Literatura científica selecionada sobre o tema "Particle cloud modeling"
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Artigos de revistas sobre o assunto "Particle cloud modeling"
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Grabowski, Wojciech W., Hugh Morrison, Shin-Ichiro Shima, Gustavo C. Abade, Piotr Dziekan e Hanna Pawlowska. "Modeling of Cloud Microphysics: Can We Do Better?" Bulletin of the American Meteorological Society 100, n.º 4 (1 de abril de 2019): 655–72. http://dx.doi.org/10.1175/bams-d-18-0005.1.
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Abstract Representation of cloud microphysics is a key aspect of simulating clouds. From the early days of cloud modeling, numerical models have relied on an Eulerian approach for all cloud and thermodynamic and microphysics variables. Over time the sophistication of microphysics schemes has steadily increased, from simple representations of bulk masses of cloud and rain in each grid cell, to including different ice particle types and bulk hydrometeor concentrations, to complex schemes referred to as bin or spectral schemes that explicitly evolve the hydrometeor size distributions within each model grid cell. As computational resources grow, there is a clear trend toward wider use of bin schemes, including their use as benchmarks to develop and test simplified bulk schemes. We argue that continuing on this path brings fundamental challenges difficult to overcome. The Lagrangian particle-based probabilistic approach is a practical alternative in which the myriad of cloud and precipitation particles present in a natural cloud is represented by a judiciously selected ensemble of point particles called superdroplets or superparticles. The advantages of the Lagrangian particle-based approach when compared to the Eulerian bin methodology are explained, and the prospects of applying the method to more comprehensive cloud simulations—for instance, targeting deep convection or frontal cloud systems—are discussed.
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Russell, Lynn M., Armin Sorooshian, John H. Seinfeld, Bruce A. Albrecht, Athanasios Nenes, Lars Ahlm, Yi-Chun Chen et al. "Eastern Pacific Emitted Aerosol Cloud Experiment". Bulletin of the American Meteorological Society 94, n.º 5 (1 de maio de 2013): 709–29. http://dx.doi.org/10.1175/bams-d-12-00015.1.
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Aerosol–cloud–radiation interactions are widely held to be the largest single source of uncertainty in climate model projections of future radiative forcing due to increasing anthropogenic emissions. The underlying causes of this uncertainty among modeled predictions of climate are the gaps in our fundamental understanding of cloud processes. There has been significant progress with both observations and models in addressing these important questions but quantifying them correctly is nontrivial, thus limiting our ability to represent them in global climate models. The Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) 2011 was a targeted aircraft campaign with embedded modeling studies, using the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft and the research vessel Point Sur in July and August 2011 off the central coast of California, with a full payload of instruments to measure particle and cloud number, mass, composition, and water uptake distributions. EPEACE used three emitted particle sources to separate particle-induced feedbacks from dynamical variability, namely 1) shipboard smoke-generated particles with 0.05–1-μm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke), 2) combustion particles from container ships with 0.05–0.2-μm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components), and 3) aircraft-based milled salt particles with 3–5-μm diameters (which showed enhanced drizzle rates in some clouds). The aircraft observations were consistent with past large-eddy simulations of deeper clouds in ship tracks and aerosol– cloud parcel modeling of cloud drop number and composition, providing quantitative constraints on aerosol effects on warm-cloud microphysics.
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Twohy, C. H., J. R. Anderson, D. W. Toohey, M. Andrejczuk, A. Adams, M. Lytle, R. C. George et al. "Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the Southeast Pacific ocean". Atmospheric Chemistry and Physics Discussions 12, n.º 8 (9 de agosto de 2012): 19715–67. http://dx.doi.org/10.5194/acpd-12-19715-2012.
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Abstract. The Southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles such as power plants, urban pollution and smelters on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics from seven flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were more numerous and smaller near shore, and there was less drizzle. Higher droplet number concentration and physically thinner clouds both contributed to the smaller droplets near shore. Satellite measurements were used to show that cloud albedo was highest 500–1000 km offshore, and actually lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, which initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.
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Annamalai, K., S. Ramalingam, T. Dahdah e D. Chi. "Group Combustion of a Cylindrical Cloud of Char/Carbon Particles". Journal of Heat Transfer 110, n.º 1 (1 de fevereiro de 1988): 190–200. http://dx.doi.org/10.1115/1.3250451.
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Extensive experiments were carried out in the past in order to obtain kinetics data on the pyrolysis of coal particles and the char reactions. The literature survey distinctively reveals two kinds of studies: (i) Individual Particle Combustion (IPC) and (ii) Combustion of Particle Streams or Clouds. The experimental data obtained with particle streams are normally interpreted using IPC models with the a priori assumption that the cloud is dilute. But the term “dilute” is rarely quantified and justified considering the collective behavior of a cloud of particles. The group combustion model accounts for the reduction in burning rate due to the collective behavior of a large number of particles. While the spherical group combustion model may be employed for coal/char spray combustion modeling, the cylindrical group combustion model is more useful in interpreting the experimental data obtained with a monosized stream of particles. Hence a cylindrical group combustion model is presented here. As in the case of spherical group combustion models, there exist three modes of combustion: (i) Individual Particle Combustion (IPC), (ii) Group Combustion (GC), and (iii) Sheath Combustion (SC). Within the range of parameters studied, it appears that the cylindrical and spherical cloud combustion models yield similar results on nondimensional cloud burning rates and on the combustion modes of a cloud of particles. The results from group theory are then used to identify the mode of combustion (IPC, GC, or SC) and to interpret the experimental data.
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Twohy, C. H., J. R. Anderson, D. W. Toohey, M. Andrejczuk, A. Adams, M. Lytle, R. C. George et al. "Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean". Atmospheric Chemistry and Physics 13, n.º 5 (5 de março de 2013): 2541–62. http://dx.doi.org/10.5194/acp-13-2541-2013.
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Abstract. The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics, including their significance, from eight flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number that influence droplet concentration. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were smaller in regions of enhanced particles near shore. However, physically thinner clouds, and not just higher droplet number concentrations from pollution, both contributed to the smaller droplets. Satellite measurements were used to show that cloud albedo was highest 500–1000 km offshore, and actually slightly lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.
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Moharreri, A., L. Craig, P. Dubey, D. C. Rogers e S. Dhaniyala. "Aircraft testing of the new Blunt-body Aerosol Sampler (BASE)". Atmospheric Measurement Techniques 7, n.º 9 (23 de setembro de 2014): 3085–93. http://dx.doi.org/10.5194/amt-7-3085-2014.
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Abstract. There is limited understanding of the role of aerosols in the formation and modification of clouds, partly due to inadequate data on such systems. Aircraft-based aerosol measurements in the presence of cloud particles have proven to be challenging because of the problem of cloud droplet/ice particle shatter and the generation of secondary artifact particles that contaminate aerosol samples. Recently, the design of a new aircraft inlet, called the Blunt-body Aerosol Sampler (BASE), which enables sampling of interstitial aerosol particles, was introduced. Numerical modeling results and laboratory test data suggested that the BASE inlet should sample interstitial particles with minimal shatter particle contamination. Here, the sampling performance of the inlet is established from aircraft-based measurements. Initial aircraft test results obtained during the PLOWS (Profiling of Winter Storms) campaign indicated two problems with the original BASE design: separated flows around the BASE at high altitudes and a significant shatter problem when sampling in drizzle. The test data were used to improve the accuracy of flow and particle trajectory modeling around the inlet, and the results from the improved flow model were used to guide design modifications of the BASE to overcome the problems identified in its initial deployment. The performance of the modified BASE was tested during the ICE–T (Ice in Clouds Experiment – Tropics) campaign, and the inlet was seen to provide near shatter-free measurements in a wide range of cloud conditions. The initial aircraft test results, design modifications, and the performance characteristics of the BASE relative to another interstitial inlet, the submicron aerosol inlet (SMAI), are presented.
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Abdelmonem, A., M. Schnaiter, P. Amsler, E. Hesse, J. Meyer e T. Leisner. "First correlated measurements of the shape and light scattering properties of cloud particles using the new Particle Habit Imaging and Polar Scattering (PHIPS) probe". Atmospheric Measurement Techniques 4, n.º 10 (12 de outubro de 2011): 2125–42. http://dx.doi.org/10.5194/amt-4-2125-2011.
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Abstract. Studying the radiative impact of cirrus clouds requires knowledge of the relationship between their microphysics and the single scattering properties of cloud particles. Usually, this relationship is obtained by modeling the optical scattering properties from in situ measurements of ice crystal size distributions. The measured size distribution and the assumed particle shape might be erroneous in case of non-spherical ice particles. We present here a novel optical sensor (the Particle Habit Imaging and Polar Scattering probe, PHIPS) designed to measure simultaneously the 3-D morphology and the corresponding optical and microphysical parameters of individual cloud particles. Clouds containing particles ranging from a few micrometers to about 800 μm diameter in size can be characterized systematically with an optical resolution power of 2 μm and polar scattering resolution of 1° for forward scattering directions (from 1° to 10°) and 8° for side and backscattering directions (from 18° to 170°). The maximum acquisition rates for scattering phase functions and images are 262 KHz and 10 Hz, respectively. Some preliminary results collected in two ice cloud campaigns conducted in the AIDA cloud simulation chamber are presented. PHIPS showed reliability in operation and produced size distributions and images comparable to those given by other certified cloud particles instruments. A 3-D model of a hexagonal ice plate is constructed and the corresponding scattering phase function is compared to that modeled using the Ray Tracing with Diffraction on Facets (RTDF) program. PHIPS is a highly promising novel airborne optical sensor for studying the radiative impact of cirrus clouds and correlating the particle habit-scattering properties which will serve as a reference for other single, or multi-independent, measurement instruments.
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Chen, Huajun, Yitung Chen, Hsuan-Tsung Hsieh e Nathan Siegel. "Computational Fluid Dynamics Modeling of Gas-Particle Flow Within a Solid-Particle Solar Receiver". Journal of Solar Energy Engineering 129, n.º 2 (25 de agosto de 2006): 160–70. http://dx.doi.org/10.1115/1.2716418.
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A detailed three-dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid-particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two-band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray-tracing algorithm. Two kinds of solid-particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the gas velocity, temperature, particle solid volume fraction, particle outlet temperature, and cavity efficiency.
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Luo, Qing, Bingqi Yi e Lei Bi. "Sensitivity of Mixed-Phase Cloud Optical Properties to Cloud Particle Model and Microphysical Factors at Wavelengths from 0.2 to 100 µm". Remote Sensing 13, n.º 12 (14 de junho de 2021): 2330. http://dx.doi.org/10.3390/rs13122330.
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The representation of mixed-phase cloud optical properties in models is a critical problem in cloud modeling studies. Ice and liquid water co-existing in a cloud layer result in significantly different cloud optical properties from those of liquid water and ice clouds. However, it is not clear as to how mixed-phase cloud optical properties are affected by various microphysical factors, including the effective particle size, ice volume fraction, and ice particle shape. In this paper, the optical properties (extinction efficiency, scattering efficiency, single scattering albedo, and asymmetry factor) of mixed-phase cloud were calculated assuming externally and internally mixed cloud particle models in a broad spectral range of 0.2–100 μm at various effective particle diameters and ice volume fraction conditions. The influences of various microphysical factors on optical properties were comprehensively examined. For the externally mixed cloud particles, the shapes of ice crystals were found to become more important as the ice volume fraction increases. Compared with the mixed-phase cloud with larger effective diameter, the shape of ice crystals has a greater impact on the optical properties of the mixed-phase cloud with a smaller effective diameter (<20 μm). The optical properties calculated by internally and externally mixed models are similar in the longwave spectrum, while the optical properties of the externally mixed model are more sensitive to variations in ice volume fraction in the solar spectral region. The bulk scattering phase functions were also examined and compared. The results indicate that more in-depth analysis is needed to explore the radiative properties and impacts of mixed-phase clouds.
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Abdelmonem, A., M. Schnaiter, P. Amsler, E. Hesse, J. Meyer e T. Leisner. "First correlated measurements of the shape and scattering properties of cloud particles using the new Particle Habit Imaging and Polar Scattering (PHIPS) probe". Atmospheric Measurement Techniques Discussions 4, n.º 3 (17 de maio de 2011): 2883–930. http://dx.doi.org/10.5194/amtd-4-2883-2011.
Texto completo da fonteResumo:
Abstract. Studying the radiative impact of cirrus clouds requires the knowledge of the link between their microphysics and the single scattering properties of the cloud particles. Usually, this link is created by modeling the optical scattering properties from in situ measurements of ice crystal size distributions. The measured size distribution and the assumed particle shape might be erroneous in case of non-spherical ice particles. We present here a novel optical sensor (the Particle Habit Imaging and Polar Scattering probe, PHIPS) designed to measure the 3-D morphology and the corresponding optical and microphysical parameters of individual cloud particles, simultaneously. Clouds containing particles ranging in size from a few micrometers to about 800 μm diameter can be systematically characterized with an optical resolution power of 2 μm and polar scattering resolution of 1° for forward scattering directions (from 1° to 10°) and 8° for side and backscattering directions (from 18° to 170°). The maximum acquisition rates for scattering phase functions and images are 262 KHz and 10 Hz, respectively. Some preliminary results collected in two ice cloud campaigns which were conducted in the AIDA cloud simulation chamber are presented. PHIPS showed reliability in operation and produced comparable size distributions and images to those given by other certified cloud particles instruments. A 3-D model of a hexagonal ice plate is constructed and the corresponding scattering phase function is compared to that modeled using the Ray Tracing with Diffraction on Facets (RTDF) program. PHIPS is candidate to be a novel air borne optical sensor for studying the radiative impact of cirrus clouds and correlating the particle habit-scattering properties which will serve as a reference for other single, or multi-independent, measurements instruments.
Teses / dissertações sobre o assunto "Particle cloud modeling"
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Goutierre, Emmanuel. "Machine learning-based particle accelerator modeling". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASG106.
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Les accélérateurs de particules reposent sur des simulations de haute précision pour optimiser la dynamique du faisceau. Ces simulations sont coûteuses en ressources de calcul, rendant leur analyse en temps réel difficilement réalisable. Cette thèse propose de surmonter cette limitation en explorant le potentiel de l'apprentissage automatique pour développer des modèles de substitution des simulations d'accélérateurs de particules. Ce travail se concentre sur ThomX, une source Compton compacte, et introduit deux modèles de substitution : LinacNet et Implicit Neural ODE (INODE). Ces modèles sont entraînés sur une base de données développée dans le cadre de cette thèse, couvrant une grande variété de conditions opérationnelles afin d'assurer leur robustesse et leur capacité de généralisation. LinacNet offre une représentation complète du nuage de particules en prédisant les coordonnées de toutes les macro-particules du faisceau plutôt que de se limiter à ses observables. Cette modélisation détaillée, couplée à une approche séquentielle prenant en compte la dynamique cumulative des particules tout au long de l'accélérateur, garantit la cohérence des prédictions et améliore l'interprétabilité du modèle. INODE, basé sur le cadre des Neural Ordinary Differential Equations (NODE), vise à apprendre les dynamiques implicites régissant les systèmes de particules sans avoir à résoudre explicitement les équations différentielles pendant l'entraînement. Contrairement aux méthodes basées sur NODE, qui peinent à gérer les discontinuités, INODE est conçu théoriquement pour les traiter plus efficacement. Ensemble, LinacNet et INODE servent de modèles de substitution pour ThomX, démontrant leur capacité à approximer la dynamique des particules. Ce travail pose les bases pour développer et améliorer la fiabilité des modèles basés sur l'apprentissage automatique en physique des accélérateursParticle accelerators rely on high-precision simulations to optimize beam dynamics. These simulations are computationally expensive, making real-time analysis impractical. This thesis seeks to address this limitation by exploring the potential of machine learning to develop surrogate models for particle accelerator simulations. The focus is on ThomX, a compact Compton source, where two surrogate models are introduced: LinacNet and Implicit Neural ODE (INODE). These models are trained on a comprehensive database developed in this thesis that captures a wide range of operating conditions to ensure robustness and generalizability. LinacNet provides a comprehensive representation of the particle cloud by predicting all coordinates of the macro-particles, rather than focusing solely on beam observables. This detailed modeling, coupled with a sequential approach that accounts for cumulative particle dynamics throughout the accelerator, ensures consistency and enhances model interpretability. INODE, based on the Neural Ordinary Differential Equation (NODE) framework, seeks to learn the implicit governing dynamics of particle systems without the need for explicit ODE solving during training. Unlike traditional NODEs, which struggle with discontinuities, INODE is theoretically designed to handle them more effectively. Together, LinacNet and INODE serve as surrogate models for ThomX, demonstrating their ability to approximate particle dynamics. This work lays the groundwork for developing and improving the reliability of machine learning-based models in accelerator physics
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Gai, Guodong. "Modeling of water sprays effects on premixed hydrogen-air explosion, turbulence and shock waves Modeling pressure loads during a premixed hydrogen combustion in the presence of water spray Numerical study on laminar flame velocity of hydrogen-air combustion under water spray effects Modeling of particle cloud dispersion in compressible gas flows with shock waves A new formulation of a spray dispersion model for particle/droplet-laden flows subjected to shock waves Particles-induced turbulence: a critical review of physical concepts, numerical modelings and experimental investigation A new methodology for modeling turbulence induced 1 by a particle-laden flow using a mechanistic model". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR14.
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Cette thèse de doctorat est dédiée au développement de modèles physiques pour l’étude des systèmes d’aspersion de gouttelettes d’eau en milieu réactif d’hydrogène-air pré-mélangée dans les centrales nucléaires. Des modèles d’ordre réduit sont développés pour décrire l’évaporation des gouttelettes d’eau dans la flamme, la dispersion des nuages de particules après le passage des ondes de choc et l’évolution de l’échelle caractéristiques de turbulence avec la présence d’un jet d’eau. Une nouvelle méthodologie est proposée pour évaluer les effets de l’évaporation par l’aspersion sur la propagation de la flamme d’hydrogène turbulente à l’intérieur d’un volume fermé et un modèle simple est développé pour la quantification de la décélération de la vitesse laminaire avec l’évaporation des gouttelettes à l’intérieur de la flamme. Également, un modèle analytique est proposé pour la prédiction de la dispersion de nuage de particule après le passage d’une onde de choc en s’appuyant sur le one-way formalisme avec une extension afin de prédire l’apparition d’un pic de densité du nombre de particules en utilisant le two-way formalisme. En ce qui concerne la modulation de la turbulence induite par les particules, un modèle simple est utilisé pour l’estimation des échelles intégrales de la turbulence induites par l’injection de nuage des particules. Ces modèles numériques développés peuvent être couplés pour être mis en œuvre dans les simulations numériques à grande échelle de l’effet du système d’aspersion sur les explosions accidentelles d’hydrogène dans les centrales nucléairesThis PhD dissertation is dedicated to develop simple models to investigate the effect of water spray system on the premixed hydrogen-air combustion in the nuclear power plants. Specific simple models are developed to describe the water droplet evaporation in the flame, particle cloud dispersion after the shock wave passage, and turbulence length scale evolution with the presence of a water spray. A methodology is proposed to evaluate the spray evaporation effects on the propagation of the turbulent hydrogen flame inside a closed volume and a simple model is developed for the quantification of the laminar velocity deceleration with the droplets evaporation inside the flame. An analytical model is proposed for the prediction of particle cloud dispersion after the shock passage in the one-way formalism and another analytical model is dedicated to describe the spray-shock interaction mechanism and predict the appearance of a particle number density peak using the two-way formalism. A review of the important criteria and physical modelings related to the particle-induced turbulence modulation is given and a mechanistic model is used for the estimation of the turbulent integral length scales induced by the injection of particle clouds. These developed numerical models can be coupled to implement in the large-scale numerical simulations of the spray system effects on the accidental hydrogen explosions in the nuclear power plants
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Saide, Peralta Pablo Enrique. "Aerosol predictions and their links to weather forecasts through online interactive atmospheric modeling and data assimilation". Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/1744.
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Atmospheric particles represent a component of air pollution that has been identified as a major contributor to adverse health effects and mortality. Aerosols also interact with solar radiation and clouds perturbing the atmosphere and generating responses in a wide range of scales, such as changes to severe weather and climate. Thus, being able to accurately predict aerosols and its effects on atmospheric properties is of upmost importance.
This thesis presents a collection of studies with the global objective to advance in science and operations the use of WRF-Chem, a regional model able to provide weather and atmospheric chemistry predictions and simultaneously representing aerosol effects on climate. Different strategies are used to obtain accurate predictions, including finding an adequate model configuration for each application (e.g., grid resolution, parameterizations choices, processes modeled), using accurate forcing elements (e.g., weather and chemical boundary conditions, emissions), and developing and applying data assimilation techniques for different observational sources. Several environments and scales are simulated, including complex terrain at a city scale, meso-scale over the southeast US for severe weather applications, and regional simulations over the three subtropical persistent stratocumulus decks (off shore California and southeast Pacific and Atlantic) and over North America. Model performance is evaluated against a large spectrum of observations, including field experiments and ground based and satellite measurements.
Overall, very positive results were obtained with the WRF-Chem system once it had been configured properly and the inputs chosen. Also, data assimilation of aerosol and cloud satellite observations contributed to improve model performance even further. The model is proven to be an excellent tool for forecasting applications, both for local and long range transported pollution. Also, advances are made to better understand aerosol effects on climate and its uncertainties. Aerosols are found to generate important perturbations, ranging from changes in cloud properties over extensive regions, up to playing a role in increasing the likelihood of tornado occurrence and intensity. Future directions are outline to keep advancing in better predictions of aerosols and its feedbacks.
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Vergara, Temprado Jesus. "Global modelling of ice-nucleating particles and impacts on mixed-phase clouds". Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/19602/.
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The process of cloud glaciation strongly alters the properties of mixed-phase clouds. Between 0C to about -37C, cloud liquid droplets can either exist in the liquid phase in metastable state known as supercooling, or they can be composed of solid ice crystals. For a liquid droplet to freeze at these temperatures, the action of an external agent, known as ice-nucleating particle (INP) is needed. The atmospheric distribution of ice-nucleating particles was simulated in past studies as a function of the aerosol concentration, however, new experimental information about the ice- nucleating ability of different aerosol species and several new atmospheric measurements of INP are now available to be used in models. In this thesis, I use this new information to develop a global atmospheric model of the distribution of ice-nucleating particles to assess the relative importance of mineral dust, marine organic aerosols and black carbon for contributing to atmospheric concentrations of INPs. The model is evaluated against several datasets of INP concentrations measured in the atmosphere to test its realism and locate regions of the world where additional currently missing sources of INP could be important. The results show that feldspar aerosols dominate the atmospheric INP concentration for most parts of the globe, whereas marine organic aerosols are more relevant in the remote Southern Ocean. Black carbon particles, in contrast, seem not to play a substantial role when new estimates of its ice-nucleating ability are used. With the information obtained by this model, I explore whether the representation of ice-nucleating particles in climate models plays a role in the Southern Ocean radiative bias. This bias is related to modelled clouds reflecting too-little solar radiation, causing large errors in sea-surface temperatures and atmospheric circulations. I combine cloud-resolving simulations over regions of 1000 km with the new estimates of the INP concentration in remote regions to show that the simulated clouds reflect much more solar radiation than predicted by a global climate model, agreeing much better with satellite observations in both magnitude and frequency. Overall, these results will improve our understanding of the role, distribution and importance of ice-nucleating particles in the atmosphere and provide the scientific community new points of view to understand model biases.
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Björklund, Per. "Visualisation of a simulated dispersion cloud based on a stochastic particle modelling and Volume Rendering in OpenGL". Thesis, Umeå universitet, Institutionen för datavetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-61506.
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When visualising a natural phenomena, such as a gas cloud, the constant movement and turbulens can pose a complex problem. With the use of a stochastic particle dispersion model a gas cloud is simulated and stored in a datafile. This thesis report describes some possible methods on how to structure and render such a datafile in an effective and realistic manner. This is achieved by using interpolation, the octree data structure and volume rendering. The end product will be used in a larger project at FOI, with the goal to facilitate the training of personal. Three different rendering methods are implemented and compared against each other. The best one will build the foundation for the FOI project. The end result of this report shows that the methods could be used with satisfying results but more development is needed.
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Lee, Graham Kim Huat. "Glass rain : modelling the formation, dynamics and radiative-transport of cloud particles in hot Jupiter exoplanet atmospheres". Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/11740.
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The atmospheres of exoplanets are being characterised in increasing detail by observational facilities and will be examined with even greater clarity with upcoming space based missions such as the James Webb Space Telescope (JWST) and the Wide Field InfraRed Survey Telescope (WFIRST). A major component of exoplanet atmospheres is the presence of cloud particles which produce characteristic observational signatures in transit spectra and influence the geometric albedo of exoplanets. Despite a decade of observational evidence, the formation, dynamics and radiative-transport of exoplanet atmospheric cloud particles remains an open question in the exoplanet community. In this thesis, we investigate the kinetic chemistry of cloud formation in hot Jupiter exoplanets, their effect on the atmospheric dynamics and observable properties. We use a static 1D cloud formation code to investigate the cloud formation properties of the hot Jupiter HD 189733b. We couple a time-dependent kinetic cloud formation to a 3D radiative-hydrodynamic simulation of the atmosphere of HD 189733b and investigate the dynamical properties of cloud particles in the atmosphere. We develop a 3D multiple-scattering Monte Carlo radiative-transfer code to post-process the results of the cloudy HD 189733b RHD simulation and compare the results to observational results. We find that the cloud structures of the hot Jupiter HD 189733b are likely to be highly inhomogeneous, with differences in cloud particle sizes, number density and composition with longitude, latitude and depth. Cloud structures are most divergent between the dayside and nightside faces of the planet due to the instability of silicate materials on the hotter dayside. We find that the HD 189733b simulation in post-processing is consistent with geometric albedo observations of the planet. Due to the scattering properties of the cloud particles we predict that HD 189733b will be brighter in the upcoming space missions CHaracterising ExOPlanet Satellite (CHEOPS) bandpass compared to the Transiting Exoplanet Space Survey (TESS) bandpass.
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Hiron, Thibault. "Experimental and modeling study of heterogeneous ice nucleation on mineral aerosol particles and its impact on a convective cloud". Thesis, Université Clermont Auvergne (2017-2020), 2017. http://www.theses.fr/2017CLFAC074/document.
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L’un des enjeux principaux dans l’appréhension de l’évolution du climat planétaire réside dans la compréhension du rôle des processus de formation de la glace ainsi que leur rôle dans la formation et l’évolution des nuages troposphériques. Un cold stage nouvellement construit permet l’observation simultanée de jusqu’à 200 gouttes monodispersées de suspensions contenant des particules de K–feldspath, connues comme étant des particules glaçogènes très actives. Les propriétés glaçogènes des particules résiduelles de chaque goutte sont ensuite comparées pour les différents modes de glaciation et le lien entre noyau glaçogène en immersion et en déposition est étudié. Les premiers résultats ont montré que les mêmes sites actifs étaient impliqué dans la glaciation par immersion et par déposition. Les implications atmosphériques des résultats expérimentaux sont discutés à l’aide de Descam (Flossmann et al., 1985), un modèle 1.5–d à microphysique détaillée dans une étude de cas visant à rendre compte du rôle des différents mécanismes de glaciation dans l’évolution dynamique du nuage convective CCOPE (Dye et al., 1986). Quatre types d’aérosol minéraux (K–feldspath, kaolinite, illite et quartz) sont utilisés pour la glaciation en immersion, par contact et par déposition, à l’aide de paramétrisations sur la densité de sites glaçogènes actifs. Des études de sensibilité, où les différents types d’aérosols et modes de glaciation sont considérés séparément et en compétition, permettent de rendre compte de leurs importances relatives. La glaciation en immersion sur les particules de K–feldspath s’est révélée comme ayant le plus d’impact sur l’évolution dynamique et sur les précipications pour un nuage convectifOne of the main challenges in understanding the evolution of Earth's climate resides in the understanding the ice formation processes and their role in the formation of tropospheric clouds as well as their evolution. A newly built humidity-controlled cold stage allows the simultaneous observation of up to 200 monodispersed droplets of suspensions containing K-feldspar particles, known to be very active ice nucleating particles. The ice nucleation efficiencies of the individual residual particles were compared for the different freezing modes and the relationship between immersion ice nuclei and deposition ice nuclei were investigated. The results showed that the same ice active sites are responsible for nucleation of ice in immersion and deposition modes.The atmospheric implications of the experimental results are discussed, using Descam (Flossmann et al., 1985), a 1.5-d bin-resolved microphysics model in a case study aiming to assess the role of the different ice nucleation pathways in the dynamical evolution of the CCOPE convective cloud (Dye et al., 1986). Four mineral aerosol types (K-feldspar, kaolinite, illite and quartz) were considered for immersion and contact freezing and deposition nucleation, with explicit Ice Nucleation Active Site density parameterizations.In sensitivity studies, the different aerosol types and nucleation modes were treated seperately and in competition to assess their relative importance. Immersion freezing on K-feldspar was found to have the most pronounced impact on the dynamical evolution and precipitation for a convective cloud
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Beer, Christof Gerhard [Verfasser], e Robert [Akademischer Betreuer] Sausen. "Global modelling of ice nucleating particles and their effects on cirrus clouds / Christof Gerhard Beer ; Betreuer: Robert Sausen". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2021. http://d-nb.info/1240145446/34.
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Hiron, Thibault [Verfasser], T. [Akademischer Betreuer] Leisner e A. [Akademischer Betreuer] Flossmann. "Experimental and modeling study of heterogeneous ice nucleation on mineral aerosol particles and its impact on a convective cloud / Thibault Hiron ; Betreuer: T. Leisner , A. Flossmann". Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1166234215/34.
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Bräuer, Peter. "Extension and application of a tropospheric aqueous phase chemical mechanism (CAPRAM) for aerosol and cloud models". Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183743.
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The ubiquitous abundance of organic compounds in natural and anthorpogenically influenced eco-systems has put these compounds into the focus of atmospheric research. Organic compounds have an impact on air quality, climate, and human health. Moreover, they affect particle growth, secondary organic aerosol (SOA) formation, and the global radiation budget by altering particle properties. To investigate the multiphase chemistry of organic compounds and interactions with the aqueous phase in the troposphere, modelling can provide a useful tool. The oxidation of larger organic molecules to the final product CO2 can involve a huge number of intermediate compounds and tens of thousands of reactions. Therefore, the creation of explicit mechanisms relies on automated mechanism construction. Estimation methods for the prediction of the kinetic data needed to describe the degradation of these intermediates are inevitable due to the infeasibility of an experimental determination of all necessary data. Current aqueous phase descriptions of organic chemistry lag behind the gas phase descriptions in atmospheric chemical mechanisms despite its importance for the multiphase chemistry of organic compounds. In this dissertation, the gas phase mechanism Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) has been advanced by a protocol for the description of the oxidation of organic compounds in the aqueous phase. Therefore, a database with kinetic data of 465 aqueous phase hydroxyl radical and 129 aqueous phase nitrate radical reactions with organic compounds has been compiled and evaluated. The database was used to evaluate currently available estimation methods for the prediction of aqueous phase kinetic data of reactions of organic compounds. Among the investigated methods were correlations of gas and aqueous kinetic data, kinetic data of homologous series of various compound classes, reactivity comparisons of inorganic radical oxidants, Evans-Polanyi-type correlations, and structure-activity relationships (SARs). Evans-Polanyi-type correlations have been improved for the purpose of automated mechanism self-generation of mechanisms with large organic molecules. A protocol has been designed based on SARs for hydroxyl radical reactions and the improved Evans-Polanyi-type correlations for nitrate radical reactions with organic compounds. The protocol was assessed in a series of critical sensitivity studies, where uncertainties of critical parameters were investigated. The advanced multiphase generator GECKO-A was used to generate mechanisms, which were applied in box model studies and validated against two sets of aerosol chamber experiments. Experiments differed by the initial compounds used (hexane and trimethylbenzene) and the experimental conditions (UV-C lights off/on and additional in-situ hydroxyl radical source no/yes). Reasonable to good agreement of the modelled and experimental results was achieved in these studies. Finally, GECKO-A was used to create two new CAPRAM version, where, for the first time, branchingratios for different reaction pathways were introduced and the chemistry of compounds with up to four carbon atoms has been extended. The most detailed mechanism comprises 4174 compounds and 7145 processes. Detailed investigations were performed under real tropospheric conditions in urban and remote continental environments. Model results showed significant improvements, especially in regard to the formation of organic aerosol mass. Detailed investigations of concentration-time profiles and chemical fluxes refined the current knowledge of the multiphase processing of organic compounds in the troposphere, but also pointed at current limitations of the generator protocol, the mechanisms created, and current understanding of aqueous phase processes of organic compoundsDas zahlreiche Vorkommen organischer Verbindungen in natürlichen und anthropogen beeinflussten Ökosystemen hat diese Verbindungen in den Fokus der Atmosphärenforschung gerückt. Organische Verbindungen beeinträchtigen die Luftqualität, die menschliche Gesundheit und das Klima. Weiterhin werden Partikelwachstum und -eigenschaften, sekundäre organische Partikelbildung und dadurch der globale Strahlungshaushalt durch sie beeinflusst. Um die troposphärische Multiphasenchemie organischer Verbindungen und Wechselwirkungen mit der Flüssigphase zu untersuchen, sind Modellstudien hilfreich. Die Oxidation großer organischer Moleküle führt zu einer Vielzahl an Zwischenprodukten. Der Abbau erfolgt in unzähligen Reaktionen bis hin zum Endprodukt CO2. Bei der Entwicklung expliziter Mechanismen muss deshalb für diese Verbindungen auf computergestützte, automatisierte Methoden zurückgegriffen werden. Abschätzungsmethoden für die Vorhersage kinetischer Daten zur Beschreibung des Abbaus der Zwischenprodukte sind unabdingbar, da eine experimentelle Bestimmung aller benötigten Daten nicht realisierbar ist. Die derzeitige Beschreibung der Flüssigphasenchemie unterliegt deutlich den Beschreibungen der Gasphase in atmosphärischen Chemiemechanismen trotz deren Relevanz für die Multiphasenchemie. In dieser Arbeit wurde der Gasphasenmechanismusgenerator GECKO-A (“Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere”) um ein Protokoll zur Oxidation organischer Verbindungen in der Flüssigphase erweitert. Dazu wurde eine Datenbank mit kinetischen Daten von 465 Hydroxylradikal- und 129 Nitratradikalreaktionen mit organischen Verbindungen angelegt und evaluiert. Mit Hilfe der Datenbank wurden derzeitige Abschätzungsmethoden für die Vorhersage kinetischer Daten von Flüssigphasenreaktionen organischer Verbindungen evaluiert. Die untersuchten Methoden beinhalteten Korrelationen kinetischer Daten aus Gas- und Flüssigphase, homologer Reihen verschiedener Stoffklassen, Reaktivitätsvergleiche, Evans-Polanyi-Korrelationen und Struktur-Reaktivitätsbeziehungen. Für die Mechanismusgenerierung großer organischer Moleküle wurden die Evans-Polanyi-Korrelationen in dieser Arbeit weiterentwickelt. Es wurde ein Protokol für die Mechanismusgenerierung entwickelt, das auf Struktur-Reaktivitätsbeziehungen bei Reaktionen von organischen Verbindungen mit OH-Radikalen und auf den erweiterten Evans-Polanyi-Korrelationen bei NO3-Radikalreaktionen beruht. Das Protokoll wurde umfangreich in einer Reihe von Sensitivitätsstudien getestet, um Unsicherheiten kritischer Parameter abzuschätzen. Der erweiterte Multiphasengenerator GECKO-A wurde dazu verwendet, neue Mechanismen zu generieren, die in Boxmodellstudien gegen Aerosolkammerexperimente evaluiert wurden. Die Experimentreihen unterschieden sich sowohl in der betrachteten Ausgangssubstanz (Hexan und Trimethylbenzen) und dem Experimentaufbau (ohne oder mit UV-C-Photolyse und ohne oder mit zusätzlicher partikulärer Hydroxylradikalquelle). Bei den Experimenten konnte eine zufriedenstellende bis gute Übereinstimmung der experimentellen und Modellergebnisse erreicht werden. Weiterhin wurde GECKO-A verwendet, um zwei neue CAPRAM-Versionen mit bis zu 4174 Verbindungen und 7145 Prozessen zu generieren. Erstmals wurden Verzweigungsverhältnisse in CAPRAM eingeführt. Außerdem wurde die Chemie organischer Verbindungen mit bis zu vier Kohlenstoffatomen erweitert. Umfangreiche Untersuchungen unter realistischen troposphärischen Bedingungen in urbanen und ländlichen Gebieten haben deutliche Verbesserungen der erweiterten Mechanismen besonders in Bezug auf Massenzuwachs des organischen Aerosolanteils gezeigt. Das Verständnis der organischen Multiphasenchemie konnte durch detaillierte Untersuchungen zu den Konzentrations-Zeit-Profilen und chemischen Flüssen vertieft werden, aber auch gegenwärtige Limitierungen des Generators, der erzeugten Mechanismen und unseres Verständnisses für Flüssigphasenprozesse organischer Verbindungen aufgezeigt werden
Livros sobre o assunto "Particle cloud modeling"
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Suzuki, Kentaroh. A study on numerical modeling of cloud microphysics for calculating the particle growth process. [Tokyo]: Center for Climate System Research, University of Tokyo, 2006.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Particle cloud modeling"
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Wang, Bei, Jingliang Peng e C. C. Jay Kuo. "Cumulus Cloud Synthesis with Similarity Solution and Particle/Voxel Modeling". In Advances in Visual Computing, 65–74. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-89639-5_7.
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Flossmann, Andrea I. "Mesoscale Modeling of Clouds and Aerosol Particles". In Air Pollution Modeling and Its Application XI, 259–74. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4615-5841-5_28.
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Solomos, Stavros, Jonilda Kushta e George Kallos. "Effects of Airborne Particles on Cloud Formation and Precipitation: A Modeling Study". In Air Pollution Modeling and its Application XXI, 571–78. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-1359-8_95.
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Saltelli, A., T. Homma, F. Raes, J. Wilson e R. Van Dingenen. "Modelling of the Sulphur Cycle. From DMS to Cloud Particles". In Dimethylsulphide: Oceans, Atmosphere and Climate, 355–73. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-1261-3_38.
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Ervens, Barbara. "Progress and Problems in Modeling Chemical Processing in Cloud Droplets and Wet Aerosol Particles". In ACS Symposium Series, 327–45. Washington, DC: American Chemical Society, 2018. http://dx.doi.org/10.1021/bk-2018-1299.ch016.
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DeMott, Paul. "Laboratory Studies of Cirrus Cloud Processes". In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0009.
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A number of processes that play a role in the formation, evolution of microphysical properties, and radiative characteristics of cirrus clouds are amenable to investigation in a laboratory setting. These laboratory studies provide fundamental data for quantifying and validating theoretical concepts and help guide investigations involving direct and remote measurements of cirrus. Laboratory data also may be used for formulating parameterizations for numerical cloud models, especially where information is incomplete or full descriptions are not possible. This chapter reviews results from laboratory studies of ice formation, ice crystal growth, radiative transfer, and aerosol scavenging and transformation in the cirrus environment. Emphasis is placed on ice formation in cirrus conditions. The related topic of contrail formation is covered separately in this book. The formation mechanisms of lower stratospheric clouds are reviewed elsewhere (e.g., Tolbert 1994; Peter 1996; Carslaw et al. 1997; Koop et al. 1997a). Laboratory studies of cirrus ice formation are at a rapidly developing stage, so it is useful to provide significant background bases for current and needed studies. Key issues are aerosol composition, ice nucleation mechanisms, and the synergy between theory and laboratory measurements. Vali (1996), Baker (1997) and Martin (2000) discuss some of these issues in review papers. Upper tropospheric aerosol particles play an important catalytic role in the formation of cirrus. The nucleation process is important in determining the microphysical properties of cirrus. Numerical modeling studies (e.g., Jensen and Toon 1994; DeMott et al. 1994, 1997; Heymsfield and Sabin 1989) indicate that variation in the factors that drive the nucleation of ice and variations in the physical and chemical characteristics of aerosol particle populations lead to the formation of cirrus with different microphysical characteristics. Knowledge of the physics and chemistry of aerosols in the upper troposphere and lower stratosphere has evolved at a rapid pace. A detailed accounting of this topic is beyond the scope of this chapter. For the purpose of the present discussion, it is sufficient to note that the aerosol from which cirrus nucleate may vary significantly from place to place. Differences in aerosol properties in time and space occur because particles can arrive to the upper troposphere in so many ways and from so many sources.
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Malyshkin, V. E. "Assembling of Parallel Programs for Large Scale Numerical Modeling". In Handbook of Research on Scalable Computing Technologies, 295–311. IGI Global, 2010. http://dx.doi.org/10.4018/978-1-60566-661-7.ch013.
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The main ideas of the Assembly Technology (AT) in its application to parallel implementation of large scale realistic numerical models on a rectangular mesh are considered and demonstrated by the parallelization (fragmentation) of the Particle-In-Cell method (PIC) application to solution of the problem of energy exchange in plasma cloud. The implementation of the numerical models with the assembly technology is based on the construction of a fragmented parallel program. Assembling of a numerical simulation program under AT provides automatically different useful dynamic properties of the target program including dynamic load balance on the basis of the fragments migration from overloaded into underloaded processor elements of a multicomputer. Parallel program assembling approach also can be considered as combination and adaptation for parallel programming of the well known modular programming and domain decomposition techniques and supported by the system software for fragmented programs assembling.
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Liou, K. N., e Y. Gu. "Radiative Transfer in Cirrus Clouds: Light Scatting and Spectral Information". In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0017.
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The importance of cirrus clouds in climate has been recognized in the light of a number of intensive composite field observations: the First ISCCP Regional Experiment (FIRE) I in October-November 1986; FIRE II in November-December 1991; the European experiment on cirrus (ICE/EUCREX) in 1989; Subsonic Aircraft: Contrail and Cloud Effect Special Study (SUCCESS) in April 1996. Based on observations from the ground-based lidar and radar, airborne instrumentation, and satellites, cirrus clouds are typically located in the upper troposphere and lower stratosphere (Liou 1986). The formation, maintenance, and dissipation of cirrus clouds are directly associated with synoptic and mesoscale disturbances as well as related to deep cumulus outflows. Increases of high cloud cover have been reported at a number of urban airports in the United States based on surface observations spanning 40 years (Liou et al. 1990; Frankel et al. 1997). These increases have been attributed to the contrails and water vapor produced by jet airplane traffic. Satellite observations from NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) using the CO2 slicing method (Wylie et al. 1994) also show that cirrus cloud cover substantially increased between 60° S and 60° N during a 4-year period from June 1989 to September 1993. Understanding the role of cirrus clouds in climate must begin with reliable modeling of their radiative properties for incorporation in climate models as well as determination of the global variability of their composition, structure, and optical properties. Development of the remote sensing methodologies for the detection and retrieval of the ubiquitous visible and subvisual cirrus clouds requires the basic scattering, absorption, and polarization data for ice crystals in conjunction with appropriate radiative transfer models. We present the fundamentals involving radiative transfer in cirrus clouds and review pertinent research. In section 13.1, an overview of the subject of light scattering by ice crystals is presented in which we discuss a unification of the geometric optics approach for large ice particles and the finite-difference time domain numerical solution for small ice particles, referred to as the unified theory. Section 13.2 presents radiative transfer in cirrus clouds involving two unique properties: orientation of nonspherical ice crystals and cloud inhomogeneity.
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Sassen, Kenneth, e Gerald Mace. "Ground-based Remote Sensing of Cirrus Clouds". In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0012.
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Cirrus clouds have only recently been recognized as having a significant influence on weather and climate through their impact on the radiative energy budget of the atmosphere. In addition, the unique difficulties presented by the study of cirrus put them on the “back burner” of atmospheric research for much of the twentieth century. Foremost, because they inhabit the frigid upper troposphere, their inaccessibility has hampered intensive research. Other factors have included a lack of in situ instrumentation to effectively sample the clouds and environment, and basic uncertainties in the underlying physics of ice cloud formation, growth, and maintenance. Cloud systems that produced precipitation, severe weather, or hazards to aviation were deemed more worthy of research support until the mid- 1980s. Beginning at this time, however, major field research programs such as the First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment (FIRE; Cox et al. 1987), International Cirrus Experiment (ICE; Raschke et al. 1990), Experimental Cloud Lidar Pilot Study (ECLIPS; Platt et al. 1994), and the Atmospheric Radiation Measurement (ARM) Program (Stokes and Schwartz 1994) have concentrated on cirrus cloud research, relying heavily on ground-based remote sensing observations combined with research aircraft. What has caused this change in research emphasis is an appreciation for the potentially significant role that cirrus play in maintaining the radiation balance of the earth-atmosphere system (Liou 1986). As climate change issues were treated more seriously, it was recognized that the effects, or feedbacks, of extensive high-level ice clouds in response to global warming could be pivotal. This fortunately came at a time when new generations of meteorological instrumentation were becoming available. Beginning in the early 1970s, major advancements were made in the fields of numerical cloud modeling and cloud measurements using aircraft probes, satellite multispectral imaging, and remote sensing with lidar, short-wavelength radar, and radiometers, all greatly facilitating cirrus research. Each of these experimental approaches have their advantages and drawbacks, and it should also be noted that a successful cloud modeling effort relies on field data for establishing boundary conditions and providing case studies for validation. Although the technologies created for in situ aircraft measurements can clearly provide unique knowledge of cirrus cloud thermodynamic and microphysical properties (Dowling and Radke 1990), available probes may suffer from limitations in their response to the wide range of cirrus particles and actually sample a rather small volume of cloud during any mission.
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Sundqvist, Hilding. "On Cirrus Modeling for General Circulation and Climate Models". In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0018.
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Cirrus clouds are significant regulators of the earth's radiation budget. Cirrus generally have low ice water content, leading to partial transparency to radiation, and a variety of ice crystal types constitutes the cloud. As a consequence, cirrus have complex optical qualities, which are discussed in other chapters of this book. In this chapter, I discuss the appearance and behavior of the cirrus clouds per se and discuss approaches to include those features in numerical models by parameterization. The number of general circulation models (GCMs) containing physically based parameterizations of cloud processes with prognostic equations for water/ice content increased remarkably during the 1990s. Model simulations of the general circulation of the atmosphere have shown a pronounced sensitivity to modeled optical properties of cirrus (e.g., Ramanathan et al. 1983; Senior and Mitchell 1993; Mitchell 1994b; Fowler and Randall 1996a,b; Kristjansson et al. 1998). Most studies with GCMs and climate models have focused on features of radiation and energy budgets and the modulation of these budgets as a consequence of changes in cloudiness quality or other conditions. Much less attention has been paid to the characteristics and realism of the model cloudiness itself (e.g., Liou 1992). Only meager discussions are generally found on these topics from studies in this context. In most cases, zonally averaged and/or bird's-eyeview cloudiness are reported. The reason for this is the sparseness of observational data, which makes it difficult to conduct a detailed verification of the simulated cloud fields. Many papers on model experimentation on this topic do indeed contain statements that uncertainties in cloud behavior constitute a severe weakness of the simulations (Senior and Mitchell 1993; Mitchell 1994). It is also emphasized that substantial improvement in our understanding of the behavior of clouds (not least cirrus) is required for satisfactory confidence in simulations of different climate scenarios. The critical need for high-accuracy measurements of upper-tropospheric water vapor is emphasized for example, in a paper by Stephens et al. (1996) discussing satellite measurements of water vapor. Clouds also have an indirect effect on climatology because their appearance and disappearance (evaporation) modulate the distribution of water vapor in the atmosphere.
Trabalhos de conferências sobre o assunto "Particle cloud modeling"
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Benedetto, E., G. Rumolo, D. Schulte, R. Tomas, F. Zimmermann, G. Franchetti, K. Ohmi et al. "Modeling incoherent electron cloud effects". In 2007 IEEE Particle Accelerator Conference. IEEE, 2007. http://dx.doi.org/10.1109/pac.2007.4440436.
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Chen, Huajun, Yitung Chen, Hsuan-Tsung Hsieh e Nathan Siegel. "CFD Modeling of Gas Particle Flow Within a Solid Particle Solar Receiver". In ASME 2006 International Solar Energy Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/isec2006-99044.
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A detailed three dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray tracing algorithm. Two kinds of solid particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the particle and gas velocity, temperature, particle solid volume fraction, and cavity efficiency.
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Cui, Helin, Min Qi e Dajian Li. "3D cloud modeling base on fractal particle method". In 2011 International Conference on Electrical and Control Engineering (ICECE). IEEE, 2011. http://dx.doi.org/10.1109/iceceng.2011.6057499.
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Furman, M. A., C. M. Celata, M. Kireeff-Covo, K. G. Sonnad, J. L. Vay, M. Venturini, R. Cohen et al. "Self-consistent 3D modeling of electron cloud dynamics and beam response". In 2007 IEEE Particle Accelerator Conference. IEEE, 2007. http://dx.doi.org/10.1109/pac.2007.4441093.
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Mukai, Nobuhiko, Yuto Hizono e Youngha Chang. "Particle based Waterfall Simulation with Spray Cloud Emerging from Basin". In 8th International Conference on Simulation and Modeling Methodologies, Technologies and Applications. SCITEPRESS - Science and Technology Publications, 2018. http://dx.doi.org/10.5220/0006896500550061.
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Abubakar, Abba A., Khaled S. Al-Athel e Syed S. Akhtar. "Computational Modeling of Extreme Particles Deformation and Grain Refinement During Cold Spray Deposition". In ASME 2023 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/imece2023-112993.
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Abstract When deposition parameters are carefully set, cold spraying can successfully deposit composite coatings with customized characteristics. To avoid conducting repeated experimental trials, numerical simulations are critically needed to optimize the cold spray deposition parameters. During cold spraying of the composite layer, extreme particle deformation and temperature rise occur due to the complex interactions among dissimilar particles; hence, the coating layer properties vary across the thickness. In the cold spray literature, particle grain refinement is not considered in numerical simulation studies. The present study uses a physics-based hybrid computational technique to simulate multi-material particle deformation during the cold spray deposition of Ni-Al2O3 coating utilized for wear applications. The hybrid approach effectively combines point cloud and finite element models to simulate particle deformation and interactions during the cold spray process. An attempt to predict the grain refinement due to extreme deformation and dynamic recrystallization of deformed particles is made for the first time using the phase field method (PFM). The strain field and temperature distribution are used to predict the grain size evolution in the deformed particles. The numerical simulation results are validated by comparing them with those of experiments. The results show that the softer Ni (matrix) particles undergo higher deformation, and their deformation pattern is strongly affected by the presence of neighboring Al2O3 particles. Due to higher plastic strain and strain rate, the particle’s deformation affects the grain size evolution, mainly in the Ni matrix material. The extremely deformed regions, such as Ni particle interfaces and edges, demonstrate the possibility for grain refinement according to simulation data on strain rate, temperature, and deformation among dissimilar particles. The current study aims to establish a reliable numerical methodology for the optimization and prediction of properties of composite made from cold spraying.
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Regele, Jonathan, Jason Rabinovitch, Tim Colonius e Guillaume Blanquart. "Numerical Modeling and Analysis of Early Shock Wave Interactions with a Dense Particle Cloud". In 42nd AIAA Fluid Dynamics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2012. http://dx.doi.org/10.2514/6.2012-3161.
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Wei, Yanfei, Yaolin Liu e Dun Wang. "A improved particle swarm optimization based on cloud model with implications for urban land use planning". In International Symposium on Spatial Analysis, Spatial-temporal Data Modeling, and Data Mining, editado por Yaolin Liu e Xinming Tang. SPIE, 2009. http://dx.doi.org/10.1117/12.838390.
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Русскова, Т. В., e Д. Н. Тимофеев. "THE INFLUENCE OF THE SHAPE AND SIZE OF THE ICE PARTICLES OF CIRRUS CLOUDS ON THE PROPORTION OF MULTIPLE SCATTERED RADIATION IN THE ECHO SIGNAL SPACE LIDAR". In XXX Юбилейный Международный симпозиум Оптика атмосферы и океана. Физика атмосферы, 285–89. Crossref, 2024. https://doi.org/10.56820/oao30b7.
Texto completo da fonteResumo:
Рассматриваются результаты статистического моделирования распространения лазерного излучения в сплошной перистой облачности. Представлены оценки доли многократно рассеянного излучения в эхосигнале космического лидара, полученные при разных значениях оптико-микроструктурных характеристик облаков (оптическая толщина, форма и размер ледяных частиц) и параметров лидара (удаленность от объекта зондирования, расходимость излучения, угол поля зрения приемника). В расчетах использованы хаотически ориентированные частицы произвольной формы, сплошные и полые столбики, пластинки, розетки полые, дроксталлы, а также смесь частиц различных форм с сильно шероховатой поверхностью, построенная с учетом экспериментальных данных о распределении частиц по размерам, лёдности облаков и диаметре средней массы. The results of statistical modeling of the propagation of laser radiation in a continuous cirrus cloud are considered. Estimates of the proportion of repeatedly scattered radiation in the echo signal of a space lidar are presented, obtained at different values of the optical and microstructural characteristics of clouds (optical thickness, shape and size of ice particles) and lidar parameters (distance from the probing object, radiation divergence, angle of field of view of the receiver). The calculations used randomly oriented particles of arbitrary shape, solid and hollow columns, plates, hollow sockets, droxtals, as well as a mixture of particles of various shapes with a strongly rough surface, constructed taking into account experimental data on the particle size distribution, cloud iciness and average mass diameter.
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Chen, Zhenfu, Qicheng Luo, Zhenlun Wang e Du Deng. "Numerical study on dynamic compression of concrete based on meso-scale particle element modeling and fractal theory". In International Conference on Cloud Computing, Internet of Things, and Computer Applications, editado por Warwick Powell e Amr Tolba. SPIE, 2022. http://dx.doi.org/10.1117/12.2642601.
Texto completo da fonteRelatórios de organizações sobre o assunto "Particle cloud modeling"
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Annamalai, K., e W. Ryan. Experimental studies on the group ignition of a cloud of coal particles: Volume 2, Pyrolysis and ignition modeling. Office of Scientific and Technical Information (OSTI), janeiro de 1992. http://dx.doi.org/10.2172/5185648.
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Modlo, Yevhenii O., Serhiy O. Semerikov, Stanislav L. Bondarevskyi, Stanislav T. Tolmachev, Oksana M. Markova e Pavlo P. Nechypurenko. Methods of using mobile Internet devices in the formation of the general scientific component of bachelor in electromechanics competency in modeling of technical objects. [б. в.], fevereiro de 2020. http://dx.doi.org/10.31812/123456789/3677.
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An analysis of the experience of professional training bachelors of electromechanics in Ukraine and abroad made it possible to determine that one of the leading trends in its modernization is the synergistic integration of various engineering branches (mechanical, electrical, electronic engineering and automation) in mechatronics for the purpose of design, manufacture, operation and maintenance electromechanical equipment. Teaching mechatronics provides for the meaningful integration of various disciplines of professional and practical training bachelors of electromechanics based on the concept of modeling and technological integration of various organizational forms and teaching methods based on the concept of mobility. Within this approach, the leading learning tools of bachelors of electromechanics are mobile Internet devices (MID) – a multimedia mobile devices that provide wireless access to information and communication Internet services for collecting, organizing, storing, processing, transmitting, presenting all kinds of messages and data. The authors reveals the main possibilities of using MID in learning to ensure equal access to education, personalized learning, instant feedback and evaluating learning outcomes, mobile learning, productive use of time spent in classrooms, creating mobile learning communities, support situated learning, development of continuous seamless learning, ensuring the gap between formal and informal learning, minimize educational disruption in conflict and disaster areas, assist learners with disabilities, improve the quality of the communication and the management of institution, and maximize the cost-efficiency. Bachelor of electromechanics competency in modeling of technical objects is a personal and vocational ability, which includes a system of knowledge, skills, experience in learning and research activities on modeling mechatronic systems and a positive value attitude towards it; bachelor of electromechanics should be ready and able to use methods and software/hardware modeling tools for processes analyzes, systems synthesis, evaluating their reliability and effectiveness for solving practical problems in professional field. The competency structure of the bachelor of electromechanics in the modeling of technical objects is reflected in three groups of competencies: general scientific, general professional and specialized professional. The implementation of the technique of using MID in learning bachelors of electromechanics in modeling of technical objects is the appropriate methodic of using, the component of which is partial methods for using MID in the formation of the general scientific component of the bachelor of electromechanics competency in modeling of technical objects, are disclosed by example academic disciplines “Higher mathematics”, “Computers and programming”, “Engineering mechanics”, “Electrical machines”. The leading tools of formation of the general scientific component of bachelor in electromechanics competency in modeling of technical objects are augmented reality mobile tools (to visualize the objects’ structure and modeling results), mobile computer mathematical systems (universal tools used at all stages of modeling learning), cloud based spreadsheets (as modeling tools) and text editors (to make the program description of model), mobile computer-aided design systems (to create and view the physical properties of models of technical objects) and mobile communication tools (to organize a joint activity in modeling).
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Annamalai, K., e W. Ryan. Experimental studies on the group ignition of a cloud of coal particles: Volume 2, Pyrolysis and ignition modeling. Final report, August 15, 1988--October 15, 1991. Office of Scientific and Technical Information (OSTI), janeiro de 1992. http://dx.doi.org/10.2172/10143683.
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