation seems worth further exploration.

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Zhu, Likuan, Boyan Song e Zhen Long Wang. "Computational Fluid Dynamics Analysis on Rupture of Gas Bubble". Applied Mechanics and Materials 339 (luglio 2013): 468–73. http://dx.doi.org/10.4028/www.scientific.net/amm.339.468.

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Hydrodynamic information of the flow occurring as a bubble ruptures at a gas liquid interface has being obtained from computer simulations. The simulation result is verified by conducting high-speed photography experiment. Process of bubble rupture is clearly captured with simulation and experiment. Shear force generated by bubble rupture increases along with decrease of bursting bubble diameter or increase of coefficient of surface tension. The maximum average shear force ranges from 0.97Pa to 1.91Pa, when bursting bubble diameter changes from 2mm to 10mm.

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Thompson, Bradley, e Hwan-Sik Yoon. "Internal Combustion Engine Modeling Framework in Simulink: Gas Dynamics Modeling". Modelling and Simulation in Engineering 2020 (3 settembre 2020): 1–16. http://dx.doi.org/10.1155/2020/6787408.

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With advancements in computer-aided design, simulation of internal combustion engines has become a vital tool for product development and design innovation. Among the simulation software packages currently available, MATLAB/Simulink is widely used for automotive system simulations, but does not contain a comprehensive engine modeling toolbox. To leverage MATLAB/Simulink’s capabilities, a Simulink-based 1D flow engine modeling framework has been developed. The framework allows engine component blocks to be connected in a physically representative manner in the Simulink environment, reducing model build time. Each component block, derived from physical laws, interacts with other blocks according to block connection. In this Part 1 of series papers, a comprehensive gas dynamics model is presented and integrated in the engine modeling framework based on MATLAB/Simulink. Then, the gas dynamics model is validated with commercial engine simulation software by conducting a simple 1D flow simulation.

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POHL, PHILLIP, GRANT HEFFELFINGER e DOUGLAS SMITH. "Molecular dynamics computer simulation of gas permeation in thin silicalite membranes". Molecular Physics 89, n. 6 (20 dicembre 1996): 1725–31. http://dx.doi.org/10.1080/00268979609482570.

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Wu, S. Z., D. N. Wormley, D. Rowell e H. M. Paynter. "Dynamic Modeling and Simulation of Gaseous Systems". Journal of Dynamic Systems, Measurement, and Control 107, n. 4 (1 dicembre 1985): 262–66. http://dx.doi.org/10.1115/1.3140733.

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A general computer-based mathematical modeling system for analyzing air/gas system dynamics has been developed. A set of generic lumped and distributed elements are interconnected by generalized junction structures to represent system configurations. The dynamic response of pressure, flow, temperature, and heat transfer rate at any point in a system, due to control actions, or fluid, thermal, or mechanical disturbances can be determined. The model has been used to analyze furnace implosion and disturbance propagation problems in fossil fuel power plants. To illustrate the modeling techniques, a model of a coal-fired plant has been constructed and pressure transients computed following a fuel trip. The model simulation predictions of the furnace pressure excursions are in close agreement with the data from field tests.

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Knoll, G., H. Peeken, R. Lechtape-Gru¨ter e J. Lang. "Computer-Aided Simulation of Piston and Piston Ring Dynamics". Journal of Engineering for Gas Turbines and Power 118, n. 4 (1 ottobre 1996): 880–86. http://dx.doi.org/10.1115/1.2817009.

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A numerical computer simulation program was developed, aiding in finding optimum design parameters in the multibody-system piston, piston-rings, and cylinder with respect to optimum sealing, minimal friction, and minimum noise stimulation (impact impulse). In the simulation of piston secondary movement and piston ring motion, forces arising from the combustion process, subsonic/supersonic gas flow between the combustion chamber and the crank case, inertial forces and forces resulting from the hydrodynamic lubrication between cylinder liner and piston shaft and piston rings and between piston ring flanks and piston grooves are considered. In addition it is possible to account for effects of global, three-dimensional ring deformation as well as local piston deformation, roughness effects in lubricated contacts, and variable viscosity and variable oil supply. The governing differential equations for the pressure as well as the deformation are solved via finite element techniques, while initial value problems are solved by efficient implicit time integration schemes. The application of the developed computer code is presented in examples.

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Ismagilov, Rinat R., Ildar R. Khamidullin, Kuo-Hui Yang e Alexander N. Obraztsov. "Computer Simulation Study of Gas Dynamics for Torches Operating at Atmosphere Pressure". Journal of Nanoelectronics and Optoelectronics 8, n. 1 (1 gennaio 2013): 119–23. http://dx.doi.org/10.1166/jno.2013.1440.

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Shi, H., e C. Kleinstreuer. "Simulation and Analysis of High-Speed Droplet Spray Dynamics". Journal of Fluids Engineering 129, n. 5 (19 ottobre 2006): 621–33. http://dx.doi.org/10.1115/1.2717621.

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An experimentally validated computer simulation model has been developed for the analysis of gas-phase and droplet characteristics of isothermal sprays generated by pressure jet atomizers. Employing a coupled Euler-Lagrange approach for the gas-droplet flow, secondary droplet breakup (based on the ETAB model), was assumed to be dominant and the k-ε model was selected for simulating the gas flow. Specifically, transient spray formation in terms of turbulent gas flow as well as droplet velocities and size distributions are provided for different back pressures. Clearly, two-way coupling of the phases is important because of the impact of significant gas entrainment, droplet momentum transfer, and turbulent dispersion. Several spray phenomena are discussed in light of low back-pressure (1atm) and high back-pressure (30atm) environments. At low back-pressure, sprays have long thin geometric features and penetrate faster and deeper than at high back-pressures because of the measurable change in air density and hence drag force. Away from the nozzle exit under relatively high back pressures, there is no distinct droplet size difference between peripheral and core regions because of the high droplet Weber numbers, leading to very small droplets which move randomly. In contrast to transient spray developments, under steady-state conditions droplets are subject to smaller drag forces due to the fully-developed gas entrainment velocities which reduce gas-liquid slip. Turbulent dispersion influences droplet trajectories significantly because of the impact of random gas-phase fluctuations.

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Turner, Dean E. "Dynamic Computer Simulation of the Motion of Gas Molecules". Journal of Chemical Education 71, n. 9 (settembre 1994): 784. http://dx.doi.org/10.1021/ed071p784.

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Sun, Jin, Francine Battaglia e Shankar Subramaniam. "Hybrid Two-Fluid DEM Simulation of Gas-Solid Fluidized Beds". Journal of Fluids Engineering 129, n. 11 (9 giugno 2007): 1394–403. http://dx.doi.org/10.1115/1.2786530.

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Simulations of gas-solid fluidized beds have been performed using a hybrid simulation method, which couples the discrete element method (DEM) for particle dynamics with the averaged two-fluid (TF) continuum equations for the gas phase. The coupling between the two phases is modeled using an interphase momentum transfer term. The results of the hybrid TF-DEM simulations are compared to experimental data and TF model simulations. It is found that the TF-DEM simulation is capable of predicting general fluidized bed dynamics, i.e., pressure drop across the bed and bed expansion, which are in agreement with experimental measurements and TF model predictions. Multiparticle contacts and large contact forces distribute in the regions away from bubbles, as demonstrated from the TF-DEM simulation results. The TF-DEM model demonstrates the capability to capture more heterogeneous structural information of the fluidized beds than the TF model alone. The implications to the solid phase constitutive closures for TF models are discussed. However, the TF-DEM simulations depend on the form of the interphase momentum transfer model, which can be computed in terms of averaged or instantaneous particle quantities. Various forms of the interphase momentum transfer model are examined, and simulation results from these models are compared.

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Wada, K., e A. Habe. "Self-Gravitating Gas Dynamics in a Nuclear Region of a Weak Barred Galaxy". International Astronomical Union Colloquium 140 (1994): 351–52. http://dx.doi.org/10.1017/s0252921100019953.

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Starburst regions are frequently located in galactic central regions and CO observations indicate that these regions contain a large amount of molecular gas (e.g. Lo et al. 1987). However, the triggering mechanism for starbursts and the mechanism of the high mass supply rate of gas into a galactic center are still unclear.It is suggested that tidal encounters of galaxies remove angular momentum of gas and trigger rapid gas accretion and starburst. Noguchi(1988) has shown by computer simulations that galaxy-galaxy interactions induce a stellar bar, and gas loses its angular momentum and accumulates to a galactic center. In his numerical simulation, non-axisymmetric potential of a stellar bar plays an important role in the accretion of gas. However, it is not obvious whether or not gas accretes into a nuclear region within a few hundred pc only by the effects of stellar bar.Wada and Habe (1992) investigated the dynamics of self-gravitating gas in a barred potential by 2-D numerical simulation, and show that even if the bar is weak, for the initial gas mass ratio to stellar mass grater than 10%, a central elongated gas ring formed at near ILRs becomes unstable and collapses. As a result, a large amount of gas can be supplied to galactic center. They conclude that both the effect of the self-gravity of the gas and the existence of ILRs are necessary to the rapid gas fueling in a weak barred potential.

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Anyanwu, Hou, Chen, Pan, Du, Xuan e Jiao. "Numerical Investigation of Liquid Water Transport Dynamics in Novel Hybrid Sinusoidal Flow Channel Designs for PEMFC". Energies 12, n. 21 (23 ottobre 2019): 4030. http://dx.doi.org/10.3390/en12214030.

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This study numerically investigates liquid water dynamics in a novel hybrid sinusoidal flow channel of a proton exchange membrane fuel cell (PEMFC). The two-phase flow is examined using a three-dimensional, transient computational fluid dynamics (CFD) simulation employing the coupled level set and volume of fluid (VOF) method. Simulations for hybrid and non-hybrid sinusoidal flow channels, including a straight flow channel, are compared based on their water exhaust capacities and pressure drops. Additionally, the effects of inlet gas velocity, wall wettability, and droplet interaction in the flow channel on the dynamic behaviour of liquid water are investigated. Results reveal that the novel hybrid sinusoidal channel designs are consistent in terms of quicker water removal under varying hydrophilic wall conditions. Also, it is found that the liquid surface coverage, detachment, and removal rate depends on droplet proximity to the walls, inlet gas velocity, and wall contact angle. Also, the time a droplet makes contact with the side walls affect the discharge time. Additionally, there is an improvement in the gas velocity magnitude and vertical component velocity across the hybrid sinusoidal channel designs. Therefore, the unique geometric configuration of the proposed hybrid design makes it a viable substitute for water management in PEMFC applications.

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CHEN, Guangqiang. "Numerical Simulation Research on Cone Self-acting Gas Lubrication Bearing Dynamics". Journal of Mechanical Engineering 52, n. 4 (2016): 185. http://dx.doi.org/10.3901/jme.2016.04.185.

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Bass, Alexander, Seth Putterman, Barry Merriman e Steven J. Ruuth. "Symmetry reduction for molecular dynamics simulation of an imploding gas bubble". Journal of Computational Physics 227, n. 3 (gennaio 2008): 2118–29. http://dx.doi.org/10.1016/j.jcp.2007.10.013.

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Boyd, Iain D. "Vectorization of a Monte Carlo simulation scheme for nonequilibrium gas dynamics". Journal of Computational Physics 91, n. 2 (dicembre 1990): 495. http://dx.doi.org/10.1016/0021-9991(90)90053-4.

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Boyd, Iain D. "Vectorization of a Monte Carlo simulation scheme for nonequilibrium gas dynamics". Journal of Computational Physics 96, n. 2 (ottobre 1991): 411–27. http://dx.doi.org/10.1016/0021-9991(91)90243-e.

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Mohammad Nejad, Shahin, Silvia Nedea, Arjan Frijns e David Smeulders. "The Influence of Gas–Wall and Gas–Gas Interactions on the Accommodation Coefficients for Rarefied Gases: A Molecular Dynamics Study". Micromachines 11, n. 3 (19 marzo 2020): 319. http://dx.doi.org/10.3390/mi11030319.

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Molecular dynamics (MD) simulations are conducted to determine energy and momentum accommodation coefficients at the interface between rarefied gas and solid walls. The MD simulation setup consists of two parallel walls, and of inert gas confined between them. Different mixing rules, as well as existing ab-initio computations combined with interatomic Lennard-Jones potentials were employed in MD simulations to investigate the corresponding effects of gas-surface interaction strength on accommodation coefficients for Argon and Helium gases on a gold surface. Comparing the obtained MD results for accommodation coefficients with empirical and numerical values in the literature revealed that the interaction potential based on ab-initio calculations is the most reliable one for computing accommodation coefficients. Finally, it is shown that gas–gas interactions in the two parallel walls approach led to an enhancement in computed accommodation coefficients compared to the molecular beam approach. The values for the two parallel walls approach are also closer to the experimental values.

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Schobeiri, M. T., M. Attia e C. Lippke. "GETRAN: A Generic, Modularly Structured Computer Code for Simulation of Dynamic Behavior of Aero- and Power Generation Gas Turbine Engines". Journal of Engineering for Gas Turbines and Power 116, n. 3 (1 luglio 1994): 483–94. http://dx.doi.org/10.1115/1.2906847.

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The design concept, the theoretical background essential for the development of the modularly structured simulation code GETRAN, and several critical simulation cases are presented in this paper. The code being developed under contract with NASA Lewis Research Center is capable of simulating the nonlinear dynamic behavior of single- and multispool core engines, turbofan engines, and power generation gas turbine engines under adverse dynamic operating conditions. The modules implemented into GETRAN correspond to components of existing and new-generation aero- and stationary gas turbine engines with arbitrary configuration and arrangement. For precise simulation of turbine and compressor components, row-by-row diabatic and adiabatic calculation procedures are implemented that account for the specific turbine and compressor cascade, blade geometry, and characteristics. The nonlinear, dynamic behavior of the subject engine is calculated solving a number of systems of partial differential equations, which describe the unsteady behavior of each component individually. To identify each differential equation system unambiguously, special attention is paid to the addressing of each component. The code is capable of executing the simulation procedure at four levels, which increase with the degree of complexity of the system and dynamic event. As representative simulations, four different transient cases with single- and multispool thrust and power generation engines were simulated. These transient cases vary from throttling the exit nozzle area, operation with fuel schedule, rotor speed control, to rotating stall and surge.

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Furukawa, Shin-ichi, e Tomoshige Nitta. "Computer Simulation Studies on Gas Permeation through Nanoporous Carbon Membranes by Non-Equilibrium Molecular Dynamics." JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 30, n. 1 (1997): 116–22. http://dx.doi.org/10.1252/jcej.30.116.

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Jain, Nishan, Luis Bravo, Dokyun Kim, Muthuvel Murugan, Anindya Ghoshal, Frank Ham e Alison Flatau. "Massively Parallel Large Eddy Simulation of Rotating Turbomachinery for Variable Speed Gas Turbine Engine Operation". Energies 13, n. 3 (6 febbraio 2020): 703. http://dx.doi.org/10.3390/en13030703.

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Gas turbine engines are required to operate at both design and off-design conditions that can lead to strongly unsteady flow-fields and aerodynamic losses severely impacting performance. Addressing this problem requires effective use of computational fluid dynamics tools and emerging models that resolve the large scale fields in detail while accurately modeling the under-resolved scale dynamics. The objective of the current study is to conduct massively parallel large eddy simulations (LES) of rotating turbomachinery that handle the near-wall dynamics using accurate wall models at relevant operating conditions. The finite volume compressible CharLES solver was employed to conduct the simulations over moving grids generated through Voronoi-based unstructured cells. A grid sensitivity analysis was carried out first to establish reliable parameters and assess the quality of the results. LES simulations were then conducted to understand the impact of blade tip clearance and operating conditions on the stage performance. Variations in tip clearance of 3% and 16% chord were considered in the analysis. Other design points included operation at 100% rotor speed and off-design conditions at 75% and 50% of the rotor speed. The simulation results showed that the adiabatic efficiency improves dramatically with reduction in tip gap due to the decrease in tip leakage flow and the resulting flow structures. The analysis also showed that the internal flow becomes highly unsteady, undergoing massive separation, as the rotor speed deviates from the design point. This study demonstrates the capability of the framework to simulate highly turbulent unsteady flows in a rotating turbomachinery environment. The results provide much needed insight and massive data to investigate novel design concepts for the US Army Future Vertical Lift program.

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Bao, Fubing, Zhihong Mao e Limin Qiu. "Study of gaseous velocity slip in nano-channel using molecular dynamics simulation". International Journal of Numerical Methods for Heat & Fluid Flow 24, n. 6 (29 luglio 2014): 1338–47. http://dx.doi.org/10.1108/hff-04-2013-0145.

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Purpose – The purpose of this paper is to investigate the gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels based on the molecular dynamics simulation. Design/methodology/approach – An external gravity force was employed to drive the flow. The density and velocity profiles across the channel, and the velocity slip on the wall were studied, considering different gas temperatures and gas-solid interaction strengths. Findings – The simulation results demonstrate that a single layer of gas molecules is adsorbed on wall surface. The density of adsorption layer increases with the decrease of gas temperature and with increase of interaction strength. The near wall region extents several molecular diameters away from the wall. The density profile is flatter at higher temperature and the velocity profile has the traditional parabolic shape. The velocity slip on the wall increases with the increase of temperature and with decrease of interaction strength linearly. The average velocity decreases with the increase of gas-solid interaction strength. Originality/value – This research presents gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels. Some interesting results in nano-scale channels are obtained.

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Mezulis, A., A. Safronov, J. Guzeyeva e J. Begens. "Computer Simulation to Optimize the VFA Alpha Prototype with a Hydraulic Piston Compressor and an Integrated Booster". Latvian Journal of Physics and Technical Sciences 57, n. 5 (1 ottobre 2020): 5–17. http://dx.doi.org/10.2478/lpts-2020-0023.

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AbstractNatural gas, including biomethane, is a sustainable alternative fuel. Widening compressed natural gas applications by now is restricted by weakly developed infrastructure. Hygen Ltd. works on “hydraulic piston” technology for natural gas and biomethane compressing, storing, delivering and discharging the storage cylinders by means of an innovative hydraulic boosting technology. Designing of the Vehicle Fuelling Appliance (VFA) demands to take into account thermodynamics and gas dynamics properties at fluid compression and motion. The present paper deals with theoretical characteristics and their link to test measurements regarding a particular VFA HYGEN+ Alpha prototype manufactured by Hygen Ltd.

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Akkaya, Volkan Ramazan, e Ilyas Kandemir. "Event-Driven Molecular Dynamics Simulation of Hard-Sphere Gas Flows in Microchannels". Mathematical Problems in Engineering 2015 (2015): 1–12. http://dx.doi.org/10.1155/2015/842837.

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Classical solution of Navier-Stokes equations with nonslip boundary condition leads to inaccurate predictions of flow characteristics of rarefied gases confined in micro/nanochannels. Therefore, molecular interaction based simulations are often used to properly express velocity and temperature slips at high Knudsen numbers (Kn) seen at dilute gases or narrow channels. In this study, an event-driven molecular dynamics (EDMD) simulation is proposed to estimate properties of hard-sphere gas flows. Considering molecules as hard-spheres, trajectories of the molecules, collision partners, corresponding interaction times, and postcollision velocities are computed deterministically using discrete interaction potentials. On the other hand, boundary interactions are handled stochastically. Added to that, in order to create a pressure gradient along the channel, an implicit treatment for flow boundaries is adapted for EDMD simulations. Shear-Driven (Couette) and Pressure-Driven flows for various channel configurations are simulated to demonstrate the validity of suggested treatment. Results agree well with DSMC method and solution of linearized Boltzmann equation. At low Kn, EDMD produces similar velocity profiles with Navier-Stokes (N-S) equations and slip boundary conditions, but as Kn increases, N-S slip models overestimate slip velocities.

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Wang, Tian, Ping Xi e Bifu Hu. "Multiphysics Modeling of Gas Turbine Based on CADSS Technology". Shock and Vibration 2020 (19 ottobre 2020): 1–21. http://dx.doi.org/10.1155/2020/8816453.

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Product modeling has been applied in product engineering with success for geometric representation. With the application of multidisciplinary analysis, application-driven models need specific knowledge and time-consuming adjustment work based on the geometric model. This paper proposes a novel modeling technology named computer-aided design-supporting-simulation (CADSS) to generate multiphysics domain models to support multidisciplinary design optimization processes. Multiphysics model representation was analyzed to verify gaps among different domain models’ parameters. Therefore, multiphysics domain model architecture was integrated by optimization model, design model, and simulation model in consideration of domain model’s parameters. Besides, CADSS uses requirement space, domain knowledge, and software technology to describe the multidisciplinary model’s parameters and its transition. Depending on the domain requirements, the CADSS system extracts the required knowledge by decomposing product functions and then embeds the domain knowledge into functional features using software technology. This research aims to effectively complete the design cycle and improve the design quality by providing a consistent and concurrent modeling environment to generate an adaptable model for multiphysics simulation. This system is demonstrated by modeling turbine blade design with multiphysics simulations including computational fluid dynamics (CFD), conjugate heat transfer (CHT), and finite element analysis (FEA). Moreover, the blade multiphysics simulation model is validated by the optimization design of the film hole. The results show that the high-fidelity multiphysics simulation model generated through CADSS can be adapted to subsequent simulations.

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Schuh, Sebastian, Jens Frühhaber, Thomas Lauer e Franz Winter. "A Novel Dual Fuel Reaction Mechanism for Ignition in Natural Gas–Diesel Combustion". Energies 12, n. 22 (19 novembre 2019): 4396. http://dx.doi.org/10.3390/en12224396.

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In this study, a reaction mechanism is presented that is optimized for the simulation of the dual fuel combustion process using n-heptane and a mixture of methane/propane as surrogate fuels for diesel and natural gas, respectively. By comparing the measured and calculated ignition delay times (IDTs) of different homogeneous methane–propane–n-heptane mixtures, six different n-heptane mechanisms were investigated and evaluated. The selected mechanism was used for computational fluid dynamics (CFD) simulations to calculate the ignition of a diesel spray injected into air and a natural gas–air mixture. The observed deviations between the simulation results and the measurements performed with a rapid compression expansion machine (RCEM) and a combustion vessel motivated the adaptation of the mechanism by adjusting the Arrhenius parameters of individual reactions. For the identification of the reactions suitable for the mechanism adaption, sensitivity and flow analyzes were performed. The adjusted mechanism is able to describe ignition phenomena in the context of natural gas–diesel, i.e., dual fuel combustion.

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Tomtas, Paweł, Amadeusz Skwiot, Elżbieta Sobiecka, Andrzej Obraniak, Katarzyna Ławińska e Tomasz P. Olejnik. "Bench Tests and CFD Simulations of Liquid–Gas Phase Separation Modeling with Simultaneous Liquid Transport and Mechanical Foam Destruction". Energies 14, n. 6 (21 marzo 2021): 1740. http://dx.doi.org/10.3390/en14061740.

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This paper presents simulation and bench test results for a special type of centrifugal pump that enables the transport of dispersive foaming liquids and simultaneous separation of the liquid phase. During the design phase, CFD (Computer Fluid Dynamics) simulations were performed using Ansys Fluent. The simulations covered changing the operating parameters of the pump (mass/volume flow rate), pressure analysis for the first impeller, and structural optimization of the pump components. In the second stage of the research, the pump and a measuring station were constructed to validate the results of the numerical simulations.

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Ridgway, H. F., B. Mohan, X. Cui, K. J. Chua e M. R. Islam. "Molecular dynamics simulation of gas-phase ozone reactions with sabinene and benzene". Journal of Molecular Graphics and Modelling 74 (giugno 2017): 241–50. http://dx.doi.org/10.1016/j.jmgm.2017.04.020.

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Watanabe, Mariko, e Daisuke Tanaka. "Brownian dynamics simulation of the aggregation of submicron particles in static gas". Computers & Chemical Engineering 54 (luglio 2013): 151–58. http://dx.doi.org/10.1016/j.compchemeng.2013.03.028.

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Woodward, Paul R., Jagan Jayaraj, Pei-Hung Lin e William Dai. "First experience of compressible gas dynamics simulation on the Los Alamos roadrunner machine". Concurrency and Computation: Practice and Experience 21, n. 17 (10 dicembre 2009): 2160–75. http://dx.doi.org/10.1002/cpe.1494.

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MAYER, BERND, e STEEN RASMUSSEN. "DYNAMICS AND SIMULATION OF MICELLAR SELF-REPRODUCTION". International Journal of Modern Physics C 11, n. 04 (giugno 2000): 809–26. http://dx.doi.org/10.1142/s0129183100000705.

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Molecular self-assembly plays a crucial role as a structural and an organizational principle in supramolecular architecture. The key feature of this process is the generation of higher order molecular structures, and is solely determined by the dynamics of the individual molecular objects, characterized by an overall minimum free energy situation. Equally important as the constructional aspect of the formation process, these macromolecular assemblies carry novel functionalities which can be solely observed at the level of the supramolecular aggregates and not at any of the organizational levels below. This paper discusses the formation and successive self-reproduction of membraneous compartments in a polar environment in 2D using a lattice gas based simulation technique, the Lattice Molecular Automaton. This method describes realistic physico-chemical interactions as well as chemical reactivity between molecular units via discrete force fields propagated on the lattice. We investigate the formation dynamics of micelles, i.e., organized amphiphilic polymers in polar environment, as well as the kinetics of a concomittant micelle self-reproduction based on the formation of catalytic interfaces closely following in vitro experimental results: Micelle self-reproduction is a complex phenomenon based on concerted dynamics of the individual polymers within the many particle aggregate. All observables, i.e., micelle formation and autocatalytic micelle self-reproduction, are solely based on the properties of the individual chemical objects (amphiphilic polymers in polar environment), and are therefore emergent phenomena generated by the implicitly defined system dynamics. We introduce the formal concept of the emergence of novel functions in dynamical hierarchies and finally discuss these issues within the context of self-reproducing dynamical hierarchies.

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LUO, K. H., J. XIA e E. MONACO. "MULTISCALE MODELING OF MULTIPHASE FLOW WITH COMPLEX INTERACTIONS". Journal of Multiscale Modelling 01, n. 01 (gennaio 2009): 125–56. http://dx.doi.org/10.1142/s1756973709000074.

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This paper presents a variety of modeling and simulation methods for complex multiphase flow at microscopic, mesoscopic and macroscopic scales. Each method is discussed in terms of its scale-resolving capability and its relationship with other approaches. Examples of application are provided using a liquid–gas system, in which complex multiscale interactions exist among flow, turbulence, combustion and droplet dynamics. Large eddy simulation (LES) is employed to study the effects of a very large number of droplets on turbulent combustion in two configurations in a fixed laboratory frame. Direct numerical simulation (DNS) in a moving frame is then deployed to reveal detailed dynamic interactions between droplets and reaction zones. In both the LES and the DNS, evaporating droplets are modeled in a Lagrangian macroscopic approach, and have two-way couplings with the carrier gas phase. Finally, droplet collisions are studied using a multiple-relaxation-time lattice Boltzmann method (LBM). The LBM treats multiphase flow with real-fluid equations of state, which are stable and can cope with high density ratios. Examples of successful simulations of droplet coalescence and off-center separation are given. The paper ends with a summary of results and a discussion on hybrid multiscale approaches.

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33

Montazeri-Gh, Morteza, e Seyed Alireza Miran Fashandi. "Modeling and simulation of a two-shaft gas turbine propulsion system containing a frictional plate–type clutch". Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 233, n. 2 (7 aprile 2018): 502–14. http://dx.doi.org/10.1177/1475090218765378.

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A marine propulsion system is composed of several sub-systems that operate in a variety of energy fields. The propulsion power of a ship can be provided from a two-shaft gas turbine. In this article, the modeling of a two-shaft gas turbine and its associated sub-systems including gears, flexible couplings and clutch is considered. These components are connected in the form of a virtual marine propulsion system, which is based on the bond-graph approach. When a clutch is used in a propulsion system, discontinuities occur in the describing model, which leads to some challenging problems when performing computer simulations. The two main difficulties are the numerical stiffness and the variable model structure. In this research, the bond-graph method is adapted as the modeling framework in order to allow a constant system structure model that minimizes the stiffness problem. Next, simulation results of a two-shaft gas turbine are presented in the off-design condition and verified with experimental tests. These results demonstrate the acceptable accuracy of computer simulations. Also, the effects of clutch performance on the dynamics of the marine propulsion system are discussed.

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34

Osintsev, Konstantin, Seregei Aliukov e Alexander Shishkov. "Improvement Dependability of Offshore Horizontal-Axis Wind Turbines by Applying New Mathematical Methods for Calculation the Excess Speed in Case of Wind Gusts". Energies 14, n. 11 (26 maggio 2021): 3085. http://dx.doi.org/10.3390/en14113085.

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The problem of increasing the reliability of wind turbines exists in the development of new offshore oil and natural gas fields. Reducing emergency situations is necessary due to the autonomous operation of drilling rigs and bulk seaports in the subarctic and Arctic climate. The relevance of the topic is linked with the development of a methodology for theoretical and practical studies of gas dynamics when gas flows in a pipe, based on a mathematical model using new mathematical methods for calculation of excess speeds in case of wind gusts. Problems in the operation of offshore wind turbines arise with storm gusts of wind, which is comparable to the wave movement of the gas flow. Thus, the scientific problem of increasing the reliability of wind turbines in conditions of strong wind gusts is solved. The authors indicate a gross error in the calculations when approximating through the use of the Fourier series. The obtained results will allow us to solve one of the essential problems of modeling at this stage of its development, namely: to reduce the calculation time and the adequacy of the model built for similar installations and devices. Experimental studies of gas-dynamic flows are carried out on the example of a physical model of a wind turbine. In addition, a computer simulation of the gas-dynamic flow process was carried out. The use of new approximation schemes in processing the results of experiments and computer simulation can reduce the calculation error by 1.2 percent.

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35

Šulc, Stanislav, Vít Šmilauer e František Wald. "COUPLED SIMULATION FOR FIRE-EXPOSED STRUCTURES USING CFD AND THERMO-MECHANICAL MODELS". Acta Polytechnica CTU Proceedings 13 (13 novembre 2017): 121. http://dx.doi.org/10.14311/app.2017.13.0121.

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Fire resistance of buildings is based on fire tests in furnaces with gas burners. However, the tests are very expensive and time consuming. This article presents a coupled simulation of an element loaded by a force and a fire loading. The simulation solves a weakly-coupled problem, consisting of fluid dynamics, heat transfer and mechanical model. The temperature field from the computational fluid dynamics simulation (CFD) creates Cauchy and radiative boundary conditions for the thermal model. Then, the temperature field from element is passed to the mechanical model, which induces thermal strain and modifies material parameters. The fluid dynamics is computed with Fire Dynamics Simulator and the thermo-mechanical task is solved in OOFEM. Both softwares are interconnected with MuPIF python library, which allows smooth data transfer across the different meshes, orchestrating simulations in particular codes, exporting results to the VTK formats and distributed computing.

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36

Aiello-Nicosia, M. L., e R. M. Sperandeo-Mineo. "Computer simulation of a two-dimensional ideal gas: a simple molecular dynamics method for teaching purposes". European Journal of Physics 6, n. 3 (1 luglio 1985): 148–53. http://dx.doi.org/10.1088/0143-0807/6/3/005.

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37

Steffen, M., D. Schönberner, K. Kifonidis e J. Stahlberg. "Through the AGB towards a Planetary: A hydrodynamical simulation". Symposium - International Astronomical Union 180 (1997): 368. http://dx.doi.org/10.1017/s0074180900131432.

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Based on the mass-loss description developed by Blöcker (1995, A&A, 297, 727), we present first exploratory computations of the dynamical evolution of a dusty stellar wind envelope around an intermediate mass star during the last 300 000 years on the AGB and its transformation into a planetary nebula during the following 5 000 years of post-AGB evolution. To model the dynamics of the cool dusty envelope, we used a two-component (gas/dust) 1D radiation hydrodynamics code which computes the radiation pressure on dust grains and the structure of the envelope in a self-consistent way, including the variable frictional coupling between dust and gas. The grains are either carbon or oxygen based and of single size and spherical shape.

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38

Yan, Jiangyan, Chang Zhou, Zhihai Rong, Haijiang Wang, Hui Li e Xuejiao Hu. "Simulation of the Dynamic Characteristics of a PEMFC System in Fluctuating Operating Conditions". Energies 13, n. 14 (13 luglio 2020): 3596. http://dx.doi.org/10.3390/en13143596.

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A greater understanding of the dynamic processes inside the stack is urgently needed to optimize the PEMFC (proton exchange membrane fuel cell). In this study, we examined the gas, water and electrochemical processes inside the stack, studied the physical dynamics of system accessories such as gas supplement, flow and pressure-regulating devices, then used Simulink to build a mathematical model of a complete PEMFC system; a segmented testing platform was built to test the spatial distribution of RH (relative humidity) and pressure, which was used to verify the simulation model; based on this model, the complicated phenomena occurring inside the stack during fluctuating operating states were calculated. Our findings showed that the pressure in the gas channel and exhaust manifolds decreased when the external load increased, changing sharply at the moment of load change. The transient pressure difference between the cathode and anode sides (several kPa) had a huge impact on the MEA (membrane electrode assembly); when the load current increased, RH in cathode and cathode channel increased gradually, and the increasing rate of anode side was bigger than that in cathode side. The influence of variance magnitude and change interval of external load were also studied based on the model.

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39

Velioglu, Sadiye, e Seda Keskin. "Simulation of H2/CH4 mixture permeation through MOF membranes using non-equilibrium molecular dynamics". Journal of Materials Chemistry A 7, n. 5 (2019): 2301–14. http://dx.doi.org/10.1039/c8ta10167a.

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40

Araújo, Bruna Sene Alves, e Kássia Graciele dos Santos. "CFD Simulation of Different Flow Regimes of the Spout Fluidized Bed with Draft Plates". Materials Science Forum 899 (luglio 2017): 89–94. http://dx.doi.org/10.4028/www.scientific.net/msf.899.89.

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Spout fluidized bed has shown promising for gas-solid contact operations with and without chemical reactions, such as drying, coating, granulation, gasification, pyrolysis, etc. This is because these beds combine features from both spouted and fluidized beds. The other point is the ability to treat chemical transformations involving both heat and mass transfer in combination with particles of various sizes. Therefore, it is extremely important the knowledge of fluid dynamic of the bed, mainly for scale-up projects, which makes computer simulation an essential tool. Researches using the Computation Fluid Dynamics (CFD) proved to be very effective in predicting of particles dynamic in this type of bed. In Computation Fluid Dynamics, the two phases are treated as interpenetration continuous, and these phases are described by equations of conservation of mass, momentum and energy. The goal of the present work was to simulate using CFD experimental fluid dynamics data of a spout fluidized bed. Eight distinct flow regimes were identified which showed up in good agreement with the regime map presented in literature. The results showed that the technique was efficient for the simulation of the hydrodynamic of the bed presented.

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41

Benderskiy, Boris, Peter Frankovský e Alena Chernova. "Numerical Simulation of Intrachamber Processes in the Power Plant". Applied Sciences 11, n. 11 (28 maggio 2021): 4990. http://dx.doi.org/10.3390/app11114990.

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This paper considers the issues of numerical modeling of nonstationary spatial gas dynamics in the pre-nozzle volume of the combustion chamber of a power plant with a cylindrical slot channel at the power plant of the mass supply surface. The numerical simulation for spatial objects is based on the solution conjugate problem of heat exchange by the control volume method in the open integrated platform for numerical simulation of continuum mechanics problems (openFoam). The calculation results for gas-dynamic and thermal processes in the power plant with a four-nozzle cover are presented. The analysis of gas-dynamic parameters and thermal flows near the nozzle cover, depending on the canal geometry, is given. The topological features of the flow structure and thermophysical parameters near the nozzle cap were studied. For the first time, the transformation of topological features of the flow structure in the pre-nozzle volume at changes in the mass channel’s geometry is revealed, described, and analyzed. The dependence of the Nusselt number in the central point of stagnation on the time of the power plants operation is revealed.

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42

Volokhova, Alina V., Elena V. Zemlyanaya, Vladimir V. Kachalov, Victor S. Rikhvitsky e Vadim N. Sokotushchenko. "Simulation of a gas-condensate mixture passing through a porous medium in depletion mode". Russian Family Doctor 27, n. 3 (15 dicembre 2019): 205–16. http://dx.doi.org/10.17816/rfd10658.

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One of important tasks in a development of gas-condensate fields is to minimize hydrocarbons loss arising from the gas condensation in pores of the gas-bearing layer. The search for the optimal gas production regime is carried out both on the basis of laboratory experiments and on the base of computer simulation. In this regard, the relevant is the verification of the constructed mathematical models by means of comparison of numerical results with experimental data obtained on the laboratory models of a hydrocarbon reservoirs. Within the classical approach on the basis of the Darcy law and the law continuity for flows, the model is formulated that describes the passing a multicomponent gas-condensate mixture through a porous medium in the depletion mode. The numerical solution of the corresponding system of nonlinear partial differential equations is implemented on the basis of the combined use of the C++ programming language and the Maple software. Shown that the approach used provides an agreement of results of numerical simulations with experimental data on the dynamics of hydrocarbon recoverability depending on the pressure obtained at VNIIGAZ, Ukhta.

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43

Volokhova, Alina V., Elena V. Zemlyanaya, Vladimir V. Kachalov, Victor S. Rikhvitsky e Vadim N. Sokotushchenko. "Simulation of a gas-condensate mixture passing through a porous medium in depletion mode". Russian Family Doctor 27, n. 3 (15 dicembre 2019): 205–16. http://dx.doi.org/10.17816/rfd10663.

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Abstract (sommario):

One of important tasks in a development of gas-condensate fields is to minimize hydrocarbons loss arising from the gas condensation in pores of the gas-bearing layer. The search for the optimal gas production regime is carried out both on the basis of laboratory experiments and on the base of computer simulation. In this regard, the relevant is the verification of the constructed mathematical models by means of comparison of numerical results with experimental data obtained on the laboratory models of a hydrocarbon reservoirs. Within the classical approach on the basis of the Darcy law and the law continuity for flows, the model is formulated that describes the passing a multicomponent gas-condensate mixture through a porous medium in the depletion mode. The numerical solution of the corresponding system of nonlinear partial differential equations is implemented on the basis of the combined use of the C++ programming language and the Maple software. Shown that the approach used provides an agreement of results of numerical simulations with experimental data on the dynamics of hydrocarbon recoverability depending on the pressure obtained at VNIIGAZ, Ukhta.

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44

Volokhova, Alina V., Elena V. Zemlyanaya, Vladimir V. Kachalov, Victor S. Rikhvitsky e Vadim N. Sokotushchenko. "Simulation of a gas-condensate mixture passing through a porous medium in depletion mode". Russian Family Doctor 27, n. 3 (15 dicembre 2019): 205–16. http://dx.doi.org/10.17816/rfd10664.

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Abstract (sommario):

One of important tasks in a development of gas-condensate fields is to minimize hydrocarbons loss arising from the gas condensation in pores of the gas-bearing layer. The search for the optimal gas production regime is carried out both on the basis of laboratory experiments and on the base of computer simulation. In this regard, the relevant is the verification of the constructed mathematical models by means of comparison of numerical results with experimental data obtained on the laboratory models of a hydrocarbon reservoirs. Within the classical approach on the basis of the Darcy law and the law continuity for flows, the model is formulated that describes the passing a multicomponent gas-condensate mixture through a porous medium in the depletion mode. The numerical solution of the corresponding system of nonlinear partial differential equations is implemented on the basis of the combined use of the C++ programming language and the Maple software. Shown that the approach used provides an agreement of results of numerical simulations with experimental data on the dynamics of hydrocarbon recoverability depending on the pressure obtained at VNIIGAZ, Ukhta.

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45

Volokhova, Alina V., Elena V. Zemlyanaya, Vladimir V. Kachalov, Victor S. Rikhvitsky e Vadim N. Sokotushchenko. "Simulation of a gas-condensate mixture passing through a porous medium in depletion mode". Russian Family Doctor 27, n. 3 (15 dicembre 2019): 205–16. http://dx.doi.org/10.17816/rfd10665.

Testo completo

Abstract (sommario):

One of important tasks in a development of gas-condensate fields is to minimize hydrocarbons loss arising from the gas condensation in pores of the gas-bearing layer. The search for the optimal gas production regime is carried out both on the basis of laboratory experiments and on the base of computer simulation. In this regard, the relevant is the verification of the constructed mathematical models by means of comparison of numerical results with experimental data obtained on the laboratory models of a hydrocarbon reservoirs. Within the classical approach on the basis of the Darcy law and the law continuity for flows, the model is formulated that describes the passing a multicomponent gas-condensate mixture through a porous medium in the depletion mode. The numerical solution of the corresponding system of nonlinear partial differential equations is implemented on the basis of the combined use of the C++ programming language and the Maple software. Shown that the approach used provides an agreement of results of numerical simulations with experimental data on the dynamics of hydrocarbon recoverability depending on the pressure obtained at VNIIGAZ, Ukhta.

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46

Volokhova, Alina V., Elena V. Zemlyanaya, Vladimir V. Kachalov, Victor S. Rikhvitsky e Vadim N. Sokotushchenko. "Simulation of a gas-condensate mixture passing through a porous medium in depletion mode". Discrete and Continuous Models and Applied Computational Science 27, n. 3 (15 dicembre 2019): 205–16. http://dx.doi.org/10.22363/2658-4670-2019-27-3-205-216.

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Abstract (sommario):

One of important tasks in a development of gas-condensate fields is to minimize hydrocarbons loss arising from the gas condensation in pores of the gas-bearing layer. The search for the optimal gas production regime is carried out both on the basis of laboratory experiments and on the base of computer simulation. In this regard, the relevant is the verification of the constructed mathematical models by means of comparison of numerical results with experimental data obtained on the laboratory models of a hydrocarbon reservoirs. Within the classical approach on the basis of the Darcy law and the law continuity for flows, the model is formulated that describes the passing a multicomponent gas-condensate mixture through a porous medium in the depletion mode. The numerical solution of the corresponding system of nonlinear partial differential equations is implemented on the basis of the combined use of the C++ programming language and the Maple software. Shown that the approach used provides an agreement of results of numerical simulations with experimental data on the dynamics of hydrocarbon recoverability depending on the pressure obtained at VNIIGAZ, Ukhta.

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47

Vesvikar, M. S., R. Varma, K. Karim e M. Al-Dahhan. "Flow pattern visualization in a mimic anaerobic digester: experimental and computational studies". Water Science and Technology 52, n. 1-2 (1 luglio 2005): 537–43. http://dx.doi.org/10.2166/wst.2005.0564.

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Advanced non-invasive experiments like computer automated radioactive particle tracking and computed tomography along with computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have appreciable effect on the flow pattern of the digesters.

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48

Högblom, Olle, e Ronnie Andersson. "Multiphysics CFD Simulation for Design and Analysis of Thermoelectric Power Generation". Energies 13, n. 17 (22 agosto 2020): 4344. http://dx.doi.org/10.3390/en13174344.

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The multiphysics simulation methodology presented in this paper permits extension of computational fluid dynamics (CFD) simulations to account for electric power generation and its effect on the energy transport, the Seebeck voltage, the electrical currents in thermoelectric systems. The energy transport through Fourier, Peltier, Thomson and Joule mechanisms as a function of temperature and electrical current, and the electrical connection between thermoelectric modules, is modeled using subgrid CFD models which make the approach computational efficient and generic. This also provides a solution to the scale separation problem that arise in CFD analysis of thermoelectric heat exchangers and allows the thermoelectric models to be fully coupled with the energy transport in the CFD analysis. Model validation includes measurement of the relevant fluid dynamic properties (pressure and temperature distribution) and electric properties (current and voltage) for a turbulent flow inside a thermoelectric heat exchanger designed for automotive applications. Predictions of pressure and temperature drop in the system are accurate and the error in predicted current and voltage is less than 1.5% at all exhaust gas flow rates and temperatures studied which is considered very good. Simulation results confirm high computational efficiency and stable simulations with low increase in computational time compared to standard CFD heat-transfer simulations. Analysis of the results also reveals that even at the lowest heat transfer rate studied it is required to use a full two way coupling in the energy transport to accurately predict the electric power generation.

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Putra, Ryan Anugrah, Martin Neumann-Kipping, Thomas Schäfer e Dirk Lucas. "Comparison of Gas–Liquid Flow Characteristics in Geometrically Different Swirl Generating Devices". Energies 12, n. 24 (7 dicembre 2019): 4653. http://dx.doi.org/10.3390/en12244653.

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The gas–liquid flow characteristics for blade, single, and the double-helical swirl elements were numerically investigated and compared in this work. The Euler–Euler model assuming bi-modal bubble size distributions was used. The experiment, conducted in a vertical pipe equipped with a static blade swirl element, was used as the basis for the computational fluid dynamics (CFD) simulations. In the experiment, high-resolution gamma-ray computed tomography (HireCT) was used to measure the gas volume fractions at several planes within the blade swirl element. The resulting calculated profiles of the pressure, liquid and gas velocities as well as the gas fraction showed a large influence of the swirl elements’ geometry. The evolution and characteristics of the calculated gas–liquid phase distributions in different measurement planes were found to be unique for each type of swirl element. A single gas core in the center of the pipe was observed from the simulation of the blade element, while multiple cores were observed from the simulations of the single and double helix elements. The cross-sectional gas distribution downstream of the single and double helical elements changed drastically within a relatively short distance downstream of the elements. In contrast, the single gas core downstream of the blade element was more stable.

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Xu, Jianping, Yuanda Yuan, Qing Xie e Xuegang Wei. "Research on the application of molecular simulation technology in enhanced oil-gas recovery engineering". E3S Web of Conferences 233 (2021): 01124. http://dx.doi.org/10.1051/e3sconf/202123301124.

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In recent years, molecular simulations have received extensive attention in the study of reservoir fluid and rock properties, interactions, and related phenomena at the atomistic scale. For example, in molecular dynamics simulation, interesting properties are taken out of the time evolution analysis of atomic positions and velocities by numerical solution of Newtonian equations for all atomic motion in the system. These technologies assists conducting “computer experiments” that might instead of be impossible, very costly, or even extremely perilous to carry out. Whether it is from the primary oil recovery to the tertiary oil recovery or from laboratory experiment to field test, it is difficult to clarify the oil displacement flow mechanism of underground reservoirs. Computer molecular simulation reveals the seepage mechanism of a certain oil displacement at the microscopic scale, and enriches the specific oil displacement flow theory system. And the molecular design and effect prediction of a certain oil-displacing agent were studied, and its role in the reservoir was simulated, and the most suitable oil-displacing agent and the best molecular structure of the most suitable oil-displacing agent were obtained. To give a theoretical basic for the development of oilfield flooding technology and enhanced oil/gas recovery. This paper presents an overview of molecular simulation techniques and its applications to explore enhanced oil/gas recovery engineering research, which will provide useful instructions for characterizing the reservoir fluid and rock and their behaviors in various oil-gas reserves, and it greatly contribute to perform optimal operation and better design of production plants.

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