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Auswahl der wissenschaftlichen Literatur zum Thema „Porous jump“
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Zeitschriftenartikel zum Thema "Porous jump"
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Avramenko, A. A., N. P. Dmitrenko, Yu Yu Kovetska und E. A. Kondratieva. „FEATURES OF HEAT TRANSFER IN A FLAT POROUS MICROCHANNEL“. Thermophysics and Thermal Power Engineering 42, Nr. 1 (12.04.2020): 12–18. http://dx.doi.org/10.31472/ttpe.1.2020.1.
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A steady heat transfer process of mixed convection in a flat vertical porous microchannel is considered.
The results of simulation showed that Knudsen number effects are more significant in the neighborhood of the wall where growth of Knudsen numbers is accompanied with the velocity and temperature jumps on wall. With increasing parameter of porosity M (decreasing permeability), the flow velocity decreases and the velocity jump decrease as well.
For all combinations of the criteria Ra, Kn and M increasing Knudsen number reduces heat transfer intensity. This can be attributed to increasing temperature jump on wall which causes deterioration of thermal interaction between the fluid and the wall.
For low Rayleigh numbers increasing parameter M leads to increasing heat transfer since the temperature jump decrease on walls. For large Rayleigh numbers the trend becomes reversed, since for larger parameters M, the near-wall velocity decreases.
For low Rayleigh numbers increasing the Knudsen number leads to decreasing hydraulic resistance coefficient, but with increasing parameter M leads to increasing this coefficient. At high Ra numbers increasing Knudsen number leads to growth of hydraulic resistance, which is due to increasing velocity gradient on the wall.
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Li, Hong Hai, und Yang Yang Cheng. „Effect of Porous-Jump Model Parameters on Membrane Flux Prediction“. Advanced Materials Research 734-737 (August 2013): 2210–13. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.2210.
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A three-dimensional computational fluid dynamics (CFD) simulation was performed to study the velocity distribution on membrane surface in membrane separation process, and the effect of face permeability, porous medium thickness, and pressure-jump coefficient of porous-jump model on membrane flux. The study shows that all the three factors have important impact on membrane flux. Membrane flux increases linearly with the increase of face permeability. When the membrane thickness is between 0.04~0.1mm, the membrane flux decreases with the increase of membrane thickness. The membrane flux decreases with the increase of pressure-jump coefficient. So that there must be a complex relationship between membrane flux and face permeability, porous medium thickness, and pressure-jump coefficient.
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Chen, Ming-Da, und Wang-Long Li. „Creeping Flow Relative to a Porous Spherical Shell“. Journal of Mechanics 16, Nr. 3 (September 2000): 137–43. http://dx.doi.org/10.1017/s1727719100001799.
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ABSTRACTIn this study, the problem of creeping flow relative to an isolated porous spherical shell has been examined. The Brinkman-extended Darcy equations and the Stokes' equations are utilized to model the flow in the porous region (shell region) and free fluid region (inside the core and outside the shell), respectively. The stress jump boundary conditions at the porous media/free fluid interfaces are included and the exact solution has been found. The drag experienced by the porous shell has been discussed for various jump parameters and shell thickness.
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Qiu, Li, Xiao-Dong Chen, Rui Wang und De-Peng Wang. „Macro fluid analysis of laminated fabric permeability“. Thermal Science 20, Nr. 3 (2016): 835–38. http://dx.doi.org/10.2298/tsci1603835q.
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A porous jump model is put forward to predict the breathability of laminated fabrics by utilizing fluent software. To simplify the parameter setting process, the methods of determining the parameters of jump porous model by means of fabric layers are studied. Also, effects of single/multi-layer fabrics and thickness on breathability are analyzed, indicating that fabric breathability reduces with the increase of layers. Multi-layer fabric is simplified into a single layer, and the fabric permeability is calculated by proportion. Moreover, the change curve of fabric layer and face permeability, as well as the equation between the fabric layer and the face permeability are obtained. Then, face permeability and pressure-jump coefficient parameters setting of porous jump model could be integrated into single parameter (i. e. fabric layers), which simplifies the fluent operation process and realizes the prediction of laminated fabric permeability.
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Liu, Fang, und Bao Ming Chen. „Natural Convection in a Cavity Partially Filled with a Vertical Porous Medium“. Advanced Materials Research 321 (August 2011): 15–18. http://dx.doi.org/10.4028/www.scientific.net/amr.321.15.
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The shear stress jump boundary condition that must be imposed at an interface between a porous medium and a free fluid in an enclosure is investigated. Two-domain approach is founded and finite element method is used to solve the problem. Three stress jump coefficients 0, 1, -1 are analyzed for different Rayleigh number, permeability and thickness of porous layer. Variation of Maximum stream function and Nusselt number show stronger convection and heat transfer when the stress jump coefficient is positive. There is little distinctive in flow and heat transfer when the value of coefficient is equal to 0 and -1.
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Zhou, Guo Li, und Zhen Ting Hou. „Stochastic generalized porous media equations with Lévy jump“. Acta Mathematica Sinica, English Series 27, Nr. 9 (15.08.2011): 1671–96. http://dx.doi.org/10.1007/s10114-011-9194-8.
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Zakirov, Timur R., und Maxim G. Khramchenkov. „Pore-scale investigation of the displacement fluid mechanics during two-phase flows in natural porous media under the dominance of capillary forces“. Georesursy 22, Nr. 1 (30.03.2020): 4–12. http://dx.doi.org/10.18599/grs.2020.1.4-12.
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This paper presents the results of numerical simulations of two-phase flows in porous media under capillary forces dominance. For modeling of immiscible two-phase flow, the lattice Boltzmann equations with multi relaxation time operator were applied, and the interface phenomena was described with the color-gradient method. The objective of study is to establish direct links between quantitative characteristics of the flow and invasion events, using high temporal resolution when detecting simulation results. This is one of the few works where Haines jumps (rapid invasion event which occurs at meniscus displacing from narrow pore throat to its wide body) are considered in three-dimensional natural pore space, but the focus is also on the displacement mechanics after jumps. It was revealed the sequence of pore scale events which can be considered as a period of drainage process: rapid invasion event during Haines jump; finish of jump and continuation of uniform invasion in current pore; switching of mobile interfaces and displacement in new region. The detected interface change, along with Haines jump, is another distinctive feature of the capillary forces action. The change of the mobile interfaces is manifested in step-like behavior of the front movement. It was obtained that statistical distributions of pressure drops during Haines jumps obey lognormal law. When investigating the flow rate and surface tension effect on the pressure drop statistics it was revealed that these parameters practically don’t affect on the statistical distribution and influence only on the magnitude of pressure drops and the number of individual Haines jumps.
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Li, Wang-Long. „Derivation of Modified Reynolds Equation—A Porous Media Model“. Journal of Tribology 121, Nr. 4 (01.10.1999): 823–29. http://dx.doi.org/10.1115/1.2834141.
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In this study, a porous media model is developed which can be applied to thin film lubrication problems. The microstructure of bearing surfaces is modeled as porous layers attached to the impermeable substrate. The Brinkman-extended Darcy equations and Stokes’ equations are utilized to model the flow in the porous region and fluid film region, respectively. The stress jump boundary condition at the porous media/fluid film interface and effects of viscous shear are included in deriving the modified Reynolds equation. The present model can correct and modify a previous study based on the Darcy model with slip-fiow effects or another based on the Brinkman-extended Darcy model with stress continuity at the porous media/fluid film interface. In the results, the effects of material properties: viscosity ratio (αi2), thickness of porous layer (Δi), permeability (Ki), stress jump parameter (βi), on the velocity distributions, and performance of one-dimensional converging wedge problems are discussed.
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Angot, Philippe. „Well-posed Stokes/Brinkman and Stokes/Darcy coupling revisited with new jump interface conditions“. ESAIM: Mathematical Modelling and Numerical Analysis 52, Nr. 5 (September 2018): 1875–911. http://dx.doi.org/10.1051/m2an/2017060.
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The global well-posedness in time is proved, with no restriction on the size of the data, for the Stokes/Brinkman and Stokes/Darcy coupled flow problems with new jump interface conditions recently derived by Angot et al. [Phys. Rev. E 95 (2017) 063302-1–063302-16] using asymptotic modelling and shown to be physically relevant. These original conditions include jumps of both stress and tangential velocity vectors at the fluid–porous interface. They can be viewed as generalizations for the multi-dimensional flow of Beavers and Joseph’s jump condition of tangential velocity and Ochoa-Tapia and Whitaker’s jump condition of shear stress. Therefore, they are different from those most commonly used in the literature. The case of Saffman’s approximation is also studied, but with a force balance for the cross-flow including the Darcy drag and inducing a law of pressure jump different from the usual one. The proof of these results follows the general framework briefly introduced by Angot [C. R. Math. Acad. Sci. Paris, Ser. I 348 (2010) 697–702; Appl. Math. Lett. 24 (2011) 803–810.] for the steady flow.
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Zhanabaev, Z. Zh. „WIDTH OF ENERGY BAND GAP OF NANOPOROUS SEMICONDUCTOR FILMS“. Eurasian Physical Technical Journal 17, Nr. 2 (24.12.2020): 39–44. http://dx.doi.org/10.31489/2020no2/39-44.
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The aim of this work is to experimentally clarify the reasons for the appearance of jumps in the current and memory of semiconductor nanoporous structures.Porous nanostructures were obtained by electrochemical etching. The current-voltage characteristics of the samples were measured for porous silicon and on thin films of a chalcogenide glassy semiconductor. The existence of jump-like switching and current hysteresis in porous silicon nanofilms under laser illumination is shown experimentally.A connection between the switching voltage values and the dependence of the band gap on the porosity of nanofilms is found. These results make it possible to construct a theory of current switching and its hysteresis based on the concepts of the theory of second-order phase transitions.
Dissertationen zum Thema "Porous jump"
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Shin, Youn-Ok 1971. „Vapor and liquid equilibria in porous media“. Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21323.
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The alteration of the vapor and liquid equilibrium (VLE) of volatile organic mixtures by using porous media at the liquid-vapor interface was studied. Kelvin, assuming ideal behavior of fluids, first introduced the vapor pressure of liquid over a meniscus as a function of its surface tension and the radius of the curvature. A thermodynamic model (SSmod model) predicting the VLE of non-ideal organic mixtures in porous media was developed as a function of pore sizes based on the pressure equations available in literature. The model was used to predict the VLE of two aqueous alcohol solutions, ethanol-water and propanol-water, and two binary alcohol solutions, methanol-isopropanol and ethanol-octane. Experiments were conducted using sintered metal and fritted glass plates as porous media and compared with the model predictions. The model predictions for the actual pore diameters tested showed good agreement with the experimental results.
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Khan, Zafar Hayat. „Modelling moving evaporation fronts in porous media“. Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16850.
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Understanding vertical heat transfer and through flow in porous media such as geothermal reservoirs is of great interest. In a geothermal system, a denser layer of liquid water may overlie a less dense layer of water vapour. Vertical and horizontal thermal diffusion stabilises such configurations, but the buoyancy contrast can cause instability. In this study, the mechanisms contributing to the stability and instability of such systems are analysed using a separate-phase model with a sharp interface be- tween liquid and vapour. The governing equations representing incompressibility, Darcy’s law and energy conservation for each phase are linearised about suitable base states and the stability of these states is investigated. We have considered two different thermal boundary conditions, both with and without a vertical through- flow. In the first case, the boundaries above and below the layer of interest are assumed to be isothermal. We found that due to the competition between thermal and hydrostatic effects, the liquid–vapour interface may have multiple positions. A two-dimensional linear stability analysis of these basic states shows that the Rayleigh–Taylor mechanism is the dominant contributor to instability, but that there are circumstances under which the basic state may be stable, especially when the front is close to one of the boundaries. In the second case, a constant heat flux is imposed at the liquid boundary and a fixed temperature at the vapour boundary. We have shown that competition between the effects of cooling and the viscosity difference between the fluid phases causes multiple liquid-vapour front positions, whether or not gravity is considered. The stability analysis has shown that along with the Rayleigh-Taylor (buoyancy- driven) mechanism, a Saffman-Taylor viscous fingering mechanism can also play an important rule in the transition to instability.
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Makris, Aristidis. „The propagation of gaseous detonations in porous media“. Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41700.
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The propagation of a gaseous detonation wave into a porous medium has been studied experimentally and theoretically. The porous medium is composed of inert spheres of equal diameter contained within a detonation tube. The propagation mechanisms were elucidated by means of high-speed Schlieren and open shutter photography of the wave-particle interactions in 2-D obstacle arrays, to simulate the phenomenon in actual porous media. It is found that a Chapman-Jouguet (CJ) detonation can transmit into a porous medium filled with detonable gas and continue to propagate as a quasi-steady combustion wave. There exists a continuous spectrum of averaged combustion wave velocities ($ rm0.3 le V/V sb{CJ} le 1)$ spanning the lean and rich propagation limits and exhibiting a maximum value at the most sensitive composition. A decrease in the particle size of the medium has the effect of narrowing the detonability range and reducing the velocity for a given mixture. It is clearly demonstrated that the propagation phenomenon, and thus the velocity, is governed by the relative length scales of the detonable mixture (critical tube diameter $ rm d sb{c})$ and of the porous medium (average pore size $ rm d sb{p}).$ An empirical correlation was established between the wave velocity (V/V$ sb{CJ})$ and the properties of the system, via the ratio $ rm d sb{c}/d sb{p}.$ The global wave propagation mechanism, for the major part of the possible range of velocities, i.e., $ rm V/V sb{CJ} ge 0.5,$ consists of periodic phases of detonation failure by diffraction around obstacles (i.e., the particles), followed by local reinitiation at detonative Mach stems formed by shock wave-particle interactions. This is essentially identical to the propagation of "quasidetonations" studied by Teodorczyk et al. (1988, 1991), in linear arrangements of obstacles. When local reinitiation of detonation is not possible, ignition transfer in the pores is controlled by the turbulent jetting of hot combustion produc
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Foroutan, Rana. „Intake shape factors for transversely isotropic porous media“. Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29536.
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The study of flow of water through porous medium is important in geotechnical and geoenvironmental engineering. For determining the in situ hydraulic conductivity characteristics of porous media, one of the most convenient and popular methods is the cased borehole technique. In this method, water is allowed to enter the excavated region of the cased borehole inserted into the ground. The rate of rise of water in the casing is then used to estimate the hydraulic conductivity characteristics of the porous medium in the vicinity of the entry point. When the porous medium has isotropic hydraulic conductivity characteristics, the "intake shape factor", which influences the flow rate is solely dependent on the geometrical arrangement of the intake region. When the intake region is located in a porous medium with transversely isotropic hydraulic conductivity characteristics, the flow rate is influenced by both the geometrical characteristics of the intake region and the mismatch in the directional hydraulic conductivity. The objective of the thesis is to investigate certain aspects of water flow in porous geomaterials that display hydraulic anisotropy. The thesis also characterizes the flow rate for entry points that are located in soils with transversely isotropic hydraulic conductivity.This study presents the application of computational procedures, based on finite element techniques, for the determination of the intake characteristics of a cylindrical intake located in a hydraulically transversely isotropic porous medium. Numerical results presented, illustrate the situations where the separate hydraulic conductivities can be estimated by a suitable alteration in the geometrical characteristics of the cylindrical intake. An approximate relationship is developed for estimation of the intake shape factor of cylindrical entry regions without a repeat of detailed finite element computations.
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Narayan, Shankar B. „Measurement of diffusion and adsorption in porous adsorbents“. Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73968.
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Galbraith, Graham H. „Heat and mass transfer within porous building materials“. Thesis, University of Strathclyde, 1992. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21508.
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The thermal and structural performance of building elements can be significantly impaired by the presence of excess moisture. At present, designers have available only simplistic steady-state techniques to predict such effects, for example that presented by Glaser in 1959. These simple models recognise moisture transport in vapour form only and do not allow information on material moisture content to be obtained directly. They are also based on the assumption that the material transport properties are independent of the prevailing environmental conditions, whereas they are in fact complex functions of parameters such as relative humidity. This research has been carried out to develop a set of model equations which account for both liquid and vapour transfer through porous structures, and which enable material moisture content profiles to be produced. The equations generated in this work are transient and enable the effects of moisture and thermal capacity to be considered. An experimental investigation has also been carried out to produce a methodology which can be used to obtain the required material properties. These equations and material properties have been combined with realistic boundary conditions to produce a finite difference model which enables simple wall structures to be analysed in terms of temperature, vapour pressure, relative humidity, moisture content and moisture flow rate. The use of this FORTRAN 77 computer code is illustrated by application to traditional and timber-framed wall constructions. The results illustrate the applicability and flexibility of such an approach and confirm the importance of its further development in the future.
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Corson, Lindsey Thomson. „Geochemical effects on natural convection in porous media“. Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18197.
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We describe a model of buoyancy-driven flow in a saturated reactive porous medium, the porosity and permeability of which evolve through precipitation and dissolution as a mineral is lost or gained from the pore fluid. We consider two scenarios: convection driven solely by solutally induced buoyancy effects with a vertically varying equilibrium solubility, and convection driven by a combination of thermally and solutally induced buoyancy effects where the solubility of the dissolved component depends on the temperature. In both cases we characterise the onset of convection using linear stability analysis, and explore the further development of the coupled reaction-convection system numerically. For solutal convection, at low Rayleigh numbers the effect of the reaction-permeability feedback is shown to be destabilising, while at higher Rayleigh numbers the porosity evolution has a stabilising effect. Over longer timescales, reaction-permeability feedback triggers secondary instabilities in quasi-steady convective circulation, leading to rapid reversals in the direction of circulation. Over very long timescales, characteristic patterns of porosity emerge, including horizontal layering as well as the development of vertical chimneys of enhanced porosity. For thermosolutal convection we find that, when the system is solutally unstable, the behaviour of the system is qualitatively the same as for solutal convection, regardless of whether the system is thermally stable or unstable. However, new, interesting behaviour is seen when the system is solutally stable. The long-term evolution of the porous layer depends on whether the underlying thermal or solutal gradient dominates. When the solutal gradient dominates, the reaction-permeability feedback triggers a secondary instability, resulting in the lateral migration of the concentration and temperature elds and rapid reversals in the direction of circulation. However, when the thermal gradient dominates, the thermal gradient dominates, the reation-permeability feedback tends to suppress the circulation, although it re-emerges after a long quiescent.
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McKenzie, Kimberly. „Skeletal distribution of bisphosphonate after elution from porous implants“. Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86584.
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Skeletal attachment to an implant can be enhanced by locally delivering the bisphosphonate zoledronic acid from an implant. The purpose of this study was to map the skeletal distribution of locally delivered zoledronic acid.A porous tantalum implant coated with hydroxyapatite and 14C-labelled zoledronic acid was implanted into the left femur of three dogs. After one year bone samples were taken from sites near to and distant from the implant. The amount of drug in each sample was determined using liquid scintillation counting and its distribution in peri-implant bone was additionally demonstrated using autoradiography.
All distant skeletal bone samples contained 11.8 ng/g zoledronic acid or less whereas bone immediately adjacent to the implant contained 388 ng/g. There was a 10-fold to 100-fold decrease in zoledronic acid content in bone just 1 or 2 cm away from the implant. Autoradiographs of thin bone-implant sections and bone sections revealed the highest concentration of zoledronic acid within and immediately adjacent to the implant. These data demonstrated for the first time that zoledronic acid eluted from an implant remained mainly local, with minimal systemic distribution.
L'attachement squelettique à un implant peut être amélioré en apportant de l'acide zoledronique de bisphosphonate de façon locale depuis l'implant. Le but de la présente étude était d'évaluer la distribution squelettique de l'acide zoledronique localement généré.
Un implant poreux de tantale enduit d'hydroxyapatite et d'acide 14C zoledronique a été implanté dans le fémur gauche de trois chiens. Après un an, plusieurs échantillons d'os, proches et éloignés de l'implant, ont été prélevés. La quantité de médicament dans chaque échantillon a ensuite été déterminée en utilisant un comptage par scintillation liquide; la distribution dans l'os autour de l'implant a aussi été demontré par autoradiographie.
Tous les échantillons prélevés loin de l'implant contenaient 11.8 ng/g d'acide zoledronique ou moins alors que ceux prélevés immédiatement à côté de l'implant contenaient 388 ng/g. Une diminution de 10 à 100 fois dans la teneur en acide zoledronique a été notée dans l'os situé seulement à 1 ou 2 cm de l'implant. Les autoradiographies des sections minces d'os-implant et des sections d'os ont indiqué que la concentration la plus élevée en acide zoledronique se situait dans l'implant et immédiatement à côté. Ces données démontrent, pour la première fois, que l'acide zoledronique élué d'un implant reste principalement local, avec une distribution systémique minimale.
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Burel, Thomas. „Investigation of smooth contact angle treatment in porous media“. Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30826.
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Some of the key challenges faced in the oil/gas extraction and carbon dioxide injection/storage processes are the presence of complex geometries and the significant effect of the capillary forces which arise at low capillary numbers. Therefore, the contact angle needs to be carefully treated. Mesoscopic techniques such as lattice Boltzmann methods are capable of dealing with lower capillary numbers as compared to the Navier-Stokes solvers, which can also implicitly capture the interface between two fluids. To investigate immiscible two-phase ows at low Reynolds and capillary numbers (Re < 1 and Ca < 1), the colour-fluid model is used i.e. the Rothman-Keller model [1]. This model includes two steps: a perturbation operator from Lishchuk et al [2] (the continuum surface force [3]) or Gunstensen et al [4] approaches and a recolouring operator [5]. However, the lattice Boltzmann implementation employs a Cartesian grid for domain discretisation that is unable to conform with curved surfaces. It misinterprets those curved surfaces as a series of stair-like patterns. On those surfaces, a non-physical contact angle could be defined which may lead to a numerically flooding of the wetting fluid inside the droplet for a non-spreading drop or outside for a spreading droplet. To remove this unphysical behaviour and take into account the flow field effect on the contact angle, interpolation techniques are employed to estimate the real contact angle on the 'stairs' boundaries. We also employ extrapolations to obtain more accurate density on concave corners, thus the grid resolution can be reduced. After the code is numerically validated on static droplets, on droplets deformed under a simple shear, and on simple geometries. Finally, we perform simulations on a Berea sandstone sample [6] to understand dynamics behaviour of immiscible fluids in porous media.
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Du, Xiangdong 1967. „Scaling laws in permeability and thermoelasticity of random media“. Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102973.
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Under consideration is the finite-size scaling of two thermomechanical responses of random heterogeneous materials. Stochastic mechanics is applied here to the modeling of heterogeneous materials in order to construct the constitutive relations. Such relations (e.g. Hooke's Law in elasticity or Fourier's Law in heat transfer) are well-established under spatial homogeneity assumption of continuum mechanics, where the Representative Volume Element (RVE) is the fundamental concept. The key question is what is the size L of RVE? According to the separation of scales assumption, L must be bounded according to d<L<<LMacro where d is the microscale (or average size of heterogeneity), and LMacro is the macroscale of a continuum mechanics problem. Statistically, for spatially ergodic heterogeneous materials, when the mesoscale is equal to or bigger than the scale of the RVE, the elements of the material can be considered homogenized. In order to attain the said homogenization, two conditions must be satisfied: (a) the microstructure's statistics must be spatially homogeneous and ergodic; and (b) the material's effective constitutive response must be the same under uniform boundary conditions of essential (Dirichlet) and natural (Neumann) types.In the first part of this work, the finite-size scaling trend to RVE of the Darcy law for Stokesian flow is studied for the case of random porous media, without invoking any periodic structure assumptions, but only assuming the microstructure's statistics to be spatially homogeneous and ergodic. By analogy to the existing methodology in thermomechanics of solid random media, the Hill-Mandel condition for the Darcy flow velocity and pressure gradient fields was first formulated. Under uniform essential and natural boundary conditions, two variational principles are developed based on minimum potential energy and complementary energy. Then, the partitioning method was applied, leading to scale dependent hierarchies on effective (RVE level) permeability. The proof shows that the ensemble average of permeability has an upper bound under essential boundary conditions and a lower bound under uniform natural boundary conditions.
To quantitatively assess the scaling convergence towards the RVE, these hierarchical trends were numerically obtained for various porosities of random disk systems, where the disk centers were generated by a planar Poisson process with inhibition. Overall, the results showed that the higher the density of random disks---or, equivalently, the narrower the micro-channels in the system---the smaller the size of RVE pertaining to the Darcy law.
In the second part of this work, the finite-size scaling of effective thermoelastic properties of random microstructures were considered from Statistical to Representative Volume Element (RVE). Similarly, under the assumption that the microstructure's statistics are spatially homogeneous and ergodic, the SVE is set-up on a mesoscale, i.e. any scale finite relative to the microstructural length scale. The Hill condition generalized to thermoelasticity dictates uniform essential and natural boundary conditions, which, with the help of two variational principles, led to scale dependent hierarchies of mesoscale bounds on effective (RVE level) properties: thermal expansion strain coefficient and stress coefficient, effective stiffness, and specific heats. Due to the presence of a non-quadratic term in the energy formulas, the mesoscale bounds for the thermal expansion are more complicated than those for the stiffness tensor and the heat capacity. To quantitatively assess the scaling trend towards the RVE, the hierarchies are computed for a planar matrix-inclusion composite, with inclusions (of circular disk shape) located at points of a planar, hard-core Poisson point field. Overall, while the RVE is attained exactly on scales infinitely large relative to microscale, depending on the microstructural parameters, the random fluctuations in the SVE response become very weak on scales an order of magnitude larger than the microscale, thus already approximating the RVE.
Based on the above studies, further work on homogenization of heterogeneous materials is outlined at the end of the thesis.
Keywords: Representative Volume Element (RVE), heterogeneous media, permeability, thermal expansion, mesoscale, microstructure.
Buchteile zum Thema "Porous jump"
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Levy, A., G. Ben-Dor, S. Sorek und J. Bear. „Jump Conditions Across Strong Compaction Waves in Gas-Saturated Rigid Porous Media“. In Shock Waves @ Marseille III, 203–8. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78835-2_34.
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„Analysis of Stress Jump Coefficient at a Fluid/Porous Interface“. In International Conference on Mechanical Engineering and Technology (ICMET-London 2011), 421–25. ASME Press, 2011. http://dx.doi.org/10.1115/1.859896.paper82.
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Nachowitz, Todd. „Identity and Invisibility“. In Indians and the Antipodes, 26–61. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199483624.003.0002.
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Shipping logs reveal that the first Indians to set foot on New Zealand soil were two young lascars from Pondicherry who arrived on a French East India Company ship in 1769—the year that James Cook first visited the country. Indian arrival in New Zealand was, therefore, contemporaneous with first European contact, a fact never before recognized in the extant literature on nation-building. Since then hundreds of Indian sepoys and lascars accompanied British East India Company ships to New Zealand, many going through Australian ports seeking work with sealing expeditions and on timber voyages. In the early nineteenth century, some of the lascars began to jump ship, marry local Maori women and settled down in New Zealand. This chapter argues that Indians in New Zealand can claim a history that goes as far back as the earliest Maori–European (Pakeha) contact.
Konferenzberichte zum Thema "Porous jump"
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Rossian, Lennart, Roland Ewert und Jan Delfs. „Evaluation of Acoustic Jump Conditions at Discontinuous Porous Interfaces“. In 23rd AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2017. http://dx.doi.org/10.2514/6.2017-3505.
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Rossian, Lennart, Benjamin W. Fassmann, Roland Ewert und Jan Delfs. „Prediction of porous trailing edge noise reduction using acoustic jump-conditions at porous interfaces“. In 22nd AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-2920.
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Liu, Fang, Baoming Chen und Li Wang. „Analysis of Stress Jump Condition at a Fluid/Porous Interface“. In ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18366.
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Natural convection in partially porous cavities driven by buoyancy force has been given the attention in this paper. Two-domain model with continuous or discontinuous interfacial conditions and One-equation model with heterogeneous interface region were analyzed. FEM with weak constraint condition was applied to solve the differential governing equations. The influence of stress jump conditions at fluid/porous interface on flow and heat transfer in two-domain model was compared with that of heterogeneous interface region in one-domain model. Numerical results showed that vertical velocity was different near the interface for continuous and discontinuous interfacial conditions. And variation of porosity and permeability in the interface region also lead to difference of vertical velocity. The influence on Nusselt number was slight.
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Valdés-Parada, Francisco J., Benoi^t Goyeau, J. Alberto Ochoa-Tapia und Kambiz Vafai. „Derivation of Complete Jump Boundary Conditions Between Homogeneous Media“. In POROUS MEDIA AND ITS APPLICATIONS IN SCIENCE, ENGINEERING, AND INDUSTRY: 3rd International Conference. AIP, 2010. http://dx.doi.org/10.1063/1.3453846.
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Chen, Hao, Jiabing Wang und Kun Yang. „Analysis of the Momentum Transport Boundary Conditions at a Fluid-Porous Interface“. In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7395.
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The porous composite system is consists of porous medium and free fluid layer, which has extensive industrial applications. The study method for the flow field in the porous composite system includes the microscopic, mesoscopic and macroscopic approaches. When the two-domain approach is adopted, which is one of the macroscopic methods, the momentum transport boundary conditions at the interface between porous medium and free fluid layer is essential to analyze the flow field in the system. When Darcy equation is adopted to describe the flow in porous region, the Beavers-Joseph (BJ) interface condition can be used. When Darcy-Brinkman equation is adopted to describe the flow in porous region, the stress-jump (Ochoa-Tapia & Whitaker: OTW) interface condition can be used. To utilize these interface conditions, the velocity slip coefficient used in the BJ interface condition and the stress-jump coefficient used in the OTW interface condition should be specified. In this paper, a brush configuration is approximately treated as the equivalent porous media in the composite system. A numerical simulation method is used to obtain the microscopic solution for the flow in the system based on the Navier-Stokes equation applied in whole system, and an analytical method is used to obtain the corresponding macroscopic solution based on the two-domain approach. By comparing the microscopic and macroscopic solutions, the velocity slip coefficient and the stress-jump coefficient are determined since they can be treated as adjustable parameters. The influence of different flow types, including Poiseuille flow, Couette flow, and free boundary flow, are investigated. Also the impact of free fluid layer thickness and porous structure on the velocity slip coefficient and the stress-jump coefficient are discussed. The results indicate that, the velocity slip coefficient and the stress-jump coefficient are not only the parameters which depend on the porous structure, but also depend on the thickness of free fluid layer and flow type. When the thickness of free fluid layer is lower than a certain value, the impact of free fluid layer thickness on the velocity slip coefficient and the stress-jump coefficient is much obvious. In addition, when the thickness of free fluid layer is small, these coefficients are found to be dependent on the flow type. However, when the thickness of free fluid layer is large, the stress jump coefficient is independent of the thickness of free fluid layer and the flow type. Thus the stress jump coefficient obtained for a specific case can be used to predict velocity for different flow types and different thickness of free fluid layers.
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Chen, Baoming, Fang Liu, Guoqing Zhang und Zhi Liu. „Influence on Stress Jump Coefficient of Porous Structure and Flow Conditions“. In The 15th International Heat Transfer Conference. Connecticut: Begellhouse, 2014. http://dx.doi.org/10.1615/ihtc15.pmd.009590.
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Chen, Baoming, Li Wang, Fang Liu, Heming Yun und Wenguang Geng. „Effect of Mesoscopic Structure of Interface on Heat and Mass Transfer in a Partially Porous Cavity“. In ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18372.
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Natural convective heat and mass transfer in a cavity partially filled with a vertical porous layer along the left wall was studied in this paper. Different uniform temperature and concentration were specified at the external vertical walls of the cavity while the horizontal walls are adiabatic and impermeable. Two-domain model together with weak constraint method at the porous/fluid interface was used to simulate the flow, heat and mass transfer in the cavity. The shear stress jump condition at the porous/fluid interface is invoked when the Brinkman-Forhheimer-extended Darcy model is used. The mesoscopic structure is homogeneous (the porosity is constant) at the interior region of porous media while the mesoscopic structure changes acutely at the porous/fluid interfacial location. The effect of the mesoscopic structure changes at the porous/fluid interface region on the macroscopic balance is preserved by prescribing the stress jump condition at the interface. This paper focused on the changes of the stress jump coefficients and their influence on heat and mass transfer at the porous/fluid interface.
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de Lemos, Marcelo J. S. „A Model for Turbulent Kinetic Energy Distribution Across the Interface Between a Porous Medium and an Unobstructed Region“. In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56763.
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The study of important environmental and engineering flows can benefit from more realistic modeling. Accordingly, grain storage and drying as well as flows over layers of vegetation can be characterized by some sort of porous structure through which a fluid permeates. For such hybrid media, involving both a porous structure and a clear flow region, difficulties arise due to the proper mathematical treatment given at the macroscopic interface. The literature proposes a jump condition in which shear stresses on both sides of the interface are not of the same value. This paper presents numerical solutions for such hybrid medium, considering here a channel partially filled with a porous layer through which fluid flows in turbulent regime. Here, diffusion fluxes of both momentum and turbulent kinetic energy across the interface present a discontinuity in their values, which is based on a certain jump coefficient. Effects of such jump parameter on mean and turbulence fields around the interface regions are numerically investigated. Results indicate that depending on the value of the stress jump parameter, a substantially different structure for the turbulent field is obtained.
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Peng, Dragon L., Zhimin Du, Baosheng Liang, Zhilin Qi und Wei Wang. „Modeling Two-Phase Flow in Porous Media With Consideration of Jump Interfaces“. In Latin American & Caribbean Petroleum Engineering Conference. Society of Petroleum Engineers, 2007. http://dx.doi.org/10.2118/107233-ms.
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Enright, Ryan, Cormac Eason, Tara Dalton und Todd Salamon. „Transport in Superhydrophobic Microchannels: A Porous Modeling Approach“. In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32823.
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Superhydrophobic surfaces combine roughness features with low energy surfaces to create materials with substantially decreased wettability and reduced drag resistance in laminar flows. These characteristics make superhydrophobic surfaces a promising technology for reducing the flow resistance of microchannels in a variety of applications, including thermal management and biofluidics. The presence of a gas layer that is trapped within the superhydrophobic surface, and which separates the majority of the microchannel wall from the working fluid, gives rise to a low shear-stress region responsible for the observed reduction in flow resistance. Although there have been numerous experimental and computational studies of fluid flow in superhydrophobic microchannels, to our knowledge no predictive analytical model capturing the essential features of the flow has been developed for the case of post-type surface roughness. In this work we propose the use of porous flow theory to predict the behavior of the fully-developed inertia-less flow of a constant viscosity Newtonian fluid in a parallel-plate, super-hydrophobic microchannel whose roughness features are composed of a square array of posts arranged transverse to the flow. The volume-averaged Navier-Stokes (VANS) equation is used to model the flow behavior in both the open and porous regions, taking into account the presence of a recirculating gas layer and the potential for partial liquid penetration into the porous region. The fluid motion in the porous and non-porous regions is coupled by imposing boundary conditions specifying the continuity of velocity and a stress jump at the interface between the two regions. An empirical factor, known as the stress jump coefficient β, appears in the stress jump boundary condition and is shown to be correlated to the geometric properties of the porous region via a scaling law inferred from non-dimensional analysis and observed in 3D computational fluid dynamics simulations. Finally, the predictions of the model are compared with existing experimental studies.