A simulated grinding wheel (GW), a numerical representative that describes the geometric and physical properties of realistic GWs, is the prerequisite and foundation of grinding research. However, most proposed numeri...
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A simulated grinding wheel (GW), a numerical representative that describes the geometric and physical properties of realistic GWs, is the prerequisite and foundation of grinding research. However, most proposed numerical GWs treated realistic GWs as continuums without internal structure (e.g., binder and pores) and analyzed realistic GWs' behaviors based on continuum-based material theories. To fill this gap, this study attempts to introduce a discontinuum-based method, discrete element method (DEM), into GW modeling and simulation. DEM GW simulation begins with two grinding-customized modifications to classic DEM theory. Then, with the aid of experimental measurement and statistical analysis, a DEM GW is modeled. Experimental validations are conducted thereafter. Results show acceptable agreements between DEM and realistic GWs in terms of topography, microscopic structure, fracture behavior in compressive test, and performance in grinding process. The proposed DEM GW's ability in describing a discontinuous structure of realistic GWs covers the shortage of existing numerical GWs and might have other promising applications (e.g., GW formula optimization in production, GW preparation technology and parameter optimization, and GW wear and life prediction).
The objective of this work is twofold. Firstly, the effects of turbulence intensity variations on the turbulent droplet dispersion, vaporization and mixing for non-reacting sprays (with and without swirl) are pointed ...
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The objective of this work is twofold. Firstly, the effects of turbulence intensity variations on the turbulent droplet dispersion, vaporization and mixing for non-reacting sprays (with and without swirl) are pointed out. Secondly, the effects of the coupling of the turbulence modulation with external parameters, such as swirl intensity, on turbulent spray combustion are analyzed in configurations of engineering importance. This is achieved by using advanced models for turbulence, evaporation and turbulence modulation implemented into FASTEST-LAG3D-codes: (1) To highlight the influence of turbulence modulation on some spray properties, a thermodynamically consistent modulation model has been considered besides the standard assumption and the well known Crowe's model. For turbulent droplet dispersion, we rely on the Markov-sequence formulation. (2) In order to characterize phase transition processes ongoing on droplets surfaces, a non-equilibrium evaporation model shows better agreement with experiments in comparison with the quasi-equilibrium-based evaporation models often used. (3) The results of turbulence intensity variations reveal the existence of a limited range out of which the increase or decrease of the turbulence intensity affects no more the efficiency of the heat and mass transfer. A derived characteristic number, a vaporization Damkholer number, possesses a critical value which separates two different behavior regimes with respect to the turbulence/droplet vaporization interactions. (4) Under reacting conditions, it is shown how the evaporation characteristics, mixing rate and combustion process are strongly influenced by swirl intensity and turbulence modulation. In particular, the turbulence modulation modifies the evaporation rate, which in turn influences the mixing and the species concentration distribution. In the case under investigation, it is demonstrated that this effect cannot be neglected for low swirl intensities (***. <= 1) in the region
The offshore oil industry functions in a team work culture, in which operations depend not only on individuals' competency, but also on team skills. Team skills are even more necessary when it comes to handling em...
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The offshore oil industry functions in a team work culture, in which operations depend not only on individuals' competency, but also on team skills. Team skills are even more necessary when it comes to handling emergency conditions as they challenge personnel on board with high risk, time pressure, and complexity. This raises the need for training that goes beyond conventional training programs and incorporates team skills exercises. The major difficulty to design such training is that it involves practicing emergency exercises with a potentially large number of participants. Such large-scale team exercises suffer from both organizational and educational drawbacks. One solution to this problem is to use artificial agents that can reproduce the behavior of the team members. This paper presents a behavior model that can simulate the response of general personnel during emergency situations. The variability in human behavior is modeled using different performance influencing factors (PIFs). Empirical evidence is used to identify the sources of variability that are encoded in the agents to allow a realistic range of human behaviors. Though variability can come from both physical and mental differences, the focus of this paper is on the later. Focus is given to across-subject variability rather than within-subject variability.
An effective energy storage approach, such as Power-to-Gas, is essential to provide the grid with a steady supply of power generated by renewable sources. In a Power-to-Gas concept, excess renewable energy is stored i...
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An effective energy storage approach, such as Power-to-Gas, is essential to provide the grid with a steady supply of power generated by renewable sources. In a Power-to-Gas concept, excess renewable energy is stored in the form of H-2 which, in turn, can react with CO2 from sources such as biogas to be converted into CH4 and generate Renewable Natural Gas (RNG). Methanation however, is an exothermic and equilibrium-limited reaction which suffers from poor heat management when carried-out in conventional packed-bed reactors. Additionally, unreacted H-2 mixed with CH4 has to be removed before the RNG is injected into the pipeline. To improve the methanation of biogas, two commercial high temperature reactive separation systems have been studied numerically in this work: (i) an extractor/distributor membrane reactor employing a carbon molecular sieve membrane;(ii) a distributor membrane reactor using a palladium membrane. Both configurations have been shown to considerably reduce the content of CO2 and H-2 in the resulting RNG and, hence, the post-processing efforts needed as compared to a packed-bed reactor operating under the same conditions.
The modeling and simulation of social networks is an important approach to better understanding complex social phenomena, especially when the inner structure has remarkable impact on behavior. With the availability of...
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The modeling and simulation of social networks is an important approach to better understanding complex social phenomena, especially when the inner structure has remarkable impact on behavior. With the availability of unprecedented data sets, simulating large-scale social networks of millions, or even billions, of entities has become a new challenge. Current simulation environments for social studies are mostly sequential and may not be efficient when social networks grow to a certain size. In order to facilitate large-scale social network modeling and simulation, this paper proposes a framework named SUPE-Net, which is based on a parallel discrete event simulation environment YH-SUPE for massively parallel architectures. The framework is designed as a layered architecture with utilities for network generation, algorithms and agent-based modeling. Distributed adjacency lists are used for graph modeling and a reaction-diffusion paradigm is adapted to model dynamical processes. Experiments are performed using PageRank and the susceptible-infected-recovered (SIR) model on social networks with millions of entities. The results demonstrate that SUPE-Net has achieved a speedup of 12, and increased the event-processing rate by 11%, with good scalability and effectiveness.
Heat pipes have been extensively studied using various methods, such as MATLAB, AMESIM, and commercial CFD software. Early numerical models employed the thermal conductance approach, which oversimplified the character...
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Heat pipes have been extensively studied using various methods, such as MATLAB, AMESIM, and commercial CFD software. Early numerical models employed the thermal conductance approach, which oversimplified the characteristics and performance of heat pipes. Newer models comprise the thermal resistance model, which emphasizes two-phase heat transfer, AI-based approaches for predicting flow patterns and thermal characteristics, and the CFD model, which accounts for phase changes and two-phase flow utilizing the VoF and phase change models. Although the thermal resistance model demands fewer computing resources, it has limited visualization of the flow pattern and wick structure. In contrast, CFD models offer advantages in visualizing the flow pattern and thermal characteristics but have limitations in terms of consuming computing resources and considering heat transfer from wick structures and mass transfer rates caused by phase changes. Consequently, most simulations are validated with experimental results. Innovative approaches for phase changes in heat pipes and wick structures are necessary to address these challenges.
Previously, several mathematical models have been proposed for liquid liquid extraction processes involving a rotating-disk-contactor (RDC) column. Most of these models reveal that hydrodynamic and mass-transfer pheno...
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Previously, several mathematical models have been proposed for liquid liquid extraction processes involving a rotating-disk-contactor (RDC) column. Most of these models reveal that hydrodynamic and mass-transfer phenomena are important for predicting the performance of the column. In this paper, a mathematical model, using a new scheme, was developed to acquire a simulation tool to predict the performance of a RDC column used in lubricating-oil production. Field data obtained in a RDC column of 4.1 m diameter, 222 m height, and 32 disks, from a commercial lubricating-oil production company, were used to evaluate the predictions. The model is used for parametric study to investigate the effects of operational data such as the solvent and feed temperatures, solvent-to-feed ratio, and disk rotation rate on the extraction yield.
Hot strips are presently being rolled out with considerable thickness accuracy. This has been made possible due to superordinated control system comprising of adaptive setup model, monitor thickness control, automatic...
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Hot strips are presently being rolled out with considerable thickness accuracy. This has been made possible due to superordinated control system comprising of adaptive setup model, monitor thickness control, automatic gauge control, tension and looper control, hydraulic gap control etc. The present work is, however, confined to modeling and simulation studies of hydraulic gap control system in the last stand of the finishing mill of a typical hot strip mill (HSM). The simulation results based on the model show that the system operates effectively to provide high thickness accuracy and good response behavior.
Large service centers are becoming widely used to host many different services on a shared computing infrastructure, for which autonomic control and management are necessary to meet the service quality targets and max...
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Large service centers are becoming widely used to host many different services on a shared computing infrastructure, for which autonomic control and management are necessary to meet the service quality targets and maximize the overall profit. This paper presents the architecture, design and implementation of a framework for modeling and simulating virtualized autonomic service centers. This provides methods of estimating the system behavior for capacity planning before real establishment or execution. In addition, the performance of an existing service center can be efficiently evaluated. Performance analysis shows that our system is moderately efficient to perform large-scale simulation. Moreover, detailed evaluation results also depict various aspects of the feasibility and the efficiency of our modeling and simulation approaches, which can help to improve the productivity of researchers via quick proof of concepts.
Ultrasonic waves have been extensively used in many industrial applications including clean devices, pipes and vessels. A clear extension of this usage is the removal of wellbore contaminants by exposing it to high-po...
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Ultrasonic waves have been extensively used in many industrial applications including clean devices, pipes and vessels. A clear extension of this usage is the removal of wellbore contaminants by exposing it to high-power ultrasonic waves. In this paper, a mathematical model for ultrasonic propagation through the porous medium around the wellbore is presented. The equations of wave propagation are written in a cylindrical coordinate according to Biot theory and the induced stress in the rock are calculated at each point using finite difference approach Comparison of imposed local stresses with adhesion forces between scales and rock, the properties of ultrasonic transducer, such as frequency and amplitude, which are needed for breaking adhesion forces, can be determined. The results show that the wave with frequency about 25 kHz and amplitude about 50 microns will apply up to 107 Pa radial stress to the adhesion surface between deposits and rock and has ability to clean the pores, if the required stress for separation of scales is smaller than this applied stress.
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