Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
9
2
2006
Endothelial Surface Reorganization: Effects of a Porous Surface Layer
Endothelial cells that constitute the wall of the blood vessels are known to change their shape responding to hydrodynamic shear. The plasma membrane of the endothelial cell is covered with a high-porosity porous macromolecular surface layer [endothelial surface layer (ESL)]. The wavy membrane surface is analyzed to examine effects of the presence of the ESL on the rate of entropy generation (viscous dissipation) due to the viscous flow over the cell, based on the Darcy-Brinkman equation for porous media. The hydrodynamic interactions at the interface between the ESL and the viscous flow as a region of signal generation is found to be sensitive to the porous structure of ESL in terms of the rate of energy dissipation at the cell peak although the total rate of energy dissipation over the entire cell surface remains approximately the same as the case neglecting the hydrodynamic effects of ESL.
Haidong
Liu
Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115
Uichiro
Narusawa
Department of Mechanical, Industrial & Manufacturing Engineering, Northeastern University, Boston, MA 02115, USA
93-107
Effect of Convergence Factors on Flow through Porous Media in Converging Boundaries
Flow behavior through porous media with converging boundaries is analyzed theoretically, and the modifications in the Forchheimer equation needed to incorporate the effect of convergence are brought out. An experimental investigation on the effect of convergence factors on the linear parameter a and nonlinear parameter b was carried out in a convergent flow permeameter, and the influence of convergence factors on the resistance law relating friction factor (fk) and Reynolds number (Rek) using the square root of intrinsic permeability as the characteristic length is examined. In the present case, crushed rock of sizes 3.48 and 4.93 mm were used as media and water as fluid, to study the variation of friction factor and Reynolds number with different ratios of the width and with convergence factors.
BHANU PRAKASHAM REDDY
N
ASSISTANT EXECUTIVE ENGINEER, FORMERLY PROFESSOR OF CIVIL ENGINEERING,NBKRIST,VIDYANAGAR
109-126
Soft Tissue Responses and Attachment to Porous Titanium with Different Surface Characteristics
In this paper, soft tissue responses and attachment strength to porous titanium scaffolds with suitable surface microstructures were studied as a comparison of with and without bonelike apatite on the surface. All of the samples were implanted subcutaneously into the backs of rabbits (n = 7). Forty days and seventy days postoperation, the samples with the surrounding tissues were harvested, respectively. Some of them were used for immediate biomechanical attachment testing and the others for histological observations. Following mechanical testing, the received cross sections were analyzed with scanning electron microscopy with X-ray energy dispersion spectroscopy (SEM-EDX) in order to view the attachment of the tissues to different surfaces. The results showed that the attachment strength of all samples increased with time. The strength of porous titanium coated by bonelike apatite was higher than that of the uncoated one, and the interface integration of the materials/tissue was also better than that of the uncoated sample at both implantation periods.
Yao
Wu
Engineering Research Center in Biomaterials, Sichuan University, Chengdu 610064, P.R. China
Hu
Li
Engineering Research Center in Biomaterials, Sichuan University, Chengdu 610064, P.R. China
Tun
Yuan
Engineering Research Center in Biomaterials, Sichuan University, Chengdu 610064, P.R. China
Chunlin
Deng
Engineering Research Center in Biomaterials, Sichuan University, Chengdu 610064, P.R. China
Bangcheng
Yang
Engineering Research Center in Biomaterials, Sichuan University, Chengdu 610064, P.R. China
Xingdong
Zhang
Engineering Research Center in Biomaterials, Sichuan University, Chengdu 610064, P.R. China
127-134
Effect of Permeability on Steady Flow in a Dendrite Layer
We consider the problem of nonlinear steady convective flow in a horizontal dendrite layer during alloy directional solidification. We analyze the effect of the permeability of the layer on the stationary modes of convection in the form of two-dimensional rolls and three-dimensional patterns. Under a near-eutectic approximation and in the limit of large far-field temperature, we determine the two- and three-dimensional solutions to the weakly nonlinear problem by using a perturbation technique, and the stability of these solutions is investigated with respect to arbitrary three-dimensional disturbances. An inverse form of the permeability function introduces two nonnegative nondimensional parameters K1 and K2 that are significant in the present problem. The results of the analyses in some particular range of values of the magnitude |ε| of the amplitude of convection indicate, in particular, that the effects of K1 and K2 on the flow features can be significant, and different types of flow pattern can become stable for particular values of these two parameters. For sufficiently small and nonzero values of |ε| and K1, the steady flow pattern in the form of subcritical hexagons can be stable. For |ε| beyond some value, and depending on the values of the parameters of the problem, supercritical rolls, squares, or rectangles can be stable. For K1 = 0.0, the only stable flow pattern is that due to steady rolls.
Daniel N.
Riahi
School of Mathematical and Statistical Sciences,
One West University Boulevard, University of Texas Rio Grande Valley, Brownsville, Texas 78520 USA
135-153
A Semi-Lagrangian Level Set Method for Capturing Interfaces in a Porous Medium
This paper presents the simulation of the interface evolution of a tracer in a porous medium by means of an upwind and a semi-Lagrangian level set method. We compare the performance of these methods and conclude that the latter approach allows for a better representation of the interface and can handle complex interface evolutions.
F. D. Moura
Neto
Instituto Politécnico, Universidade do Estado do Rio de Janeiro C. P. 97282, 28601-970, Nova Friburgo, RJ, Brazil
F.
Goncalves
Instituto Politécnico, Universidade do Estado do Rio de Janeiro C. P. 97282, 28601-970, Nova Friburgo, RJ, Brazil
M. Moura
Carmona
Instituto de Matemática Pura e Aplicada, Estrada Dona Castorina, 110, 22460-320, Rio de Janeiro, RJ, Brazil
155-168
Flow Through a High Porosity Medium in the Presence of Radiation
Steady two-dimensional flow of an incompressible and viscous fluid through a high-porosity medium in the presence of heat transfer and radiation is investigated when the thermal conductivity varies linearly with temperature and the porous medium is bounded by a stretching sheet in its own plane with a velocity proportional to the distance from the origin of the sheet. The temperature distribution is found numerically for different parameters of the problem.
A.
Raptis
Department of Mathematics, University of Ioannina, Ioannina 451 10, Greece
C.
Perdikis
Department of Mathematics, University of Ioannina, Ioannina 451 10, Greece
169-175
Curing Time Effect on the Fraction of 137Cs from Cement-Ion Exchange Resins-Bentonite Clay Composition
To assess the safety of disposal of radioactive waste material in cement, curing conditions and time of leaching radionuclides 137Cs have been studied. Leaching tests in cement-ion exchange resins-bentonite matrix were carried out in accordance with a method recommended by IAEA. Curing conditions and curing time prior to commencing the leaching test are critically important in leach studies because the extent of hydration of the cement materials determines how much hydration product develops and whether it is available to block the pore network, thereby reducing leaching. Incremental leaching rates Rn (cm/d) of 137Cs from cement-ion exchange resins-bentonite matrix after 180 days were measured. The results presented in this paper are examples of results obtained in a 20 yr concrete testing project that will influence the design of the engineer trenches system for future central Serbian radioactive waste storing centers.
Ilija
Plecas
VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro
Slavko
Dimovic
VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro
177-180
Immobilization of 137Cs and 60Co in Concrete Matrix
To assess the safety for disposal of radioactive waste-cement composition, the leaching of 137Cs and 60Co, from a waste composite into a surrounding fluid has been studied. Leaching tests were carried out in accordance with a method recommended by IAEA. Determination of retardation factors KF and coefficients of distribution kd, using a simplified mathematical model for analyzing the migration of radionuclides, has been developed. In our experiment, we have analyzed mechanism of 137Cs and 60Co leaching values during a period of 60 days. Results presented in this paper are examples of results obtained in a 25 yr mortar and concrete testing project, which will influence the design of the engineered trenches system for a future central Serbian radioactive waste storage center.
Ilija
Plecas
VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro
Slavko
Dimovic
VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro
181-184