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Porous Solid (porous + solid)

Distribution by Scientific Domains

Polymers and Materials Science	27%
Mathematics and Statistics	27%
Engineering	27%

Selected Abstracts

Bifurcated Mechanical Behavior of Deformed Periodic Porous Solids

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2009
Srikanth Singamaneni
Abstract The transformation of periodic microporous structures fabricated by interference lithography followed by their freezing below glass transition is described. Periodic porous microstructures subjected to internal compressive stresses can undergo sudden structural transformation at a critical strain. The pattern transformation of collapsed pores is caused by the stresses originated during the polymerization of acrylic acid (rubbery component) inside of cylindrical pores and the subsequent solvent evaporation in the organized microporous structure. By confining the polymerization of acrylic acid to localized porous areas complex microscopic periodic structures can be obtained. The control over the mechanical instabilities in periodic porous solids at a sub-micron scale demonstrated here suggests the potential mechanical tunability of photonic, transport, adhesive, and phononic properties of such periodic porous solids. [source]

Modeling fluid saturated porous media under frost attack

GAMM - MITTEILUNGEN, Issue 1 2010
Tim Ricken
Abstract Freezing and thawing are important processes in civil engineering. On the one hand frost damage of porous building materials like road pavements and concrete in regions with periodical freezing is well known. On the other hand, artificial freezing techniques are widely used, e.g. for tunneling in non-cohesive soils and other underground constructions as well as for the protection of excavation and compartmentalization of contaminated tracts. Ice formation in porous media results from a coupled heat and mass transport and is accompanied by the ice expansion. The volume increase in space and time is assigned to the moving freezing front inside the porous solid. In this paper, a macroscopic ternary model is presented within the framework of the Theory of Porous Media (TPM) in view of the description of phase transition. For the mass exchange between ice and water an evolution equation based on the local balance of the heat flux vector is used. Examples illustrate the application of the model for saturated porous solids under thermal loading (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Modelling radiation and moisture content in fire spread

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 9 2007
L. Ferragut
Abstract A numerical method is developed for fire spread simulation modelling. The model is a two-dimensional one which takes into account moisture content and radiation. We consider the combustion of a porous solid, where a simplified energy conservation equation is applied. The effect of the vegetation moisture and endothermic pyrolysis is incorporated in the model by means of a multivalued function representing the enthalpy. Some of the three-dimensional effects are incorporated in the model, i.e. heat losses in the vertical direction and non-local radiation from the flame above the vegetal layer. Also the radiation model allows to cope with wind and slope effects. The approximate solution is obtained using a finite element method. A semi-implicit Euler algorithm in time is applied. The resolution of the multivalued operator is done using the Yosida approximation of a perturbed multivalued operator. The characteristic method combined with a discrete ordinate method is used to solve the radiation equation. Finally, several representative examples are solved and compared with experimental data. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Prediction of gas sorption kinetics for porous media using MRI

AICHE JOURNAL, Issue 9 2006
Matthew J. Watt-Smith
Abstract Diffusion and reaction within porous media involving condensable vapors are important processes in catalysis, fuel cells, and membrane separations. In this work, 3-D maps of the spatial variation of porosity, pore size and network tortuosity within a porous solid, derived from magnetic resonance images, have been used to construct a structural model for a mesoporous catalyst pellet. Simulations of the kinetic uptake, adsorption and capillary condensation of butane vapor within the porous solid, conducted on the structural model, have successfully predicted experimental measurements of the effects of the onset of capillary condensation on mass transfer rates without the need of the various adjustable parameters prevalent in other models. These findings suggest that accurate mathematical models for both the complex void space of the porous medium, and the mass transport processes taking place within it, have been successfully developed. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

Diffusion in poro-plastic media

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2004
R. E. Showalter
Abstract A model is developed for the flow of a slightly compressible fluid through a saturated inelastic porous medium. The initial-boundary-value problem is a system that consists of the diffusion equation for the fluid coupled to the momentum equation for the porous solid together with a constitutive law which includes a possibly hysteretic relation of elasto-visco-plastic type. The variational form of this problem in Hilbert space is a non-linear evolution equation for which the existence and uniqueness of a global strong solution is proved by means of monotonicity methods. Various degenerate situations are permitted, such as incompressible fluid, negligible porosity, or a quasi-static momentum equation. The essential sufficient conditions for the well-posedness of the system consist of an ellipticity condition on the term for diffusion of fluid and either a viscous or a hardening assumption in the constitutive relation for the porous solid. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Modeling of a Constrained Porous Material with an Inclusion

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
Pasquale Giovine Prof. Dr.
A recently developed theory allows to describe a porous solid with very large lacunae partially, or totally, filled by a uid inclusion like an atypical immiscible mixture which consists of a solid with an ellipsoidal microstructure and of a classical fluid. Here we investigate the condition of saturation when the fluid inclusion is incompressible. [source]

Modeling fluid saturated porous media under frost attack

Bifurcated Mechanical Behavior of Deformed Periodic Porous Solids

Computational homogenization of uncoupled consolidation in micro-heterogeneous porous media

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2010
Fredrik Larsson
Abstract Variationally consistent homogenization is exploited for the analysis of transient uncoupled consolidation in micro-heterogeneous porous solids, whereby the classical approach of first-order homogenization for stationary problems is extended to transient problems. Homogenization is then carried out in the spatial domain on representative volume elements (RVE), which are introduced in quadrature points in standard fashion. Along with the classical averages, a higher-order conservation quantity is obtained. An iterative FE2 -algorithm is devised for the case of nonlinear permeability and storage coefficients, and it is applied to pore pressure changes in asphalt-concrete (particle composite). Various parametric studies are carried out, in particular, with respect to the influence of the ,substructure length scale' that is represented by the size of the RVE's. Copyright © 2009 John Wiley & Sons, Ltd. [source]

An investigation of the mechanisms of ultrasonically enhanced desorption

AICHE JOURNAL, Issue 2 2007
Oualid Hamdaoui
Abstract In this work, the mechanisms underlying ultrasonic desorption of 4-chlorophenol from granular activated carbon have been explored. Desorption experiments are investigated in the absence and presence of 516 kHz ultrasound of different intensities. Using three regenerating solutions and two temperatures, it has been shown that ultrasonic irradiation considerably improves both the amount and the rate of desorption. Desorption increases with increasing temperature and ultrasound intensity. The addition of sodium hydroxide or a mixture of sodium hydroxide and ethanol to the regenerating medium leads to an enhancement of the desorption, especially in the presence of ultrasound. The mechanisms of ultrasonically enhanced desorption is due both to the thermal and non-thermal (hydrodynamical) effects of ultrasound. Hydrodynamical phenomena are principally produced by the acoustic vortex microstreaming within porous solids as well as at the solid-liquid interface and by the high-speed micro-jets and high-pressure shock waves produced by acoustic cavitation. The thermal effects are evaluated as localized hot spots formed when bubbles cavitated as well as by global heating of the medium and piezoelectric transducer heating-up. Additionally, the non-thermal effect of ultrasound is greater than the thermal effect, and it is more noticeable when the ultrasonic irradiation is carried out in a high temperature regenerating medium. © 2007 American Institute of Chemical Engineers AIChE J 2007 [source]

Flow Kinetics in Porous Ceramics: Understanding with Non-Uniform Capillary Models

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2007
Debdutt Patro
The present work describes the development of a two-parameter non-uniform capillary model to describe kinetics of flow in porous solids with complex tortuous varying paths. Experimentally, the rate of fluid flow in such a non-uniform capillary is found to be orders of magnitude slower compared with a corresponding average uniform capillary. This slow rate is explained in terms of an extremely small ,effective' hydrodynamic radius. The origin of such an ,unphysical' radius is rationalized based on geometrical considerations and effective driving forces for flow through a stepped capillary. Infiltration rate parameters are derived from the geometry of the porous medium for both wetting and non-wetting conditions. [source]