Articoli di riviste: "Simulation validée"

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Secretan, Y., M. Leclerc, S. Duchesne e M. Heniche. "Une méthodologie de modélisation numérique de terrain pour la simulation hydrodynamique bidimensionnelle". Revue des sciences de l'eau 14, n. 2 (12 aprile 2005): 187–212. http://dx.doi.org/10.7202/705417ar.

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L'article pose la problématique de la construction du Modèle Numérique de Terrain (MNT) dans le contexte d'études hydrauliques à deux dimensions, ici reliées aux inondations. La difficulté est liée à l'hétérogénéité des ensembles de données qui diffèrent en précision, en couverture spatiale, en répartition et en densité, ainsi qu'en géoréférentiation, notamment. Dans le cadre d'un exercice de modélisation hydrodynamique, toute la région à l'étude doit être documentée et l'information portée sur un support homogène. L'article propose une stratégie efficace supportée par un outil informatique, le MODELEUR, qui permet de fusionner rapidement les divers ensembles disponibles pour chaque variable qu'elle soit scalaire comme la topographie ou vectorielle comme le vent, d'en préserver l'intégrité et d'y donner accès efficacement à toutes les étapes du processus d'analyse et de modélisation. Ainsi, quelle que soit l'utilisation environnementale du modèle numérique de terrain (planification d'aménagement, conservation d'habitats, inondations, sédimentologie), la méthode permet de travailler avec la projection des données sur un support homogène de type maillage d'éléments finis et de conserver intégralement l'original comme référence. Cette méthode est basée sur une partition du domaine d'analyse par type d'information : topographie, substrat, rugosité de surface, etc.. Une partition est composée de sous-domaines et chacun associe un jeu de données à une portion du domaine d'analyse par un procédé déclaratoire. Ce modèle conceptuel forme à notre sens le MNT proprement dit. Le processus de transfert des données des partitions à un maillage d'analyse est considéré comme un résultat du MNT et non le MNT lui-même. Il est réalisé à l'aide d'une technique d'interpolation comme la méthode des éléments finis. Suite aux crues du Saguenay en 1996, la méthode a pu être testée et validée pour en démontrer l'efficacité. Cet exemple nous sert d'illustration.

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Mueller, Patrick, Matthias Lehmann e Alexander Braun. "Simulating tests to test simulation". Electronic Imaging 2020, n. 16 (26 gennaio 2020): 149–1. http://dx.doi.org/10.2352/issn.2470-1173.2020.16.avm-148.

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Simulation is an established tool to develop and validate camera systems. The goal of autonomous driving is pushing simulation into a more important and fundamental role for safety, validation and coverage of billions of miles. Realistic camera models are moving more and more into focus, as simulations need to be more then photo-realistic, they need to be physical-realistic, representing the actual camera system onboard the self-driving vehicle in all relevant physical aspects – and this is not only true for cameras, but also for radar and lidar. But when the camera simulations are becoming more and more realistic, how is this realism tested? Actual, physical camera samples are tested in laboratories following norms like ISO12233, EMVA1288 or the developing P2020, with test charts like dead leaves, slanted edge or OECF-charts. In this article we propose to validate the realism of camera simulations by simulating the physical test bench setup, and then comparing the synthetical simulation result with physical results from the real-world test bench using the established normative metrics and KPIs. While this procedure is used sporadically in industrial settings we are not aware of a rigorous presentation of these ideas in the context of realistic camera models for autonomous driving. After the description of the process we give concrete examples for several different measurement setups using MTF and SFR, and show how these can be used to characterize the quality of different camera models.

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BIAŁASZ, Sebastian, e Ramon PAMIES. "NUMERICAL SIMULATION OF THE DESIGN OF EXTRUSION PROCESS OF POLYMERIC MINI-TUBES". Applied Computer Science 14, n. 3 (30 settembre 2018): 81–95. http://dx.doi.org/10.35784/acs-2018-23.

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In this paper we represent a study reporting the numerical simulation of small-diameter pipes extrusion process. Polypropylene and low density polyethylene were chosen as plastics and a selected transverse head as a tool in the simulations. The aim of the study is to examine the distribution of temperature in the individual sections of the bagasse and tools, in order to optimize the parameters and process flow extrusion and validate the implementation tools, by simulating the flow of plastic by the head.

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Youngman, Benjamin D., e David B. Stephenson. "A geostatistical extreme-value framework for fast simulation of natural hazard events". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, n. 2189 (maggio 2016): 20150855. http://dx.doi.org/10.1098/rspa.2015.0855.

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We develop a statistical framework for simulating natural hazard events that combines extreme value theory and geostatistics. Robust generalized additive model forms represent generalized Pareto marginal distribution parameters while a Student’s t -process captures spatial dependence and gives a continuous-space framework for natural hazard event simulations. Efficiency of the simulation method allows many years of data (typically over 10 000) to be obtained at relatively little computational cost. This makes the model viable for forming the hazard module of a catastrophe model. We illustrate the framework by simulating maximum wind gusts for European windstorms, which are found to have realistic marginal and spatial properties, and validate well against wind gust measurements.

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Jones, Jenny. "Researchers Validate Alternative Seismic Simulation Method". Civil Engineering Magazine Archive 83, n. 9 (ottobre 2013): 38–39. http://dx.doi.org/10.1061/ciegag.0000656.

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Cavargna, Augusto, Luigi Mongibello, Marcello Iasiello e Nicola Bianco. "Analysis of a Phase Change Material-Based Condenser of a Low-Scale Refrigeration System". Energies 16, n. 9 (28 aprile 2023): 3798. http://dx.doi.org/10.3390/en16093798.

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This study concerns the numerical simulation and the experimental implementation of a low-scale Phase Change Material-based (PCM-based) condenser, to be included in a PCM-based portable cooling systems. In this category of cooling systems, the PCM can be integrated either in the condenser or in the evaporator. In the present study, the PCM is integrated in the condenser of the vapor compression cycle to absorb the heat power released from the refrigerant fluid (R134a) during condensation, thus eliminating the need to transfer heat to the external environment. The main objective of the present study is to realize and validate a numerical model capable of simulating both the refrigerant fluid and the PCM thermofluid dynamics. For this purpose, a commercial solver was used for the implementation of the developed numerical model, and experimental tests were performed to validate the numerical simulations results. The paper reports the details and test results of both the numerical model and the experimental apparatus. The simulation results indicate a good accordance between the numerical and experimental data.

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Sheng, Chunyang, Kenichi Nomura, Pankaj Rajak, Aiichiro Nakano, Rajiv K. Kalia e Priya Vashishta. "Quantum Molecular Dynamics Validation of Nanocarbon Synthesis by High-Temperature Oxidation of Nanoparticles". MRS Advances 1, n. 24 (2016): 1811–16. http://dx.doi.org/10.1557/adv.2016.413.

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ABSTRACTThis study uses ab initio quantum molecular dynamics (QMD) simulations to validate multimillion-atom reactive molecular dynamics (RMD) simulations, and predicts unexpected condensation of carbon atoms during high-temperature oxidation of silicon-carbide nanoparticles (nSiC). For the validation process, a small nSiC in oxygen environment is chosen to perform QMD simulation. The QMD results provide the number of Si-O and C-O bonds as a function of time. RMD simulation is then performed under the identical condition. The time evolutions of different bonds are compared between the QMD and RMD simulations. We observe the condensation of large number of C-cluster nuclei into larger C clusters in both simulations, thereby validating RMD. Furthermore, we use the QMD simulation results as an input to a multi-objective genetic algorithm to train the RMD force-field parameters. The resulting force field far better reproduces the ground-truth QMD simulation results.

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Nemes, Dániel, e Sándor Hajdu. "Simulation of BLDC Motor Drive Systems for Electric Vehicles Using Matlab Simulink". International Journal of Engineering and Management Sciences 8, n. 1 (30 aprile 2023): 48–52. http://dx.doi.org/10.21791/ijems.2023.1.6.

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The defining scientific developments of our time would not have been possible without the use of simulations. The aim of the research is to create a simulation of a BLDC motor. When creating a simulation, great emphasis must be placed on defining the purpose of the simulation. This basically determines the structure and complexity of the model. The model discussed here was created so that an optimization task could be defined more precisely by inserting it as a sub-model into a vehicle dynamics model. Scalability was another aspect, that is, to be able to increase the accuracy of the model with measured data in the future, as well as to be able to validate it. During the research, a BLDC motor efficiency map generation program was created, as well as an environment for testing the generated data. The created system gives researchers the opportunity to use a shape-correct efficiency model when simulating a BLDC motor even without measured data. This makes it possible to discover real relationships between model parameters when performing optimization.

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Durst, Phillip J., Derek T. Anderson e Cindy L. Bethel. "A historical review of the development of verification and validation theories for simulation models". International Journal of Modeling, Simulation, and Scientific Computing 08, n. 02 (9 gennaio 2017): 1730001. http://dx.doi.org/10.1142/s1793962317300011.

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Modeling and simulation (M&S) play a critical role in both engineering and basic research processes. Computer-based models have existed since the 1950s, and those early models have given way to the more complex computational and physics-based simulations used today. As such, a great deal of research has been done to establish what level of trust should be given to simulation outputs and how to verify and validate the models used in these simulations. This paper presents an overview of the theoretical work done to date defining formal definitions for, and methods of, verification and validation (V&V) of computer models. Simulation models are broken down into three broad categories: analytical and simulation models, computational and physics-based models, and simulations of autonomous systems, and the unique theories and methods developed to address V&V of these models are presented. This paper also presents the current problems in the theoretical field of V&V for models as simulations move from single system models and simulations to more complex simulation tools. In particular, this paper highlights the lack of agreed-upon methods for V&V of simulations of autonomous systems, such as an autonomous unmanned vehicles, and proposes some next steps needed to address this problem.

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Bindle, Liam, Randall V. Martin, Matthew J. Cooper, Elizabeth W. Lundgren, Sebastian D. Eastham, Benjamin M. Auer, Thomas L. Clune et al. "Grid-stretching capability for the GEOS-Chem 13.0.0 atmospheric chemistry model". Geoscientific Model Development 14, n. 10 (6 ottobre 2021): 5977–97. http://dx.doi.org/10.5194/gmd-14-5977-2021.

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Abstract. Modeling atmospheric chemistry at fine resolution globally is computationally expensive; the capability to focus on specific geographic regions using a multiscale grid is desirable. Here, we develop, validate, and demonstrate stretched grids in the GEOS-Chem atmospheric chemistry model in its high-performance implementation (GCHP). These multiscale grids are specified at runtime by four parameters that offer users nimble control of the region that is refined and the resolution of the refinement. We validate the stretched-grid simulation versus global cubed-sphere simulations. We demonstrate the operation and flexibility of stretched-grid simulations with two case studies that compare simulated tropospheric NO2 column densities from stretched-grid and cubed-sphere simulations to retrieved column densities from the TROPOspheric Monitoring Instrument (TROPOMI). The first case study uses a stretched grid with a broad refinement covering the contiguous US to produce simulated columns that perform similarly to a C180 (∼ 50 km) cubed-sphere simulation at less than one-ninth the computational expense. The second case study experiments with a large stretch factor for a global stretched-grid simulation with a highly localized refinement with ∼10 km resolution for California. We find that the refinement improves spatial agreement with TROPOMI columns compared to a C90 cubed-sphere simulation of comparable computational demands. Overall, we find that stretched grids in GEOS-Chem are a practical tool for fine-resolution regional- or continental-scale simulations of atmospheric chemistry. Stretched grids are available in GEOS-Chem version 13.0.0.

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Fan, Pengfei, Fei Ding, Xichun Luo, Yongda Yan, Yanquan Geng e Yuzhang Wang. "A Simulated Investigation of Ductile Response of GaAs in Single-Point Diamond Turning and Experimental Validation". Nanomanufacturing and Metrology 3, n. 4 (13 novembre 2020): 239–50. http://dx.doi.org/10.1007/s41871-020-00080-5.

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AbstractIn this paper, molecular dynamic (MD) simulation was adopted to study the ductile response of single-crystal GaAs during single-point diamond turning (SPDT). The variations of cutting temperature, coordination number, and cutting forces were revealed through MD simulations. SPDT experiment was also carried out to qualitatively validate MD simulation model from the aspects of normal cutting force. The simulation results show that the fundamental reason for ductile response of GaAs during SPDT is phase transition from a perfect zinc blende structure (GaAs-I) to a rock-salt structure (GaAs-II) under high pressure. Finally, a strong anisotropic machinability of GaAs was also found through MD simulations.

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Li, Wanwan. "Fast Fluid Thermodynamics Simulation by Solving Heat Diffusion Equation". International Journal of Computer Graphics & Animation 11, n. 04 (31 ottobre 2021): 1–11. http://dx.doi.org/10.5121/ijcga.2021.11401.

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In mechanical engineering educations, simulating fluid thermodynamics is rather helpful for students to understand the fluid’s natural behaviors. However, rendering both high-quality and realtime simulations for fluid dynamics are rather challenging tasks due to their intensive computations. So, in order to speed up the simulations, we have taken advantage of GPU acceleration techniques to simulate interactive fluid thermodynamics in real-time. In this paper, we present an elegant, basic, but practical OpenGL/SL framework for fluid simulation with a heat map rendering. By solving Navier-Stokes equations coupled with the heat diffusion equation, we validate our framework through some real-case studies of the smoke-like fluid rendering such as their interactions with moving obstacles and their heat diffusion effects. As shown in Fig. 1, a group of experimental results demonstrates that our GPU-accelerated solver of Navier-Stokes equations with heat transfer could give the observers impressive real-time and realistic rendering results.

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Behera, Abhinna K., Emmanuel D. Rivière, Sergey M. Khaykin, Virginie Marécal, Mélanie Ghysels, Jérémie Burgalat e Gerhard Held. "On the cross-tropopause transport of water by tropical convective overshoots: a mesoscale modelling study constrained by in situ observations during the TRO-Pico field campaign in Brazil". Atmospheric Chemistry and Physics 22, n. 2 (19 gennaio 2022): 881–901. http://dx.doi.org/10.5194/acp-22-881-2022.

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Abstract. Deep convection overshooting the lowermost stratosphere is well known for its role in the local stratospheric water vapour (WV) budget. While it is seldom the case, local enhancement of WV associated with stratospheric overshoots is often published. Nevertheless, one debatable topic persists regarding the global impact of this event with respect to the temperature-driven dehydration of air parcels entering the stratosphere. As a first step, it is critical to quantify their role at a cloud-resolving scale before assessing their impact on a large scale in a climate model. It would lead to a nudging scheme for large-scale simulation of overshoots. This paper reports on the local enhancements of WV linked to stratospheric overshoots, observed during the TRO-Pico campaign conducted in March 2012 in Bauru, Brazil, using the BRAMS (Brazilian version of the Regional Atmospheric Modeling System; RAMS) mesoscale model. Since numerical simulations depend on the choice of several preferred parameters, each having its uncertainties, we vary the microphysics or the vertical resolution while simulating the overshoots. Thus, we produce a set of simulations illustrating the possible variations in representing the stratospheric overshoots. To better resolve the stratospheric hydration, we opt for simulations with the 800 m horizontal-grid-point presentation. Next, we validate these simulations against the Bauru S-band radar echo tops and the TRO-Pico balloon-borne observations of WV and particles. Two of the three simulations' setups yield results compatible with the TRO-Pico observations. From these two simulations, we determine approximately 333–2000 t of WV mass prevailing in the stratosphere due to an overshooting plume depending on the simulation setup. About 70 % of the ice mass remains between the 380 and 385 K isentropic levels. The overshooting top comprises pristine ice and snow, while aggregates only play a role just above the tropopause. Interestingly, the horizontal cross section of the overshooting top is about 450 km2 at the 380 K isentrope, which is similar to the horizontal-grid-point resolution of a simulation that cannot compute overshoots explicitly. In a large-scale simulation, these findings could provide guidance for a nudging scheme of overshooting hydration or dehydration.

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Lino, Rafael Luis Bressani, Suelen Alves Oliveira, Kellyn Patrícia Da Silva e Regimar Carla Machado. "Validação de checklist para avaliação da capacitação com simulação clínica do atendimento ao paciente séptico". Enfermería Global 18, n. 4 (17 settembre 2019): 159–97. http://dx.doi.org/10.6018/eglobal.18.4.341171.

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Aims: Development and validation of the contents of a checklist to evaluate the qualification of health professionals in septic patient care with clinical simulation.Method: instrument validation study, with two-stage structural design: instrument construction and validation of the checklist contents using the Delphi technique in two rounds.Results: The content validation was composed of ten items and forty-three sub-items analyzed by the evaluators. Through the Content Validity Index, four items with strong validation evidence were identified, Content Validity Index ≥ 0.8. We restructured the checklist according to the evaluators recommendations, maintaining the ten items, but reducing them to twenty-six sub-items, which in the second round Delphi presented a percentage of agreement above 80% for all variables relevant to the instrument.Conclusion: This method was effective to validate the checklist contents that will evaluate the qualification of health professionals in septic patient care, through clinical simulation. Objetivo: Construir y validar el contenido de un checklist para evaluación de la capacitación de profesionales del área de la salud en la atención al paciente séptico con simulación clínica.Método: Estudio de validación metodológica de instrumento, con delineamiento estructural en dos etapas: construcción del instrumento y validación de contenido del checklist utilizando la técnica Delphi en dos rondas.Resultados: La validación de contenido fue compuesta por diez ítems y cuarenta y tres subítems analizados por los evaluadores. A través del Índice de Validez de Contenido, se identificaron cuatro ítems con fuerte evidencia de validación, Índice de Validez de Contenido ≥ 0,8. En la segunda ronda Delphi presentó un porcentaje de concordancia superior al 80% para todas las variables pertinentes al instrumento. Se reestructuró el checklist según recomendaciones de los evaluadores, manteniendo los diez ítems, pero con reducción para veintiséis subítems, que en la segunda ronda Delphi presentó un porcentaje de concordancia superior al 80% para todas las variables pertinentes al instrumento.Conclusión: Método fue eficaz para validar el contenido de un checklist que evaluará la capacitación de profesionales de la salud en la atención al paciente séptico, por medio de simulación clínica. Objetivos: Construir e validar o conteúdo de um checklist para avaliação da capacitação de profissionais da área da saúde no atendimento ao paciente séptico com simulação clínica.Método: Estudo de validação metodológica de instrumento, com delineamento estrutural em duas etapas: construção do instrumento e validação de conteúdo do checklist utilizando a técnica Delphi em duas rodadas. Resultados: A validação de conteúdo foi composta por dez itens e quarenta e três subitens analisados pelos avaliadores. Por meio do Índice de Validade de Conteúdo, identificaram-se quatro itens com forte evidência de validação, Índice de Validade de Conteúdo ≥ 0,8. Reestruturou o checklist conforme recomendações dos avaliadores, mantendo os dez itens, porém com redução para vinte e seis subitens, que na 2ª rodada Delphi apresentou percentual de concordância acima de 80% para todas as variáveis pertinentes ao instrumento. Conclusão: Método foi eficaz para validar o conteúdo de um checklist que avaliará a capacitação de profissionais da saúde no atendimento ao paciente séptico, por meio de simulação clínica.

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Joßberger, Simon, Christa Stadler, Ulf Barkmann, Nicholas Kaufmann e Stefan Riedelbauch. "Interaction between two horizontal axis tidal turbines in model scale – experiment and simulation". International Marine Energy Journal 5, n. 2 (7 ottobre 2022): 173–82. http://dx.doi.org/10.36688/imej.5.173-182.

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Up to 6 Schottel Instream Turbines (SIT250) can be mounted on the tidal platform PLAT-I developed by Sustainable Marine Energy. Due to the close proximity of the turbines interactions can occur between them. Two horizontal axis tidal turbines in model scale are investigated experimentally and numerically to analyze these interactions. Experimental data were measured in a towing tank and consist of integral values for torque, thrust and rotational speed. Both a steady state and an unsteady three-dimensional Reynolds Averaged Navier Stokes (RANS) approach are utilized for simulating the turbine ﬂow ﬁeld. The ﬁrst part of the paper compares simulation results of a single turbine at different tip speed ratios with measurements to validate the numerical approach and its employed models. The second part analyses the interaction between two turbines. The axial distance in main ﬂow direction between the turbines is half the rotor diameter. The radial distance measured between the hubs of the turbines is varied in steps of 0.2 between 0.0 and 2.0 times the rotor diameter in the experiment and between 0.0 and 1.4 in the simulations. Measurements were conducted for tip speed ratios of 3, 4 and 5. In the simulations the tip speed ratio was ﬁxed at 4. The used simulation domain replicates the actual width and height of the towing tank and a sufﬁcient length up- and downstream of the turbines. The water surface is modeled with a free slip wall. Both thrust and torque are compared between simulation results and experimental data. Furthermore, a detailed analysis of the results and ﬂow ﬁeld in the numerical simulations is presented and the interaction between the turbines is discussed.

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Kitis, George, e Vasilis Pagonis. "On the Need for Deconvolution Analysis of Experimental and Simulated Thermoluminescence Glow Curves". Materials 16, n. 2 (16 gennaio 2023): 871. http://dx.doi.org/10.3390/ma16020871.

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Simulation studies of thermoluminescence (TL) and other stimulated luminescence phenomena are a rapidly growing area of research. The presence of competition effects between luminescence pathways leads to the complex nature of luminescence signals, and therefore, it is necessary to investigate and validate the various methods of signal analysis by using simulations. The present study shows that in simulations of luminescence signals originating from multilevel phenomenological models, it is not possible to extract mathematically the individual information for each peak in the signal. It is further shown that computerized curve deconvolution analysis is the only reliable tool for extracting the various kinetic parameters. Simulation studies aim to explain experimental results, and therefore, it is necessary to validate simulation results by comparing with experiments. In this paper, testing of simulation results is performed using two methods. In the first method, the influence of competition effects is tested by comparing the input model parameters with the output values from the deconvolution analysis. In the second method, the agreement with experimental results is tested using the properties of well-known glow peaks with very high repeatability among TL laboratories, such as the 110 °C glow peak of quartz.

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Shan, Jinjun, e Piotr Wenderski. "Hardware-in-the-Loop Simulation for Spacecraft Formation Flying". Journal of Control Science and Engineering 2010 (2010): 1–13. http://dx.doi.org/10.1155/2010/572526.

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This paper presents a hardware-in-the-loop (HITL) simulation approach for multiple spacecraft formation flying. Considering a leader-follower formation flying configuration, a Fuzzy Logic controller is developed first to maintain the desired formation shape under external perturbations and the initial position offsets. Cold-gas on/off thrusters are developed to be introduced to the simulation loop, and the HITL simulations are conducted to validate the effectiveness of the proposed simulation configuration and Fuzzy Logic control.

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Jones, P. N., e P. S. Carberry. "A technique to develop and validate simulation models". Agricultural Systems 46, n. 4 (gennaio 1994): 427–42. http://dx.doi.org/10.1016/0308-521x(94)90105-o.

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Zhang, Wen Jing, Bao Qin Wang, Xu Fang, Xu Yang Zhou e Wei Chao Sha. "Research on Symbol Synchronization Algorithm of LTE System". Applied Mechanics and Materials 347-350 (agosto 2013): 2164–67. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.2164.

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This paper designs and realizes algorithm of symbol synchronization for LTE system. In order to validate the feasibility of symbol timing synchronization algorithm, a series of simulations are performed with LTE channel models and the simulation results are analyzed carefully. Simulation shows that this algorithm has a great advantage of system implementation. It can be found the symbol start position within the shortest time.

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Zadravec, Matej, Blaž Orešnik, Matjaž Hriberšek e Jure Marn. "Two-step validation process of particle mixing in a centrifugal mixer with vertical axis". Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 232, n. 1 (4 novembre 2016): 29–37. http://dx.doi.org/10.1177/0954408916678267.

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Two-step approach of validation is proposed to validate a numerical model, capable of accurate prediction of mixing power characteristics of a centrifugal mixer with vertical axis. Two sets of experiments and two sets of numerical simulations are presented—the first set to determine physical characteristics of the particles comparing the numerical simulations results with experimental data, and the second set to validate predicted behavior of anchor type vertical axis impeller for mixing of same particles. Zeolite particles were used for actual calculations. After determining shear modulus, coefficient of interaction, static friction coefficient, and rolling friction coefficient through optimization process based on numerical simulations with subject function of diameter and angle of repose derived from experiment, using these values in numerical simulation of impeller mixer mixing zeolite particles led to results, which were in good agreement with results of the second set of experiments. The obtained zeolite material parameter values can therefore serve as a solid basis for discrete elements method based numerical simulation of zeolite granular materials.

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Chiou, Rong Nan, e Chia-Nian Shyi. "Adaptive Maximums of Random Variables for Network Simulations". Journal of Computer Systems, Networks, and Communications 2009 (2009): 1–6. http://dx.doi.org/10.1155/2009/383720.

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In order to enhance the precision of network simulations, the paper proposes an approach to adaptively decide the maximum of random variables that create the discrete probabilities to generate nodal traffic on simulated networks. In this paper, a statistical model is first suggested to manifest the bound of statistical errors. Then, according to the minimum probability that generates nodal traffic, a formula is proposed to decide the maximum. In the formula, a precision parameter is used to present the degree of simulative accuracy. Meanwhile, the maximum adaptively varies with the traffic distribution among nodes because the decision depends on the minimum probability generating nodal traffic. In order to verify the effect of the adaptive maximum on simulative precision, an optical network is introduced. After simulating the optical network, the theoretic average waiting time of nodes on the optical network is exploited to validate the exactness of the simulation. The proposed formula deciding the adaptive maximum can be generally exploited in the simulations of various networks. Based on the precision parameterK, a recursive procedure will be developed to automatically produce the adaptive maximum for network simulations in the future.

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Rodríguez-Ocampo, Paola Elizabeth, Michael Ring, Jassiel Vladimir Hernández-Fontes, Juan Carlos Alcérreca-Huerta, Edgar Mendoza e Rodolfo Silva. "CFD Simulations of Multiphase Flows: Interaction of Miscible Liquids with Different Temperatures". Water 12, n. 9 (16 settembre 2020): 2581. http://dx.doi.org/10.3390/w12092581.

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The incorporation of new equations to extend the applicability of open-source computational fluid dynamics (CFD) software according to the user’s needs must be complemented with code verification and validation with a representative case. This paper presents the development and validation of an OpenFOAM®-based solver suitable for simulating multiphase fluid flow considering three fluid phases with different densities and temperatures, i.e., two miscible liquids and air. A benchmark “dam-break” experiment was performed to validate the solver. Ten thermistors measured temperature variations in different locations of the experimental model and the temperature time series were compared against those of numerical probes in analogous locations. The accuracy of the temperature field assessment considered three different turbulence models: (a) zero-equation, (b) k-omega (Reynolds averaged simulation; RAS), and (c) large eddy simulation (LES). The simulations exhibit a maximum time-average relative and absolute errors of 9.3% and 3.1 K, respectively; thus, the validation tests proved to achieve an adequate performance of the numerical model. The solver developed can be applied in the modeling of thermal discharges into water bodies.

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Ghate, Aditya S., e Sanjiva K. Lele. "Subfilter-scale enrichment of planetary boundary layer large eddy simulation using discrete Fourier–Gabor modes". Journal of Fluid Mechanics 819 (27 aprile 2017): 494–539. http://dx.doi.org/10.1017/jfm.2017.187.

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A new multiscale simulation methodology is introduced to facilitate computationally efficient simulations of high Reynolds number turbulence seen in wall-bounded flows. The scale splitting methodology uses traditional large eddy simulation (LES) with a wall model to simulate the larger scales which are subsequently enriched using a space–time compatible kinematic simulation. Computational feasibility and robustness of the methodology are investigated using two idealized problems that emulate turbulence within the planetary boundary layer (PBL), and a finite Reynolds number channel flow problem which serves to validate the methodology against direct numerical simulation. The space–time correlations and spectra generated using enriched LES show excellent agreement with LES conducted at high resolution for all three problems; thereby demonstrating the potential of this approach for high resolution PBL simulations with a drastic reduction in the computational costs when compared to the conventional approach.

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Sang, Zhongqing, Shaojie Li, Yuanyuan Huang, Xin Gao e Rui Qiao. "Indirect Matrix Converter Hardware-in-the-Loop Semi-Physical Simulation Based on Latency-Free Decoupling". Electronics 12, n. 23 (27 novembre 2023): 4802. http://dx.doi.org/10.3390/electronics12234802.

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In the process of hardware-in-the-loop simulations (HILs) of indirect matrix converters (IMCs), solving the mathematical models of complex multiswitching converter topologies has become a major problem. The conventional approach is to split the complex mathematical model into multiple serial subsystems; however, this inevitably produces delays in the simulation steps between different subsystems, leading to numerical oscillations. In this paper, the method of latency-free decoupling is adopted, which has no time-step delay between different subsystems, making each subsystem a parallel operation. This can improve the numerical stability of the simulations and can effectively reduce the step size of the real-time simulation and alleviate the problem of real-time simulation resource consumption. In this paper, we discuss in detail the modeling process of IMC hardware-in-the-loop simulations with Finite Control Set Model Predictive Control (FCS-MPC), and experimentally validate our method using the Speedgoat test platform, resulting in a simulation step size of less than 200 ns. The simulation results are compared with the results of Matlab’s Simpower power system, which allows us to evaluate the accuracy of our model.

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Malaspinas, Orestis, e Pierre Sagaut. "Consistent subgrid scale modelling for lattice Boltzmann methods". Journal of Fluid Mechanics 700 (30 aprile 2012): 514–42. http://dx.doi.org/10.1017/jfm.2012.155.

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AbstractThe lattice Boltzmann method has become a widely used tool for the numerical simulation of fluid flows and in particular of turbulent flows. In this frame the inclusion of subgrid scale closures is of crucial importance and is not completely understood from the theoretical point of view. Here, we propose a consistent way of introducing subgrid closures in the BGK Boltzmann equation for large eddy simulations of turbulent flows. Based on the Hermite expansion of the velocity distribution function, we construct a hierarchy of subgrid scale terms, which are similar to those obtained for the Navier–Stokes equations, and discuss their inclusion in the lattice Boltzmann method scheme. A link between our approach and the standard way on including eddy viscosity models in the lattice Boltzmann method is established. It is shown that the use of a single modified scalar relaxation time to account for subgrid viscosity effects is not consistent in the compressible case. Finally, we validate the approach in the weakly compressible case by simulating the time developing mixing layer and comparing with experimental results and direct numerical simulations.

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Sato, Kenta, e Shunichi Koshimura. "A LATTICE BOLTZMANN APPROACH FOR THREE-DIMENSIONAL TSUNAMI SIMULATION BASED ON THE PLIC-VOF METHOD". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 90. http://dx.doi.org/10.9753/icce.v36.papers.90.

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Free surface flow problems occur in numerous disaster simulations, such as tsunamis inland penetration in urban area. Simulation models for these problems have to be non-hydrostatic and three-dimensional because of the strong non-linearity and higher-order physical phenomena. Despite all the progress in the modern computational fluid dynamics, such simulations still present formidable challenges both from numerical and computational cost point of view. The lattice Boltzmann method (LBM) has been attracting attention as an alternative fluid simulation tool to overcome the problems. In current study, LBM for three-dimensional tsunami simulations is developed which are coupled with the piecewise linear interface calculation with the Volume of Fluid (VOF) approach. This model is for an efficient three-dimensional tsunami simulation by a one-fluid formulation, where the lattice Boltzmann equation is assigned to solve for a single virtual fluid. Various benchmark problems are also carried out to validate the utility of the proposed models in term of coastal engineering.

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Zheng, Xing, Gu Chang Wang, He Yang e Hong Xiang Liu. "Design and Implementation of UAV 3D Visual Simulation Training System". Applied Mechanics and Materials 336-338 (luglio 2013): 1361–65. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.1361.

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UAV visual simulation training system is a vital part of the UAV simulation training system. It is made up of simulation models for UAV and airborne platform mathematical, UAV visual and ground-station control system. It prevents a realistic virtual environment for UAV operator by simulating UAV flight control law and the actual flight environments. In order to train operational level, test weapons and validate tactical thinking economically and efficiently. This paper prevented the function, architecture, hardware deployment, running conditions and realization of real simulation module.

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Okyere, Samuel, Joseph Ackora-Prah, Saleem Abdullah, Samuel Akwasi Adarkwa, Frank Kofi Owusu, Kwame Bonsu, Mary Osei Fokuo e Mary Ann Yeboah. "Analysis of Turberculosis-COVID-19 Coinfection Using Fractional Derivatives". International Journal of Mathematics and Mathematical Sciences 2023 (24 aprile 2023): 1–14. http://dx.doi.org/10.1155/2023/2831846.

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Fractional-order derivative modeling continues to receive great interest among researchers across the globe. In this study, Tuberculosis-COVID-19 coinfection is studied using Atangana–Baleanu fractional-order derivatives defined in Caputo sense. We confirmed the existence and singularity of the solution and investigated the model’s equilibrium points. Additionally, we examined the model’s stability in terms of the Ulam–Hyers and generalized Ulam–Hyers stability criteria. The basic reproduction number R 0 was calculated using the next-generation matrix approach. We also looked into the model’s disease-free equilibrium point’s regional stability. Numerical scheme for simulating the fractional-order system with Mittag–Leffler Kernels are presented. Numerical simulations are given to validate the model. Results of the simulation showed a decline in the number of COVID-19 infections within the population when the fractional operator was reduced.

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Lin, James C., e Robert L. Graney. "Combining Computer Simulation with Physical Simulation: An Attempt to Validate Turf Runoff Models". Weed Technology 6, n. 3 (settembre 1992): 688–95. http://dx.doi.org/10.1017/s0890037x0003606x.

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Predicting the off-target movement of agrochemicals applied to turf is an essential component for assessing risk to aquatic environments. For surface transport, a fully validated model does not exist. Such a model is required to make cost effective risk assessments and regulatory evaluations. To address this deficiency, a turf model validation program is outlined in this paper. The effect of turf characteristics on the fate and movement of pesticides is presented followed by the discussion of the selection for a proper turf runoff model. The design and implementation of small plot runoff studies and their usefulness in model validation are discussed. The procedures of model calibration and model verification are explained for model validation purpose.

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Müller, Armin, Ekaterina Kovacheva, Marc Alexander Fritz, Olaf Dössel e Axel Loewe. "Validating a Numerical Simulation of Human Heart Motion Using Clinical Data". Current Directions in Biomedical Engineering 6, n. 3 (1 settembre 2020): 547–50. http://dx.doi.org/10.1515/cdbme-2020-3140.

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AbstractNumerical simulations are increasingly often involved in developing new and improving existing medical therapies. While the models involved in those simulations are designed to resemble a specific phenomenon realistically, the results of the interplay of those models are often not sufficiently validated. We created a plugin for a cardiac simulation framework to validate the simulation results using clinical MRI data. The MRI data were used to create a static wholeheart mesh as well as slices from the left ventricular short axis, providing the motion over time. The static heart was a starting point for a simulation of the heart’s motion. From the simulation result, we created slices and compared them to the clinical MRI slices using two different metrics: the area of the slices and the point distances. The comparison showed global similarities in the deformation of simulated and clinical data, but also indicated points for potential improvements. Performing this comparison with more clinical data could lead to personalized modeling of elastomechanics of the heart.

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Smietanska, Joanna, Tomasz Kozik, Radoslaw Strzalka, Ireneusz Buganski e Janusz Wolny. "Molecular Dynamics Investigation of Phenolic Oxidative Coupling Protein Hyp-1 Derived from Hypericum perforatum". Crystals 11, n. 1 (6 gennaio 2021): 43. http://dx.doi.org/10.3390/cryst11010043.

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Molecular dynamics (MD) simulations provide a physics-based approach to understanding protein structure and dynamics. Here, we used this intriguing tool to validate the experimental structural model of Hyp-1, a pathogenesis-related class 10 (PR-10) protein from the medicinal herb Hypericum perforatum, with potential application in various pharmaceutical therapies. A nanosecond MD simulation using the all-atom optimized potentials for liquid simulations (OPLS–AA) force field was performed to reveal that experimental atomic displacement parameters (ADPs) underestimate their values calculated from the simulation. The average structure factors obtained from the simulation confirmed to some extent the relatively high compliance of experimental and simulated Hyp-1 models. We found, however, many outliers between the experimental and simulated side-chain conformations within the Hyp-1 model, which prompted us to propose more reasonable energetically preferred rotameric forms. Therefore, we confirmed that MD simulation may be applicable for the verification of refined, experimental models and the explanation of their structural intricacies.

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Erdik, Atıl, Vahdet Ucar e Namik Kilic. "Finite Element and Experimental Analyses of an Armoured Vehicle Subjected to Landmine Blast". Defence Science Journal 65, n. 6 (10 novembre 2015): 477. http://dx.doi.org/10.14429/dsj.65.8594.

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Landmines severely threaten the armoured vehicles. The principal objective is to present a methodology for blast simulations of vehicles subjected to landmine explosions. First, free field blast experiment of 2 kg TNT charge in a steel pot is carried out to validate the blast parameters used in the numerical simulation. Overpressure-time history collected in the free field blast experiment is compared to the numerical simulation results. Numerical simulations are performed in LS-DYNA hydrocode that employs Arbitrary Lagrangian Eulerian formulation enabling a fully coupled interaction between the blast wave, the detonation gases, and the vehicle. Second, the full-scale field test of an armoured vehicle exposed to 6 kg of TNT charge in a steel pot underneath the rear end of the vehicle is conducted. Maximum dynamic deformations measured inside the vehicle are compared to the results calculated in the numerical simulation. Results show that the numerical simulation is in good agreement with the full-scale field test.

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Santos, Alexandre Assis Rezende, Leomar Santos Marques, Marcus Vinicius Ferreira de Moura e Ricardo Rodrigues Magalhães. "Stress-strain analysis of the tow hook of a commercial truck by numerical simulations". Acta Scientiarum. Technology 44 (28 luglio 2022): e60577. http://dx.doi.org/10.4025/actascitechnol.v44i1.60577.

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Numerical simulations have been widely used in the industry, although with some limitations. One of these limitations is the fact that the thermal effects derived from component manufacturing processes are normally disregarded in the analysis. Thus, the main goal of this study is to evaluate strains near the weld beads of a geometric model for a truck tow hook using numerical simulations by finite element method, considering thermal loads applied before the field loading. To validate the simulation results, an experiment was performed using a tow hook found in a commercial truck. Strain gauge rosettes were placed on the body base plate, and a load of 181.050 N was applied to the hook. This loading was the result of a commercial truck being pulled on level terrain, simulating a normal operation condition of the tow hook. The Von Mises stress found in simulations was approximately 302.23 MPa at the same position where the strain gauges were glued, when the load was applied. The difference between the simulated and experimental values of the equivalent specific strains in the area of the weld beads was 19.2%, and the difference between the permanent displacement values, resulting from plastic strain, in the X-direction was 0.1%. These results justify conducting new studies involving numerical simulations and considering thermal effects on static and dynamic loads in the automotive industry.

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Kosey, Vimit V., Prof Harish N. Sayankar e Dr Vinod S. Gorantiwar. "Ballistic Impact Analysis of Thin Shell and Curved Surface against Different Projectile Nose Shape". International Journal for Research in Applied Science and Engineering Technology 11, n. 3 (31 marzo 2023): 1287–96. http://dx.doi.org/10.22214/ijraset.2023.49636.

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Abstract: Numerical simulations are increasingly becomingan important tool to obtain efficient designs of protectivestructures, and the existing literature shows that manyphenomena can be accurately described by standard methodsand models. This thesis, specifically, focuses on novelmethods of modeling and simulating ballistic impact.Experiments are needed to validate such simulations, so numerous tests were studied to investigate how projectile nose-shape, plate layering, target strength, ductility, and workhardening affect the penetration and perforation behavior of various structural configurations. These tests provide new information about the behavior of materials subjected to ballistic impact, and are valuable input for the evaluation ofthe numerical simulations. As more complex materialssystems are introduced in engineering practice, the design engineer faces the of utilizing homogenization techniques or detailed numerical models. The latter offers a number of advantages, such as the ability to introduce separateconstitutive laws and failure criteria for each phase, at theexpense of computation cost. The aim of this study is to givegeneral information about the most commonly used materialsand ballistic test methods. In addition, to summarize the topicsrelated to simulation methods such as FEM and numericalmethods which are use most in ballistics.A generalizednumerical and experimental formulation is presented for theprediction of ballistic impact behavior on various surfacesagainst different projectile nose shape. The ballistic resistance,failure mechanism and the energy absorption of the structurewas investigated thoroughly through experimentation andnumerical simulations. influence of projectile shape, incidencevelocity of the projectile.

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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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Khan, Muhammad A. A., e Anwar K. Sheikh. "Virtual Casting: State of the Art in Metal Casting Simulation Tools". Journal of Engineering Research [TJER] 15, n. 2 (7 novembre 2018): 142. http://dx.doi.org/10.24200/tjer.vol15iss2pp142-154.

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The demands on the productivity and robustness of metal casting processes for high quality components are continuously increasing. Moreover, the financial considerations necessitate meticulous and reliable planning of the entire casting process before it is actually put into practice. A holistic approach to perform cradle to grave analysis of cast products is simulation-based metal casting. This method allows engineers to model, verify, and validate the process followed by its optimization and performance prediction in virtual reality. This paper provides insights on state of the art in simulation-based metal casting with reference to some case studies. Casting simulations software, mathematical models and solution methods, and casting process simulation together with the results obtained are clearly explained. The current practices revealed extensive utilization of simulation packages for defect minimization, yield maximization, and improved quality. The ongoing research on integration of casting simulations with mechanical performance simulations makes it possible to analyze the serviceability of cast parts. The reliability of cast part in service with dynamic loading of varying thermal and mechanical load cycles can be predicted through this integration. However, more rigorous work is needed in this area, particularly by developing the reliability prediction modules embedded in advanced simulation tools.

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Khan, Muhammad A. A., e Anwar K. Sheikh. "Virtual Casting: State of the Art in Metal Casting Simulation Tools". Journal of Engineering Research [TJER] 15, n. 2 (7 novembre 2018): 42. http://dx.doi.org/10.24200/tjer.vol15iss2pp42-54.

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Abstract (sommario):

The demands on the productivity and robustness of metal casting processes for high quality components are continuously increasing. Moreover, the financial considerations necessitate meticulous and reliable planning of the entire casting process before it is actually put into practice. A holistic approach to perform cradle to grave analysis of cast products is simulation-based metal casting. This method allows engineers to model, verify, and validate the process followed by its optimization and performance prediction in virtual reality. This paper provides insights on state of the art in simulation-based metal casting with reference to some case studies. Casting simulations software, mathematical models and solution methods, and casting process simulation together with the results obtained are clearly explained. The current practices revealed extensive utilization of simulation packages for defect minimization, yield maximization, and improved quality. The ongoing research on integration of casting simulations with mechanical performance simulations makes it possible to analyze the serviceability of cast parts. The reliability of cast part in service with dynamic loading of varying thermal and mechanical load cycles can be predicted through this integration. However, more rigorous work is needed in this area, particularly by developing the reliability prediction modules embedded in advanced simulation tools.

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Saito, Yoshiyuki, e Chitoshi Masuda. "Modelling of Grain Boundary Stability of Materials under Severe Plastic Deformation and Experimental Verification". Materials Science Forum 638-642 (gennaio 2010): 2724–29. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.2724.

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Thermodynamic stability of Grain boundary in materials under severe plastic deformation was simulated by the Monte Carlo and the phase field methods. Computer simulations were performed on 3-dimensional textured materials. The Monte Carlo simulation results were qualitatively in good agreement with those by the phase field model. The classification of the solution of differential equations based on the mean-field Hillert model describing temporal evolution of the scaled grain size distribution function was in good agreement with those given by the Computer simulations. The ARB experiments were performed for pure Al and Al alloys-sheets in order to validate the computer simulation results concerning the grain boundary stability of textured materials. With use of the Monte Carlo and the phase field methods. Effect of grain boundary mobilises and interface energy given by the computer simulations.

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Alqurashi, Raghda, e Tom Altman. "Hierarchical Agent-Based Modeling for Improved Traffic Routing". Applied Sciences 9, n. 20 (16 ottobre 2019): 4376. http://dx.doi.org/10.3390/app9204376.

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Agent-based model (ABM) simulation is a bottom–up approach that can describe the phenomena generated from actions and interactions within a multiagent system. An ABM is an improvement over model simulations which only describe the global behavior of a system. Therefore, it is an appropriate technology to analyze emergent phenomena in social sciences and complex adaptive systems such as vehicular traffic and pedestrian crowds. In this paper, a hybrid agent-based modeling framework designed to automate decision-making processes during traffic congestion is proposed. The model provides drivers with real-time alternative routes, computed via a decentralized multi-agent model, that tries to achieve a system-optimal traffic distribution within an entire system, thus reducing the total travel time of all the drivers. The presented work explores a decentralized ABM technique on an autonomous microgrid that is represented through cellular automata (CA). The proposed model was applied to high-density traffic congestion events such as car accidents or lane closures, and its effectiveness was analyzed. The experimental results confirm the efficiency of the proposed model in not only accurately simulating the driver behaviors and improving vehicular traffic flows during congestion but also by suggesting changes to traffic dynamics during the simulations, such as avoiding obstacles and high-density areas and then selecting the best alternative routes. The simulation results validate the ability of the proposed model and the included decision-making sub-models to both predict and improve the behaviors and intended actions of the agents.

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Narowski, Przemysław, e Krzysztof Wilczyński. "Simulation of Polymer Injection Molding: A New Practical Approach to Improve Computation Accuracy". Challenges of Modern Technology 7, n. 3 (29 settembre 2016): 25–28. http://dx.doi.org/10.5604/01.3001.0009.5446.

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Simulation of injection molding of polymeric materials is still a series scientific and engineering problem. The quality of the input data is crucial for computation accuracy. The original, relatively simple tool has been designed to validate simulations. This allows a fast identification of the critical input data, and next their proper adjustment to computations. FEM simulations have been compared with directly registered pictures of cavity filling process in a special injection mold with a sight-glass.

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Yun, R. H., e Jan Hermans. "Conformation equilibria of valine studies by dynamics simulation". "Protein Engineering, Design and Selection" 4, n. 7 (1991): 761–66. http://dx.doi.org/10.1093/protein/4.7.761.

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Hosser, D., O. Riese e R. Dobbernack. "Fire tests to validate fire simulation codes: experimental results". Kerntechnik 72, n. 3 (maggio 2007): 102–9. http://dx.doi.org/10.3139/124.100325.

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Klein-Heßling, W., e O. Riese. "Fire tests to validate fire simulation codes: numerical results". Kerntechnik 72, n. 3 (maggio 2007): 110–19. http://dx.doi.org/10.3139/124.100326.

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Hora, Joana, e Pedro Campos. "A review of performance criteria to validate simulation models". Expert Systems 32, n. 5 (14 maggio 2015): 578–95. http://dx.doi.org/10.1111/exsy.12111.

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Martens, J., F. Put e E. Kerre. "A Fuzzy-neural Resemblance Approach to Validate Simulation Models". Soft Computing 11, n. 3 (18 marzo 2006): 299–307. http://dx.doi.org/10.1007/s00500-006-0071-9.

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Martens, Jurgen, Ferdi Put e Etienne Kerre. "A fuzzy set theoretic approach to validate simulation models". ACM Transactions on Modeling and Computer Simulation 16, n. 4 (ottobre 2006): 375–98. http://dx.doi.org/10.1145/1176249.1176253.

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Foley, Michael J., Patrick S. Cottler, Silvia S. Blemker, Arlen D. Denny e Jonathan S. Black. "Computer Simulation and Optimization of Cranial Vault Distraction". Cleft Palate-Craniofacial Journal 55, n. 3 (14 dicembre 2017): 356–61. http://dx.doi.org/10.1177/1055665617738999.

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Objective: The objective of this study was to validate the proof of concept of a computer-simulated cranial distraction, demonstrating accurate shape and end volume. Design: Detailed modeling was performed on pre- and postoperative computed tomographic (CT) scans to generate accurate measurements of intracranial volume. Additionally, digital distraction simulations were performed on the preoperative scan and the resultant intracranial volume and shape were evaluated. Setting: Tertiary Children’s Hospital. Patients, Participants: Preoperative and postoperative CT images were used from 10 patients having undergone cranial distraction for cephalocranial disproportion. Interventions: None; computer simulation. Main Outcome Measure: Computer simulation feasibility of cranial vault distraction was demonstrated through creation of digital osteotomies, simulating distraction through translating skull segments, followed by simulated consolidation. Accuracy of the model was evaluated through comparing the intracranial volumes of actual and simulated distracted skulls. Results: The developed digital distraction simulation was performed on the CT images of 10 patients. Plotting the relationship between the actual and simulated postdistraction volumes for the 10 patients yielded a slope of 1.0 and a correlation coefficient of 0.99. The average actual resultant volume change from distraction was 77.0 mL, compared to a simulated volume change of 76.9 mL. Conclusions: Digital simulation of cranial distraction was demonstrated through manipulation of the CT images and confirmed by comparing the actual to simulated volume change. This process may provide objective data in designing an individual distraction plan to optimize volume expansion and resultant cranial shape as well as patient education.

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Bati, Mégane, Stéphane Blanco, Christophe Coustet, Vincent Eymet, Vincent Forest, Richard Fournier, Jacques Gautrais, Nicolas Mellado, Mathias Paulin e Benjamin Piaud. "Coupling Conduction, Convection and Radiative Transfer in a Single Path-Space: Application to Infrared Rendering". ACM Transactions on Graphics 42, n. 4 (26 luglio 2023): 1–20. http://dx.doi.org/10.1145/3592121.

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In the past decades, Monte Carlo methods have shown their ability to solve PDEs, independently of the dimensionality of the integration domain and for different use-cases (e.g. light transport, geometry processing, physics simulation). Specifically, the path-space formulation of transport equations is a key ingredient to define tractable and scalable solvers, and we observe nowadays a strong interest in the definition of simulation systems based on Monte Carlo algorithms. We also observe that, when simulating combined physics (e.g. thermal rendering from a heat transfer simulation), there is a lack of coupled Monte Carlo algorithms allowing to solve all the physics at once, in the same path space, rather than combining several independent MC estimators, a combination that would make the global solver critically sensitive to the complexity of each simulation space. This brings to our proposal: a coupled, single path-space, Monte Carlo algorithm for efficient multi-physics problems solving. In this work, we combine our understanding and knowledge of Physics and Computer Graphics to demonstrate how to formulate and arrange different simulation spaces into a single path space. We define a tractable formalism for coupled heat transfer simulation using Monte Carlo, and we leverage the path-space construction to interactively compute multiple simulations with different conditions in the same scene, in terms of boundary conditions and observation time. We validate our proposal in the context of infrared rendering with different thermal simulation scenarios: e.g., room temperature simulation, visualization of heat paths within materials (detection of thermal bridges), heat diffusion capacity of thermal exchanger. We expect that our theoretical framework will foster collaboration and multidisciplinary studies. The perspectives this framework opens are detailed and we suggest a research agenda towards the resolution of coupled PDEs at the interface of Physics and Computer Graphics.

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Jan, C. D., C. J. Chang, J. S. Lai e W. D. Guo. "Characteristics of Hydraulic Shock Waves in an Inclined Chute Contraction – Numerical Simulations". Journal of Mechanics 25, n. 1 (marzo 2009): 75–84. http://dx.doi.org/10.1017/s1727719100003610.

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AbstractThis paper presents the results of numerical simulations on the characteristics of hydraulic shockwaves in an inclined chute contraction. A two-dimensional numerical hydraulic simulation model is used to simulate the hydraulic shockwaves, based on the finite-volume multi-stage (FMUSTA) scheme proposed by Guo et al. [1]. This numerical model has been proved having good ability in simulating hydraulic shockwaves through the comparison with the exact solution of idealized shockwaves in a horizontal contraction provided by Ippen and Dawson [2], and the comparison with experimental results provided in the companion paper by Jan et al. [3]. The simulated shockwave parameters such as the shock angle, maximum shockwave height and maximum shockwave position for various conditions are compared with those calculated by the empirical relations obtained in the companion paper. The numerical results validate the applicability of these empirical relations and also extend their applicability to higher approach Froude numbers.

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Sukamta, Rama Putrantyo Anwar, Sudarja, Sri Sundari e Mochamad Syamsiro. "Computational Fluid Dynamics of Two-Phase Flow Pressure Gradient of Air-Sodium Chloride and Glucose in Horizontal Capillary Channels". CFD Letters 14, n. 1 (11 gennaio 2022): 52–65. http://dx.doi.org/10.37934/cfdl.14.1.5265.

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One of the problems in the two-phase flow is investigating the type of flow pattern that occurs in a mini channel without experimenting first. Computational Fluid Dynamics (CFD) is one way that can be used to predict pressure drop, flow pattern, void fraction, other parameters in fluid flow through a channel of a specific size. This research used the CFD simulations to predict the pressure gradient in a two-phase flow of air-sodium chloride 0.9% and glucose in a horizontal capillary tube with a diameter of 1.6 mm, and length of 70 mm. This research aims to obtain the simulation results of 2D and 3D pressure gradients to validate the experimental data. The simulation was carried out with a variation of the superficial gas velocity 0.1 - 8.3 m / s against the superficial velocity of the liquid constant 0.207 m / s. Simulations were carried out using the Volume of Fluid (VOF) model with the "ANSYS Fluent 2020 R1" software. In 2D and 3D simulations, the gradient values of pressure gradients tend to increase as JG increases. The pressure gradient fluctuates linearly at first, then exponentially from mid-to-end. The findings demonstrate that simulations may properly model physical processes like pattern creation and phase interactions. However, due to several physical elements considered in 3D simulation but missed in 2D simulation, the findings of the 2D and 3D simulations were dramatically different when looking at the pressure gradient values.

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