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Статті в журналах з теми "Collision de navire"
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Li, Xiang-Yu, Axel Brandenburg, Gunilla Svensson, Nils E. L. Haugen, Bernhard Mehlig, and Igor Rogachevskii. "Condensational and Collisional Growth of Cloud Droplets in a Turbulent Environment." Journal of the Atmospheric Sciences 77, no. 1 (December 26, 2019): 337–53. http://dx.doi.org/10.1175/jas-d-19-0107.1.
Повний текст джерелаАнотація:
Abstract We investigate the effect of turbulence on the combined condensational and collisional growth of cloud droplets by means of high-resolution direct numerical simulations of turbulence and a superparticle approximation for droplet dynamics and collisions. The droplets are subject to turbulence as well as gravity, and their collision and coalescence efficiencies are taken to be unity. We solve the thermodynamic equations governing temperature, water vapor mixing ratio, and the resulting supersaturation fields together with the Navier–Stokes equation. We find that the droplet size distribution broadens with increasing Reynolds number and/or mean energy dissipation rate. Turbulence affects the condensational growth directly through supersaturation fluctuations, and it influences collisional growth indirectly through condensation. Our simulations show for the first time that, in the absence of the mean updraft cooling, supersaturation-fluctuation-induced broadening of droplet size distributions enhances the collisional growth. This is contrary to classical (nonturbulent) condensational growth, which leads to a growing mean droplet size, but a narrower droplet size distribution. Our findings, instead, show that condensational growth facilitates collisional growth by broadening the size distribution in the tails at an early stage of rain formation. With increasing Reynolds numbers, evaporation becomes stronger. This counteracts the broadening effect due to condensation at late stages of rain formation. Our conclusions are consistent with results of laboratory experiments and field observations, and show that supersaturation fluctuations are important for precipitation.
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BARANGER, C. "MODELLING OF OSCILLATIONS, BREAKUP AND COLLISIONS FOR DROPLETS: THE ESTABLISHMENT OF KERNELS FOR THE T.A.B. MODEL." Mathematical Models and Methods in Applied Sciences 14, no. 05 (May 2004): 775–94. http://dx.doi.org/10.1142/s0218202504003441.
Повний текст джерелаАнотація:
In this work, we consider a spray consisting of droplets surrounded by a gas. The droplets are described by a kinetic equation and the gas verifies an equation of fluid dynamics such as Navier–Stokes. We write down the kernels corresponding to complex phenomena such as oscillations, breakup and collisions/coalescences. We use for that the T.A.B. model of oscillations introduced in particular in the KIVA code of combustion of Los Alamos, and the collision model introduced by Villedieu. We briefly explain the numerical method for solving such equations, and present results.
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INOUE, O., Y. HATTORI, and T. SASAKI. "Sound generation by coaxial collision of two vortex rings." Journal of Fluid Mechanics 424 (November 16, 2000): 327–65. http://dx.doi.org/10.1017/s0022112000002123.
Повний текст джерелаАнотація:
Sound pressure fields generated by coaxial collisions of two vortex rings with equal/unequal strengths are simulated numerically. The axisymmetric, unsteady, compressible Navier–Stokes equations are solved by a finite difference method, not only for a near field but also for a far field. The sixth-order-accurate compact Padé scheme is used for spatial derivatives, together with the fourth-order-accurate Runge–Kutta scheme for time integration. The results show that the generation of sound is closely related to the change of direction of the vortex ring motion induced by the mutual interaction of the two vortex rings. For the case of equal strength (head-on collision), the change of direction is associated with stretching of the vortex rings. Generated sound waves consist of compression parts and rarefaction parts, and have a quadrupolar nature. For the case of unequal strengths, the two vortex rings pass through each other; the weaker vortex ring moves outside the stronger vortex ring which shows a loop motion. The number of generated waves depends on the relative strength of the two vortex rings. The sound pressure includes dipolar and octupolar components, in addition to monopolar and quadrupolar components which are observed for the case of a head-on collision.
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Lohrasbi, Alireza, and Moharram D. Pirooz. "Navier Stokes model of solitary wave collision." Chaos, Solitons & Fractals 68 (November 2014): 139–50. http://dx.doi.org/10.1016/j.chaos.2014.08.003.
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Almady, Wasif. "Analytical Solution for Boltzmann Collision Operator for the1-D Diffusion equation." International Journal for Research in Applied Science and Engineering Technology 9, no. 9 (September 30, 2021): 1514–17. http://dx.doi.org/10.22214/ijraset.2021.38189.
Повний текст джерелаАнотація:
Abstract: In this paper, we have presented the analytical solution of the collision operator for the Boltzmann equation of onedimensional diffusion equation using the analytical solution of the one-dimensional Navier Stoke diffusion equation. Keywords: Boltzmann equation; analytical collision operator; one-dimensional diffusion equation.
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Naso, Aurore, Jennifer Jucha, Emmanuel Lévêque, and Alain Pumir. "Collision rate of ice crystals with water droplets in turbulent flows." Journal of Fluid Mechanics 845 (April 27, 2018): 615–41. http://dx.doi.org/10.1017/jfm.2018.238.
Повний текст джерелаАнотація:
Riming, the process whereby ice crystals get coated by impacting supercooled liquid droplets, is one of the dominant processes leading to precipitation in mixed-phase clouds. How a settling crystal collides with very small water droplets has been mostly studied in laminar conditions. The present numerical study aims at providing further insight on how turbulent flow motion affects the riming of ice crystals. We model the crystals as narrow oblate ellipsoids, smaller than the Kolmogorov elementary scale. By neglecting the effect of fluid inertia on the motion of the crystals and droplets, and using direct numerical simulations of the Navier–Stokes equations in a moderately turbulent regime, over a range of kinetic energy dissipation $1~\text{cm}^{2}~\text{s}^{-3}\lesssim \unicode[STIX]{x1D700}\lesssim 256~\text{cm}^{2}~\text{s}^{-3}$, we determine the collision rate between disk-shaped ice crystals and very small liquid water droplets. Whereas differential settling plays the dominant role in determining the collision rate at small turbulence intensity, the role of turbulence becomes more important at the large values of $\unicode[STIX]{x1D700}$ simulated, an effect that can be partly attributed to the increased role of inertia. We always find that collisions occur with a large probability on the rim of the ellipsoids, a phenomenon that can be explained to a large extent by kinematic considerations. The difference in the settling velocity of crystals and droplets induces a strong asymmetry in the probability of collision between the faces of the ellipsoids. Our results shed light on the physical mechanisms involved in the riming of ice crystals in clouds.
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Lin, S. C., T. C. Kuo, and C. C. Chieng. "Particle Trajectories Around a Flying Slider." Journal of Tribology 120, no. 1 (January 1, 1998): 69–74. http://dx.doi.org/10.1115/1.2834192.
Повний текст джерелаАнотація:
The Eulerian-Lagrangian approach is employed to simulate droplet trajectories due to the large-velocity gradient between two solid surfaces: a stationery block (slider) and a rotating plane (disk). Sudden expansion after the extremely small spacing will trap the particles in the open spaces. The fluid phase flowfield is obtained by solving Navier-Stokes equations with slip boundary correction in the Eulerian approach, and the droplet trajectories are calculated by integrating equations of motion with slip correction in the Lagrangian approach. Because of the extremely small spacing and the droplet size, Brownian motion effectively increases the probability of slider-head collisions, especially for extremely small particles. This study demonstrates that the effect due to particle size is the dominant factor in determining the probability of particle-slider collision, especially for particle sizes comparable with the air mean free path and the flowfield immediately adjacent to the solid surfaces. The results also show that lowering the flying height of the slider and increasing the disk velocity attracts the particles toward the gap between the disk and the slider.
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XU, KUN, and ZHAOLI GUO. "GENERALIZED GAS DYNAMIC EQUATIONS WITH MULTIPLE TRANSLATIONAL TEMPERATURES." Modern Physics Letters B 23, no. 03 (January 30, 2009): 237–40. http://dx.doi.org/10.1142/s0217984909018096.
Повний текст джерелаАнотація:
Based on a multiple stage BGK-type collision model and the Chapman–Enskog expansion, the corresponding macroscopic gas dynamics equations in three-dimensional space will be derived. The new gas dynamic equations have the same structure as the Navier–Stokes equations, but the stress strain relationship in the Navier–Stokes equations is replaced by an algebraic equation with temperature differences. In the continuum flow regime, the new gas dynamic equations automatically recover the standard Navier–Stokes equations. The current gas dynamic equations are natural extension of the Navier–Stokes equations to the near continuum flow regime and can be used for near continuum flow study.
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Mayhew, Kent W. "Illusions of Elastic Collisions in the Sciences:." European Journal of Engineering Research and Science 5, no. 1 (January 23, 2020): 87–90. http://dx.doi.org/10.24018/ejers.2020.5.1.1693.
Повний текст джерелаАнотація:
Employing elastic collisions rather than the reality of inelastic collisions simplifies much of the theoretical sciences. The consequences of such simplification is completely ignored/unrealized by the majority, hence must be addressed. At the crux of the problem is arguably the illusion of elastic collisions in kinetic theory, but this extends to other realms of physics including statistical theory, Lagrangian mechanics and the Navier-Stokes equations.
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Mayhew, Kent W. "Illusions of Elastic Collisions in the Sciences:." European Journal of Engineering and Technology Research 5, no. 1 (January 23, 2020): 87–90. http://dx.doi.org/10.24018/ejeng.2020.5.1.1693.
Повний текст джерелаАнотація:
Employing elastic collisions rather than the reality of inelastic collisions simplifies much of the theoretical sciences. The consequences of such simplification is completely ignored/unrealized by the majority, hence must be addressed. At the crux of the problem is arguably the illusion of elastic collisions in kinetic theory, but this extends to other realms of physics including statistical theory, Lagrangian mechanics and the Navier-Stokes equations.
Дисертації з теми "Collision de navire"
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Ladeira, Icaro. "Développement d'un solveur rapide et fiable basé sur des formules simplifiées pour évaluer la réponse des supports tubulaires d'éoliennes offshore soumis à l 'impact d'un navire." Electronic Thesis or Diss., Ecole centrale de Nantes, 2023. http://www.theses.fr/2023ECDN0016.
Повний текст джерелаАнотація:
Cette thèse traite du développementde méthodes analytiques pour l’analyse de laréponse aux collisions de navires d’éoliennesoffshores tubulaires telles que les monopieux etles flotteurs de type Spar, en considérant lesdéformations non seulement plastiques maisaussi élastiques, ceci afin de traiter des impactsà faible et à haute énergies.Le travail de recherche s’articule en deuxparties. La première concerne la réponse àl’impact d’éoliennes classiques tubulaires endéformation élastoplastique quasi-statique. Unalgorithme « pas à pas » est développé sur labase de formulations théoriques puisimplémenté dans un solveur permettant deprédire le processus de déformation complet del'éolienne.Dans la seconde partie, la réponse dynamiqueélastique d’un monopieu impacté par un navireest étudiée. Une méthode basée sur desmatrices de transfert est développée pourquantifier la réponse de l'éolienne à une chargeimpulsionnelle donnée et en particulierl'accélération vue par la nacelle.Ce travail de thèse s’inscrit dans le cadre duprojet de recherche ColFOWT, qui vise àdévelopper un outil complet et rapide d'analysede collisions navire-éolienne offshore. L'outilpermettra à terme de modéliser le processusde transfert d'énergie multi-mécanismes qui alieu lors d'une collision de navire, y compris lesmodes de déformation locaux et globaux ainsique l’effet des chargements hydrodynamiqueset des lignes d’ancrageThis thesis focuses on thedevelopment of simplified methodologies toassess the ship collision response of offshorewind turbines (OWT) supported by standalonetubular members such as monopiles and sparfloaters, with the inclusion of elasticcontributions, and the capability to address bothlow and high-energy impactsThe research is divided into two parts. The firstpart concerns the quasi-static elasto-plasticimpact response of typical OWTs. A timesteppingalgorithm was developed based ontheoretical formulations and implemented in astructural solver that is capable of predicting theOWT’s complete deformation process.The second part examines the dynamic elasticresponse of a monopile to a ship impact. Asimplified two-step framework based ontransfer matrices was developed to assess theresponse of the OWT to a given collision load,in particular the RNA acceleration.This thesis was conducted in the framework ofthe ColFOWT project, which aims to develop acomprehensive and rapid assessment tool forship-OWT collisions. The tool will be capable ofmodelling the multi-mechanism energy transferprocess that takes place during a collisionevent, including local and global deformationmechanisms, hydrodynamic effects, andmooring response
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Arlemark, Erik Johan. "Extending the applicability of the Navier-Stokes equations to micro gas flows by considering molecular collisions with boundaries." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12398.
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Baranger, Céline. "Modélisation, étude mathématique et simulation des collisions." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2004. http://tel.archives-ouvertes.fr/tel-00008826.
Повний текст джерелаАнотація:
Dans ce travail, nous nous intéressons à des problèmes issus de la Mécanique des Fluides et plus particulièrement au cas des aérosols (ou sprays, c'est-à-dire un ensemble de particules en suspension dans un fluide environnant). Les phénomènes physiques mis en jeu sont modélisés par des équations aux dérivées partielles (EDP). La phase continue (fluide environnant) est décrite par des équations issues de la mécanique des milieux continus de type Navier-Stokes ou Euler. La phase dispersée est décrite par une équation cinétique de type Boltzmann.Le premier résultat que nous présentons est consacré à l'étude mathématique d'un couplage entre une équation cinétique de type Vlasov et les équations d'Euler isentropiques. Ces équations modélisent un spray fin. Nous démontrons l'existence en temps petit d'une solution régulière pour le couplage Vlasov-Euler isentropique.
Ensuite, nous présentons les équations précises relatives à la modélisation des collisions, coalescences et fragmentations dans un spray.
Nous décrivons par la suite la simulation numérique du couplage fluide-cinétique dans un code industriel (Commissariat à l'Énergie Atomique), en particulier l'ajout des phénomènes de collisions.
Un deuxième modèle de fragmentation est également présenté. Ce modèle est plus pertinent dans les cas où les particules de la phase dispersée ont un grand nombre de Weber.
Enfin, nous présentons un résultat concernant une estimation explicite de trou spectral pour l'opérateur de Boltzmann avec potentiels durs linéarisé, et pour l'opérateur de Landau avec potentiels durs linéarisé.
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Huang, Zhujun. "Efficacité de Capture dans les Procédés de Flottation." Toulouse, INSA, 2009. http://eprint.insa-toulouse.fr/archive/00000335/.
Повний текст джерелаАнотація:
Ce travail est consacré à la détermination de l’efficacité de capture de particules par des inclusions fluides (bulles d’air), qui est la base du procédé de flottation. Cette capture, parfois appelée hétérocoagulation, couple l’hydrodynamique de collision bulle-particule et les forces interfaciales entre deux surfaces. Avec l’objectif d’une meilleure compréhension de différents mécanismes, l’étude s’appuie sur la simulation numérique directe (DNS) à l’aide du code JADIM de l’IMFT et l’approche expérimentale locale par la visualisation et divers outils de quantification. L’étude numérique est focalisée sur l’étape collision de la capture. La résolution des équations Navier-Stokes permet d’obtenir le champ de vitesse autour d’une bulle et l’approche lagrangienne d’une particule dans ce champ permet de calculer la trajectoire critique qui détermine finalement l’efficacité de collision. Les simulations couvrent une large gamme de paramètres caractéristiques du problème (nombre de Reynolds de bulle, rapport de diamètre particule/bulle, nombre de Stokes des particules, rapport de vitesse de sédimentation des particule/vitesse de bulle et degré de contamination de la surface de la bulle). L’efficacité de collision est fonction croissante du nombre de Reynolds et du ratio de taille. L’inertie des particules a un effet positif pour les grands nombres de Stokes, ce qui entraine une augmentation remarquable de l’efficacité de collision. Pour les petits nombres de Stokes, un effet négatif a été observé, connu comme force centrifuge qui éloigne la particule de la bulle et en conséquence diminue l’efficacité. La mobilité de la surface de la bulle montre un impact important sur l’efficacité de collision, car elle change totalement l’écoulement autour de la bulle. D’un point de vue expérimental, la visualisation directe de l’interaction entre la bulle et les particules nous permet de lier le modèle de capsule stagnante et le recouvrement de la surface de la bulle par les particules. Ce dernier diminue la vitesse d’ascension de la bulle lors de la capture, du fait de l’alourdissement de la bulle par les particules attachées, ainsi que par le changement de la mobilité de l’interface qui engendre une augmentation de la force de traînée. Une nouvelle approche expérimentale de la mesure de l’efficacité de capture est établie, basée sur la relation entre la vitesse d’ascension de la bulle, la surface recouverte par les particules et le nombre de particules capturées. La confrontation des valeurs des efficacités de capture expérimentales avec celles de la simulation numérique démontre une bonne concordanceThis work is devoted to determine the efficiency of particles capture by the fluid inclusion (air bubble), which is the basis of the flotation process. This capture process, sometimes called heterocoagulation, combines the dynamics of particle-bubble collision and film drainage with the thermodynamics of the interfacial forces which link the bubble and the particles forming an aggregate. With the aim of better understanding of different mechanisms, the study is based on direct numerical simulation (DNS) by using the code JADIM of IMFT and the experimental approach is performed by the local visualization and various measurements. The numerical study focuses on the collision of the capture process. The resolution of Navier- Stokes equations gives the local flow field around a bubble and the Lagrangian tracking of a particle in this flow field allows us to find out the critical trajectory that determines the collision efficiency. The numerical simulations cover a wide range of the parameters which characterize this problem (bubble’s Reynolds number, particle to bubble size ratio, particle’s Stokes number, particle to bubble terminal velocity ratio and bubble surface contamination level). The collision efficiency increases with the bubble’s Reynolds number and the particle to bubble size ratio. Particle’s inertia has a positive effect for large Stokes numbers, which leads a significant augmentation of the collision efficiency. Meanwhile for small Stokes numbers, a negative inertial effect has been observed, known as centrifuge force that pushes the particles from the bubble surface and therefore reduces the collision efficiency. Bubble’s surface mobility (surface contamination level) shows an important impact on the collision efficiency, because it totally changes the liquid flow around the bubble. On the experimental point of view, direct visualization of the interaction between the bubble and the particles allows us to link the stagnant cap model and surface coverage of the bubble by the captured particles. The later one reduces the bubble rising velocity during the particles capture, since on one hand, the captured particles reduced the bubble’s buoyancy by increases the bubbles affective density, and on the other hand, the change of interface mobility results in an important increase of bubble drag force. A new experimental approach to measure the capture efficiency is established based on the relationship between the bubble rising velocity, the surface covered by particles and the number of particles captured. The comparison between the experimental values with those given by the numerical simulation shows a good agreement
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Despringre-Bessière, Karine. "Détection d'obstacles sur route par télémétrie laser : évaluation des caractéristiques d'un système intégré." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0071.
Повний текст джерелаАнотація:
Les caracteristiques d'un systeme de detection d'obstacles sur autoroute, a grande vitesse, sont evaluees. La technologie de base est la telemetrie laser temps de vol, utilisee au leti. Un bilan sur la securite routiere en france souligne le besoin des usagers pour ce type de systeme. La revue sur les systemes de detection d'obstacles experimentaux actuels montre leurs limitations pour l'application autoroutiere. Les capteurs telemetriques developpes au leti sont ensuite presentes. Un systeme a balayage multiligne, base sur une evolution de ces capteurs, est propose, pour repondre au besoin defini. Le systeme est informatif. Le contexte de fonctionnement du systeme est decrit precisement, ainsi que ses objectifs et les contraintes qu'il doit tenir. Une description fonctionnelle est presentee. Le systeme est constitue de trois parties: (1) la partie acquisition, qui comporte essentiellement la mesure de distance et le balayage, (2) la partie traitement, constituee de la detection et du suivi des obstacles puis de l'estimation du danger qu'ils representent (3) et enfin la partie visualisation des informations pour le conducteur. Le simulateur sitam (simulateur d'images telemetriques acquises en mouvement), developpe lors de la these pour valider l'approche, est presente ensuite. Le systeme d'acquisition est dimensionne. Ainsi les parametres necessaires au systeme sont determines dans les conditions de fonctionnement definies auparavant. En particulier, le champ de vue est defini (en site, azimut et profondeur), ainsi que la frequence d'echantillonnage et la puissance adequates. Une etude parametrique est effectuee. Des simulations permettent d'evaluer la variation de la zone percue en fonction des variations des parametres du systeme. Des solutions sont proposees pour le traitement des donnees fournies par le futur capteur defini
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Tine, Léon Matar. "Analyse mathématique et numérique de modèles de coagulation-fragmentation." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10147/document.
Повний текст джерелаАнотація:
Ce mémoire de thèse concerne l’analyse mathématique et numérique du comportement asymptotique de certains modèles de type coagulation-fragmentation intervenant en physique ou en biologie.Dans la première partie, on considère le système d’équations de Lifshitz-Slyozov qui modélise l’immersion d’une population de macro-particules en interaction avec un bain de monomères. Ce modèle développe en temps long un comportement dépendant d’une manière très particulière de l’état initial et ses spécificités techniques en font un véritable challenge pour la simulation numérique.On introduit un nouveau schéma numérique de type volumes finis basé sur une stratégie anti-dissipative ; ce schéma parvient à capturer les profils asymptotiques attendus par la théorie et dépasse en performances les méthodes utilisées jusqu’alors. L’investigation numérique est poursuivie en prenant en compte dans le modèle des phénomènes de coalescence entremacro-particules à travers l’opérateur de Smoluchowski. La question est de déterminer par l’expérimentation numérique comment ces phénomènes influencent le comportement asymptotique. On envisage aussi une extension du modèle classique de Lifshitz-Slyozov qui prend en compte des effets spatiaux via la diffusion des monomères. On établit l’existence et l’unicité des solutions du système couplé hyperbolique-parabolique correspondant. La seconde partie de ce mémoire aborde des modèles d’agrégation fragmentation issus de la biologie. On s’intéresse en effet à des équations décrivant les phénomènes de croissance et de division pour une population de cellules caractérisée par sa densité de répartition en taille. Le comportement asymptotique de cette densité de répartition est accessible à l’expérience et peut être établi théoriquement. L’enjeu biologique consiste, à partir de données mesurées de la densité cellulaire, à estimer le taux de division cellulaire qui, lui, n’est pas expérimentalement mesurable. Ainsi, retrouver ce taux de division cellulaire fait appel à l’étude d’un problème inverse que nous abordons théoriquement et numériquement par des techniques de régularisations par quasi-reversibilité et par filtrage.La troisième partie de ce travail de thèse est consacrée à des systèmes couplés décrivant des interactions fluide-particules, avec des termes de coagulation–fragmentation, de type Becker–Döring. On étudie les propriétés de stabilité du modèle et on présente des résultats d’asymptotiques correspondant à des régimes de forte frictionThis thesis concerns the mathematical and numerical analysis of the asymptotic behavior of some coagulation-fragmentation type models arising in physics or in biology.In the first part we consider the Lifshitz-Slyozov system that models the dumping of a population of macro-particles in interaction with a bath of monomers. This model develops in long time a behavior depending in a very particular way on the initial data abd its technical specificities make a real challenge for the numerical simulation. We introduce a new numerical finite volume type scheme based on an anti-dissipative strategy; this scheme succeeds in capturing the asymptotic profiles waited by the theory and exceeds in performances the methods used before. The numerical investigation ispursued by taking into account in the model the phenomena of coalescence between macro-particles through the Smoluchowski operator. The question is to find by numerical experiment how these phenomena influence the asymptotic behavior. We also consider an extension of the classical Lifshitz-Slyozov model which takes into account the spatial effects via the diffusion of monomers. We establish the existence and the uniqueness of the solutions of the corresponding hyperbolic-parabolic coupled system.The second part of this thesis deals with approaches coagulation-fragmentation models stemming from biology. Indeed, we are interest in equations describing the phenomena of growth and division for a celles population caracterised by its size density repartition. The asymptotic behavior of this size density repartition is accessible to the experiment and can be established in theory. The biological stake consists, from measured data of the cellular density, to estimate the cellular division rate which is not experimentally measurable. So, to find this cellular division rate requires the study of an inverse problem which we approach numerically and theoretically by techniques of regularizations by quasi-reversibility and by filtering.This third part of this thesis work is devoted to coupled systems describing fluid-particles interactions with coagulation-fragmentation terms of Becker-Döring type. We study the stability properties of the model and we present some asymptotic results corresponding to the regime with strong friction force
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Andeme, Raeann. "Development of an Oriented-Eddy Collision Model for Turbulence." 2008. https://scholarworks.umass.edu/theses/161.
Повний текст джерелаАнотація:
The exact governing equations of fluid dynamics are too computationally expensive to solve on a computer for practical applications. Hence, it is currently not possible to analytically describe the behavior of a turbulent flow -in particular its internal structures-, making turbulence one of the major remaining unsolved problems in Classical Physics. One solution to computationally predict the performance of engineering applications involving fluids is the formulation of alternative and computationally tractable equations. This work demonstrates the feasibility of modeling turbulence as a collection of interacting particles with intrinsic orientation. It also discusses current efforts regarding its accuracy and computational overhead in numerous turbulent flows. The goal of this thesis is to focus on numerical implementation as well as model evaluation and validation. The Oriented-Eddy Collision Model is tested for basic flow cases and incorporated inhomogeneity. The project is successful in demonstrating that with appropriate extensions, the model can be applied to a very wide variety of turbulent flows with high predictive accuracy.
Книги з теми "Collision de navire"
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Parsons, Robert Charles. Collision at dawn: And other thrilling stories of the sea. St. John's, N.L: Creative Publishers, 2008.
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Collision at dawn: And other thrilling stories of the sea. St. John's, N.L: Creative Publishers, 2008.
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Gretar, Tryggvason, and United States. National Aeronautics and Space Administration., eds. Numerical simulations of drop collisions. [Washington, DC]: National Aeronautics and Space Administration, 1994.
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European Court of Human Rights. Affaire Pressos Compania Naviera S.A. et autres c. Belgique : arrêt du 20 Novembre 1995 =: Case of Pressos compania Naviera S.A. and others v. Belgium : judgment of 20 November 1995. Strasbourg: Greffe de la Cour, Conseil de l'Europe, 1996.
Знайти повний текст джерелаЧастини книг з теми "Collision de navire"
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Sathish, P., and D. Krishna Reddy. "Predictive Data Optimization of Doppler Collision Events for NavIC System." In Numerical Optimization in Engineering and Sciences, 583–89. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-3215-3_57.
Повний текст джерелаТези доповідей конференцій з теми "Collision de navire"
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Wang, Y., and C. Shu. "Numerical Investigation on Head-On Collisions of Binary Micro-Droplets by an Improved Multiphase Lattice Boltzmann Flux Solver." In ASME 2016 5th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/mnhmt2016-6533.
Повний текст джерелаАнотація:
Head-on collisions of binary micro-droplets are of great interest in both academic research and engineering applications. Numerical simulation of this problem is challenging due to complex interfacial changes and large density ratio between different fluids. In this work, the recently proposed lattice Boltzmann flux solver (LBFS) is applied to study this problem. The LBFS is a finite volume method for the direct update of macroscopic flow variables at cell centers. The fluxes of the LBFS are reconstructed at each cell interface through lattice moments of density distribution functions (DDFs). As compared with conventional multiphase lattice Boltzmann method, the LBFS can be easily applied to study complex multiphase flows with large density ratio. In addition, external forces can be implemented more conveniently and the tie-up between the time step and mesh spacing is also removed. Moreover, it can deal with complex boundary conditions directly as those do in the conventional Navier-Stokes solvers. At first, the reliability of the LBFS is validated by simulating a micro-droplet impacting on a dry surface at density ratio 832 (air to water). The obtained result agrees well with experimental measurement. After that, numerical simulations of head-on collisions of two micro droplets are carried out to examine different collisional behaviors in a wide range of Reynolds numbers and Weber numbers of 100 ≤ Re ≤ 2000 and 10 ≤ We ≤ 500. A phase diagram parameterized by these two control parameters is obtained to classify the outcomes of these collisions. It is shown that, at low Reynolds number (Re=100), two droplets will be coalescent into a bigger one for all considered Weber numbers. With the increase of the Reynolds number, separation of the collision into multiple droplets appears and the critical Weber number for separation is decreased. When the Reynolds number is sufficiently high, the critical Weber number for separation is between 20 and 25.
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Vance, Marion W., and Kyle D. Squires. "An Approach to Parallel Computing in an Eulerian-Lagrangian Two-Phase Flow Model." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31225.
Повний текст джерелаАнотація:
An approach to parallel solution of an Eulerian-Lagrangian model of dilute gas-solid flows is presented. Using Lagrangian treatments for the dispersed phase, one of the principal computational challenges arises in models in which inter-particle interactions are taken into account. Deterministic treatment of particle-particle collisions in the present work pose the most computationally intensive aspect of the simulation. Simple searches lead to algorithms whose cost is O(N2p) where Np is the particle population. The approach developed in the current effort is based on localizing collision detection neighborhoods using a cell-index method and spatially distributing those neighborhoods for parallel solution. The method is evaluated using simulations of the gas-solid turbulent flow in a vertical channel. The instantaneous position and the velocity of any particle is obtained by solving the equation of motion for a small rigid sphere assuming that the resulting force induced by the fluid reduces to the drag contribution. Binary particle collisions without energy dissipation or inter-particle friction are considered. The carrier flow is computed using Large Eddy Simulation of the incompressible Navier-Stokes equations. The entire dispersed-phase population is partitioned via static spatial decomposition of the domain to maximize parallel efficiency. Simulations on small numbers of distributed memory processors show linear speedup in processing of the collision detection step and nearly optimal reductions in simulation time for the entire solution.
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Ahmadi, Goodarz, Hojjat Nasr, and John B. McLaughlin. "Turbulent Two-Phase Flows and Particle Deposition in a Duct at High Concentrations." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30828.
Повний текст джерелаАнотація:
Two-phase flows including particle-particle collisions and two-way coupling in a turbulent duct flow were simulated using a direct simulation approach. The direct numerical simulation (DNS) of the Navier-Stokes equation was performed via a pseudospectral method was extended to cover two-way coupling effects. The effect of particles on the flow was included in the analysis via a feedback force that acted on the fluid on the computational grid points. The point particle equation of motion included the Stokes drag, the Saffman lift, and the gravitational forces. Several simulations for different particle relaxation times and particle mass loading were performed, and the effects of the inter-particle collisions and two-way coupling on the particle deposition velocity, fluid and particle fluctuating velocities, particle normal mean velocity, and particle concentration were determined. It was found that when particle-particle collisions were included in the computation, the particle deposition velocity increased. When the particle collision was neglected but the particle-fluid two-way coupling was accounted for, the particle deposition velocity decreased slightly. When both inter-particle collisions and two-way coupling effects were taken into account in the simulations, the particle deposition velocity increased. Comparisons of the present simulation results with the available experimental data and earlier numerical results are also presented.
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Fujimoto, Hitoshi, Yu Shiotani, Albert Y. Tong, and Hirohiko Takuda. "Numerical and Experimental Study on Oblique Collision of Water Droplet With a Solid Substrate." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80338.
Повний текст джерелаАнотація:
This study is concerned with the collision behavior of water droplets impacting onto a solid. Three-dimensional computer simulations are performed to understand the physics of phenomena. The Navier-Stokes equations for unsteady, incompressible, viscous fluid in a three-dimensional Cartesian coordinate system are approximated and solved by a finite difference method. The VOF (Volume-of-Fluid) technique is used to track free liquid surface. The effects of liquid viscosity, surface tension, gravity, and wettability between liquid and solid are taken into account. Normal and oblique collisions of droplets with the substrate are simulated at relatively low impact inertia of droplets. Experiments are also carried out in order to validate the numerical results. The numerical results agree reasonably well with experiments. The physics of phenomena is discussed in detail from theoretical aspects.
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Sathish, P., D. Krishna Reddy, A. D. Sarma, and K. Sudershan Reddy. "Investigations of Doppler Collision Effects on NavIC." In 2018 3rd IEEE International Conference on Recent Trends in Electronics, Information & Communication Technology (RTEICT). IEEE, 2018. http://dx.doi.org/10.1109/rteict42901.2018.9012450.
Повний текст джерела
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Arlemark, Erik J., S. Kokou Dadzie, and Jason M. Reese. "An Extension to the Navier-Stokes-Fourier Equations by Considering Molecular Collisions With Boundaries." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62222.
Повний текст джерелаАнотація:
In this paper we propose a model for micro gas flows consisting of the Navier-Stokes-Fourier equations (NSF) extended by a description of molecular collisions with solid boundaries and discontinuous velocity slip and temperature jump boundary conditions. By considering the molecular collisions with the solid boundaries in gas flows we capture some of the near wall effects that the conventional NSF with linear stress/strain-rate and heat-flux/temperature-gradient relationships seem to be unable to describe. The model that we propose incorporates the molecular collisions with solid boundaries as an extension to the conventional definition of the average travelling distance of molecules before experiencing intermolecular collisions (the mean free path). By considering both of these types of collisions we obtain an effective mean free path expression, which varies with distance to surfaces. The effective mean free path is proposed to be used to obtain new definitions of effective viscosity and effective thermal conductivity, which will extend the applicability of NSF equations to higher Knudsen numbers. We show results of simple flow cases that are solved using this extended NSF model and discuss limitations to the model due to various assumptions. We also mention interesting ideas for further development of the model based on a more detailed gas description.
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Finn, Justin R., Sourabh V. Apte, and Ming Li. "Numerical Simulation of Sand Ripple Evolution in Oscillatory Boundary Layers." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-22065.
Повний текст джерелаАнотація:
We perform simulations of sand ripple evolution in an oscillatory boundary layer flow typical of the ripple regime. The simulation framework is a parallel implementation of a three dimensional, variable density, incompressible flow solver, which solves the ensemble averaged Navier-Stokes equations on a fixed, structured grid. The sediment phase is evolved by computing hydrodynamic and inter-particle forces acting on each Lagrangian particle. Particle-particle collisions are treated with a soft sphere model incorporating both normal and tangential collision forces. Realistic and consistent coupling of the sediment to the Eulerian fluid phase is achieved through a typical inter-phase drag force term as well as the effects of volume displacement by the sediment. The Euler-Lagrange computational approach is developed in three-dimensions and its accuracy is verified using two test cases with analytic or empirically known solutions. It is then applied to simulate ripple evolution in oscillatory boundary layers and results are compared with Nielsens ripple predictor model as well as mixture-theory based Eulerian computations.
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Fujimoto, Hitoshi, Natsuo Hatta, and Hirohiko Takuda. "Collision Dynamics of Two Droplets." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0770.
Повний текст джерелаАнотація:
Abstract This paper treats the numerical analysis of the deformation behavior of liquid after head-on collision of two droplets. The simulation of the liquid deformation process has been performed using the MAC-type solution method to solve a finite differencing approximation of the Navier-Stokes equations governing an axisymmetric incompressible fluid flow. When a water droplet collides head-on into another one with small initial Weber numbers, two droplets coalesce and remain permanently united. For larger Weber numbers, two droplets merge temporarily and subsequently separate into two or more drops. The calculated free surface configurations have been in qualitative agreement with the experimental results observed by other researchers. Also, the critical Weber number to predict coalescence/separation of liquid after head-on collision has agreed with the experimental data. The details of droplet deformation mechanism have been discussed from a qualitative as well as quantitative point of view.
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Wang, S., and H. Ninokata. "Numerical Simulation of 3D Flow in Turbomolecular Pump by Direct Simulation Monte Carlo Method." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77364.
Повний текст джерелаАнотація:
A Turbomolecular pump (TMP) is one of the key apparatus to produce high and ultrahigh vacuum. It works mainly in the conditions of free molecular and transitional regimes, where the Navier-Stokes equations of continuum gas dynamics can not be correctly applied. In this study, the flow field in single blade row of one stage TMP is investigated by direct simulation Monte Carlo (DSMC) method with a 3D analysis in a rotating reference frame. Considering the Coriolis and centrifugal accelerations, the equations about the molecular velocities and position are deduced on this frame. The VSS model and NTC collision schemes are used to calculate the intermolecular collisions. The diffuse reflection is employed on the molecular reflection from the surfaces of boundary. The transmission probabilities are calculated and applied to analyze the relationship between the outlet pressure and the maximum pressure ratio. The pumping performances between H2 and N2 on the same blade speed and same blade speed ratio are compared and analyzed carefully. The maximum pumping efficiencies on the different blade angles are also calculated. Numerical results show good quantitative agreement with existing experiment data.
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Volkov, Aleksei N., and Yury M. Tsirkunov. "CFD/Monte Carlo Simulation of Collision-Dominated Gas-Particle Flows Over Bodies." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31222.
Повний текст джерелаАнотація:
An efficient algorithm of numerical simulation of two-way coupled viscous flows of a dusty gas with collisions between particles is described. The flow of a carrier gas which is treated as a continuum is simulated by solving the modified Navier-Stokes equations using a CFD-method. The reverse effect of particles on a gas flow is modelled by the source terms entered into the momentum and energy equations. A dispersed phase is treated as a discrete set of particles which move in the carrier gas and can collide with each other. The particle drag force, the Magnus lift force, the damping torque and the heat exchange are taken into account in gas-particle interaction. Particles are assumed to collide inelastically and frictionally. A modified majorant frequency scheme of the Direct Simulation Monte Carlo (DSMC) method is proposed for computations of flow fields of a collisional “gas” of particles. The developed combined CFD / DSMC method is applied to the study of the supersonic gas-particle flow over a blunt body.