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Littérature scientifique sur le sujet « Tracers dispersion »

Auteur : Grafiati

Publié le 10 mars 2023

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Articles de revues sur le sujet "Tracers dispersion"

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Istók, Balázs, and Gergely Kristóf. "Dispersion and Travel Time of Dissolved and Floating Tracers in Urban Sewers." Slovak Journal of Civil Engineering 22, no. 1 (2014): 1–8. http://dx.doi.org/10.2478/sjce-2014-0001.

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Abstract Environmental impacts of oil spills affecting urban sewage networks can be eliminated if timely intervention is taken. The design of such actions requires knowledge of the transport of surface pollutants in open channels. In this study we investigated the travel time and dispersion of pollutants by means of tracer experiments in sewage networks and a creek. The travel time of surface tracers has been found to be significantly shorter than that of a bulk flow tracer. The ratio of the travel times of a bulk flow tracer and surface tracers agreed with the known correlations obtained for rivers. An increasing tendency in the ratio of travel times has been observed for increasing bulk flow velocity. A segment-wise dispersion model was implemented in the existing hydraulic model of a sewer system. The simulation results were compared with the experimental observations. The dispersion rate of the bulk flow tracer has been found to obey Taylor’s mixing theory for long channels and was more intensive than that of surface tracers in community sewage channels.

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Ayuba, Ibrahim, Lateef T. Akanji, Jefferson L. Gomes, and Gabriel K. Falade. "Investigation of Drift Phenomena at the Pore Scale during Flow and Transport in Porous Media." Mathematics 9, no. 19 (2021): 2509. http://dx.doi.org/10.3390/math9192509.

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This paper reports an analytical study conducted to investigate the behaviour of tracers undergoing creeping flow between two parallel plates in porous media. A new coupled model for the characterisation of fluid flow and transport of tracers at pore scale is formulated. Precisely, a weak-form solution of radial transport of tracers under convection–diffusion-dominated flow is established using hypergeometric functions. The velocity field associated with the radial transport is informed by the solution of the Stokes equations. Channel thickness as a function of velocities, maximum Reynolds number of each thickness as a function of maximum velocities and concentration profile for different drift and dispersion coefficients are computed and analysed. Analysis of the simulation results reveals that the dispersion coefficient appears to be a significant factor controlling the concentration distribution of the tracer at pore scale. Further analysis shows that the drift coefficient appears to influence tracer concentration distribution but only after a prolonged period. This indicates that even at pore scale, tracer drift characteristics can provide useful information about the flow and transport properties of individual pores in porous media.

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Davis, P. M., T. C. Atkinson, and T. M. L. Wigley. "Longitudinal dispersion in natural channels: 2. The roles of shear flow dispersion and dead zones in the River Severn, U.K." Hydrology and Earth System Sciences 4, no. 3 (2000): 355–71. http://dx.doi.org/10.5194/hess-4-355-2000.

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Abstract. The classical one-dimensional advection-diffusion equation (ADE) gives an inadequate description of tracer cloud evolution in the River Severn, U.K. A solute transport model incorporating the effects of tracer storage in dead zones is presented in which the channel is conceived as being divided into two parallel regions. The bulk flow region occurs in the central part. Its longitudinal dispersive properties are described by the ADE. Adjacent to this, an additional cross-sectional area is defined in which tracer can be stored temporarily in regions of slowly moving water called dead zones. Exchange between the two regions follows a first order rate equation. Applying the model to the River Severn shows that a dispersing cloud’s evolution occurs in two distinct stages with a rapid transitional phase. Initially, shear-dispersion is dominant while the tracer particles mix fully over the bulk flow. Once this has occurred, dead zone storage accounts well for the non-Fickian evolution of the cloud. After the transitional phase the dead zone storage mechanism clearly dominates over shear-dispersion. Overall, the combined shear flow dispersion – dead zone model (D-DZM) provides a much better, physically consistent description of the tracer cloud’s evolution than the simple classical ADE approach can do alone. Keywords: Channels; dispersion; dead zones; tracers; River Severn

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Richards, K. J., Y. Jia, and C. F. Rogers. "Dispersion of Tracers by Ocean Gyres." Journal of Physical Oceanography 25, no. 5 (1995): 873–87. http://dx.doi.org/10.1175/1520-0485(1995)025<0873:dotbog>2.0.co;2.

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Lee, Mei-Man, A. J. George Nurser, Andrew C. Coward, and Beverly A. de Cuevas. "Effective Eddy Diffusivities Inferred from a Point Release Tracer in an Eddy-Resolving Ocean Model." Journal of Physical Oceanography 39, no. 4 (2009): 894–914. http://dx.doi.org/10.1175/2008jpo3902.1.

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Abstract This study uses tracer experiments in a global eddy-resolving ocean model to examine two diagnostic methods for inferring effective eddy isopycnic diffusivity from point release tracers. The first method is based on the growth rate of the area occupied by the tracers (the equivalent variance). During the period when tracer dispersion is dominated by stirring, the equivalent variance is found to increase at a rate between the second power law (for a pure shearing flow regime) and the exponential law (for a pure stretching flow regime). The second method is based on the length of the tracer contours. In the framework of equivalent radius, the two methods of inferring eddy diffusivity can be understood as two different averagings over the tracer patch. Over a shorter period of tracer dispersion the two methods give different eddy diffusivities, and only over a longer time when tracer dispersion approaches the final stage of diffusion do they give a similar value of diffusivity. A new diagnostic quantity called stirring efficiency is introduced to indicate different flow regimes by measuring the efficiency of stirring against mixing. The new diagnostic quantity has the advantage that it can be calculated directly from the gradients of tracer distribution without needing to estimate strain rate or background diffusivity.

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Smith, Ronald. "Effect of islands upon dispersion in rivers." Journal of Fluid Mechanics 292 (June 10, 1995): 249–70. http://dx.doi.org/10.1017/s0022112095001510.

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A general formulation is given for the dispersion of conservative tracers in steady flow in multi-connected channels. A multi-index is used to distinguish the different routes for tracer between the source and the observation position. For each route exact formulae are obtained for the time integral, time centroid, and cross-channel average of the temporal variance. The total concentration is the superposition of the contributions from the different routes.

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HASZPRA, TÍMEA, PÉTER KISS, TAMÁS TÉL, and IMRE M. JÁNOSI. "ADVECTION OF PASSIVE TRACERS IN THE ATMOSPHERE: BATCHELOR SCALING." International Journal of Bifurcation and Chaos 22, no. 10 (2012): 1250241. http://dx.doi.org/10.1142/s0218127412502410.

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Extensive numerical experiments are performed on tracer dispersion in global reanalysis wind fields. Particle trajectories are computed both along an isobaric (500 hPa) and an isentropic (315 K) surface in a time interval of one year. Besides mean quantities such as advection of the center of mass and growth of tracer clouds, special attention is paid to the evaluation of particle pair separation dynamics. The characteristic behavior for intermediate time scales is Batchelor's dispersion along both surfaces, where the zonal extent of the tracer cloud increases linearly in time. The long-time evolution after 70–80 days exhibits a slower, diffusive dispersion (Taylor regime), in agreement with expectations. Richardson–Obukhov scaling (superdiffusion with an exponent of 3/2) could not be identified in the numerical tests. The results confirm the classical prediction by Batchelor that the initial pair-separation determines subsequent time evolution of tracers. The quantitative dependence on the initial distance differs however from the prediction of the theory.

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Yuan (原), Yuxuan (宇轩), Mark R. Krumholz, and Blakesley Burkhart. "Understanding biases in measurements of molecular cloud kinematics using line emission." Monthly Notices of the Royal Astronomical Society 498, no. 2 (2020): 2440–55. http://dx.doi.org/10.1093/mnras/staa2432.

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ABSTRACT Molecular line observations using a variety of tracers are often used to investigate the kinematic structure of molecular clouds. However, measurements of cloud velocity dispersions with different lines, even in the same region, often yield inconsistent results. The reasons for this disagreement are not entirely clear, since molecular line observations are subject to a number of biases. In this paper, we untangle and investigate various factors that drive linewidth measurement biases by constructing synthetic position–position–velocity cubes for a variety of tracers from a suite of self-gravitating magnetohydrodynamic simulations of molecular clouds. We compare linewidths derived from synthetic observations of these data cubes to the true values in the simulations. We find that differences in linewidth as measured by different tracers are driven by a combination of density-dependent excitation, whereby tracers that are sensitive to higher densities sample smaller regions with smaller velocity dispersions, opacity broadening, especially for highly optically thick tracers such as CO, and finite resolution and sensitivity, which suppress the wings of emission lines. We find that, at fixed signal-to-noise ratio, three commonly used tracers, the J = 4 → 3 line of CO, the J = 1 → 0 line of C18O, and the (1,1) inversion transition of NH3, generally offer the best compromise between these competing biases, and produce estimates of the velocity dispersion that reflect the true kinematics of a molecular cloud to an accuracy of $\approx 10{{\ \rm per\ cent}}$ regardless of the cloud magnetic field strengths, evolutionary state, or orientations of the line of sight relative to the magnetic field. Tracers excited primarily in gas denser than that traced by NH3 tend to underestimate the true velocity dispersion by $\approx 20{{\ \rm per\ cent}}$ on average, while low-density tracers that are highly optically thick tend to have biases of comparable size in the opposite direction.

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Govender, Elaine, Athanasios Kotsiopoulos, and Sue T. L. Harrison. "A Study of Permeability and Diffusion at the Agglomerate-Scale in Heap (Bio)Leaching Systems." Advanced Materials Research 1130 (November 2015): 316–20. http://dx.doi.org/10.4028/www.scientific.net/amr.1130.316.

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Multiple mini-column reactors, loaded with identically constructed ore samples representing grab samples of a larger heap, were used to study the behaviour of solution tracers to elucidate solution diffusion, dispersion and transport. The tracers were either introduced to the ore bed as a pulse, included during agglomeration of the ore or introduced to the system by submerging the ore bed. These methods of tracer introduction allowed for the characterisation of flow interchange in unsteady state systems. The resulting concentration-time distribution curves were analysed to allow characterisation of flow dispersion and diffusion, which facilitates exchange between the fast flowing and largely stagnant liquid phases. Preliminary results support the presence of distinct stagnant and flowing regions within the agglomerated ore bed. Agglomeration with the tracer promotes increased retention on the ore; potentially enhancing microbial transport via increased solution exchange after the initial period of attachment.

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Fast, Jerome D., K. Jerry Allwine, Russell N. Dietz, Kirk L. Clawson, and Joel C. Torcolini. "Dispersion of Perfluorocarbon Tracers within the Salt Lake Valley during VTMX 2000." Journal of Applied Meteorology and Climatology 45, no. 6 (2006): 793–812. http://dx.doi.org/10.1175/jam2371.1.

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Abstract Six perfluorocarbon tracer experiments were conducted in Salt Lake City, Utah, during October 2000 as part of the Vertical Transport and Mixing (VTMX) field campaign. Four tracers were released at different sites to obtain information on dispersion during stable conditions within down-valley flow, canyon outflow, and interacting circulations in the downtown area. Some of the extensive tracer data that were collected are presented in the context of the meteorological field campaign measurements. Tracer measurements at building-top sites in the downtown area and along the lower slopes of the Wasatch Front indicated that vertical mixing processes transported material up to at least 180 m above the valley floor, although model simulations suggest that tracers were transported upward to much higher elevations. Tracer data provided evidence of downward mixing of canyon outflow, upward mixing within down-valley flow, horizontal transport above the surface stable layer, and transport within horizontal eddies produced by the interaction of canyon and down-valley flows. Although point meteorological measurements are useful in evaluating the forecasts produced by mesoscale models, the tracer data provide valuable information on how the time-varying three-dimensional mean and turbulent motions over urban and valley spatial scales affect dispersion. Although the mean tracer transport predicted by the modeling system employed in this study was qualitatively similar to the measurements, improvements are needed in the treatment of turbulent vertical mixing.

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Thèses sur le sujet "Tracers dispersion"

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Fabbroni, Nicoletta <1979&gt. "Numerical simulations of passive tracers dispersion in the sea." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1733/1/Fabbroni_Nicoletta_Tesi.pdf.

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Fabbroni, Nicoletta <1979&gt. "Numerical simulations of passive tracers dispersion in the sea." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1733/.

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Ferrari, Raffaele. "Dispersion of passive and active tracers in the upper ocean /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035412.

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Oms, Pierre-Emmanuel. "Transferts multi-échelles des apports continentaux dans le golfe de Gascogne." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0038/document.

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Lors de rejets chroniques ou accidentels de tritium des installations nucléaires dans l’eau de mer ou via les fleuves, la dispersion des radionucléides dans l’environnement marin est soumise à des processus de dispersion multiples. Ces processus dépendent de la zone considérée et des forçages tels que la marée, le vent, les flux de chaleurs et d’eau douce. Prédire la dispersion du tritium dans le golfe de Gascogne nécessite la prise en compte de l’ensemble de ces processus et des différents apports que représentent les eaux de surface de l’Atlantique Nord, les rejets des installations nucléaires, les entrées d’eau douces et les échanges avec l'atmosphère. L'objectif général de cette thèse est d'améliorer la connaissance sur l’hydrodynamisme du golfe de Gascogne, en couplant la mesure in-situ d’un traceur des masses d’eau : le tritium, avec un modèle hydrodynamique de dispersion (modèle MARS3D). Dans ce but, prélèvements ont été effectuées dans le golfe de Gascogne et dans les deux principaux contributeurs continentaux de tritium : la Loire et la Gironde. L’utilisation conjointe de la salinité et du tritium en tant que traceurs des eaux continentales a permis de différencier de manière innovante les apports provenant de ces deux fleuves à l'échelle du golfe. Les stocks mesurés et simulés de tritium au sein du plateau ont permis une première estimation du temps de résidence des masses d’eau continentales<br>During chronic or accidental releases of tritium from nuclear facilities to seawater or through river discharges, the dispersion of radionuclides in the marine environment is subject to multiple dispersion processes. These processes depend on the area under consideration and forcings such as tide, wind, heat and freshwater flows.Predicting the dispersion of tritium in the Bay of Biscay requires taking into account all these processes and the various inputs: the North Atlantic surface waters, discharges from nuclear facilities, freshwater inputs and exchanges with the atmosphere. The main objective of this thesis is to improve the knowledge on the hydrodynamics of the Bay of Biscay by coupling in-situ measurements of a water masses tracer: the tritium, with a hydrodynamic dispersion model (MARS 3 D).To achieve this goal, samplings were carried out in the Bay of Biscay and the two main continental contributors of tritium: the Loire and Gironde rivers.The combined use of salinity and tritium as tracers of continental waters makes it possible to differentiate into an innovative way the inputs from these two rivers at the scale of the continental shelf. The measured and simulated stocks of tritium within the shelf provided a first estimate of the residence time of continental water in the Bay of Biscay

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Charlaix, Elisabeth. "Dispersion en milieu poreux : mise en evidence de longueurs caracteristiques." Paris 6, 1987. http://www.theses.fr/1987PA066302.

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Pelosi, Anna. "Numerical modeling of traces in gravel-bed rivers." Doctoral thesis, Universita degli studi di Salerno, 2015. http://hdl.handle.net/10556/1922.

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2012 - 2013<br>The erosion, transport and deposition of pebbles in rivers have often been studied by considering the motion of tracer particles. There are reports of bedload tracing programs in field and laboratory since the late 1930s. The theoretical basis for the study of the dispersal of sediment tracer particles was delineated for the first time in 1950 by Einstein, who formulated the problem in terms of a standard 1D random walk in which each particle moves in a series of steps punctuated by waiting times. Subsequent to Einstein’s original work on tracers, the study of random walks has been extended to the case of continuous time random walks (CTRW). CTRW, accompanied by appropriate probability distribution functions (PDFs) for walker step length and waiting time, yields asymptotically the standard advectiondiffusion equation (ADE) for thin-tailed PDFs, and the fractional advection-diffusion equation (fADE) for heavy-tailed PDFs, the latter allowing the possibilities of subdiffusion or superdiffusion of particles, which is often referred as non-local behavior or anomalous diffusion. In latest years, considerable emphasis has been placed on non-locality associated with heavy-tailed PDFs for particle step length. This appears to be in part motivated by the desire to construct fractional advective-diffusive equations for pebble tracer dispersion corresponding to the now-classical fADE model. Regardless of the thin tail of the PDF, the degree of non-locality nevertheless increases with increasing mean step length. In the thesis, we firstly consider the general case of 1D morphodynamics of an erodible bed subject to bedload transport analysing the effects of non-locality mediated by both heavyand thin-tailed PDFs for particle step length on transient aggradational- degradational bed profiles. Then, we focus on tracers. (i) We show that the CTRW Master Equation is inappropriate for river pebbles moving as bed material load and (ii) by using the Parker-Paola-Leclair (PPL) framework for the Exner equation of sediment conservation, which captures the vertical structure of bed elevation variation as particles erode and deposit, we develop a new ME for tracer transport and dispersion for alluvial morphodynamics. The new ME is derived from the Exner equation of sediment continuity and it yields asymptotic forms for ADE and fADE that differ significantly from CTRW. It allows a) vertical dispersion, as well as streamwise advection-diffusion, and b) mean waiting time to vary in the vertical. We also show that vertical dispersion is nonlocal (subdiffuive), but cannot be expressed with fractional derivatives. Vertical dispersion is the likely reason for the slowdown of streamwise advection of tracer pebbles observed in the field, which is the key result of our modeling when co-evolution of vertical and streamwise dispersion are considered. [edited by author]<br>XII n.s.

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WILSON, JR GERALDO. "Etude du transport et de la dispersion des sediments en tant que processus aleatoires." Paris 6, 1987. http://www.theses.fr/1987PA066670.

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Etude de la dispersion longitudinale par charriage et en suspension des particules d'un ecoulement turbulent a surface libre a l'aide de la theorie des processus aleatoires. Les expressions generales des modeles aleatoires unidimensionnels sont remaniees de facon a englober le transport en suspension. On examine plusieurs modeles. On propose d'autres expressions analytiques plus adaptees a la nature non-constante des probabilites de deplacement du grain ou fonctions d'intensite de changement d'etat cinematique. Enfin, on presente la technique de tracage utilisee pour verifier experimentalement la theorie probabiliste du transport de sediments

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Lesouëf, Dorothée. "Étude numérique des circulations locales à la Réunion : application à la dispersion de polluants." Phd thesis, Université de la Réunion, 2010. http://tel.archives-ouvertes.fr/tel-00633096.

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Les régimes dynamiques dans les basses couches de l'atmosphère à l'île de la Réunion sont conditionnés par l'action du relief et du rayonnement sur l'écoulement synoptique. L'île est située en permanence dans le flux des alizés de sud-est et son relief élevé, culminant à 3000 m dans le centre de l'île et 2600 m au sud, constitue un obstacle important pour l'écoulement moyen. Le relief, le chauffage différentiel des pentes et le contraste thermique avec l'océan influent sur les échanges locaux entre la couche limite marine et la troposphère libre.L'analyse des phénomènes complexes de l'écoulement atmosphérique au niveau de l'île a pour but initial de caractériser les transferts de polluants émis localement. Cette étude a deux applications : * La première rentre dans le cadre préparatoire à la mise en place, à 2200 m d'altitude sur le Piton Maïdo, de l'observatoire atmosphérique de l'OPAR, à l'horizon 2011. L'objectif est de comprendre les circulations locales induites par le relief et les transports associés afin de discriminer d'éventuelles pollutions par les sources locales sur le signal qui sera mesuré in situ au sommet du Maïdo.* La seconde vise à étudier la diffusion des panaches volcaniques du Piton de la Fournaise. L'éruption majeure d'avril 2007 du volcan réunionnais a montré que des panaches pouvaient générer d'importantes pollutions dans diverses parties de l'île allant jusqu'à poser de réels problèmes environnementaux et de santé publique.Ces applications s'appuient sur une étude par modélisation numérique à haute résolution des écoulements atmosphériques dans les basses couches au niveau de l'île, au moyen du modèle météorologique de recherche MésoNH, permettant de conduire un ensemble de simulations sur cas idéalisés puis sur cas réels avec diffusion de traceurs passifs.

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Machado, da Silva Luis Carlos. "Transport d'un traceur passif dans l'atmosphère : expériences et simulations numériques (relief complexe : le site de Grenoble)." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10008.

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La dispersion d'un traceur passif (sf#6) a partir du site du commissariat de l'energie atomique (cea - grenoble) a ete etudiee a l'aide de simulations numeriques et des campagnes experimentales. Dans ce travail on a utilise comme site d'etude l'agglomeration grenobloise, puisque c'est un cas typique de relief complexe au confluent de vallees. Les releves experimentaux de mesure de concentration de traceur en divers points de la ville ont ete compares avec les resultats des modeles numeriques bases sur la solution analytique de l'equation de transport-diffusion. Les donnees meteorologiques obtenues a partir d'un pylone ont servi a determiner un spectre d'energie et des valeurs de rugosite. Les donnees meteorologiques, celles d'un sodar et d'un radiosondage ont determine les conditions initiales utilisees par le code submeso. Ce code est base sur la simulation numerique des grandes echelles (les) par la solution des equations de mecanique des fluides, avec resolution explicite des grandes echelles et modelisation des echelles sous-maille. Pour la validation du modele submeso on a simule le passage d'un ecoulement au dessus d'un saut de rugosite et on a compare les resultats avec ceux obtenus experimentalement par bradley. On verifie aussi le comportement du scalaire passif dans une atmosphere convective en se basant sur l'experience de laboratoire de willis et deardorff. Les resultats des modeles gaussiens et les montrent un bon accord avec ceux des campagnes experimentales de dispersion de sf#6 sur la ville de grenoble. Cependant la les possede les avantages supplementaires d'un calcul tridimensionnel des champs de vitesses, temperature, pression et l'energie cinetique dans tout le domaine de calcul. On montre que la les peut etre utilisee pour definir une statistique de dispersion applicable a des conditions meteorologiques particulieres du site d'emission. Cette statistique pourrait etre introduite dans les modeles gaussiens avec une prise en compte des classifications de types de journees.

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Roht, Yanina Lucrecia. "Transport et dispersion d’un traceur dans un écoulement de suspensions oscillant." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS065/document.

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On étudie le transport et la dispersion hydrodynamique d’un traceur passif et/ou d’une suspension de particules dans deux fractures modèles avec deux parois lisses ou avec une distribution aléatoire d’obstacles dans l’ouverture. On utilise un écoulement oscillant d’un fluide newtonien afin d’observer les effets sur la dispersion de la réversibilité du déplacement. On caractérise de manière quantitative l’influence des paramètres caractéristiques de l’écoulement: période T et amplitude A des oscillations et temps caractéristique τ_m de diffusion moléculaire sur l’épaisseur.Dans le cas de parois lisses, on montre que les régimes de dispersion sont déterminés par le rapport τ_m/T . Pour τ_m/T≤2, le régime de dispersion de Taylor est dominant et irréversible à l’échelle globale. Pour τ_m/T≥20, on a un régime partiellement réversible pour lequel le mélange reste diffusif à l’échelle globale mais où, localement, la distribution des particules de traceur dans l’épaisseur suit les oscillations de la vitesse locale v_x (z,t) . Dans ce cas, il existe une composante purement convective et réversible de la dispersion.Dans le cas d’une cellule rugueuse, le désordre induit par les obstacles fait apparaitre une composante de dispersion géométrique quand τ_m/T≤0,6, pour laquelle la dispersivité normalisée par l’amplitude l_d/A ne dépend pas de la période T. On observe le régime de dispersion de Taylor dans une gamme 〖0,8≤τ〗_m/T≤1 dépendant de l’amplitude de l’oscillation. Lorsque τ_m/T≥20, on observe le régime de dispersion partiellement réversible déjà observé précédemment dans la cellule lisse. En comparant ces mesures avec celles obtenues par des techniques complémentaires (écho et transmission), on a pu séparer la composante irréversible de la dispersion de la composante réversible associée à des chenaux macroscopiques d’écoulement préférentiel dus à la géométrie de la fracture. L’influence sur la dispersion de particules de 40 µm de diamètre en suspension dans l’écoulement oscillant a été ensuite étudiée dans la cellule lisse. La mesure globale de dispersion a mis en évidence les mêmes régimes d’écoulement qu’en l’absence de particules avec des domaines d’existence déterminés, comme dans ce cas, par la valeur du rapport τ_m/T.Pour mieux comprendre l’origine microscopique des résultats, nous avons suivi les trajectoires individuelles des particules dans un écoulement oscillant. Leur mouvement et la distribution de leurs vitesses ont été mesurés dans plusieurs couches à différentes distances dans l’épaisseur. On observe que les particules suivent les lignes de courant et que le profil de leurs vitesses dans l’épaisseur a la forme parabolique d’un profil de Poiseuille. Par ailleurs, nous avons comparé les distributions des particules après un certain nombre d’oscillations à celles au temps initial et observé, pour de longues périodes T, une migration des particules vers les parois de la cellule. Enfin, certaines particules présentant une réversibilité cinématique de leur mouvement, avec des allers retours suivant la même trajectoire, même en présence d’interactions entre elles.Enfin, en augmentant la concentration des particules, on observe une structuration de la suspension en bandes perpendiculaires à l’écoulement. On a étudié la longueur d’onde λ de cette instabilité en fonction de paramètres géométriques (épaisseur H et largeur de la cellule, diamètre des particules), physiques (viscosité et densité du fluide, densité des particules) et de l’écoulement (variation sinusoïdale ou carrée du débit, amplitude A et période T). La longueur d’onde normalisée λ/H augmente linéairement avec l’amplitude normalisée A/H mais est constante avec T et H et avec le diamètre des particules. Au niveau local, l’instabilité correspond à des variations périodiques de concentration suivant la largeur de la cellule et présentes dans toute l’épaisseur<br>We study the transport and the hydrodynamical dispersion of a passive tracer and/or a suspension of non-Brownian particles in two model fractures with smooth walls or a random distribution of obstacles in the aperture. We use an oscillating flow of a Newtonian fluid in order to study the effects of the reversibility of the displacement on dispersion. We characterize quantitatively the effects of the characteristic parameters of the flow: period T and amplitude A of the oscillations, and characteristic time τ_m of molecular diffusion across the thickness of the cell.In the case of smooth walls, we show that the dispersion regimes are determined by the value of the ratio τ_m/T. For τ_m/T≤2, the Taylor dispersion mechanism is dominant and irreversible at the global scale. For τ_m/T≥20, one has a partly reversible regime in which mixing remains diffusive at the global scale but, locally, the distribution of the particles in the thickness of the cell follows the oscillations v_x (z,t) of the local velocity. In this case, there exists a purely convective and reversible dispersion component.In the case of a cell with rough walls, flow disorder due to the obstacles results in a geometrical dispersion component when τ_m/T≤0,6, for which the dispersivity normalized by the amplitude l_d/A does not depend on the period T. The Taylor dispersion regime is observed in a range 0,8≤τ_m/T≤1 depending on the amplitude of the oscillation. When τ_m/T≥20, one obtains the partly reversible dispersion regime already observed previously for the smooth cell. Comparing these results to those obtained by complementary techniques (echo and transmission) allows us to separate the irreversible component of dispersion from the reversible one associated to macroscopic preferential flow channels due to the fracture geometry.The influence on dispersion of a suspension of 40 µm diameter non Brownian particles in the oscillating flow has then be studied in the cell with smooth walls. The global tracer dispersion measurements have shown the same dispersion regimes than without particles with domains of existence determined, like in this latter case, by the value of the ratio τ_m/T.In order to understand better the origin of these results at the microscopic scale, we tracked the individual trajectories of the particles in an oscillating flow. Their motion and the distribution of their velocities have been measured in several layers at different distances from the walls in the cell thickness. The particles are observed to follow the flow liens; the profile of their velocities in the thickness displays the parabolic shape of a Posieuille profile. Moreover, we compared the distribution of the particles after a certain number of oscillations to those at the initial time and observed, for long periods T, a migration of the particles towards the vicinity of the cell walls. Moreover, the motion of some particles display a kinematic reversibility and follow the same trajectory for both directions of the flow, even when there are interactions with the others.Finally, when the concentration of the particles is increased, one observes a structuration of the suspension into bands perpendicular to the flow. The wavelength λ of this instability has been studied as a function of geometrical (thickness H and width of the cell, particle diameter) and physical parameters (viscosity and density of the fluid, particle density) and of the characteristics of the flow (sine or square wave variation of the flow, amplitude A et period T). The normalized wavelength λ/H increases linearly with the normalized amplitude A/H but is constant with T and H and with the particle diameter. At the local level, the instability corresponds to periodic variations of the particle concentration along the length of the cell which extend across its whole thickness H<br>Se estudió el transporte y dispersión hidrodinámica de un trazador pasivo y/o de una suspensión de partículas en una fractura de paredes lisas y en otra, con una distribución aleatoria de obstáculos en su espesor. Se utiliza un flujo oscilante de un fluido newtoniano, permitiéndonos observar los efectos de la reversibilidad del desplazamiento sobre el fenómeno. En todos los casos se buscó cuantificar la influencia de los parámetros característicos del flujo: el período T y la amplitud A de las oscilaciones, el tiempo característico de difusión molecular sobre el espesor τ_m, la concentración y el tamaño de las partículas. En el caso de paredes lisas, se puso en evidencia que los regímenes de dispersión están gobernados por la relación τ_m /T. Se encontró que, a bajos τ_m /T ≤ 2, el régimen de dispersión de Taylor es dominante y, a escala global, es irreversible. Para τ_m /T ≥ 20 encontramos un régimen parcialmente reversible donde la mezcla continúa siendo difusiva a escala global; sin embargo, localmente, las simulaciones numéricas de tipo Monte Carlo mostraron que la distribución de partículas de trazador en el espesor sigue las oscilaciones de la velocidad local v_x (z, t). En este caso, el coeficiente de dispersión tiene una componente puramente convectiva, que es reversible. En el caso de una celda rugosa, el desorden introducido por los obstáculos hizo aparecer la dispersión geométrica a τ_m /T ≤ 0,6, donde la dispersividad ldg varía con la amplitud y no depende del período de la oscilación del flujo. El régimen de dispersión de Taylor se detectó en un intervalo de la relación entre los tiempos característicos más estrecho que en el caso de celda lisa, 〖0,8≤τ〗_m/T≤1, este rango depende de la amplitud de la oscilación. También se encontró el régimen de dispersión parcialmente reversible, para τ_m /T ≥ 20, correspondiendo con lo visto previamente en la celda de paredes lisas. Con técnicas complementarias (eco y transmisión), se aisló la componente de la dispersión irreversible de la reversible indicando la existencia de canales de flujo macroscópicos generados por la geometría de la fractura. Luego, se estudió el efecto sobre la dispersión por la presencia de una suspensión de partículas de poliestireno de 40 μm de diámetro, en la celda de Hele-Shaw lisa, con un flujo oscilante. En la medida global de la dispersión, se encontraron básicamente los mismos regímenes que en la celda lisa. Luego, en una escala microscópica, para terminar de comprender lo que sucede en el fenómeno de dispersión, se realizó el seguimiento de las trayectorias individuales de las partículas dentro de la celda sometidas a un flujo oscilante. Se analizó el movimiento en diferentes capas del espesor y se obtuvieron las distribuciones de velocidades. Se pudo observar que, las partículas se mueven siguiendo las diferentes líneas de corriente y su perfil de velocidades mantiene la forma parabólica característica de Poiseuille. Por otro lado, se aislaron las trayectorias que presentan reversibilidad cinemática, comprobando que hay partículas que van y vienen por el mismo camino, aún en presencia de interacciones débiles entre ellas. Por último, se aumentó la concentración de partículas presentes en la suspensión y se observó que, con un flujo oscilante, la suspensión dentro de la celda se estructura formando bandas periódicas transversales al flujo. Se caracterizó la dependencia de la longitud de onda λ de esta inestabilidad en función de parámetros geométricos (apertura y ancho de la celda, diámetro de partículas); físicos (viscosidad del fluido, densidad de las partículas) y geometría de flujo (sinusoidal, onda cuadrada, T y A). Se encontró que: para cada espesor de la celda, diferente diámetro y densidad de las partículas, viscosidades del fluido, λ resulta constante con T y aumenta linealmente con A. Localmente, se observó que la inestabilidad corresponde a variaciones de la concentración de las partículas en el espesor de la celda

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Livres sur le sujet "Tracers dispersion"

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Iller, Edward. Dyspersyjny model transportu mediów w radioznacznikowych badaniach pracy wybranych instalacji przemysłowych. Instytut Chemii i Techniki Ja̜drowej, 1999.

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Sundermeyer, Miles Aaron. Studies of lateral dispersion in the ocean. Massachusetts Institute of Technology, Woods Hole Oceanographic Institution, Joint Program in Oceanography/Applied Ocean Science and Engineering, 1998.

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Draxler, Roland R. Metropolitan Tracer Experiment (METREX). National Oceanic and Atmospheric Administration, Environmental Research Laboratories, 1985.

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Cowperthwaite, N. A. Scale model wind tunnel measurements on the Leyland T45 and DAF 3300 vehicles used for the T.R.R.L. spray dispersion programme. College of Aeronautics, Cranfield Institute of Technology, 1986.

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Cowperthwaite, N. A. Full scale and wind tunnel surface pressure measurements on the T.R.R.L. spray dispersion programme vehicles. College of Aeronautics, Cranfield Institute of Technology, 1987.

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Alberta. Energy Resources Conservation Board. and Concord Environmental Corporation, eds. Field measurement program: Atmospheric dispersion tracer study under stable conditions and meteorological study. Energy Resources Conservation Board, 1990.

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NATO, Advanced Research Workshop on Chaotic Advection Tracer Dynamics and Turbulent Dispersion (1993 Sereno di Gavi Italy). Chaoticadvection, tracer dynamics and turbulent dispersion: Proceedings of the NATO Advanced Research Workshop and EGS Topical Workshop on Chaotic Advection, Tracer Dynamics and Turbulent Dispersion, conference centre Sereno di Gavi, Italy, 24-29May 1993. North-Holland, 1994.

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Lee, Karl K. Stream velocity and dispersion characteristics determined by dye-tracer studies on selected stream reaches in the Willamette River Basin, Oregon. U.S. Dept. of the Interior, U.S. Geological Survey, 1995.

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Lee, Karl K. Stream velocity and dispersion characteristics determined by dye-tracer studies on selected stream reaches in the Willamette River Basin, Oregon. U.S. Dept. of the Interior, U.S. Geological Survey, 1995.

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Lee, Karl K. Stream velocity and dispersion characteristics determined by dye-tracer studies on selected stream reaches in the Willamette River Basin, Oregon. U.S. Dept. of the Interior, U.S. Geological Survey, 1995.

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Chapitres de livres sur le sujet "Tracers dispersion"

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Bedmar, A. Plata. "Use of Artificial Tracers for Pollution Dispersion Studies in Surface Water." In Water Pollution: Modelling, Measuring and Prediction. Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3694-5_24.

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Moroni, Monica, and John H. Cushman. "Anomalous Dispersion of Conservative Tracers: Theory and Three-Dimensional Particle Tracking Velocimetry Experiments." In Stochastic Methods in Subsurface Contaminant Hydrology. American Society of Civil Engineers, 2002. http://dx.doi.org/10.1061/9780784405321.ch10.

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Koplik, Joel. "The Tracer Transit-Time Tail in Multipole Reservoir Flows." In Dispersion in Heterogeneous Geological Formations. Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-017-1278-1_10.

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Benson, David A., Rina Schumer, Mark M. Meerschaert, and Stephen W. Wheatcraft. "Fractional Dispersion, Lévy Motion, and the MADE Tracer Tests." In Dispersion in Heterogeneous Geological Formations. Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-017-1278-1_11.

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Buhmann, Stefan Yoshi. "Introduction: Dispersion Forces." In Springer Tracts in Modern Physics. Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-32484-0_1.

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Buhmann, Stefan Yoshi. "Common Properties of Dispersion Forces." In Springer Tracts in Modern Physics. Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-32466-6_3.

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Silliman, S. E., and L. Zheng. "Comparison of Observations from a Laboratory Model with Stochastic Theory: Initial Analysis of Hydraulic and Tracer Experiments." In Dispersion in Heterogeneous Geological Formations. Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-017-1278-1_5.

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Pannone, Marilena, and Peter K. Kitanidis. "Large-Time Spatial Covariance of Concentration of Conservative Solute and Application to the Cape Cod Tracer Test." In Dispersion in Heterogeneous Geological Formations. Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-017-1278-1_6.

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Kuznetsov, Alexander, and Nickolay Mikheev. "Particle Dispersion in External Active Media." In Springer Tracts in Modern Physics. Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-36226-2_4.

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Graziani, Giovanni, Franco Girardi, Gianni Grippa, and Christine Vernetti. "Simulation of Transport and Dispersion of Tracer Releases." In Air Pollution Modeling and Its Application IX. Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3052-7_28.

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Actes de conférences sur le sujet "Tracers dispersion"

1

Assemat, P., A. Bergeon, and F. Plouraboue´. "Inertia Driven Dispersion Between Patterned Surfaces." In ASME 3rd International Conference on Microchannels and Minichannels. ASMEDC, 2005. http://dx.doi.org/10.1115/icmm2005-75243.

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Understanding and controlling stirring in micro-systems is necessary for the design of efficient passive micro-mixer. In this study, we focus on the dispersion of passive tracers injected in flows in between two rough surfaces under weak inertia influence (small but non-zero Reynolds number). The flow is induced by a constant applied pressure gradient between two cross-sections of the channel and the velocity field is calculated thanks to an extension of the lubrication approximation taking into account the first order inertial corrections. Tracers trajectories are obtained by integrating numerically the quasi-analytic velocity field. Our purpose is to examine the flow structure for various surface patterns and various Reynolds number. We focus on a simplified aperture field which is a smooth periodic function. This study puts forward interesting behavior of streamlines and show the dispersion of passive tracers in various geometries.

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Eckstein, Eugene C., Vinay Bhal, JoDe M. Lavine, Baoshun Ma, Mark Leggas, and Jerome A. Goldstein. "Nested First-Passages of Tracer Particles in Flows of Blood and Control Suspensions: Symmetry and Lorentzian Transformations." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69549.

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Theory of molecular Taylor-Aris dispersion (TAD) is an accepted framework describing tracer dispersion in suspension flows and determining effective diffusion coefficients. Our group reported a pseudo-Lagrangian method to study dispersion in suspension flows at FEDSM-2000. Tracer motions were studied in a steadily moving inertial reference frame (SMIRF) aligned with the flow direction; increments of change of axial position of individual tracers were collected to demonstrate how the tracer moved as they, individually, interacted with similar collections of other bodies brought to and from the region. First, individual tracers with no apparent axial velocity component (NAAVC) were identified; they exhibited fixed positions in video recordings of images collected in the SMIRF. Then, time increments were measured for tracers to pass at least 5, but usually 10 pre-selected, nested distances in the up- or downstream direction laid out with respect to the zero-site in the SMIRF. Such data were richer than measurements of tracer spread over time because stations along each path were serial first-passages (FP) with probabilistic meaning. Dispersion of various types of suspension and two transformation rules for combining velocity components are discussed herein. Traditional low-speed continuum theory and particle dynamics use Galilean transforms. Yet, to recognize the limited speed in laws for channel flows, Lorentzian transformations may be appropriate. In a four-space, deterministic paths would begin at NAAVC sites and continue in time-like conical regions of four-space. Distances in this space are measured using Minkowski’s metric; at the NAAVC site and on the boundary of the space-time cone, this metric has the format of the Fürth, Ornstein, and Taylor (FOT) equation when only terms to order t2 are used. Data shown at FEDSM-2000 can be reinterpreted as “prospective paths” in time-like regions that were consolidated in normalized cumulative probability distributions to provide retrospective descriptions. The ad hoc sign alteration of the FOT equation to fit the data of FEDSM-2000 is now taken as a part of measuring lengths using a Minkowski metric, which signifies a hyperbolic geometry, for which an inherent scaling constant is a negative curvature. The space also has an intrinsic distance of ℓ = Sτ, obtained from fitting parameters (S, τ) for the FOT equation. Integrals of the area under the FOT curve have units of volume, which are considered as describing an average volume of dispersion on S3, the 3-sphere. Path motion through this volume was kinematic dispersion, S2τ, which was the form for effective diffusivity in continuum theory used in FEDSM-2000. Weiner and Wilmer describe transformations in four-spaces in terms of commutating rotations on orthogonal planes, a concept readily linked to symmetries in the hyperbolic space typical of Lorentzian transformations; they also describe a second order ODE like the FOT equation.

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Velasco-Lozano, Moises, and Matthew Thomas Balhoff. "Modeling of Chemical Tracers to Estimate Oil Volume Contacted and Sweep Efficiency in Porous Media Under Countercurrent Spontaneous Imbibition." In SPE Improved Oil Recovery Conference. SPE, 2022. http://dx.doi.org/10.2118/209382-ms.

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Abstract Modeling of chemical tracers is an important technique to estimate oil saturation in porous media. Although numerous models exist to analyze the flow of tracers in systems under dynamic conditions, modeling in capillarity-dominated systems has not been sufficiently examined. In tight porous media and the matrix of fractured reservoirs, spontaneous imbibition (SI) represents a key driving mechanism for fluid infiltration because the low permeability in these systems results in a negligible transport by advection. We present a new semi-analytical solution for the flow of tracers under countercurrent SI valid during the infinite-acting and boundary-dominated flow regimes. The model presented is derived from the analysis of fluid imbibition driven by capillarity and numerically solved as a function of water distribution and initial tracer concentration. We model ideal and partitioning tracers to investigate the average oil saturation in the contacted region by tracer and sweep efficiency of countercurrent SI as a recovery mechanism in porous media. To verify the applicability of our solution, we compared it against numerical simulation cases under flow conditions with diverse solute and phase properties. The concentration profiles exhibit a significant delay in displacement behind the imbibition front when hydrodynamic dispersion is ignored and for high partitioning coefficients, demonstrating the importance of determining these properties before conducting a field test. The solution presented is the first to examine countercurrent SI for the modeling of oil volume contacted by tracers in porous media. We consider the model can be extended for the analysis of the flow of tracers in systems such as fractured reservoirs to estimate oil saturation in the matrix medium, and those using chemical solutions that promote SI by altering wettability and capillary pressure.

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Uthe, Edward E., William Viezee, and Jason K. S. Ching. "Airborne Lidar Tracking of Fluorescent Tracers for Atmospheric Transport and Diffusion Studies." In Optical Remote Sensing. Optica Publishing Group, 1985. http://dx.doi.org/10.1364/ors.1985.wc26.

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Development and validation of transport models for the study of regional acid deposition require improved observations of pollutant transport and dispersion processes for various atmospheric conditions. No suitable method for air-parcel tracking along non-constant density surfaces is available. Following a technique described by Rowland and Konrad (1979), SRI International has demonstrated the feasibility of using an airborne lidar system to observe atmospheric transport and dispersion of fluorescent dye particle (FDP) tracers. The Airborne Lidar Plume and Haze Analyzer (ALPHA-1) constructed and operated for the Electric Power Research Institute (EPRI) was used for this purpose.

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Niu, Haibo, and Shihan Li. "Modeling the dispersion of tracers in the marine environment: A model sensitivity study." In OCEANS 2016 - Shanghai. IEEE, 2016. http://dx.doi.org/10.1109/oceansap.2016.7485528.

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Cevheri, Necmettin, and Minami Yoda. "Evanescent-Wave Particle Velocimetry Studies of Electrokinetically Driven Flows: Divalent Counterion Effects." In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75274.

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Characterizing the mainly incompressible and laminar flows of aqueous electrolyte solutions through channels with an overall dimension of O(1–100 μm) is of interest in a variety of microfluidics applications. Solid surfaces such as the channel wall become (usually negatively) charged due to direct ionization or dissociation of surface groups, where the charge is typically characterized by the wall zeta-potential ζw. The surface in turn attracts mobile counterions from the fluid to form a (usually positively) charged screening, or electric double, layer (EDL). An external electric field can therefore be used to “pump” fluids through microfluidic Labs-on-a-Chip (LOC) by driving the charged fluid in the EDL. The resulting electroosmotic flow (EOF) is uniform outside the EDL, which has a thickness less than 50 nm in most cases. This uniform flow results in a more favorable scaling of the volume flowrate with channel diameter for microchannels, and also has less convective dispersion than shear flows. Electroosmotic flow is, however, very sensitive to changes in ζw. Various studies have shown, for example, that adding multivalent counterions to a monovalent electrolyte solution can greatly change ζw through both electrostatic and chemical interactions, even leading to “charge inversion” where the zeta-potential changes its sign. Evanescent-wave particle velocimetry, which tracks the motion of colloidal fluorescent tracer particles illuminated by evanescent waves within ∼400 nm of the wall, was therefore used to study the flow of various aqueous monovalent electrolyte solutions with small amounts of divalent cations such as Mg++ driven by an electric field through channels with a minimum dimension of ∼30 μm. The technique measures both the velocity components parallel to the wall and the steady-state distribution of these near-wall tracers. In these experiments, the tracers are convected parallel to the wall by both the EOF and directly by the applied electric field via electrophoresis because the surfaces of the particles also become negatively charged when suspended in the electrolyte solution. The electrophoretic contribution to the measured particle velocity was determined by measuring the particle zeta-potential with light scattering, and subtracted from the particle velocity to determine the actual EOF velocity.

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Pirrone, Marco, Satria Andrianata, Sara Moriggi, Giuseppe Galli, and Simone Riva. "Full Analytical Modeling Of Intrawell Chemical Tracer Concentration For Robust Production Allocation In Challenging Environments." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206245-ms.

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Abstract Conventional downhole dynamic characterization is based on data from standard production logging tool (PLT) strings. Such method is not a feasible option in long horizontal drains, deep water scenarios, subsea clusters, pump-assisted wells and in presence of asphaltenes/solids deposition, mainly due to high costs and risk of tools stuck. In this respect, intrawell chemical tracers (ICT) can represent a valid and unobtrusive monitoring alternative. This paper deals with a new production allocation interpretation model of tracer concentration behavior that can overcome the limitation of standard PLT analyses in challenging environments. ICT are installed along the well completion and are characterized by a unique oil and/or water tracer signature at each selected production interval. Tracer concentration is obtained by dedicated analyses performed for each fluid sample taken at surface during transient production. Next, tracer concentration behavior over time is interpreted, for each producing interval, by means of an ad-hoc one-dimensional partial differential equation model with proper initial and boundary conditions, which describes tracer dispersion and advection profiles in such transient conditions. The full time-dependent analytical solutions are then utilized to obtain the final production allocation. The methodology has been developed and validated using data from a dozen of tracer campaigns. The approach is here presented through a selected case study, where a parallel acquisition of standard PLT and ICT data has been carried out in an offshore well. The aim was to understand if ICT could be used in substitution of the more impacting PLT for the future development wells in the field. At target, the well completion consists of a perforated production liner with tubing. The latter, which is slotted in front of the perforations, includes oil and water tracer systems. The straightforward PLT interpretation shows a clear dynamic well behavior with an oil production profile in line with the expectations from petrophysical information. Then, after a short shut-in period, the ICT-based production allocation has been performed in transient conditions with a very good match with the available outcomes from PLT: in fact, the maximum observed difference in the relative production rates is 5%. In addition, the full analytical solution of the ICT model has been fundamental to completely characterize some complex tracer concentration behaviors over time, corresponding to non-simultaneous activation of the different producing intervals. Given the consistency of the independent PLT and ICT interpretations, the monitoring campaign for the following years has been planned based on ICT only, with consequent impact on risk and cost mitigations. Although the added value of ICT is relatively well known, the successful description of the tracer signals through the full mathematical model is a novel topic and it can open the way for even more advanced applications.

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Kabelka, V., A. V. Masalov, S. Nikitin, and H. Milchberg. "Tracing the phase distortion of a single femtosecond light pulse." In The European Conference on Lasers and Electro-Optics. Optica Publishing Group, 1998. http://dx.doi.org/10.1364/cleo_europe.1998.cma6.

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A frequency tracer (FT) based on noncollinear second harmonic generation autocorrelator for two-dimensional time-frequency imaging of a single femtosecond light pulse without using a spectral apparatus [1] had implemented for a first time. An experimental test of frequency tracer has been performed by measuring the instantaneous frequency of femtosecond pulses produced by a chirped pulse amplification Ti:sapphire laser system. In a normal operation the system is able to produce pulses up to 1.5 mJ energy and about 90 fs duration FWHM. The frequency traces were collected for pulses at different compressor grating separations. Experimental data on the linear chirp and pulse duration have been checked against a simple model, where the shape of the gausian pulse changes due to propagation through a dispersive path between pair of diffraction grating in a compressor. Detuning of the grating separation from its optimal value results in quadratic (in terms of frequency) phase shift of spectral components of output pulse. The data on chirp and pulse duration versus grating separation are in a good agreement with the estimations of dispersions at the system output. The registered images shown not only linear chirp of pulses (which was measured unambiguously) but also the fourth order phase distortion (cubic chirp). We prove by numerical calculations that images produced by the frequency tracer have simple intuitive meaning: the frequency trace is formed by maxima of two-dimensional image and does not require any iterative retrieval algorithm for visualising the phase distortions [2]. The calculations show that the second-harmonic frequency tracer allows to measure the even-order phase distortions of femtosecond light pulses: chirp, fourth-order, etc. These distortions include the phase self-modulation (Kerr-nonlinear contribution) of symmetric pulse.

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Yaralidarani, Muhammad, Shokoufeh Aghabozorgi, Seyed Amir Farzaneh, and Mehran Sohrabi. "Evaluation of Different Numerical Techniques for Accurate Modelling of Tracer Flow in Porous Media." In SPE Reservoir Characterisation and Simulation Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212598-ms.

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Abstract Inter-well tracer tests have numerous applications in determining the volumetric sweep, levels of heterogeneity, and delineation of flow barriers such as the faults in subsurface in reservoirs. Tracer tests are also performed in the laboratory to determine core samples’ heterogeneity. Simulation of physical dispersion requires refined models, which inevitably increase the numerical dispersion in the obtained results. In this paper, we quantify the numerical dispersion associated with various techniques available for the simulation of tracer flow. Numerical dispersion in the simulations can be quantified by comparing the simulation results with the experimental data. For this purpose, we first reviewed the fundamentals of tracer flow and introduced the Convection-dispersion equation as a basic model to describe tracer flow in porous media. Then we constructed a refined model to simulate a series of tracer flood scenarios. A detailed sensitivity analysis was carried out in a systematic manner to specify the individual impact of physical and numerical dispersion. Finally, we modelled tracer experiments performed on Indiana Limestone (IL) carbonate rocks to examine the accuracy of Fick's and Darcy's equations, and the results are presented. The impact of both numerical (non-physical) and physical dispersion was examined during the core scale simulations. It was concluded that the numerical TVD algorithm (embedded within the commercial ECLIPSE software) can appropriately model the tracer flow in porous media with minimal numerical errors during simulations. It was also shown that physical dispersion significantly affects tracer test results and that it must be considered when simulating tracer flows by defining an appropriate Peclet number. Finally, the results showed that solving the conventional convection-dispersion equation along with the numerical TVD algorithm can perfectly match the experimental data of several tracer flood tests performed on outcrop Indiana limestone core samples.

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Galani, A. N., M. E. Kainourgiakis, E. S. Kikkinides, et al. "Tracer Dispersion in Stochastically Reconstructed Porous Media." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/htd-24156.

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Abstract Aim of the present study is the simulation of tracer transport in porous media. Three-dimensional images of porous materials are generated using stochastic reconstruction techniques. Two phases, one mobile and one immobile, fill the pore space. A simulated annealing algorithm determines the spatial distribution of the immobile phase. A finite amount (slug) of tracer is injected at a certain position of the domain and its concentration at the outlet is monitored with respect to time. The resulting response curves depend on the spatial distribution of the immobile phase, the diffusivity ratio and the relative solubility of the tracer in the two phases. A sensitivity study is performed to investigate the effect of the tracer partitioning coefficient and its diffusive properties in water and oil, on the predicted outlet concentration curve.

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Rapports d'organisations sur le sujet "Tracers dispersion"

1

Feddersen, Falk. Dispersion in the Surfzone: Tracer Dispersion Studies. Defense Technical Information Center, 2011. http://dx.doi.org/10.21236/ada557187.

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2

Abernathy, R. N., I. A. Min, B. L. Lundblad, and W. S. Kempf. Tracer Puff Dispersion at Launch Sites. Defense Technical Information Center, 1999. http://dx.doi.org/10.21236/ada368855.

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3

Junker, D. Tracer studies for determining dispersion coefficients in isotope exchange columns. Office of Scientific and Technical Information (OSTI), 1990. http://dx.doi.org/10.2172/7070309.

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Guza, R. T., and Falk Feddersen. Lagrangian Tracer Transport and Dispersion in Tidal Inlets and River Mouths. Defense Technical Information Center, 2013. http://dx.doi.org/10.21236/ada580343.

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5

Allwine, K. Jerry, and Julia E. Flaherty. Urban Dispersion Program MSG05 Field Study: Summary of Tracer and Meteorological Measurements. Office of Scientific and Technical Information (OSTI), 2006. http://dx.doi.org/10.2172/890733.

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Guza, R. T., and Falk Feddersen. Transport and Dispersion of Dye-tracer and Drifters at a Tidal Inlet. Defense Technical Information Center, 2015. http://dx.doi.org/10.21236/ada614273.

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Guza, R. T., and Falk Feddersen. Lagrangian Tracer Transport and Dispersion in Shallow Tidal Inlets & River Mouths. Defense Technical Information Center, 2011. http://dx.doi.org/10.21236/ada540572.

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Guza, R. T., and Falk Feddersen. Lagrangian Tracer Transport and Dispersion in Shallow Tidal Inlets & River Mouths. Defense Technical Information Center, 2013. http://dx.doi.org/10.21236/ada598302.

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Guza, R. T., and Falk Feddersen. Lagrangian Tracer Transport and Dispersion in Shallow Tidal Inlets & River Mouths. Defense Technical Information Center, 2011. http://dx.doi.org/10.21236/ada557205.

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Senum, G., R. Dietz, T. D'Ottavio, R. Goodrich, E. Cote, and D. Spandau. A perfluorocarbon tracer transport and dispersion experiment in the North Sea Ekofisk oil field. Office of Scientific and Technical Information (OSTI), 1989. http://dx.doi.org/10.2172/7270738.

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