scholarly journals Dynamics of osmosis in a porous medium

2014 ◽  
Vol 1 (3) ◽  
pp. 140352 ◽  
Author(s):  
Silvana S. S. Cardoso ◽  
Julyan H. E. Cartwright
Keyword(s):  
Porous Medium ◽  
Permeability Coefficient ◽  
Driving Forces ◽  
Pore Space ◽  
Solute Permeability ◽  
Empirical Relations ◽  
Solvent Molecules ◽  
Semi Empirical ◽  
Osmotic Effects ◽  
Solute Permeability Coefficient

We derive from kinetic theory, fluid mechanics and thermodynamics the minimal continuum-level equations governing the flow of a binary, non-electrolytic mixture in an isotropic porous medium with osmotic effects. For dilute mixtures, these equations are linear and in this limit provide a theoretical basis for the widely used semi-empirical relations of Kedem & Katchalsky (Kedem & Katchalsky 1958 Biochim. Biophys. Acta 27 , 229–246 ( doi:10.1016/0006-3002(58)90330-5 ), which have hitherto been validated experimentally but not theoretically. The above linearity between the fluxes and the driving forces breaks down for concentrated or non-ideal mixtures, for which our equations go beyond the Kedem–Katchalsky formulation. We show that the heretofore empirical solute permeability coefficient reflects the momentum transfer between the solute molecules that are rejected at a pore entrance and the solvent molecules entering the pore space; it can be related to the inefficiency of a Maxwellian demi-demon.

Differential action of plasma and albumin on transcapillary exchange of anionic solute

1993 ◽  
Vol 264 (5) ◽  
pp. H1428-H1437 ◽  
Author(s):  
V. H. Huxley ◽  
F. E. Curry ◽  
M. R. Powers ◽  
B. Thipakorn
Keyword(s):  
Reflection Coefficient ◽  
Permeability Coefficient ◽  
Protein Composition ◽  
Solvent Drag ◽  
Solute Permeability ◽  
Charge Selectivity ◽  
Microvessel Wall ◽  
Solute Permeability Coefficient ◽  
Differential Action ◽  
Alpha Lactalbumin

We tested two hypotheses to account for the reduction in coupling of anionic solute to water flow (solvent drag) in microvessels during perfusion with plasma compared with albumin. Solvent drag is determined by both hydraulic conductivity (Lp) and solute reflection coefficient (sigma). Accordingly, decreased solvent drag during plasma perfusion must be the result of an increase in sigma (hypothesis 1) or reduction of Lp (hypothesis 2) or some combination of both mechanisms. These hypotheses were assessed by measuring Lp, sigma, and diffusive solute permeability (Psd) to the anionic protein alpha-lactalbumin in frog mesenteric exchange microvessels during plasma or albumin perfusion. The solute permeability coefficient to alpha-lactalbumin (Ps alpha-lactalbumin) was lower during exposure to plasma than bovine serum albumin (BSA) [(Ps alpha-lactalbumin)plasma/(Ps alpha-lactalbumin)BSA = 0.31 +/- 0.11 (means +/- SE, n = 9)]. Solute reflection coefficient to alpha-lactalbumin (sigma alpha-lactalbumin) was 0.69 +/- 0.02 in plasma and 0.34 +/- 0.03 in BSA (n = 7). Lp was not significantly influenced by perfusate protein composition (Lp plasma/Lp BSA = 1.02 +/- 0.11; n = 20). These data lead to the conclusion that the actions of plasma are to confer charge selectivity for anionic solute and, to a lesser extent, modify the porous pathways of the microvessel wall. Taken together, these results indicate that porous pathways contribute significantly to macromolecular flux in plasma-perfused vessels.

Modulation of microvessel wall charge by plasma glycoprotein orosomucoid

1989 ◽  
Vol 257 (5) ◽  
pp. H1354-H1359 ◽  
Author(s):  
F. E. Curry ◽  
J. C. Rutledge ◽  
J. F. Lenz
Keyword(s):  
Permeability Coefficient ◽  
Net Charge ◽  
Solute Permeability ◽  
Stokes Radius ◽  
Plasma Glycoprotein ◽  
Albumin Clearance ◽  
Wall Charge ◽  
Microvessel Wall ◽  
Solute Permeability Coefficient ◽  
Alpha Lactalbumin

Haraldsson and Rippe suggested that the circulating glycoprotein orosomucoid (alpha 1-acid glycoprotein) contributes to the net charge on microvessel walls (Acta Physiol. Scand. 129: 127-135, 1987). We tested their hypothesis in individually perfused microvessels of frog mesentery by measuring solute permeability coefficients of two globular proteins (alpha-lactalbumin and ribonuclease) having approximately the same size (Stokes radius, 2 nm) but different charge (-11 and +3, respectively). In vessels perfused with orosomucoid (0.1 and 1 mg/ml) in a Ringer-albumin perfusate, the solute permeability coefficient of alpha-lactalbumin decreased to one-half [0.47 +/- 0.25 (SD)] the value in the absence of orosomucoid, and the solute permeability coefficient of ribonuclease was close to six times as large as alpha-lactalbumin permeability. Both results may be accounted for if orosomucoid increases the net negative charge on microvessel walls in frog mesentery from 11.2 to 28 meq/l. A similar change in microvessel charge would be more than sufficient to account for the decrease in albumin clearance in the presence of orosomucoid reported by Haraldsson and Rippe in rat muscle microvessels.

Interaction Between Two Closely Spaced Azimuthing Thrusters

1998 ◽  
Vol 42 (01) ◽  
pp. 15-32 ◽  
Author(s):  
Paul Brandner ◽  
Martin Renilson
Keyword(s):  
Mathematical Model ◽  
Satisfactory Agreement ◽  
Vehicle Dynamics ◽  
Operating Conditions ◽  
Towing Tank ◽  
Empirical Relations ◽  
Series Of Experiments ◽  
Flow Effects ◽  
Semi Empirical

To assist in predicting the performance of omni-directional propelled vehicles a series of experiments has been conducted to measure the interaction between two closely spaced ductedazimuthing thrusters. The thrusters were tested below a shallow draft ground board in a towing tank at a spacing of approximately 2 propeller diameters. Measurements were made of forces acting on a single thruster for a range of operating conditions and similarly on two thrusters for a range of relative positions. The results show that forces from the trailing thruster are heavily affected by interaction, particularly due to impingement of the race from the leading thruster, where as forces from the leading thruster remain essentially unaffected despite its proximity to the trailing thruster. A semi-empirical mathematical model suitable for simulation of omni-directional vehicle dynamics is presented. The model is based on the trajectory of the race from the leading thruster derived from momentum considerations with additional empirical relations to account for other more minor flow effects. Comparison of the predicted and measured results show satisfactory agreement.

The air permeability of composite fiber material

2021 ◽  
Vol 1 ◽  
pp. 42-48
Author(s):  
T. A. Leshchenko ◽  
◽  
N. V. Chernousova ◽  
A. V. Dedov ◽  
◽  
...  
Keyword(s):  
Composite Materials ◽  
Permeability Coefficient ◽  
Pore Space ◽  
Fiber Material ◽  
Composite Fiber ◽  
Air Permeability ◽  
Rubber Content ◽  
Limited Mobility ◽  
Fibrous Matrix ◽  
Composite Fiber Material

The air permeability of composite materials obtained by impregnating a non-woven needle-punched cloth with latex was investigated. The permeability of composite materials with different rubber content was estimated by the coefficient of air permeability at a pressure drop of 49 and 100 Pa. The dependence of the air permeability coefficient on the degree of impregnation of the fabric showed that at 15 – 20 % of the rubber content, the maximum air permeability coefficient is observed, and when the degree of impregnation increases, the air permeability coefficient decreases. The process of forming a porous structure of composite materials and its influence on air transport is considered. The increase of the coefficient of permeability is explained by the fixation of the fibers of the surface layer with limited mobility under the action of air flow, and a reduction in the coefficient of air permeability by reducing pore space and an increase in fiber matrix composite materials in the process of sushi-Ki-impregnated material. The air permeability of composite materials is determined by the ratio between the processes of increasing the volume of the fibrous matrix and reducing porosity when filling the space between the portages with rubber particles. A model is proposed for calculating the coefficient of breathability of composite materials of known density.

scholarly journals The transport of liquids in softwood: timber as a model porous medium

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
H. C. Burridge ◽  
G. Wu ◽  
T. Reynolds ◽  
D. U. Shah ◽  
R. Johnston ◽  
...  
Keyword(s):  
Experimental Data ◽  
Porous Medium ◽  
Fluid Flow ◽  
Transport Properties ◽  
Pore Space ◽  
Construction Material ◽  
Sustainable Construction ◽  
Natural Material ◽  
Full Potential ◽  
Treatment Processes

AbstractTimber is the only widely used construction material we can grow. The wood from which it comes has evolved to provide structural support for the tree and to act as a conduit for fluid flow. These flow paths are crucial for engineers to exploit the full potential of timber, by allowing impregnation with liquids that modify the properties or resilience of this natural material. Accurately predicting the transport of these liquids enables more efficient industrial timber treatment processes to be developed, thereby extending the scope to use this sustainable construction material; moreover, it is of fundamental scientific value — as a fluid flow within a natural porous medium. Both structural and transport properties of wood depend on its micro-structure but, while a substantial body of research relates the structural performance of wood to its detailed architecture, no such knowledge exists for the transport properties. We present a model, based on increasingly refined geometric parameters, that accurately predicts the time-dependent ingress of liquids within softwood timber, thereby addressing this long-standing scientific challenge. Moreover, we show that for the minimalistic parameterisation the model predicts ingress with a square-root-of-time behaviour. However, experimental data show a potentially significant departure from this $$\sqrt{{\boldsymbol{t}}}$$t behaviour — a departure which is successfully predicted by our more advanced parametrisation. Our parameterisation of the timber microstructure was informed by computed tomographic measurements; model predictions were validated by comparison with experimental data. We show that accurate predictions require statistical representation of the variability in the timber pore space. The collapse of our dimensionless experimental data demonstrates clear potential for our results to be up-scaled to industrial treatment processes.

Graded modulation of frog microvessel permeability to albumin using ionophore A23187

1990 ◽  
Vol 258 (2) ◽  
pp. H587-H598 ◽  
Author(s):  
F. E. Curry ◽  
W. L. Joyner ◽  
J. C. Rutledge
Keyword(s):  
Endothelial Cells ◽  
Permeability Coefficient ◽  
Ionophore A23187 ◽  
Solvent Drag ◽  
Solute Permeability ◽  
Fibrous Matrix ◽  
Microvessel Permeability ◽  
Quantitative Fluorescence ◽  
Peak Value ◽  
Sustained Increase

We investigated the exchange of water and macromolecules across venular microvessels after permeability was increased. Quantitative fluorescence microscopy was used to measure albumin permeability coefficients in individually perfused microvessels of decerebrate frogs. Control permeability coefficient was 2.3 +/- 0.25 X 10(-7) cm/s. Solvent drag increased the apparent solute permeability coefficient (Ps) by 0.57 +/- 0.05 X 10(-7) cm/s for each cmH2O increase in microvessel pressure. The divalent cation ionophore A23187 (0.1–5 microM) produced a transient increase in Ps to a peak value (within 1–3 min), followed (after 4–8 min) by a sustained increase in permeability (16–34% of peak values). Peak values of Ps were 13 and 80 times control for 0.1 and 5 microM A23187, respectively. Both diffusion and solvent drag contributed to the sustained increase in Ps. The equivalent pore radius of the structures determining diffusion and solvent drag was less than or equal to 25 nm during the sustained increase in permeability, smaller than observed gaps between adjacent endothelial cells. The basement membrane and a fibrous matrix secreted by endothelial cells into the gaps may offer resistance to exchange in the high permeability state.

An Experimental Data Based Correction Method of Biomass Gasification Equilibrium Modeling

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
L. Damiani ◽  
A. Trucco
Keyword(s):  
Experimental Data ◽  
Gas Flow ◽  
Biomass Gasification ◽  
Correction Method ◽  
Solid Product ◽  
Gasification Process ◽  
Empirical Relations ◽  
Semi Empirical ◽  
Main Operating ◽  
Equilibrium Simulation

This paper presents a modified equilibrium simulation model for biomass gasification performance prediction. The model, implemented in the MATLAB-SIMULINK® environment, is able to calculate the reactor main operating parameters such as reaction temperature, gas composition, gas flow rate and solid product (typically charcoal). The comparison of model output with experimental data puts in evidence the insufficient precision of equilibrium models due to their incapability of taking into account the nonequilibrium effects always present in the gasification process. To obtain a better prediction of measured values, the pure equilibrium model has been modified on the basis of literature experimental data, introducing semi-empirical relations with the aim to consider the most meaningful effects of nonequilibrium. The results demonstrate that this modification leads to an increased precision of the model in reproducing experimental data.

Effets de la texture petrographique sur les proprietes petrophysiques d'un calcaire en zone de diagenese meteorique (calcaire oligocene d'Aquitaine, France)

2000 ◽  
Vol 171 (4) ◽  
pp. 419-430 ◽  
Author(s):  
Adrian Cerepi ◽  
Louis Humbert ◽  
Rene Burlot
Keyword(s):  
Porous Medium ◽  
Specific Surface ◽  
Pore Space ◽  
Space Complexity ◽  
Petrophysical Properties ◽  
Chemical Analyses ◽  
Reservoir Properties

Abstract 120 samples of three quarries of the Oligocene Aquitaine limestone were subjected to petrographic, petrophysical and chemical analyses. Strong variations of depositional and diagenetic textures were observed. Four main depositional textures characterize this limestone: mudstone-wackestone, packstone, packstone-grainstone and grainstone. The diagenetic transformations recognized and specially meteoric leaching increases the heterogeneity of porous medium. The "Pierre de Bordeaux" shows a high variation of porosity (12,8 % to 42,51%), permeability (4,27 to 4755 mD), specific surface (0,78 to 3,73 m 2 /g) and distribution of pore throats (from monomodal to three modal distribution). Petrophysical properties depend strongly on depositional and diagenetic patterns. Textures with two and three modal distribution of porous medium, packstone-grainstone and grainstone have the best reservoir properties. The meteoric dissolution associated to microfracturing improves strongly both the macroporosity, permeability in mudstone-wackestone and packstone and increases the pore space complexity in all textures.

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