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Опубліковано: 1 лютого 2023

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Статті в журналах з теми "Analyse de la dispersion de Taylor":

1

GARCIA-SCHWARZ, G., M. BERCOVICI, L. A. MARSHALL, and J. G. SANTIAGO. "Sample dispersion in isotachophoresis." Journal of Fluid Mechanics 679 (May 12, 2011): 455–75. http://dx.doi.org/10.1017/jfm.2011.139.

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We present an analytical, numerical and experimental study of advective dispersion in isotachophoresis (ITP). We analyse the dynamics of the concentration field of a focused analyte in peak mode ITP. The analyte distribution is subject to electromigration, diffusion and advective dispersion. Advective dispersion results from strong internal pressure gradients caused by non-uniform electro-osmotic flow (EOF). Analyte dispersion strongly affects the sensitivity and resolution of ITP-based assays. We perform axisymmetric time-dependent numerical simulations of fluid flow, diffusion and electromigration. We find that analyte properties contribute greatly to dispersion in ITP. Analytes with mobility values near those of the trailing (TE) or leading electrolyte (LE) show greater penetration into the TE or LE, respectively. Local pressure gradients in the TE and LE then locally disperse these zones of analyte penetration. Based on these observations, we develop a one-dimensional analytical model of the focused sample zone. We treat the LE, TE and LE–TE interface regions separately and, in each, assume a local Taylor–Aris-type effective dispersion coefficient. We also performed well-controlled experiments in circular capillaries, which we use to validate our simulations and analytical model. Our model allows for fast and accurate prediction of the area-averaged sample distribution based on known parameters including species mobilities, EO mobility, applied current density and channel dimensions. This model elucidates the fundamental mechanisms underlying analyte advective dispersion in ITP and can be used to optimize detector placement in detection-based assays.
2

Chen, G. Q., and L. Zeng. "Taylor dispersion in a packed tube." Communications in Nonlinear Science and Numerical Simulation 14, no. 5 (May 2009): 2215–21. http://dx.doi.org/10.1016/j.cnsns.2008.07.018.

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3

Rubinstein, I., and B. Zaltzman. "Convective diffusive mixing in concentration polarization: from Taylor dispersion to surface convection." Journal of Fluid Mechanics 728 (July 8, 2013): 239–78. http://dx.doi.org/10.1017/jfm.2013.276.

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AbstractWe analyse the steady-state convection–diffusion mixing of a solute by a creeping circulatory flow in a long sealed rectangular two-dimensional channel with impermeable sidewalls and fixed different solute concentrations at the two opposite edges. Solution circulation is due to a constant velocity slip along the sidewalls and a back flow along the channel axis. This simple model distils the essence of circulation in concentration polarization of an electrolyte solution under a DC electric current in a micro-channel sealed by an ion-selective element (a nano-channel or a cation exchange membrane). It is observed that in the slow circulation regime (small $Pe$ numbers) the solute flux through the channel is governed by the Taylor–Aris dispersion mechanism, i.e. the flux is driven by the cross-sectional average axial concentration gradient, whereas upon increase in $Pe$ this mechanism fails. The general question addressed is where the system goes after the breakdown of the Taylor–Aris dispersion regime. In order to find out the answer, the following specific questions have to be addressed. (1) How does the Taylor–Aris dispersion mechanism break down upon increase in $Pe$? (2) Why does it break down? (3) What is the role of the channel aspect ratio in this breakdown? The answers to these questions are obtained through analysing a hierarchy of suitable auxiliary model problems, including the unidirectional zero discharge channel flow and the circulatory analogue of plane-parallel Couette flow, for which most of the analysis is done. They may be summarized as follows. Upon increase in circulation velocity, the Taylor–Aris dispersion mechanism fails due to the formation of lateral non-uniformities of longitudinal solute concentration gradient driving the dispersion flux. These non-uniformities accumulate in protrusion-like disturbances of the solute concentration (wall fingers) emerging near the channel sidewall at the flow exit from the edge. Wall fingers propagate along the sidewalls with increase in $Pe$ and eventually reach the opposite channel edges, transforming into narrow surface convection layers. These layers, together with the edge diffusion layers, form a closed mass transport pattern carrying most of the mass flux through the channel with the bulk largely excluded from the transport. The formation of this pattern finalizes the transition from Taylor–Aris dispersion to the surface convection regime. For large circulation velocities, concentration distribution in the surface convection layers attains an oscillatory spiral structure reminiscent of thermal waves in heat conduction.
4

Al Mukahal, F. H. H., B. R. Duffy, and S. K. Wilson. "Advection and Taylor–Aris dispersion in rivulet flow." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2207 (November 2017): 20170524. http://dx.doi.org/10.1098/rspa.2017.0524.

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Motivated by the need for a better understanding of the transport of solutes in microfluidic flows with free surfaces, the advection and dispersion of a passive solute in steady unidirectional flow of a thin uniform rivulet on an inclined planar substrate driven by gravity and/or a uniform longitudinal surface shear stress are analysed. Firstly, we describe the short-time advection of both an initially semi-infinite and an initially finite slug of solute of uniform concentration. Secondly, we describe the long-time Taylor–Aris dispersion of an initially finite slug of solute. In particular, we obtain the general expression for the effective diffusivity for Taylor–Aris dispersion in such a rivulet, and discuss in detail its different interpretations in the special case of a rivulet on a vertical substrate.
5

Jordan, P. M., and C. Feuillade. "A note on Love's equation with damping." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 462, no. 2071 (February 21, 2006): 2063–76. http://dx.doi.org/10.1098/rspa.2006.1674.

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The dynamic propagation of a Heaviside input signal in a semi-infinite, dissipative/dispersive medium is considered. The exact solution to this problem, which corresponds to Stokes' first problem of fluid mechanics, is obtained and analysed using integral transform methods. Special/limiting cases are noted and numerical methods are used to illustrate the analytical findings. Specifically, the following results are presented: (i) critical values of the dispersion coefficient are noted and examined; (ii) for large values of time, the solution exhibits Taylor shock-like behaviour; (iii) the half-peak point of the Taylor shock exhibits a phase shift that depends on the dispersion coefficient. Lastly, links to other fields are noted and some associated mathematical relations are presented.
6

Beck, Margaret, Osman Chaudhary, and C. Eugene Wayne. "Rigorous Justification of Taylor Dispersion via Center Manifolds and Hypocoercivity." Archive for Rational Mechanics and Analysis 235, no. 2 (August 7, 2019): 1105–49. http://dx.doi.org/10.1007/s00205-019-01440-2.

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7

Brenner, H., A. Nadim, and S. Haber. "Long-time molecular diffusion, sedimentation and Taylor dispersion of a fluctuating cluster of interacting Brownian particles." Journal of Fluid Mechanics 183 (October 1987): 511–42. http://dx.doi.org/10.1017/s002211208700274x.

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Generalized Taylor dispersion theory, incorporating so-called coupling effects, is used to calculate the transport properties of a single deformable ‘chain’ composed of hydrodynamically interacting rigid Brownian particles bound together by internal potentials and moving through an unbounded quiescent viscous fluid. The individual rigid particles comprising the flexible chain or cluster may each be of arbitrary shape, size and density, and are supposed ‘joined’ together to form the chain by a configuration-dependent internal potential V. Each particle separately undergoes translational and rotational Brownian motions; together, their relative motions give rise to a conformational or vibrational Brownian motion of the chain (in addition to a translational motion of the chain as a whole). Sufficient time is allowed for all accessible chain configurations to be sampled many times in consequence of this internal Brownian motion. As a result, an internal equilibrium Boltzmann probabilistic distribution of conformations derived from V effectively obtains.In contrast with prior analyses of such chain transport phenomena, no ad hoc preaveraging hypotheses are invoked to effect the averaging of the input conformation-specific hydrodynamic mobility data. Rather, the calculation is effected rigorously within the usual (quasi-static) context of configuration-specific Stokes-Einstein equations.Explicit numerical calculations serving to illustrate the general scheme are performed only for the simplest case, namely dumb-bells composed of identically sized spheres connected by a slack tether. In this context it is pointed out that prior calculations of flexible-body transport phenomena have failed to explicitly recognize the existence of a Taylor dispersion contribution to the long-time diffusivity of sedimenting deformable bodies. This fluctuation phenomenon is compounded of shape-sedimentation dispersion (arising as a consequence of the intrinsic geometrical anisotropy of the object) and size-sedimentation dispersion (arising from fluctuations in the instantaneous ‘size’ of the object). Whereas shape dispersion exists even for rigid objects, size dispersion is manifested only by flexible bodies. These two Taylor dispersion mechanisms are relevant to interpreting the non-equilibrium sedimentation-diffusion properties of monodisperse polymer molecules in solutions or suspensions.
8

Feng, Shirani, and Inglis. "Droplets for Sampling and Transport of Chemical Signals in Biosensing: A Review." Biosensors 9, no. 2 (June 20, 2019): 80. http://dx.doi.org/10.3390/bios9020080.

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The chemical, temporal, and spatial resolution of chemical signals that are sampled and transported with continuous flow is limited because of Taylor dispersion. Droplets have been used to solve this problem by digitizing chemical signals into discrete segments that can be transported for a long distance or a long time without loss of chemical, temporal or spatial precision. In this review, we describe Taylor dispersion, sampling theory, and Laplace pressure, and give examples of sampling probes that have used droplets to sample or/and transport fluid from a continuous medium, such as cell culture or nerve tissue, for external analysis. The examples are categorized, as follows: (1) Aqueous-phase sampling with downstream droplet formation; (2) preformed droplets for sampling; and (3) droplets formed near the analyte source. Finally, strategies for downstream sample recovery for conventional analysis are described.
9

El-Dib, Yusry O. "Nonlinear hydrodynamic Rayleigh—Taylor instability of viscous magnetic fluids: effect of a tangential magnetic field." Journal of Plasma Physics 51, no. 1 (February 1994): 1–11. http://dx.doi.org/10.1017/s0022377800017359.

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The nonlinear Rayleigh—Taylor instability of viscous magnetic fluids is considered under the influence of gravity and surface tension in the presence of a constant tangential magnetic field. The method of multiple-scales expansion is employed. A nonlinear Schrödinger equation with complex coefficients is imposed from the solvability conditions and used to analyse the stability of the system. A quadratic dispersion relation with complex coefficients is obtained. The Hurwitz criterion for a quadratic polynomial with complex coefficients is used to control the stability of the system. It is found that an increase in the viscosity increases the extent of the stable region in the presence of a magnetic field. Finally it is shown that the magnetic permeability of the fluid affects the stability conditions.
10

Froitzheim, A., S. Merbold, and C. Egbers. "Velocity profiles, flow structures and scalings in a wide-gap turbulent Taylor–Couette flow." Journal of Fluid Mechanics 831 (October 13, 2017): 330–57. http://dx.doi.org/10.1017/jfm.2017.634.

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Fully turbulent Taylor–Couette flow between independently rotating cylinders is investigated experimentally in a wide-gap configuration ($\unicode[STIX]{x1D702}=0.5$) around the maximum transport of angular momentum. In that regime turbulent Taylor vortices are present inside the gap, leading to a pronounced axial dependence of the flow. To account for this dependence, we measure the radial and azimuthal velocity components in horizontal planes at different cylinder heights using particle image velocimetry. The ratio of angular velocities of the cylinder walls $\unicode[STIX]{x1D707}$, where the torque maximum appears, is located in the low counter-rotating regime ($\unicode[STIX]{x1D707}_{max}(\unicode[STIX]{x1D702}=0.5)=-0.2$). This point coincides with the smallest radial gradient of angular velocity in the bulk and the detachment of the neutral surface from the outer cylinder wall, where the azimuthal velocity component vanishes. The structure of the flow is further revealed by decomposing the flow field into its large-scale and turbulent contributions. Applying this decomposition to the kinetic energy, we can analyse the formation process of the turbulent Taylor vortices in more detail. Starting at pure inner cylinder rotation, the vortices are formed and strengthened until $\unicode[STIX]{x1D707}=-0.2$ quite continuously, while they break down rapidly for higher counter-rotation. The same picture is shown by the decomposed Nusselt number, and the range of rotation ratios, where turbulent Taylor vortices can exist, shrinks strongly in comparison to investigations at much lower shear Reynolds numbers. Moreover, we analyse the scaling of the Nusselt number and the wind Reynolds number with the shear Reynolds number, finding a communal transition at approximately $Re_{S}\approx 10^{5}$ from classical to ultimate turbulence with a transitional regime lasting at least up to $Re_{S}\geqslant 2\times 10^{5}$. Including the axial dispersion of the flow into the calculation of the wind amplitude, we can also investigate the wind Reynolds number as a function of the rotation ratio $\unicode[STIX]{x1D707}$, finding a maximum in the low counter-rotating regime slightly larger than $\unicode[STIX]{x1D707}_{max}$. Based on our study it becomes clear that the investigation of counter-rotating Taylor–Couette flows strongly requires an axial exploration of the flow.
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Статті в журналах Дисертації

Дисертації з теми "Analyse de la dispersion de Taylor":

1

Deleanu, Mihai. "Taylor dispersion analysis : a powerful size-based characterization technique for monitoring the aggregation of β-amyloid peptides". Thesis, Université de Montpellier (2022-….), 2022. http://www.theses.fr/2022UMONS003.

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La maladie d'Alzheimer (MA) est l'un des principaux défis de santé publique du 21ème siècle et son développement repose sur l'hypothèse amyloïde qui stipule que la formation extracellulaire de plaques amyloïdes et l'accumulation intracellulaire d'enchevêtrements neurofibrillaires Tau (NFTs) sont causées par l'agrégation de peptides β-amyloïdes (Aβ). Plusieurs techniques biophysiques ont été employées pour étudier le processus d'agrégation des peptides Aβ, comme le dosage de la thioflavine T (ThT), la diffusion dynamique de la lumière (DLS), l'électrophorèse capillaire (CE), la microscopie électronique (EM) et la microscopie à force atomique (AFM), mais malgré les informations utiles qu'elles fournissent, toutes ne sont pas adaptées au suivi des premières étapes du processus agrégatif. L'objectif principal de cette thèse et d’évaluer l'analyse de dispersion de Taylor (TDA) pour le suivi des mécanismes d'agrégation des peptides Aβ. Le TDA est une technique moderne qui permet de déterminer le rayon hydrodynamique et de quantifier des espèces en solution pour des objets moléculaires dont la tailles est comprise entre 0,1 nm et centaines de nm. Jusqu'à présent, la TDA n'a pas encore été employée pour un suivi en temps réel de l'agrégation des peptides Aβ. La TDA a révélé que le processus d'agrégation des isoformes Aβ(1-40) et Aβ(1-42) se produit selon des mécanismes distincts. Ces résultats ont été corrélés avec le test ThT et la DLS. La co-agrégation des mélanges Aβ(1-40):Aβ(1-42) a aussi été explorée conjointement par TDA et AFM, mettant en évidence l'influence de la composition du mélange sur la cinétique et la formation d'espèces oligomériques potentiellement toxiques. Enfin, le processus d'agrégation des peptides Aβ par TDA a été réalisé à l'aide d'une détection simultanée UV-LIF utilisant des peptides fluorescents marqués FITC. Cette étude a démontré que les voies d'agrégation des peptides Aβ natifs sont modifiées par la présence du fluorophore. En conclusion, la TDA permet une spéciation des espèces solubles (monomères, oligomères, protofibriles) lors de l'agrégation des peptides Aβ, ce qui apporte des informations très précises sur le mécanisme d’agrégation.Mots-clés: Maladie d'Alzheimer ; peptides β-amyloïdes ; analyse de dispersion de Taylor ; études d'agrégation ; microscopie à force atomique ; ThT assay; diffusion dynamique de la lumière
Alzheimer Disease (AD) is one of the major public health challenges of the 21st century and its development is centered around the amyloid hypothesis which states that extracellular formation of amyloid plaques and the intracellular accumulation of neurofibrillary Tau tangles (NFTs) are caused by the aggregation of β-amyloid (Aβ) peptides. Several biophysical techniques have been employed for studying the aggregation process of Aβ peptides such as thioflavin T (ThT) assay, dynamic light scattering (DLS), capillary electrophoresis (CE), electron microscopy (EM) and atomic force microscopy (AFM). Despite the useful information these methods provide, not all of them are suitable for monitoring the early stages of the process. The main objective of this thesis is to apply Taylor dispersion analysis (TDA) for the monitoring of the Aβ peptide aggregation mechanism. TDA is a modern technique that can size and quantify soluble species ranging from 0.1 nm to a few hundred nm. TDA has yet been employed for a real-time monitoring of the Aβ peptide aggregation. TDA revealed that the aggregation process of Aβ(1-40) and Aβ(1-42) isoforms occurs through distinct pathways. These results have been correlated with ThT assay and DLS. The co-aggregation of Aβ(1-40):Aβ(1-42) mixtures was further explored by TDA and AFM, highlighting the influence of the peptide ratios on the kinetics and the formation of potentially toxic oligomeric species. Finally, the aggregation process of Aβ peptides by TDA was conducted using a simultaneous UV-LIF detection in the presence of FITC-tagged Aβ peptides. This study demonstrated that the aggregation pathways of the native Aβ peptides are altered by the presence of the fluorophore. In conclusion, TDA provided a complete speciation of the different soluble species (monomer, oligomers, protofibrils) during Aβ aggregation, which brings valuable information on the mechanism of aggregation.Keywords: Alzheimer disease; β-amyloid peptides; Taylor dispersion analysis; aggregation studies; atomic force microscopy; ThT assay; dynamic light scattering
2

Neri, Quiroz José Antonio. "Développement d’un lab-on-chip pour la mesure d’acidité libre de solutions chargées en cations hydrolysables." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1247/document.

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Une étude conjointe du CEA et d'AREVA la Hague a montré qu'une des voies d'amélioration majeure des usines de traitement/recyclage du combustible nucléaire usagé, actuelles et futures, concerné le domaine de l'analyse. En effet, le suivi et le pilotage des procédés déployés dans ces usines nécessitent de nombreuses analyses générant de grandes quantités d'effluents radioactifs. Réduire les volumes mis en jeu lors de ces analyses permettrait donc de réduire la nocivité des échantillons et des effluents et donc d'accroitre la sureté pour le personnel et de réduire l'impact sur l'environnement et le coût de fonctionnement des usines. Parmi toutes les analyses effectuées, la mesure d'acidité libre est la plus fréquente, car c'est un paramètre indispensable pour pouvoir piloter correctement le procédé. C'est pourquoi, ces travaux de thèse ont abouti à l'amélioration de la méthode de mesure via une réduction d'échelle de l'analyse et une automatisation du protocole de mesure. Deux voies ont été étudiées : - le titrage par injection séquentielle (SIA), qui est un dispositif de 25 L de volume et qui par rapport à la méthode d'analyse de référence, réduit 1000 fois le volume d'échantillon nécessaire à l'analyse, 8 fois le temps d'analyse et 40 fois le volume d'effluents générés. - le titrage ballist-mix emploie un dispositif microfluidique qui, après intégration et réduction des composants, peut atteindre un volume de 25 mL et offre des performances analytiques comparables à celles obtenues en SIA. La méthode par SIA a été validée sur des solutions chargées en uranium alors que la technologie utilisée pour développer les titrages ballist-mix est en cours de validation. Cependant le principe opératoire du titrage ballist-mix est plus avantageux puisqu'il simplifie le travail de développement analytique du fait de la possibilité de simuler en avance les phénomènes physicochimiques ayant lieu lors du titrage
A joint study between the CEA and Areva La Hague has shown that chemical analysis is a crucial parameter for achieving a better performance in present and future spent nuclear fuel reprocessing plants. In fact, each plant’s process monitoring and control require a significant amount of laboratory analysis leading in overall to a considerable amount of nuclear waste. Hence, reducing the sample’s required volume for analysis would reduce its toxicity and subsequent waste, therefore increasing personnel safety, decreasing the environmental impact and the plant’s operation cost. Among the process control analytical workload, the free acidity measurement has been identified as a key analysis due to its measurement frequency. For this reason, the main objective of this research has been focused in the improvement of a reference method for free acidity measurement. The following work has been divided in two main studies seeking for the reduction of the sample volume and the automation of the analytical method protocol: - Sequential Injection Analysis (SIA) titration, whose application requires the employment of a device occupying a 25 L space, and which reduces 1000 fold the sample volume per analysis, 8 times the analysis time and 40 fold the amount of waste generated when compared to the reference analytical method. - Ballist-mix titration, whose analytical performance is equivalent to the SIA titration, but whose implementation is done inside a microfluidic device occupying a volume as low as 25 mL after integration of all of the elements needed for analysis. At the present time, the SIA titration has been validated using nitric acid samples containing uranyl cations, whereas the ballist-mix titration is being validated with the same sample conditions. However, this last analytical technique features a simplified operating principle which allows the user to shorten the analytical development process by opening the possibility to simulate the process before any experimentation
3

Dorfman, Kevin David 1977. "Taylor-Aris dispersion in microfluidic networks." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/33161.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (leaves 172-183).
This thesis constitutes the development and application of a theory for the lumped parameter, convective-diffusive-reactive transport of individual, non-interacting Brownian solute particles ("macromolecules") moving within spatially periodic, solvent-filled networks - the latter representing models of chip-based microfluidic devices, as well as porous media. The use of a lumped parameter transport model and network geometrical description affords the development of a discrete calculation scheme for computing the relevant network-scale (macrotransport) parameters, namely the mean velocity vector U*, dispersivity dyadic D* and, if necessary, the mean volumetric solute depletion rate K*. The ease with which these discrete calculations can be performed for complex networks renders feasible parametric studies of potential microfluidic chip designs, particularly those pertinent to biomolecular separation schemes. To demonstrate the computational and conceptual advantages of this discrete scheme, we consider: (i) a pair of straightforward examples, dispersion analysis of (non-reactive) pressure-driven flow in spatially periodic serpentine microchannels and reactive transport in an elementary geometric model of a porous medium; and (ii) a pair of case studies based upon the microfluidic separation techniques of vector chromatography and entropic trapping.
(cont.) The straightforward examples furnish explicit proof that the present theory produces realistic results within the context of a simple computational scheme, at least when compared with the prevailing continuous generalized Taylor-Aris dispersion theory. In the case study on vector chromatography, we identify those factors which break the symmetry of the chip-scale particle mobility tensor, most importantly the hydrodynamic wall effects between the particles and the obstacle surfaces. In the entropic trapping case study, analytical expressions derived for the solute dispersiviy, number of theoretical plates, and separation resolution are shown to furnish results that accord, at least qualitatively, with experimental trends and data reported in the literature.
by Kevin David Dorfman.
Ph.D.
4

Delannay, Renaud. "Dispersion de taylor en milieux poreux fractals." Paris 6, 1990. http://www.theses.fr/1990PA066102.

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La dispersion de taylor dans les milieux poreux est abordee a l'aide des moments de la distribution de probabilite de presence du solute. La geometrie des milieux poreux est ici modelisee par des fractals. Apres avoir defini les fractals comme des points fixes d'applications contractantes, nous discutons quelques-unes des techniques qui peuvent etre employees pour etudier les phenomenes de transport dans ces structures. C'est sur deux exemples (l'arbre et le tamis de sierpinski) que nous avons mene une etude de la dispersion de taylor dans une structure capillaire (dans le cadre de l'hypothese, des nuds parfaitement melangeants). La resolution analytique complete dans le cas de l'arbre permet de montrer que la repartition de solute se comporte a grands temps comme une vague qui se translate sans se deformer, la forme de cette vague etant independante de la facon d'introduire le solute. Un argument analytique applique au tamis de sierpinski (mais generalisable a d'autres fractals) montre que le premier moment suit, en fonction du temps, une loi de puissance ayant pour exposant l'inverse de la dimension fractale du tamis. Le deuxieme moment centre est obtenu numeriquement. La vitesse interstitielle moyenne, et le tenseur de dispersion sont determines numeriquement dans des cellules (constituees de cylindres paralleles le long desquels s'ecoule le fluide) reproduites par periodicite. Deux cas sont etudies des cellules issues d'une percolation de site ou du tapis de sierpinski. La convergence de la vitesse interstitielle moyenne avec, le nombre de generations du tapis, qui est ainsi constatee, est ensuite demontree
5

Lu, Ruanhui. "Taylor dispersion studies of diffusion in electrolyte solutions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32493.pdf.

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6

MIMOUNI, STEPHANE. "Analyse fractale d'interfaces pour les instabilites de rayleigh-taylor." Palaiseau, Ecole polytechnique, 1995. http://www.theses.fr/1995EPXX0042.

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L'interface separant un fluide lourd place sur un fluide leger dans le champ gravitationnel est le siege d'une instabilite dite de rayleigh-taylor. L'instabilite de rayleigh-taylor est simulee numeriquement sur un calculateur parallele en resolvant les equations 2d d'euler compressible pour deux fluides. Notre objectif est de caracteriser la morphologie de la zone de melange entre les deux fluides. On modelise l'interface par une fractale. On calcule alors la dimension fractale de l'ensemble de particules traceuses placees a l'interface entre les deux materiaux. Un premier resultat est que la dimension fractale tend vers la valeur stationnaire 1,7. Ce resultat est ensuite utilise pour determiner une loi de melange impliquant la geometrie de l'interface. Nous en deduisons l'opacite effective du melange. Pour generaliser cette premiere approche, nous appliquons le formalisme multifractal a l'etude de la morphologie de la zone de melange. Ainsi, nous developpons un cadre d'etude pour definir et etudier des interfaces multifractales. Dans ce contexte, la transformee en ondelettes s'avere etre un outil puissant pour definir un formalisme multifractal adapte aux interfaces et pour calculer les dimensions fractales generalisees
7

Andrews, David J. "Taylor-Aris dispersion theory and its application in the study of partitioning in organised solvents." Thesis, University of Kent, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385844.

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8

Jbeli, Haïsam. "Analyse élémentaire par fluorescence X en dispersion d'énergie." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21138.

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Principe, caractéristiques des spectres d'excitation. Effets de matrice, notion d'énergie équivalente, méthode de correction des effets interéléments. Résultats d'analyse. Caractérisation de couches minces
9

Jbeli, Haïsam. "Analyse élémentaire par fluorescence X en dispersion d'énergie." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376145227.

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10

Chouippe, Agathe. "Étude numérique de la réduction de traînée par injection de bulles en écoulement de Taylor-Couette." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0052/document.

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La thèse porte sur l'étude de la réduction de traînée par injection de bulles. La réduction de traînée présente un intérêt pour les applications navales puisqu'elle est issue d'une modification des structures cohérentes qui contribuent le plus à la résistance à l'avancement. Le but de cette étude est d'analyser les mécanismes à l'origine de cette diminution du frottement pariétal. L'approche utilisée dans le cadre de cette étude est numérique, elle emploie le code JADIM par une approche Euler-Lagrange : la phase continue est simulée par Simulation Numérique Directe et la phase dispersée est simulée en suivant individuellement chaque bulle. La configuration retenue dans le cadre de cette étude est celle de l'écoulement de Taylor-Couette (écoulement compris entre deux cylindres en rotation). La première partie de la thèse vise à adapter l'outil numérique employé, afin de pouvoir prendre en compte le retour de la phase dispersée via des termes de forçage dans les équations bilan de matière et de quantité de mouvement. La deuxième partie de la thèse vise à étudier l'écoulement porteur en configuration monophasique, afin de disposer d'une référence sur l'écoulement non perturbé. La troisième partie de la thèse a pour objectif d'étudier la dispersion passive des bulles dans le système, afin d'analyser les mécanismes de migrations mis en jeu. Enfin la dernière partie de la thèse vise à étudier l'influence des bulles sur l'écoulement porteur en analysant l'effet de certains paramètres, notamment le taux de vide et la flottabilité
The study deals with drag reduction induced by bubble injection, its application concerns naval transport. The aim of the study is to shed more light on mechanisms that are involved in this wall friction reduction. The study is based on a numerical approach, and use the JADIM code with an Euler-Lagrange approach: the continuous phase is solved by Direct Numerical Simulation, and the disperse phase by a tracking of each bubble. Within the framework of this study we consider the Taylor-Couette flow configuration (flow between two concentric cylinders in rotation). The first part of the study deals with the modification of the numerical tool, in order to take into account the influence of the disperse phase on the continuous one through forcing terms in the mass and momentum balance equations. The aim of the second part is to study de Taylor-Couette flow in its monophasic configuration, for the purpose of providing a reference of the undisturbed flow. The third part deals with the passive dispersion of bubble in Taylor-Couette flow, in order to analyze the migration mechanisms involved. And the aim of the last part is to study the effects of the disperse phase on the continuous one, by analyzing the influence of bubbly phase parameters (like void fraction and buoyancy)
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Книги з теми "Analyse de la dispersion de Taylor":

1

Meyer-Spasche, Rita. Pattern formation in viscous flows: The Taylor-Couette problem and Rayleigh-Bénard convection. Basel: Birkhäuser, 1999.

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2

Meyer-Spasche, Rita. Pattern formation in viscous flows: The Taylor-Couette problem and Rayleigh-Benard convection. Basel: Birkhäuser, 1999.

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3

Meyer-Spasche, Rita. Pattern Formation in Viscous Flows: The Taylor-Couette Problem and Rayleigh-Bénard Convection. Birkhauser Verlag, 2012.

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4

Meyer-Spasche, Rita. Pattern Formation in Viscous Flows: The Taylor-Couette Problem and Rayleigh-Bénard Convection. Springer, 2012.

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5

Alexander, Peter D. G., and Malachy O. Columb. Presentation and handling of data, descriptive and inferential statistics. Edited by Jonathan G. Hardman. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0028.

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The need for any doctor to comprehend, assimilate, analyse, and form an opinion on data cannot be overestimated. This chapter examines the presentation and handling of such data and its subsequent statistical analysis. It covers the organization and description of data, measures of central tendency such as mean, median, and mode, measures of dispersion (standard deviation), and the problems of missing data. Theoretical distributions, such as the Gaussian distribution, are examined and the possibility of data transformation discussed. Inferential statistics are used as a means of comparing groups, and the rationale and use of parametric and non-parametric tests and confidence intervals is outlined. The analysis of categorical variables using the chi-squared test and assessing the value of diagnostic tests using sensitivity, specificity, positive and negative predictive values, and a likelihood ratio are discussed. Measures of association are covered, namely linear regression, as is time-to-event analysis using the Kaplan–Meier method. Finally, the chapter discusses the statistical analysis used when comparing clinical measurements—the Bland and Altman method. Illustrative examples, relevant to the practice of anaesthesia, are used throughout and it is hoped that this will provide the reader with an outline of the methodologies employed and encourage further reading where necessary.

Частини книг з теми "Analyse de la dispersion de Taylor":

1

Beck, Margaret, Osman Chaudhary, and C. Eugene Wayne. "Analysis of Enhanced Diffusion in Taylor Dispersion via a Model Problem." In Hamiltonian Partial Differential Equations and Applications, 31–71. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4939-2950-4_2.

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2

Barrantes, A., A. Calvo, M. Rosen, and J. E. Wesfreid. "Velocity Field Structure and Semiquantitative Analysis of Tracer Dispersion in a Taylor-Vortex Flow of Wide Gap." In Instabilities and Nonequilibrium Structures III, 233–38. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3442-2_21.

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3

Bakunin, Oleg G. "The Taylor Shear Dispersion." In Chaotic Flows, 107–25. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-20350-3_7.

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4

Jou, David, José Casas-Vázquez, and Manuel Criado-Sancho. "Taylor Dispersion and Anomalous Diffusion." In Thermodynamics of Fluids Under Flow, 187–209. Dordrecht: Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-94-007-0199-1_9.

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5

Piva, M., A. Calvo, A. Barrantes, S. Gabanelli, M. Rosen, I. Ippolito, and J. E. Wesfreid. "Tracer Dispersion in the Taylor-Couette Instability with Axial Flow." In Instabilities and Nonequilibrium Structures IV, 343–49. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1906-1_35.

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6

Ribeiro, Ana C. F., Cecilia Isabel A. V. Santos, Victor M. M. Lobo, Artur J. M. Valente, Pedro M. R. A. Prazeres, and Hugh D. Burrows. "Diffusion Coefficients of Aqueous Solutions of Carbohydrates as Seen by Taylor Dispersion Technique at Physiological Temperature (37 ºC)." In Defect and Diffusion Forum, 305–9. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-36-1.305.

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7

Chamieh, Joseph, and Hervé Cottet. "Size-based characterisation of nanomaterials by Taylor dispersion analysis." In Colloid and Interface Science in Pharmaceutical Research and Development, 173–92. Elsevier, 2014. http://dx.doi.org/10.1016/b978-0-444-62614-1.00009-0.

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8

Rapp, Bastian E. "Taylor-Aris Dispersion." In Microfluidics: Modelling, Mechanics and Mathematics, 401–17. Elsevier, 2017. http://dx.doi.org/10.1016/b978-1-4557-3141-1.50019-8.

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9

Rapp, Bastian E. "Taylor-Aris dispersion." In Microfluidics, 427–43. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-12-824022-9.00037-1.

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10

Khurana, Tarun, Rajiv Bharadwaj, David Huber, and Juan Santiago. "Taylor Dispersion in Sample Preconcentration Methods." In Handbook of Capillary and Microchip Electrophoresis and Associated Microtechniques, Third Edition, 1085–120. CRC Press, 2007. http://dx.doi.org/10.1201/9780849333293.ch38.

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Тези доповідей конференцій з теми "Analyse de la dispersion de Taylor":

1

Sa´nchez, F., A. Medina, and J. L. Montan˜es. "Thermal Convection and Dispersion in Folded Gaps Embedded in Impervious Rocks." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56671.

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It is presented a numerical and experimental study related to thermal convection and Taylor dispersion in a symmetrical folded gap of small aspect ratio. The gap is surrounded by an impervious rock which is affected by a constant vertical temperature gradient. Two cases were analyzed, the fluid-filled gap and the fluid-saturated porous layer. Their corresponding convective flows were calculated for small Rayleigh number regimes. Taylor dispersion of a passive contaminant, in both cases, was studied. It was found that dispersion is strongly limited by the convective flows. Indeed, the Peclet number and the gap aspect ratio seem to be tight related to an eventually limited dispersive transport rate.
2

Hulse, Wendy, and Rob Forbes. "A Taylor Dispersion Analysis Method for the Sizing of Therapeutic Proteins and their Aggregates Using Nanolitre Sample Quantities." In The 1st Electronic Conference on Pharmaceutical Sciences. Basel, Switzerland: MDPI, 2011. http://dx.doi.org/10.3390/ecps2011-00522.

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3

Liu, Cuicui, Zeyi Jiang, Huafei Liu, Xinxin Zhang, and Shunhua Xiang. "Atomization and Droplet Dispersion of Low-Momentum Water Jet by High-Speed Crossflow Air Stream." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22506.

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In this paper, a low-momentum water liquid jet emanating transversely into a high-speed air stream is investigated analytically and numerically. Viscous instability followed by Rayleigh-Taylor instability is used in the jet breakup analysis to obtain the Sauter Mean Diameter and the droplet group velocity after the breakup. With the analytical results, droplet dispersion in the air stream is simulated by the coupled Eulerian-Lagrangian approach, in which the root-normal distribution is adopted to represent the droplet diameter distribution. Water flux distribution and spray angle are obtained and validated by experimental data. The results show that the air velocity is a dominant factor on the Sauter Mean Diameter and droplet group velocity in the water jet breakup process and the spray angle is influenced by the water mass flux.
4

Akbari, M., M. Bahrami, and D. Sinton. "Optothermal Control of Local Fluid Temperature in Microfluidics." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30412.

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This paper outlines an optothermal approach to manipulate local fluid temperatures in microfluidic and lab-on-chip systems. The system has the ability to control the size, location and the source heat flux using an external computer and is not constrained by predefined geometries, complex fabrication or control system. The thermal performance is evaluated using a temperature-dependent fluorescent dye. Experiments demonstrate localized heating up to 35°C over ambient temperature for a heat source spanning a downstream length of 1.5 mm. Experimental results are compared with a 1D thermal analysis of the system based on the Taylor-Aris dispersion.
5

Narayanan, Venkat R. T., Jianbo Li, Jeffrey D. Zahn, and Hao Lin. "Numerical Modeling of Microfluidic Two-Phase Electrohydrodynamic Instability." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67757.

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Organic-aqueous liquid (phenol) extraction is one of many standard techniques to efficiently purify DNA directly from cells. Effective dispersion of one fluid phase in the other increases the surface area over which biological component partitioning may occur, and hence enhances DNA extraction efficiency. Electrohydrodynamic (EHD) instability can be harnessed to achieve this goal and has been experimentally demonstrated by one of the co-authors (JDZ). In this work, analysis and simulation are combined to study two-phase EHD instability. In the problem configuration, the organic (phenol) phase flows into the microchannel in parallel with and sandwiched between two aqueous streams, creating a three-layer planar geometry; the two liquid phases are immiscible. An electric field is applied to induce instability and to break the organic stream into droplets. The Taylor-Melcher leaky-dielectric model is employed to investigate this phenomenon. A linear analysis is carried out with a Chebyshev pseudo-spectral method, whereas a fully nonlinear numerical simulation is implemented using a finite volume, immersed boundary method (IBM). The results from both models compare favorably with each other. The linear analysis reveals basic instability characteristics such as kink and sausage modes. On the other hand, the nonlinear simulation predicts surface deformation in the strongly nonlinear regime pertinent to droplet formation. These numerical tools will be used to investigate the effects of the applied electric field, geometry, and convective flow rate on mixing and dispersion. The eventual objective is to maximize surface area of the organic phase under given experimental conditions for optimized DNA extraction.
6

Mikelić, Andro, Theodore E. Simos, George Psihoyios, and Ch Tsitouras. "A Hyperbolic Model for Taylor’s Dispersion." In NUMERICAL ANALYSIS AND APPLIED MATHEMATICS: International Conference on Numerical Analysis and Applied Mathematics 2009: Volume 1 and Volume 2. AIP, 2009. http://dx.doi.org/10.1063/1.3241309.

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7

Miessner, Ulrich, Ralph Lindken, and Jerry Westerweel. "Velocity Measurements in Microscopic Two-Phase Flows by Means of Micro PIV." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62093.

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This article examines the velocity distributions of microscopic liquid-liquid two-phase flows by means of micro particle image velocimetry (micro-PIV). Aqueous droplets are dispersed into an oil bulk at the T-junction of a micro fluidic Polydimethylsiloxane (PDMS) device. The channel geometry is rectangular (H: 100μm, W: 100μm). The flow is pressure driven. Tracer particles (D: 0.5–1.2μm) are added to either phase, enabling simultaneous measurements in both phases. However, the use of immiscible liquids causes optical disturbances due to a difference in refractive indices of the two liquids and due to a curved interface geometry. Particle images are thus imaged in a distorted field of view. The results of a PIV analysis will be inaccurate in scaling as well as in location of the velocity vectors — depending on the mismatch of the refractive index. We present a basic analysis on the effect of mismatched refractive indices on the precision of the velocity measurements. The estimation is based on Snell’s law and the simplified geometry of a spherical droplet. Furthermore, we propose a method to match not only the index of refraction accurately but also to leave one additional degree of freedom to set an additional property of the liquid-liquid system, e.g. viscosity ratio or density ratio. The latter ensures that properties of the modified liquid-liquid system are close to those of the non-modified two-phase system. The findings of this study are part of the design of a Lab-on-a-Chip device. It performs a DNA analysis in an online quality control application. The miniaturization of a two-phase flow combines the benefits of confined sample compartments (i.e. droplets) with the easy-to-control process parameters of a miniaturized device (e.g. temperature, pressure). Thus band broadening of the sample by Taylor-Aris dispersion is avoided and the processes can be set accurately.
8

De Leebeeck, Angela, and David A. Sinton. "Taylor-Like Dispersion of Charged Species in Electrokinetically-Driven Nanoflows." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81852.

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In this paper, electrokinetic dispersion of charged and uncharged species in nanochannels with finite electric double layers is modelled numerically. The relatively thick electrical double layers in these flows influence dispersion through the coupled effects of both cross-stream electromigration and advection in the presence of cross-stream velocity gradients. It is found that valence charge has a significant effect on axial dispersion in these flows, in addition to other established dependencies. Effective diffusion coefficients were found to vary over 30% from the case of neutral species for single charged ions. An effective diffusion coefficient similar to Taylor dispersion is calculated and a relationship between effective diffusion coefficient, Peclet number, relative electric double layer thickness, and valence charge is plotted.
9

Song, Hongjun, Yi Wang, and Kapil Pant. "Three-Dimensional Analytical Model for Pressure-Driven Cross-Stream Diffusion in Microchannels With Arbitrary Aspect Ratios." 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/mnhmt2012-75134.

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The utilization of cross-stream diffusion under laminar flow for precise analyte handling plays a critical role in microfluidic biochemical assays such as sample preparation, concentration gradient generation, and molecular interactions. The non-uniform velocity profile along the cross-section of a rectangular microchannel with arbitrary aspect ratio under pressure-driven flow results in unique, heterogeneous species transport including Taylor dispersion and position-dependent diffusion scaling law. Although numerical methods such as finite difference method, finite element method, the method of lines and lattice Boltzmann (LB) method have been used for quantitative study of the phenomena, they inherently suffer from several limitations, such as difficulty to provide direct, physical insight into the underlying transport mechanism and prohibitive computational cost to suppress the artificial numerical diffusion (ND). To address these issues, several analytical models have been proposed, which share several common assumptions such as large aspect ratio and neglecting depth-wise diffusion due to the non-uniform axial velocity in the 3D convection-diffusion equation, markedly limiting their utility. In this paper, we present a three dimensional (3D) analytical model to investigate the diffusion of analyte between two cross streams in rectangular microchannels with arbitrary aspect ratios under pressure-driven flow. The 3D convection-diffusion equation is solved in a Fourier series form using a double integral transformation method and associated eigensystem calculation. Therefore, the model for the first time is capable of capturing the non-uniform transport rate (i.e., the ‘butterfly effect’) and the position-dependent scaling-law of diffusion (1/3-power at the channel wall and 1/2-pwer at the half-depth plane) through an analytical solution. Our analytical model was extensively validated against both experimental and numerical data in terms of the concentration distribution, diffusion scaling law and the mixing efficiency with excellent agreement (the relative error is much less than 0.5% in various benchmark test cases.) Quantitative comparison between our analytical model and other prior analytical models in extensive parameter space was also performed, which convincingly demonstrates that our model accommodates much broader transport regimes and more practical microfluidic applications.
10

Chun, Sejong, and Jonghan Jin. "Wave Dispersion Analysis of Pulsating Flows in a Circular Conduit Using a Lumped Parameter Model." In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-10101.

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Wave dispersion is a key element in understanding the pulsating flows in a circular rigid pipe. This study suggests that an extended Taylor’s frozen field hypothesis should make the lumped parameter model be more practical because pressure instead of pressure gradient can be measured with simpler instrumentation. Lumped parameter model as well as wave dispersion is introduced, and then some experimental results with a blood flow simulator were analyzed to validate its idea.

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