Network model for hydraulic conductivity of sand-bentonite mixtures

2004 ◽  
Vol 41 (4) ◽  
pp. 698-712 ◽  
Author(s):  
Tarek Abichou ◽  
Craig H Benson ◽  
Tuncer B Edil
Keyword(s):  
Hydraulic Conductivity ◽  
Unit Area ◽  
Network Models ◽  
Element Model ◽  
Sand Particle ◽  
Particle Interactions ◽  
One Dimensional ◽  
Flow Through ◽  
Sand Particles ◽  
The Relationship

A network formulation was used to model the hydraulic conductivity of sand–bentonite mixtures (SBMs) as a function of bentonite content. The sand particles were assumed to be spheres, and their arrangement was defined using a discrete element model simulating sand particle interactions. Pores between the spheres were approximated as a network of straight capillary tubes. The space defined by the spheres was divided into a collection of neighboring tetrahedrons, and the geometry of the tetrahedrons was used to define tube diameters and lengths in the network. Hydraulic heads throughout the network were computed by solving a system of equations describing flow through the tubes. Hydraulic conductivity of the network was calculated as the rate of flow per unit area for a given network of tubes driven by a one-dimensional hydraulic gradient. Bentonite was introduced into the network in several schemes to simulate SBMs. SBMs prepared with powdered bentonite were modeled as a packing of sand, where the sand particles are coated with bentonite (grain coating model and pipe blocking model), whereas SBMs prepared with granular bentonite were modeled as a packing of sand with bentonite occupying pores between the sand particles (junction blocking model). The relationship between hydraulic conductivity and bentonite content obtained from the grain coating model was similar to that measured on sand – powdered bentonite mixtures. A comparable relationship was also obtained for hydraulic conductivities predicted with the junction blocking model using a size-based filling approach and hydraulic conductivities measured on sand – granular bentonite mixtures.Key words: sand–bentonite mixtures, network models, hydraulic conductivity, degree of bentonation, bentonite distribution.

SHOCK PROPAGATION IN A FLOW THROUGH DEFORMABLE POROUS MEDIA: ASYMPTOTIC BEHAVIOUR AS THE POROSITY APPROXIMATES A CONSTANT

2007 ◽  
Vol 17 (08) ◽  
pp. 1261-1278
Author(s):  
ELENA COMPARINI ◽  
MAURA UGHI
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Hydraulic Conductivity ◽  
Asymptotic Behaviour ◽  
Incompressible Flow ◽  
Shock Propagation ◽  
One Dimensional ◽  
Deformable Porous Media ◽  
Flux Intensity ◽  
Flow Through

We consider a one-dimensional incompressible flow through a porous medium undergoing deformations such that the porosity and the hydraulic conductivity can be considered as functions of the flux intensity. We prove that if one approximates the porosity with a constant then the solution of the hyperbolic problem converges to the classical continuous Green–Ampt solution, also in the presence of shocks. In general, however, the shocks remain present in any approximating solution.

Empirical Equations Jor the Thrust Generated by an Ideal Supersonic Nozzle

1957 ◽  
Vol 61 (564) ◽  
pp. 830-831
Author(s):  
P. N. Rowe
Keyword(s):  
Supersonic Flow ◽  
Pressure Ratio ◽  
Supersonic Nozzle ◽  
Empirical Equations ◽  
One Dimensional ◽  
Dimensional Flow ◽  
Flow Through ◽  
Image Position ◽  
The Relationship

The dimensionless thrust generated by supersonic flow through a convergent-divergent nozzle is given by Ref. 1,1which takes its optimum value, bmax when pe = pa.For ideal one-dimensional flow, the relationship between Ae and pe is given by2and the optimum dimensionless thrust by3Where4From equations (2) and (3), the constant D in equation (1) can be evaluated and thence the thrust of an ideal nozzle at any pressure ratio provided that no separation occurs.Equations (2) and (3) are tedious to evaluate and it is not easy to estimate the effect of changes in γ.

Calculation of ceramic pot filter hydraulic conductivity using falling-head data

2011 ◽  
Vol 11 (3) ◽  
pp. 358-363 ◽  
Author(s):  
A. C. Elmore ◽  
W. G. Fahrenholtz ◽  
L. G. Glauber ◽  
A. N. Sperber
Keyword(s):  
Hydraulic Conductivity ◽  
Open Porosity ◽  
Production Efficiency ◽  
Lower Cost ◽  
Pore Space ◽  
Porous Media Equations ◽  
Side Walls ◽  
Flow Through ◽  
The Impact ◽  
The Relationship

Flowrate is used as a predictor of ceramic pot filter (CPF) disinfection effectiveness, and the relationship between flowrate and porosity has been examined in several studies. However, hydraulic conductivity, not porosity, is the constant of proportionality that describes flow through porous media. Equations have been developed to estimate the hydraulic conductivity of CPF side walls and bottom as well an effective overall hydraulic conductivity. The equations are intended to be used with falling head data that may be collected in the field. The results of flowrate testing and open porosity testing using experimental CPFs provide preliminary indication that hydraulic conductivity is a better predictor of flowrate relative to open porosity. The results of the preliminary testing suggest that the shape and orientation of open pore space may have significant impact on filter flowrates, and that filter researchers and producers may want to evaluate the material used to form the pores as well as the impact of the filter formation process on any spatial orientation of open pore space. A better understanding of hydraulic conductivity may improve the production efficiency of filter factories which could make lower cost filters available to a greater number of households in developing areas.

On the validity of the theory of flow in saturated swelling materials

Soil Research ◽  
1976 ◽  
Vol 14 (3) ◽  
pp. 389 ◽  
Author(s):  
DE Smiles
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Transient Flow ◽  
Initial Water Content ◽  
Approximate Theory ◽  
Initial Water ◽  
One Dimensional ◽  
Physically Based ◽  
Conductivity Water ◽  
The Relationship

Recently there has been concern that the reorientation of particles during transient flow of water in a saturated swelling material might result in the hydraulic conductivity and capillary potential not being well-defined functions of the water content. If this were the case, the conventional theory of one-dimensional liquid flow in these materials would be invalid. This paper shows that the hydraulic-conductivity/water-content relationship calculated using physically based approximate theory applied to outflow data obtained from red mud, is single-valued and independent of initial water content. Furthermore, the relationship permits recalculation, using a correct iterative procedure, of the data from which it was derived. It is concluded that the data provide no evidence to reject the theory, and that particle reorientation, if it occurs, is parametrized by the water content.

Radiation Damage, Contrast and Statistics in High Resolution Biological Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 260-261
Author(s):  
Robert M. Glaeser
Keyword(s):  
High Resolution ◽  
Particle Flux ◽  
Unit Area ◽  
Signal To Noise ◽  
Resolution Image ◽  
High Resolution Image ◽  
Pass Through ◽  
Counting Statistics ◽  
The Relationship ◽  
Picture Element

It is well known that a large flux of electrons must pass through a specimen in order to obtain a high resolution image while a smaller particle flux is satisfactory for a low resolution image. The minimum particle flux that is required depends upon the contrast in the image and the signal-to-noise (S/N) ratio at which the data are considered acceptable. For a given S/N associated with statistical fluxtuations, the relationship between contrast and “counting statistics” is s131_eqn1, where C = contrast; r2 is the area of a picture element corresponding to the resolution, r; N is the number of electrons incident per unit area of the specimen; f is the fraction of electrons that contribute to formation of the image, relative to the total number of electrons incident upon the object.

IMPROVEMENT OF SPRING DURUM WHEAT SELECTION METHODOLOGIES UNDER CLIMATE CHANGE CONDITIONS

1970 ◽  
pp. 33-36
Author(s):  
А. I. Grabovets ◽  
V. P. Kadushkina ◽  
S. А. Kovalenko
Keyword(s):  
Grain Yield ◽  
Durum Wheat ◽  
Correlation Coefficient ◽  
Harvest Index ◽  
Unit Area ◽  
Correlation Coefficients ◽  
Chemical Mutagenesis ◽  
Main Method ◽  
The Relationship ◽  
Selection Of

With the growing aridity of the climate on the Don, it became necessary to improve the methodology for conducting the  breeding of spring durum wheat. The main method of obtaining the source material remains intraspecific step hybridization. Crossings were performed between genetically distant forms, differing in origin and required traits and properties. The use of chemical mutagenesis was a productive way to change the heredity of genotypes in terms of drought tolerance. When breeding for productivity, both in dry years of research and in favorable years, the most objective markers were identified — the size of the aerial mass, the mass of grain per plant, spike, and harvest index. The magnitude of the correlation coefficients between the yield per unit area and the elements of its structure is established. It was most closely associated with them in dry years, while in wet years it decreased. Power the correlation of the characteristics of the pair - the grain yield per square meter - the aboveground biomass averaged r = 0.73, and in dry years it was higher (0.91) than in favorable ones (0.61 - 0.70) , between the harvest and the harvest index - r = 0.81 (on average). In dry years, the correlation coefficient increased to 0.92. Research data confirms the greatest importance of the mass of grain from one ear and the plant in the formation of grain yield per unit area in both dry and wet years. In dry years, the correlation coefficient between yield and grain mass per plant was on average r = 0.80; in favorable years, r = 0.69. The relationship between yield and grain mass from the ear was greater — r = 0.84 and r = 0.82, respectively. Consequently, the breeding significance of the aboveground mass and the productivity of the ear, as a criterion for the selection of the crop, especially increases in the dry years. They were basic in the selection.

Certain Problems with the Application of Stochastic Diffusion Processes for the Description of Chemical Engineering Phenomena. Stochastic Model of Non-Isothermal Flow Chemical Reactor

1996 ◽  
Vol 61 (2) ◽  
pp. 242-258 ◽  
Author(s):  
Vladimír Kudrna ◽  
Libor Vejmola ◽  
Pavel Hasal
Keyword(s):  
Stochastic Model ◽  
Chemical Engineering ◽  
Diffusion Processes ◽  
Dispersion Model ◽  
Chemical Reactor ◽  
Segregation Index ◽  
One Dimensional ◽  
A Value ◽  
Isothermal Case ◽  
Flow Through

Recently developed stochastic model of a one-dimensional flow-through chemical reactor is extended in this paper also to the non-isothermal case. The model enables the evaluation of concentration and temperature profiles along the reactor. The results are compared with the commonly used one-dimensional dispersion model with Danckwerts' boundary conditions. The stochastic model also enables to evaluate a value of the segregation index.

‘Each Song Was Just Like a Little Sermon’

2018 ◽  
Author(s):  
Isaac Land
Keyword(s):  
Nineteenth Century ◽  
Golden Age ◽  
Military Training ◽  
One Dimensional ◽  
National Pride ◽  
Recent Scholarship ◽  
The Relationship

This chapter is central to the volume’s chronological contentions, as its argument accounts for the specialized, one-dimensional Dibdin of ‘Tom Bowling’ that has endured into recent scholarship. Focusing on Dibdin’s posthumous reception, it examines the moral and rhetorical difficulties of repackaging Dibdin’s works for a Victorian sensibility; it explores the specifics of mid-century concert culture previously highlighted by Derek Scott and William Weber as central to changes in nineteenth-century taste and programming; and it develops the theme of nostalgia into a revelatory consideration of the relationship between new naval technologies, national pride, and military training, and the songs, people, and language of a remembered Napoleonic ‘golden age’—to which Dibdin proves to have been as central, in the Victorian imagination, as Nelson.

Effect of mechanical restraint on the rate of corrosion in concrete

1998 ◽  
Vol 25 (1) ◽  
pp. 81-86 ◽  
Author(s):  
N Hearn ◽  
J Aiello
Keyword(s):  
Mix Design ◽  
Concrete Repair ◽  
Accelerated Corrosion ◽  
One Dimensional ◽  
Mechanical Restraint ◽  
Corrosion Rates ◽  
Accelerated Corrosion Tests ◽  
The Matrix ◽  
The Relationship

Experimental work on prismatic concrete specimens was conducted to determine the relationship between mechanical restraint and the rate of corrosion. The current together with the changes in strain of the confining frame were monitored during the accelerated corrosion tests. The effect of mix design and cracking on the corrosion rates was also investigated. The results show that one-dimensional mechanical restraint retards the corrosion process, as indicated by the reduction in the steel loss. Improved quality of the matrix, with and without cracking, reduces the rate of steel loss. In the inferior quality concrete, the effect of cracking on the corrosion rate is minimal.Key words: corrosion, concrete, repair.

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