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Статті в журналах з теми "Inertial particle dynamics":
1
Jayaram, Rohith, Yucheng Jie, Lihao Zhao, and Helge I. Andersson. "Dynamics of inertial spheroids in a decaying Taylor–Green vortex flow." Physics of Fluids 35, no. 3 (March 2023): 033326. http://dx.doi.org/10.1063/5.0138125.
Анотація:
Inertial spheroids, prolates and oblates, are studied in a decaying Taylor–Green vortex (TGV) flow, wherein the flow gradually evolves from laminar anisotropic large-scale structures to turbulence-like isotropic Kolmogorov-type vortices. Along with particle clustering and its mechanisms, preferential rotation and alignment of the spheroids with the local fluid vorticity are examined. Particle inertia is classified by a nominal Stokes number [Formula: see text] which to first-order aims to eliminate the shape effect. The clustering varies with time and peaks when the physically relevant flow and particle time scales are of the same order. Low inertial ([Formula: see text]) spheroids are subjected to the centrifuging mechanism, thereby residing in stronger strain-rate regions, while high inertial ([Formula: see text]) spheroids lag the flow evolution and modestly sample strain-rate regions. Contrary to the expectations, however, spheroids reside in high strain-rate regions when the particle and flow time scales are comparable due to the dynamic interactions between the particles and the evolving flow scales. Moderately inertial ([Formula: see text]) prolates preferentially spin and oblates tumble throughout the qualitatively different stages of the TGV flow. These preferential modes of rotation correlate with parallel and perpendicular alignments of prolate and oblate spheroids, respectively, with the local fluid vorticity. However, for high inertial spheroids preferential rotation and alignment are decorrelated due to a memory effect, i.e., inertial particles require longer time to adjust to the local fluid flow. This memory effect is not only due to high particle inertia, as in statistically steady turbulence, but also caused by the continuously evolving TGV flow scales.
2
Sapsis, Themistoklis, and George Haller. "Inertial Particle Dynamics in a Hurricane." Journal of the Atmospheric Sciences 66, no. 8 (August 1, 2009): 2481–92. http://dx.doi.org/10.1175/2009jas2865.1.
Анотація:
Abstract The motion of inertial (i.e., finite-size) particles is analyzed in a three-dimensional unsteady simulation of Hurricane Isabel. As established recently, the long-term dynamics of inertial particles in a fluid is governed by a reduced-order inertial equation, obtained as a small perturbation of passive fluid advection on a globally attracting slow manifold in the phase space of particle motions. Use of the inertial equation enables the visualization of three-dimensional inertial Lagrangian coherent structures (ILCS) on the slow manifold. These ILCS govern the asymptotic behavior of finite-size particles within a hurricane. A comparison of the attracting ILCS with conventional Eulerian fields reveals the Lagrangian footprint of the hurricane eyewall and of a large rainband. By contrast, repelling ILCS within the eye region admit a more complex geometry that cannot be compared directly with Eulerian features.
3
Riggs, Peter J. "Inertia and inertial resistance in the Special Theory of Relativity." Canadian Journal of Physics 99, no. 9 (September 2021): 795–98. http://dx.doi.org/10.1139/cjp-2021-0087.
Анотація:
A broader concept of “resistance to acceleration” than used in classical dynamics, called “inertial resistance”, is quantified for both inertial and non-inertial relativistic motion. Special Relativity shows that inertial resistance is more than particle inertia and originates from Minkowski spacetime structure. Current mainstream explanations of inertia do not take inertial resistance into account and are, therefore, incomplete.
4
Li, Gaojin, Gareth H. McKinley, and Arezoo M. Ardekani. "Dynamics of particle migration in channel flow of viscoelastic fluids." Journal of Fluid Mechanics 785 (November 23, 2015): 486–505. http://dx.doi.org/10.1017/jfm.2015.619.
Анотація:
The migration of a sphere in the pressure-driven channel flow of a viscoelastic fluid is studied numerically. The effects of inertia, elasticity, shear-thinning viscosity, secondary flows and the blockage ratio are considered by conducting fully resolved direct numerical simulations over a wide range of parameters. In a Newtonian fluid in the presence of inertial effects, the particle moves away from the channel centreline. The elastic effects, however, drive the particle towards the channel centreline. The equilibrium position depends on the interplay between the elastic and inertial effects. Particle focusing at the centreline occurs in flows with strong elasticity and weak inertia. Both shear-thinning effects and secondary flows tend to move the particle away from the channel centreline. The effect is more pronounced as inertia and elasticity effects increase. A scaling analysis is used to explain these different effects. Besides the particle migration, particle-induced fluid transport and particle migration during flow start-up are also considered. Inertial effects, shear-thinning behaviour, and secondary flows are all found to enhance the effective fluid transport normal to the flow direction. Due to the oscillation in fluid velocity and strong normal stress differences that develop during flow start-up, the particle has a larger transient migration velocity, which may be potentially used to accelerate the particle focusing.
5
Zhao, Lihao, Niranjan R. Challabotla, Helge I. Andersson, and Evan A. Variano. "Mapping spheroid rotation modes in turbulent channel flow: effects of shear, turbulence and particle inertia." Journal of Fluid Mechanics 876 (July 31, 2019): 19–54. http://dx.doi.org/10.1017/jfm.2019.521.
Анотація:
The rotational behaviour of non-spherical particles in turbulent channel flow is studied by Lagrangian tracking of spheroidal point particles in a directly simulated flow. The focus is on the complex rotation modes of the spheroidal particles, in which the back reaction on the flow field is ignored. This study is a sequel to the letter by Zhao et al. (Phys. Rev. Lett., vol. 115, 2015, 244501), in which only selected results in the near-wall buffer region and the almost-isotropic channel centre were presented. Now, particle dynamics all across the channel is explored to provide a complete picture of the orientational and rotational behaviour with consideration of the effects of particle aspect ratio ranging from 0.1 to 10 and particle Stokes number from 0 (inertialess) to 30. The rotational dynamics in the innermost part of the logarithmic wall layer is particularly complex and affected not only by modest mean shear, but also by particle inertia and turbulent vorticity. While inertial disks exhibit modest preferential orientation in either the wall-normal or cross-stream direction, inertial rods show neither preferential tumbling nor spinning. Examination of the co-variances between particle orientation, particle rotation and fluid rotation vectors explains the qualitatively different ‘wall mode’ rotation and ‘centre mode’ rotation. Inertialess spheroids transition between the two modes within a narrow zone ($15<z^{+}<35$) in the buffer region. If the spheroids have inertia, the transition zone between the two modes shifts to the inner part of the logarithmic layer, i.e. $z^{+}\geqslant 40$. We ascribe the transition of inertialess spheroids from the ‘wall mode’ to the ‘centre mode’ rotation to the changeover between the time scales associated with mean shear and small-scale turbulence. Inertial spheroids, however, transition between the two rotational modes when the Kolmogorov time scale becomes comparable to the time scale for particle rotation, i.e. the effective Stokes number is of order unity. The aforementioned findings reveal, in addition to the effects of particle shape and alignment, the importance of the characteristic local time scale of fluid flow for the rotation of both tracer and inertial spheroids in turbulent channel flows.
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Ireland, Peter J., and Lance R. Collins. "Direct numerical simulation of inertial particle entrainment in a shearless mixing layer." Journal of Fluid Mechanics 704 (July 2, 2012): 301–32. http://dx.doi.org/10.1017/jfm.2012.241.
Анотація:
AbstractWe present the first computational study of the dynamics of inertial particles in a shearless turbulence mixing layer. We parametrize our direct numerical simulations to isolate the effects of turbulence, Reynolds number, particle inertia, and gravity on the entrainment process. By analysing particle concentrations, particle and fluid velocities, particle size distributions, and higher-order velocity moments, we explore the impact of particle inertia and gravity on the mechanism of turbulent mixing. We neglect thermodynamic processes, including phase changes between the drops and surrounding air, which is equivalent to assuming the air is saturated (i.e. 100 % humidity). Entrainment is found to be governed by the large scales of the flow and is relatively insensitive to the Reynolds number over the range considered. Our results show that both fluid and particle velocities exhibit intermittency and that gravity and turbulent diffusion interact in unexpected ways to dictate particle dynamics. An analysis of the temporal evolution of fluid and particle statistics suggests that particle concentration profiles and velocities are self-similar under certain circumstances. We also observe large fluctuations in particle concentrations resulting from entrainment and introduce a model to estimate the impact these fluctuations have on the radial distribution function, a statistic that is often used to quantify inertial particle clustering. Our study is both a computational counterpart to and an extension of the wind tunnel experiments by Gerashchenko, Good & Warhaft (J. Fluid Mech., vol. 668, 2011, pp. 293–303) and Good, Gerashchenko, & Warhaft (J. Fluid Mech., vol. 694, 2012, pp. 371–398). We find good agreement between these experimental studies and our computational results. We anticipate that a better understanding of the role of gravity and turbulence in inertial particle entrainment will lead to improved cloud evolution predictions.
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Tsuda, A., J. P. Butler, and J. J. Fredberg. "Effects of alveolated duct structure on aerosol kinetics. II. Gravitational sedimentation and inertial impaction." Journal of Applied Physiology 76, no. 6 (June 1, 1994): 2510–16. http://dx.doi.org/10.1152/jappl.1994.76.6.2510.
Анотація:
We studied the effects of alveolated duct structure on deposition processes for particle diameters > or = 1 micron. For such large particles, Brownian motion is insignificant but gravity and inertial forces play an important role. A Lagrangian description of particle dynamics in an alveolated duct flow was developed, and computational analysis was performed over the physiologically relevant range. At low flow rates gravity caused deposition. Gravitational cross-streamline motion depended on the coupled effects of curvature of gas streamlines and duct orientation relative to gravity. The detailed convective flow pattern was an important factor in determining deposition. At higher flow rates, inertial impaction contributed markedly to deposition. The curved nature of streamlines again played a major role on deposition, but duct orientation had little effect. In the medium range of flow rates, both gravitational and inertial forces simultaneously influenced particle motion. Particle inertia, per se, did not cause deposition but substantially suppressed gravitational deposition. The deposition mechanism was complex; contrary to what is often assumed in past analyses, the interaction between gravitational and inertial effects could not be described in a simple additive fashion. We conclude that the structure of the alveolar duct has an important role in gravitational sedimentation and inertial impaction in the lung acinus.
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Gibert, Mathieu, Haitao Xu, and Eberhard Bodenschatz. "Where do small, weakly inertial particles go in a turbulent flow?" Journal of Fluid Mechanics 698 (March 27, 2012): 160–67. http://dx.doi.org/10.1017/jfm.2012.72.
Анотація:
AbstractWe report experimental results on the dynamics of heavy particles of the size of the Kolmogorov scale in a fully developed turbulent flow. The mixed Eulerian structure function of two-particle velocity and acceleration difference vectors $\langle {\delta }_{r} \mathbi{v}\boldsymbol{\cdot} {\delta }_{r} {\mathbi{a}}_{\mathbi{p}} \rangle $ was observed to increase significantly with particle inertia for identical flow conditions. We show that this increase is related to a preferential alignment between these dynamical quantities. With increasing particle density the probability for those two vectors to be collinear was observed to grow. We show that these results are consistent with the preferential sampling of strain-dominated regions by inertial particles.
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Schaaf, Christian, Felix Rühle, and Holger Stark. "A flowing pair of particles in inertial microfluidics." Soft Matter 15, no. 9 (2019): 1988–98. http://dx.doi.org/10.1039/c8sm02476f.
Анотація:
A flowing pair of particles in inertial microfluidics gives important insights into understanding and controlling the collective dynamics of particles like cells or droplets in microfluidic devices. For rigid particles we determine the two-particle lift force profiles, which govern their coupled dynamics.
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Banerjee, I., M. E. Rosti, T. Kumar, L. Brandt, and A. Russom. "Analogue tuning of particle focusing in elasto-inertial flow." Meccanica 56, no. 7 (March 23, 2021): 1739–49. http://dx.doi.org/10.1007/s11012-021-01329-z.
Анотація:
AbstractWe report a unique tuneable analogue trend in particle focusing in the laminar and weak viscoelastic regime of elasto-inertial flows. We observe experimentally that particles in circular cross-section microchannels can be tuned to any focusing bandwidths that lie between the “Segre-Silberberg annulus” and the centre of a circular microcapillary. We use direct numerical simulations to investigate this phenomenon and to understand how minute amounts of elasticity affect the focussing of particles at increasing flow rates. An Immersed Boundary Method is used to account for the presence of the particles and a FENE-P model is used to simulate the presence of polymers in a Non-Newtonian fluid. The numerical simulations study the dynamics and stability of finite size particles and are further used to analyse the particle behaviour at Reynolds numbers higher than what is allowed by the experimental setup. In particular, we are able to report the entire migration trajectories of the particles as they reach their final focussing positions and extend our predictions to other geometries such as the square cross section. We believe complex effects originate due to a combination of inertia and elasticity in the weakly viscoelastic regime, where neither inertia nor elasticity are able to mask each other’s effect completely, leading to a number of intermediate focusing positions. The present study provides a fundamental new understanding of particle focusing in weakly elastic and strongly inertial flows, whose findings can be exploited for potentially multiple microfluidics-based biological sorting applications.
Дисертації з теми "Inertial particle dynamics":
1
Huck, Peter Dearborn. "Particle dynamics in turbulence : from the role of inhomogeneity and anisotropy to collective effects." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN073/document.
Анотація:
La turbulence est connue pour sa capacité à disperser efficacement de la matière, que ce soit des polluantes dans les océans ou du carburant dans les moteurs à combustion. Deux considérations essentielles s’imposent lorsqu’on considère de telles situations. Primo, l’écoulement sous-jacente pourrait avoir une influence non-négligeable sur le comportement des particules. Secundo, la concentration locale de la matière pourrait empêcher le transport ou l’augmenter. Pour répondre à ces deux problématiques distinctes, deux dispositifs expérimentaux ont été étudiés au cours de cette thèse. Un premier dispositif a été mis en place pour étudier l’écoulement de von Kàrmàn, qui consiste en une enceinte fermé avec de l’eau forcé par deux disques en contra-rotation. Cette écoulement est connu pour être très turbulent, inhomogène, et anisotrope. Deux caméras rapides ont facilité le suivi Lagrangien des particules isodenses avec l’eau et petites par rapport aux échelles de la turbulence. Ceci a permis une étude du bilan d’énergie cinétique turbulente qui est directement relié aux propriétés de transport. Des particules plus lourdes que l’eau ont aussi été étudiées et montrent le rôle de l’anisotropie de l’écoulement dans la dispersion des particules inertielles. Un deuxième dispositif, un écoulement de soufflerie ensemencé avec des gouttelettes d’eau micrométriques a permis une étude de l’effet de la concentration locale de l’eau sur la vitesse de chute des gouttelettes grâce à une montage préexistant. Un modèle basé sur des méthodes théorique d'écoulements multiphasiques a été élaboré enfin de prendre en compte les effets collectifs de ces particules sedimentant dans un écoulement turbulent. Les résultats théoriques et expérimentaux mettent en évidence le rôle de la polydispersité et du couplage entre les deux phases dans l’augmentation de la sédimentation des gouttelettesTurbulence is well known for its ability to efficiently disperse matter, whether it be atmospheric pollutants or gasoline in combustion motors. Two considerations are fundamental when considering such situations. First, the underlying flow may have a strong influence of the behavior of the dispersed particles. Second, the local concentration of particles may enhance or impede the transport properties of turbulence. This dissertation addresses these points separately through the experimental study of two different turbulent flows. The first experimental device used is the so-called von K\'arm\'an flow which consists of an enclosed vessel filled with water that is forced by two counter rotating disks creating a strongly inhomogeneous and anisotropic turbulence. Two high-speed cameras permitted the creation a trajectory data base particles that were both isodense and heavier than water but were smaller than the smallest turbulent scales. The trajectories of this data base permitted a study of the turbulent kinetic energy budget which was shown to directly related to the transport properties of the turbulent flow. The heavy particles illustrate the role of flow anisotropy in the dispersive dynamics of particles dominated by effects related to their inertia. The second flow studied was a wind tunnel seeded with micrometer sized water droplets which was used to study the effects of local concentration of the settling velocities of these particles. A model based on theoretical multi-phase methods was developed in order to take into account the role of collective effects on sedimentation in a turbulent flow. The theoretical results emphasize the role of coupling between the underlying flow and the dispersed phase
2
Lashgari, Iman. "Stability analysis and inertial regimes in complex flows." Doctoral thesis, KTH, Fysiokemisk strömningsmekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177850.
Анотація:
In this work we rst study the non-Newtonian effects on the inertial instabilities in shear flows and second the inertial suspensions of finite size rigid particles by means of numerical simulations. In the first part, both inelastic (Carreau) and elastic models (Oldroyd-B and FENE-P) have been employed to examine the main features of the non-Newtonian fluids in several congurations; flow past a circular cylinder, in a lid-driven cavity and in a channel. In the framework of the linear stability analysis, modal, non-modal, energy and sensitivity analysis are used to determine the instability mechanisms of the non-Newtonian flows. Signicant modifications/alterations in the instability of the different flows have been observed under the action of the non-Newtonian effects. In general, shear-thinning/shear-thickening effects destabilize/stabilize the flow around the cylinder and in a lid driven cavity. Viscoelastic effects both stabilize and destabilize the channel flow depending on the ratio between the viscoelastic and flow time scales. The instability mechanism is just slightly modied in the cylinder flow whereas new instability mechanisms arise in the lid-driven cavity flow. In the second part, we employ Direct Numerical Simulation together with an Immersed Boundary Method to simulate the inertial suspensions of rigid spherical neutrally buoyant particles in a channel. A wide range of the bulk Reynolds numbers, 500<Re<5000, and particle volume fractions, 0<\Phi<3, is studied while fixing the ratio between the channel height to particle diameter, 2h/d = 10. Three different inertial regimes are identied by studying the stress budget of two-phase flow. These regimes are laminar, turbulent and inertial shear-thickening where the contribution of the viscous, Reynolds and particle stress to transfer the momentum across the channel is the strongest respectively. In the inertial shear-thickening regime we observe a signicant enhancement in the wall shear stress attributed to an increment in particle stress and not the Reynolds stress. Examining the particle dynamics, particle distribution, dispersion, relative velocities and collision kernel, confirms the existence of the three regimes. We further study the transition and turbulence in the dilute regime of finite size particulate channel flow. We show that the turbulence can sustain in the domain at Reynolds numbers lower than the one of the unladen flow due to the disturbances induced by particles.QC 20151127
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Schaaf, Christian [Verfasser], Holger [Akademischer Betreuer] Stark, Holger [Gutachter] Stark, and Roland [Gutachter] Netz. "Particle dynamics in inertial microfluidics / Christian Schaaf ; Gutachter: Holger Stark, Roland Netz ; Betreuer: Holger Stark." Berlin : Technische Universität Berlin, 2020. http://d-nb.info/1219573906/34.
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Ramaprabhu, Praveen Kumar. "On the dynamics of Rayleigh-Taylor mixing." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/378.
Анотація:
The self-similar evolution of a turbulent Rayleigh-Taylor (R-T) mix is investigated through experiments and numerical simulations. The experiments consisted of velocity and density measurements using thermocouples and Particle Image Velocimetry techniques. A novel experimental technique, termed PIV-S, to simultaneously measure both velocity and density fields was developed. These measurements provided data for turbulent correlations, power spectra, and energy balance analyses. The self-similarity of the flow is demonstrated through velocity profiles that collapse when normalized by an appropriate similarity variable and power spectra that evolve in a shape-preserving form. In the self-similar regime, vertical r.m.s. velocities dominate over the horizontal r.m.s. velocities with a ratio of 2:1. This anisotropy, also observed in the velocity spectra, extends to the Taylor scales. Buoyancy forcing does not alter the structure of the density spectra, which are seen to have an inertial range with a -5/3 slope. A scaling analysis was performed to explain this behavior. Centerline velocity fluctuations drive the growth of the flow, and can hence be used to deduce the growth constant. The question of universality of this flow was addressed through 3D numerical simulations with carefully designed initial conditions. With long wavelengths present in the initial conditions, the growth constant was found to depend logarithmically on the initial amplitudes. In the opposite limit, where long wavelengths are generated purely by the nonlinear interaction of shorter wavelengths, the growth constant assumed a universal lower bound value of
5
Bagge, Joar. "Numerical simulation of an inertial spheroidal particle in Stokes flow." Thesis, KTH, Numerisk analys, NA, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-180290.
Анотація:
Particle suspensions occur in many situations in nature and industry. In this master’s thesis, the motion of a single rigid spheroidal particle immersed in Stokes flow is studied numerically using a boundary integral method and a new specialized quadrature method known as quadrature by expansion (QBX). This method allows the spheroid to be massless or inertial, and placed in any kind of underlying Stokesian flow. A parameter study of the QBX method is presented, together with validation cases for spheroids in linear shear flow and quadratic flow. The QBX method is able to compute the force and torque on the spheroid as well as the resulting rigid body motion with small errors in a short time, typically less than one second per time step on a regular desktop computer. Novel results are presented for the motion of an inertial spheroid in quadratic flow, where in contrast to linear shear flow the shear rate is not constant. It is found that particle inertia induces a translational drift towards regions in the fluid with higher shear rate.Partikelsuspensioner förekommer i många sammanhang i naturen och industrin. I denna masteruppsats studeras rörelsen hos en enstaka stel sfäroidisk partikel i Stokesflöde numeriskt med hjälp av en randintegralmetod och en ny specialiserad kvadraturmetod som kallas quadrature by expansion (QBX). Metoden fungerar för masslösa eller tröga sfäroider, som kan placeras i ett godtyckligt underliggande Stokesflöde. En parameterstudie av QBX-metoden presenteras, tillsammans med valideringsfall för sfäroider i linjärt skjuvflöde och kvadratiskt flöde. QBX-metoden kan beräkna kraften och momentet på sfäroiden samt den resulterande stelkroppsrörelsen med små fel på kort tid, typiskt mindre än en sekund per tidssteg på en vanlig persondator. Nya resultat presenteras för rörelsen hos en trög sfäroid i kvadratiskt flöde, där skjuvningen till skillnad från linjärt skjuvflöde inte är konstant. Det visar sig att partikeltröghet medför en drift i sidled mot områden i fluiden med högre skjuvning.
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Ferran, Amélie. "Dynamique des particules d'inertie dans une interface turbulente/non turbulente." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALI102.
Анотація:
Ce projet expérimental étudiera la dynamique des gouttelettes dans une interface turbulente / non turbulente, avec présence de cisaillement. Pour mener à bien cette recherche, nous utiliserons des installations et des techniques de mesure uniques, à savoir deux souffleries équipées de systèmes produisant de la turbulence qui peuvent être activés différentiellement pour générer une interface turbulente / non turbulente. Cette collaboration permettra de couvrir une large gamme de gradients d'intensité turbulente, de taux de cisaillement et de nombres de Reynolds pour l'étude de la dynamique des particules inertielles dans des conditions turbulentes / non turbulentes. L'étude produira des données sur les différentes tailles de gouttelettes qui couvrent la plage des nombres de Stokes, et qui caractérisent l'inertie des particules par rapport à l'échelle micrométrique de turbulence. Les domaines d'application peuvent être l'injection de carburant dans les systèmes de conversion d'énergie, le revêtement par pulvérisation industriel, la formation de pluie chaude dans les nuages et les embruns des vagues déferlantes dans la zone de surfThis experimental project will investigate the dynamics of droplets at the interface between turbulent and non-turbulent regions, with shear. To conduct this research, we will utilize unique facilities and measurement techniques, namely two wind tunnels equipped with turbulence-generating systems that can be differentially activated to create a turbulent/non-turbulent interface. This collaboration will cover a wide range of turbulent intensity gradients, shear rates, and Reynolds numbers for studying the dynamics of inertial particles in turbulent/non-turbulent conditions. The study will produce data on various droplet sizes spanning the range of Stokes numbers, characterizing particle inertia relative to the micrometric scale of turbulence. Potential applications include fuel injection in energy conversion systems, industrial spray coating, warm rain formation in clouds, and sea spray in the surf zone
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Li, Qing. "Near-wall dynamics of neutrally buoyant particles in a wall-normal flow." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0125.
Анотація:
Les suspensions rencontrées dans diverses applications d’ingénierie (telles que l’extraction de pétrole brut, l’élaboration d’aliments, de béton ou de produits cosmétiques) peuvent présenter une dynamique riche lorsqu’elles sont soumises à un écoulement dans des géométries complexes. Il est important de savoir prédire la réponse de ces matériaux hétérogène sous écoulement compte tenu des applications. Pour construire des modèles prédictifs, il est indispensable de comprendre les phénomènes à différentes échelles, dans diverses configurations telles que l’écoulement d’une dispersion solide-liquide dans un coude ou dans un canal en forme de T, le mélange de cette dispersion par un agitateur, etc. Les écoulements de suspension normaux à un obstacle ont reçu peu d’attention (le fluide porteur étant liquide). Dans ce contexte, nous avons examiné la dynamique des particules dans l’écoulement de Hiemenz (un écoulement de type couche limite incident à une paroi), à l’aide de simulations numériques. Nous nous sommes concentrés essentiellement sur une ou deux particules de même densité que le fluide, et de taille finie comparée à l’épaisseur de couche limite (les particules ont une inertie finie près de la paroi car elles sont forcées de s’arrêter à la paroi). Nous avons utilisé des simulations numériques directes afin de mesurer le glissement des particules par rapport à l’écoulement local, la force d’interaction de nature hydrodynamique ainsi que la perte d’énergie. Toutes ces quantités ont été déterminées en tant que fonctions uniques du rapport entre la taille des particules et l’épaisseur de la couche limite visqueuse. Les simulations ont mis en évidence que l’approche d’une particule vers la paroi, suivant l’axe de symétrie de l’écoulement, subit une transition d’un régime de ralentissement dominé par les effets visqueux à un régime de type rebond, cette transition prenant place pour une taille de particule O. Nous avons établi un modèle pour la force hydrodynamique exercée sur la particule s’approchant de la paroi et pour le coefficient de restitution en écoulement normal à la paroi. Pour deux particules identiques sur l’axe, certaines séparations conduisent à une collision de particules avant que la particule inférieure (la plus proche de la paroi) ne touche la paroi; l’échange de quantité de mouvement qui en résulte conduit à une vitesse d’impact supérieure à celle d’une particule particule isolée. Les simulations révèlent que la dynamique de la paire inclut un rebond sans contact de la particule inférieure avec la paroi, en raison de la mise à l’abri par la particule supérieure contre la tranée, permettant à la force de pression de dominerTwo-phase suspensions encountered in various engineering applications(like crude oil extraction, elaboration of food, concrete or cosmetics), can exhibit rich dynamics when submitted to flow in complex geometries. Predicting the response of such heterogeneous material under flow is an important issue in view of applications. To build these predictive models, basic understanding of the dif- ferent scales is required for configurations such as pipe flow through an elbow or T-shape section, mixing a solid-liquid dispersion by a rotating impeller, etc. Suspension flows normal to an obstacle have seen limited attention with the carrier fluid being liquid phase. In this context, we examined particle dynamics in the well-known Hiemenz boundary-layer flow, with the aid of numerical simu- lations. We focused essentially on one or two neutrally buoyant particles, which are of finite size compared to the boundary layer thickness (particles have a finite inertia near the wall because they are forced to stop at the wall), and which are located at the symmetry axis of the flow. We used direct numerical simulations in order to measure the particle slip with respect to the local flow, the hydrodynamic force experienced by the particle and the energy loss during solvent-mediated particle-wall interaction. All these quantities were determined as unique functions of the ratio between the particle size and the thickness of the viscous boundary layer. When the particle size is increased, the simulations highlighted a transition of the particle dynamics from viscous damping to rebound, occurring for particle size O(). We established a model for the hydrodynamic force experienced by the incident particle, and for the restitution coefficient in wall-normal flow. For two identical particles on the axis, certain separations lead to particle collision before the lower (closer to wall) particle hits the wall; the resulting momentum exchange leads to larger impact velocity than for one particle. The simulations reveal that dynamics of the colliding pair includes unexpected rebound without contact with the wall for the lower of two particles, due to sheltering by the upper particle from drag allowing the pressure force to dominate
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Vosskuhle, Michel. "Particle collisions in turbulent flows." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2013. http://tel.archives-ouvertes.fr/tel-00946618.
Анотація:
Cette thèse est consacrée au mécanisme conduisant à des taux de collisions importants dans les suspensions turbulentes de particules inertielles. Le travail a été effectué en suivant numériquement des particules, par simulations directes des équations de Navier-Stokes, et également par étude de modèles simplifiés. Les applications de ce domaine sont nombreuses aussi bien dans un contexte industriel que naturel (astrophysique, géophysique). L'approximation des collisions fantômes (ACF), souvent utilisée pour déterminer les taux de collision numériquement, consiste à compter dans une simulation, le nombre de fois que la distance entre les centres de deux particules devient plus faible qu'une distance seuil. Plusieurs arguments théoriques suggéreraient que cette approximation conduit à une surestimation du taux de collision. Cette thèse fournit non seulement une estimation quantitative de cette surestimation, mais également une compréhension détaillée des mécanismes des erreurs faites par l'ACF. Nous trouvons qu'une paire de particules peut subir des collisions répétées avec une grande probabilité. Ceci est relié à l'observation que, dans un écoulement turbulent, certaines paires de particules peuvent rester proches pendant très longtemps. Une deuxième classe de résultats obtenus dans cette thèse a permis une compréhension quantitative des très forts taux de collisions souvent observés. Nous montrons que lorsque l'inertie des particules n'est pas très petite, l'effet " fronde/caustiques ", à savoir, l'éjection de particules par des tourbillons intenses, est responsable du taux de collision élevé. En comparaison, la concentration préférentielle de particules dans certaines régions de l'espace joue un rôle mineur.
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Kilimnik, Alexander. "Cross stream migration of compliant capsules in microfluidic channels." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43669.
Анотація:
An understanding of the motion of soft capsules in microchannels is useful for a number applications. This knowledge can be used to develop devices to sort biological cells based on their size and stiffness. For example, cancer cells have a different stiffness from healthy cells and thus can be readily identified. Additionally, devices can be developed to detect flaws in synthetic particles. Using a 3D hybrid lattice Boltzmann and lattice spring method, the motion of rigid and soft capsules in a pressure-driven microfluidic flow was probed. The effect of inertial drift is evaluated in channels different Reynolds numbers. Other system parameters such as capsule elasticity and channel size are also varied to determine their effect. The equilibrium position of capsules in the channel is also obtained. The equilibrium position of rigid and soft capsules depends on the relative particle size. If the capsule is small, the equilibrium position is found to be closer to the channel wall. Conversely, for larger capsules, the equilibrium position is closer to the channel centerline. The capsule stiffness affects the magnitude of the cross-stream drift velocity. For a given Reynolds number, the equilibrium position of softer capsules is closer to the channel centerline. However, It is found that the equilibrium position of soft capsules is insensitive to the magnitude of the Reynolds number.
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Post, E. Rehmi 1966. "Inertial measurement via dynamics of trapped particles." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29991.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2003.Includes bibliographical references (leaves 69-70).
We describe theoretical and practical aspects of the particle trap as an inertial sensor. The insight motivating this approach is that a trapped particle acts like a mass on a spring, but the restoring forces are provided by electrostatic fields. Exquisitely machined physical mechanisms can be replaced by carefully tuned mechanical physics. Such inertial sensors could be simpler to build yet exhibit superior performance because their operating parameters can be dynamically controlled. Most currently available inertial sensors are inherently planar devices that obtain no more than two degrees of motional sensitivity from a given proof mass. The availability of an accurate, inexpensive, integrated six-degree-of-freedom inertial sensor would enable new applications of inertial sensing that are presently either infeasible or unconsidered. By adding inertial terms to the Paul trap dynamics we derive classical observables that depend on the local acceleration field. We also confirm that these observables appear in practice, in what we believe to be the first electrodynamic particle trap accelerometer. An important (and unusual) aspect of our accelerometer is its dynamic tunability: its effective spring constant depends on the trap drive parameters. Our roughly constructed trap also exhibits a large region of linear response to acceleration, and we present evidence suggesting that our accelerometer has performance comparable to commercially available sensors.
by Ernest Rehmatulla Post.
Ph.D.
Книги з теми "Inertial particle dynamics":
1
Deruelle, Nathalie, and Jean-Philippe Uzan. Dynamics of a point particle. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198786399.003.0024.
Анотація:
This chapter attributes an inertial ‘mass–energy’ to particles. It also distinguishes between the action of an external field and of long-range and short-range internal forces, which is useful for establishing the laws of dynamics of an interacting body—that is, the equations determining its world line. The chapter also presents the 4-momentum conservation law for massive particles and light particles in inertial reference frames. It then gives some examples which illustrate the role played by this law in collisions. Finally, the chapter illustrates the conservation law by the Compton experiment, that is, the collision of a light corpuscle with a particle, and the concept of the quantum of action that can be derived from it.
2
Deruelle, Nathalie, and Jean-Philippe Uzan. Rotating systems. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198786399.003.0025.
Анотація:
This chapter continues the discussion of the laws of relativistic dynamics for systems of point particles, beginning with the law of angular momentum conservation in collisions. It considers an ensemble of free particles each characterized by its (constant) momentum pa. The total momentum p = Σapa does not depend on the inertial frame used, but the angular momentum will depend on the frame, because its definition involves radius vectors between an event reference point and points qa on the particle world lines. Furthermore, these are chosen to be simultaneous in a given frame. The chapter also formulates the equations of motion for particles possessing an internal rotation or ‘spin’.
3
Furst, Eric M., and Todd M. Squires. Light scattering microrheology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0005.
Анотація:
The fundamentals and best practices of passive microrheology using dynamic light scattering and diffusing wave spectroscopy are discussed. The principles of light scattering are introduced and applied in both the single and multiple scattering regimes, including derivations of the light and field autocorrelation functions. Applications to high-frequency microrheology and polymer dynamics are presented, including inertial corrections. Methods to treat gels and other non-ergodic samples, including multi-speckle and optical mixing designs are discussed. Dynamic light scattering (DLS) is a well established method for measuring the motion of colloids, proteins and macromolecules. Light scattering has several advantages for microrheology, especially given the availability of commercial instruments, the relatively large sample volumes that average over many probes, and the sensitivity of the measurement to small particle displacements, which can extend the range of length and timescales probed beyond those typically accessed by the methods of multiple particle tracking and bulk rheology.
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Deruelle, Nathalie, and Jean-Philippe Uzan. Relativity in Modern Physics. Translated by Patricia de Forcrand-Millard. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198786399.001.0001.
Анотація:
Newton’s ideas about how to represent space and time, his laws of dynamics, and his theory of gravitation established the conceptual foundation from which modern physics developed. This book offers a modern view of Newtonian theory, emphasizing those aspects needed for understanding quantum and relativistic contemporary physics. In 1905, Albert Einstein proposed a novel representation of space and time, special relativity. The text also presents relativistic dynamics in inertial and accelerated frames, as well as a detailed overview of Maxwell’s theory of electromagnetism, thus providing the background necessary for studying particle and accelerator physics, astrophysics, and Einstein’s theory of general relativity. In 1915, Einstein proposed a new theory of gravitation, general relativity. Finally, the text develops the geometrical framework in which Einstein’s equations are formulated and presents several key applications: black holes, gravitational radiation, and cosmology.
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Mercati, Flavio. Origins of the Mach–Poincaré Principle. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789475.003.0003.
Анотація:
The problem with the definition of inertia was solved, in the simple case of free point particles, by Tait, who introduced the concept of inertial frame. Tait’s solution would have satisfied Leibniz’ request that inertia be determined dynamically, however it only works in the absence of interactions between the material bodies. Later Mach posed again the question of the origin of inertia, suggesting the idea that it should be dynamical, which was later dubbed ‘Mach’s principle’. Moreover Mach criticized also Newton’s absolute time, and introduced the basic idea of temporal relationalism, i.e. that time should be a concept that is abstracted from change and has no independent existence. This idea is at the basis of SD and many other relational approaches to physics. This chapter concludes with the Barbour–Bertotti formulation of Mach’s principle, which they called ‘Mach–Poincaré Principle’. This formulation removes the vagueness of Mach’s original idea, and puts the principle into a precise mathematical form, which is one of the basic axioms of SD.
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Mashhoon, Bahram. Nonlocal Gravity. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198803805.001.0001.
Анотація:
A postulate of locality permeates through the special and general theories of relativity. First, Lorentz invariance is extended in a pointwise manner to actual, namely, accelerated observers in Minkowski spacetime. This hypothesis of locality is then employed crucially in Einstein’s local principle of equivalence to render observers pointwise inertial in a gravitational field. Field measurements are intrinsically nonlocal, however. To go beyond the locality postulate in Minkowski spacetime, the past history of the accelerated observer must be taken into account in accordance with the Bohr-Rosenfeld principle. The observer in general carries the memory of its past acceleration. The deep connection between inertia and gravitation suggests that gravity could be nonlocal as well and in nonlocal gravity the fading gravitational memory of past events must then be taken into account. Along this line of thought, a classical nonlocal generalization of Einstein’s theory of gravitation has recently been developed. In this nonlocal gravity (NLG) theory, the gravitational field is local, but satisfies a partial integro-differential field equation. A significant observational consequence of this theory is that the nonlocal aspect of gravity appears to simulate dark matter. The implications of NLG are explored in this book for gravitational lensing, gravitational radiation, the gravitational physics of the Solar System and the internal dynamics of nearby galaxies as well as clusters of galaxies. This approach is extended to nonlocal Newtonian cosmology, where the attraction of gravity fades with the expansion of the universe. Thus far only some of the consequences of NLG have been compared with observation.
Частини книг з теми "Inertial particle dynamics":
1
Gasteuil, Yoann, and Jean-François Pinton. "Linear and angular dynamics of an inertial particle in turbulence." In Springer Proceedings in Physics, 19–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03085-7_4.
2
Borowska, Bożena. "Dynamic Inertia Weight in Particle Swarm Optimization." In Advances in Intelligent Systems and Computing II, 79–88. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-70581-1_6.
3
Miao, Ai-min, Xin-ling Shi, Jun-hua Zhang, En-yong Wang, and Shu-qing Peng. "A Modified Particle Swarm Optimizer with Dynamical Inertia Weight." In Advances in Intelligent and Soft Computing, 767–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03664-4_84.
4
Liao, Wudai, Junyan Wang, and Jiangfeng Wang. "Nonlinear Inertia Weight Variation for Dynamic Adaptation in Particle Swarm Optimization." In Lecture Notes in Computer Science, 80–85. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-21515-5_10.
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Joshi, Suraj, and R. Subha. "A Particle Swarm Optimization-Based Maximum Power Point Tracking Scheme Employing Dynamic Inertia Weight Strategies." In Lecture Notes in Electrical Engineering, 461–72. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-4975-3_37.
6
Niu, Dongxiao, Bingen Kou, Yunyun Zhang, and Zhihong Gu. "A Short-Term Load Forecasting Model Based on LS-SVM Optimized by Dynamic Inertia Weight Particle Swarm Optimization Algorithm." In Advances in Neural Networks – ISNN 2009, 242–50. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-01510-6_28.
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Nolte, David D. "Relativistic Dynamics." In Introduction to Modern Dynamics, 385–425. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198844624.003.0012.
Анотація:
The invariance of the speed of light with respect to any inertial observational frame leads to a surprisingly large number of unusual results that defy common intuition. Chief among these are time dilation, length contraction, and loss of simultaneity. The Lorentz transformation intermixes space and time, but an overarching structure is provided by the metric tensor of Minkowski space-time. The pseudo-Riemannian metric supports 4-vectors whose norms are invariants, independent of any observational frame. These invariants constitute the proper objects of reality to study in the special theory of relativity. Relativistic dynamics defines the equivalence of mass and energy, which has many applications in nuclear energy and particle physics. Forces have transformation properties between relatively moving frames that set the stage for a more general theory of relativity that describes physical phenomena in noninertial frames.
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Zubairy, M. Suhail. "Particle Dynamics." In Quantum Mechanics for Beginners, 32–49. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198854227.003.0003.
Анотація:
In Newtonian mechanics, a particle is described as an object that is characterized by certain properties. The most important characteristics of a particle are its mass, position, velocity, and acceleration. In this chapter, it is shown how a particle follows a well defined classical trajectory. The main characteristics of the dynamics of particles such as linear and angular momentum, force, energy, moment of inertia, and torque are presented. An understanding of these effects is essential in understanding and appreciating the laws of quantum mechanics. As an example of the Newtonian mechanics, the motion of an electron in electric and magnetic fields experiencing Lorentz force is discussed. This example explains how Thomson discovered the electron in the late nineteenth century.
9
Dendy, R. O. "Non-linear plasma physics." In Plasma Dynamics, 124–46. Oxford University PressOxford, 1990. http://dx.doi.org/10.1093/oso/9780198519911.003.0007.
Анотація:
Abstract We shall now consider the connection between the two major ways of describing plasma that have been used so far. First, we considered the dynamics of a single particle in the plasma, which leads directly to a simple model for the dielectric properties of the plasma. By including the single-particle dynamics of ions as well as of electrons, it is possible to predict the normal modes of the plasma over a wide range of frequencies. There is also the magneto hydrodynamic approach. By treating the plasma as a magnetized conducting fluid, whose inertia is provided by the mass of the ions, we can describe the bulk stability of the plasma and its lower-frequency normal modes-those modes which do not involve the movement of electrons independently of ions.
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Stuart, Andrew. "Perturbation Theory for Infinite Dimensional Dynamical Systems." In Theory and Numerics of Ordinary and Partial Differential Equations, 181–290. Oxford University PressOxford, 1995. http://dx.doi.org/10.1093/oso/9780198511939.003.0005.
Анотація:
Abstract When considering the effect of perturbations on initial value problems over long time intervals it is not possible, in general, to uniformly approximate individual trajectories. This is because well posed initial value problems allow exponential divergence of trajectories and this fact is reflected in the error bound relating trajectories of the perturbed and unperturbed problems. In order to interpret data obtained from numerical simulations over long time intervals, and from other forms of perturbations, it is hence often necessary to ask different questions concerning the behavior as the approximation is refined. One possibility, which we concentrate on in this review, is to study the effect of perturbation on sets which are invariant under the evolution equation. Such sets include equilibria, periodic solutions, stable and unstable manifolds, phase portraits, inertial manifolds and attractors; they are crucial to the understanding of long-time dynamics.
Тези доповідей конференцій з теми "Inertial particle dynamics":
1
Barone, Dominic, Eric Loth, and Philip H. Snyder. "Particle Dynamics of a 2-D Inertial Particle Separator." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26922.
Анотація:
The effects of sand and dust ingestion often limit the useful life of turbine engines operating in austere environments and efforts are needed to reduce the quantity of particulate entering the engine. Several Engine Air Particle Separation (EAPS) systems exist to accomplish this task. Inertial Particle Separators (IPS) are of particular interest because they offer significant weight savings and are more compact. This study focuses on the how small particles are affected by the dynamic fluid forces present in the IPS. Using Multi-Phase Particle Image Velocimetry (MP-PIV), 10um and 35um glass spheres were tracked through the IPS. Further, the data was also used to analyze the particles Coefficient of Restitution, (CORn̂), where they impact the Outer Surface Geometry (OSG) of the IPS.
2
Snyder, Philip H., Eric Loth, and Dominic L. Barone. "Unsteady Particle Dynamics within an Inertial Particle Separator." In 53rd AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2015. http://dx.doi.org/10.2514/6.2015-0871.
3
Barone, Dominic L., Eric Loth, and Philip H. Snyder. "Fluid Dynamics of an Inertial Particle Separator." In 52nd Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2014. http://dx.doi.org/10.2514/6.2014-1314.
4
Valani, Rahil, Brendan Harding, and Yvonne Stokes. "Poster: Inertial particle focusing in curved ducts." In 75th Annual Meeting of the APS Division of Fluid Dynamics. American Physical Society, 2022. http://dx.doi.org/10.1103/aps.dfd.2022.gfm.p0014.
5
Valani, Rahil, Brendan Harding, and Yvonne Stokes. "Video: Inertial particle focusing in curved ducts." In 75th Annual Meeting of the APS Division of Fluid Dynamics. American Physical Society, 2022. http://dx.doi.org/10.1103/aps.dfd.2022.gfm.v0049.
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Snyder, Philip H., Dominic Barone, and Eric Loth. "Unsteady Flow Dynamics Within an Inertial Particle Separator." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43783.
Анотація:
Inertial Particle Separators are utilized in the inlet of a gas turbine engine to remove a significant fraction of the damaging sand and dust particulate ingested by the engine. In gas turbine propulsion applications these devices have pressure loss, space claim, and maintainability characteristics that are more favorable than other types of particle separating devices. Maximizing the particle separation efficient of such devices is the subject of continuing importance. A more complete understanding of the underlying fluid and particulate flow mechanisms present has been undertaken. This study focuses on the how particulate is affected by the unsteady flow dynamics within the inertial particle separator (IPS). The work utilized a particle separator test rig with flow path scale and airflow velocities relevant to that used in current production designs. The techniques of surface flow visualization, net separation efficiency measurement, specific geometry changes, traditional Particle Image Velocimetry (PIV), Multi-Phase PIV (MP-PIV), and high speed video were each applied to examine the fundamental flow physics of the fluid flow field and the particle motion created by the IPS geometries.
7
Musgrove, Grant O., Michael D. Barringer, Karen A. Thole, Eric Grover, and Joseph Barker. "Computational Design of a Louver Particle Separator for Gas Turbine Engines." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-60199.
Анотація:
The extreme temperatures in a jet engine require the use of thermal barrier coatings and internal cooling channels to keep the components in the turbine section below their melting temperature. The presence of solid particles in the engine’s gas path can erode thermal coatings and clog cooling channels, thereby reducing part life and engine performance. This study uses computational fluid dynamics to design the geometry of a static, inertial particle separator to remove small particles, such as sand, from the engine flow. The concept for the inertial separator includes the usage of a multiple louver array followed by a particle collector. The results of the study show a louver design can separate particles while not incurring large pressure loss.
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Melhem, Omar A. "CFD Simulations of Aerosol Particles Deposition in a Venturi Meter Used in Smoke Sampling Devices." In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7657.
Анотація:
Smoke sampling devices are used in several fields to study dynamics of smoke aerosols. An important criterion in designing smoke sampling devices is that flow paths leading to where the sample is characterized are constructed such that deposition of aerosol particles along the paths is minimized. Sampling devices often include a Venturi flow meter installed downstream of the smoke source, which may significantly alter the composition of the aerosol reaching the sample analyzer. The current work employs Computational Fluid Dynamics (CFD) to model particle deposition within the flow meter and to examine the effects of different design parameters. This study focuses on particles with sizes ranging from 0.01 to 100 microns, for which three main mechanisms for deposition can be identified: inertial impaction, gravitational sedimentation, and Brownian diffusion. It has been shown that inertial deposition is negligible for ultrafine particles (5–560 nm) and it becomes noticeable for particles in the micron size range. Also, deposition fractions increase with increasing particle sizes. Moreover, inertial particle deposition increases with increasing volume flow rates.
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Parisi, Giovanni, Horst Deitinghoff, Klaus Bongardt, and Michael Pabst. "Particle dynamics in a DTL for high intensity heavy ion beams for inertial fusion." In Space charge dominated beam physics for heavy ion fusion. AIP, 1999. http://dx.doi.org/10.1063/1.59497.
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Chen, Jim S., and Jinho Kim. "Micro Particle Transport and Deposition in Human Upper Airways." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42928.
Анотація:
The hazard caused by inhaled particles depends on the site at which they deposit within the respiratory system. Knowledge of respiratory aerosol deposition rates and locations is necessary to (1) evaluate potential health effects and establish critical exposure limits and (2) design effective inhaled medications that target specific lung regions. Particles smaller than 10 μm in diameter can be breathed into lungs and are known as inhalable particles, while most of larger particles settle in mouth and nose. Inhalable particles settle in different regions of the lungs and the settling regions depends on the particle size. The motion of a particle is mainly affected by the inertia of the particle and by the particle’s aerodynamic drag. The most important dimensionless parameters in the prediction of particle motion are the flow Reynolds number and the Stoke number, which combines the effects of particle diameter, particle density, shape factor and slip factor. The purpose of this study is to investigate the airflows in human respiratory airways. The influence of particle size on transport and deposition patterns in the 3-D lung model of the human airways is the primary concern of this research. The lung model developed for this research extends from the trachea to the segmental bronchi and it is based on Weibel’s model. The velocity field of air is studied and particle transport and deposition are compared for particles in the diameter range of 1 μm – 100 μm (G0 to G2) and 0.1 μm – 10 μm (G3 to G5) at airflow rates of 6.0, 16.7, and 30.0 L/min, which represent breathing at rest, light activity, and heavy activity, respectively. The investigation is carried out by computational fluid dynamics (CFD) using the software Fluent 6.2. Three-dimensional, steady, incompressible, laminar flow is simulated to obtain the flow field. The discrete phase model (DPM) is then employed to predict the particle trajectories and the deposition efficiency by considering drag and gravity forces. In the present study, the Reynolds number in the range of 200 – 2000 and the Stoke number in the range of 10−5 – 0.12 are investigated. For particle size over 10 μm, deposition mainly occurs by inertial impaction, where deposition generally increases with increases in particle size and flow rate. Most of the larger micron sized particles are captured at the bifurcations, while submicron sized particles flow with the fluid into the lung lower airways. The trajectories of submicron sized particles are strongly influenced by the secondary flow in daughter branches. The present results of particle deposition efficiency in the human upper airways compared well with data in the literature.
Звіти організацій з теми "Inertial particle dynamics":
1
Smith, Sarah. Dynamic Effects of Inertial Particles on the Wake Recovery of a Model Wind Turbine. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.7418.