Unsaturated flow properties of soils

Soil Research ◽  
1963 ◽  
Vol 1 (1) ◽  
pp. 1 ◽  
Author(s):  
DE Elrick
Keyword(s):  
Steady State ◽  
Diffusion Equation ◽  
Unsaturated Flow ◽  
Diffusion Theory ◽  
Coarse Sand ◽  
Flow Properties ◽  
High Moisture ◽  
Transient Behaviour ◽  
Moisture Contents ◽  
Transient Methods

Experiments to determine the unsaturated flow properties of soils are based either on the steady-state Darcy equation or on the transient diffusion equation. An apparatus has been designed to compare the steady-state and transient methods on the same sample. Results indicate that the transient outflow pattern at high moisture contents (using a coarse sand) differs considerably from that predicted by diffusion theory. The extended theory which takes into account the air as well as the water phase also does not agree with the observed transient behaviour at the high moisture contents. At low moisture contents the agreement between the two methods is considerably better. The transient outflow method was found to be inapplicable at the high moisture contents. Much of the difficulty is attributed to the inaccessibility of air to drainable pores under these conditions.

Steady-state thermal measurement of moist granular earthen materials

2016 ◽  
Vol 41 (2) ◽  
pp. 101-119 ◽  
Author(s):  
Robin E Clarke ◽  
Andrea Pianella ◽  
Bahman Shabani ◽  
Gary Rosengarten
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Contact Resistance ◽  
Test Method ◽  
Single Specimen ◽  
Thermal Measurement ◽  
Moisture Contents ◽  
Difference Measurement ◽  
Transient Methods ◽  
Loose Fill

A technique based on the heat flow meter method is proposed for measuring the thermal conductivity of moist earthen and granular loose-fill materials. Although transient methods have become popular, this steady-state approach offers an uncertainty that can be reliably estimated and a test method that is widely accepted for building certification purposes. Variations to the standard method are proposed, including the use of a rigid holding frame with stiff base and silicone sponge buffer sheets, in conjunction with difference measurement to factor out the contributions from base, buffers and contact resistance. Using this approach, results are presented for green-roof substrates based on scoria, terracotta and furnace-ash at different moisture contents. Thermal conductivity ranged from 0.13 to 0.80 W/m K and fitted well to linear regression plots against moisture content. Further comparative measurements of a single specimen showed that direct measurement was less consistent than difference measurement and thus indicated that thermal resistance was higher by 0.023 m2 K/W, attributable to the presence of contact resistance.

Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

1992 ◽  
Vol 23 (2) ◽  
pp. 89-104 ◽  
Author(s):  
Ole H. Jacobsen ◽  
Feike J. Leij ◽  
Martinus Th. van Genuchten
Keyword(s):  
Experimental Data ◽  
Unsaturated Flow ◽  
Transport Model ◽  
Time Moment ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Retardation Factor ◽  
Parameter Determination ◽  
Model Parameters ◽  
Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

Evaluation of Single-Hole Hydraulic Tests in Fractured Crystalline Rock by Steady-State and Transient Methods: A Comparison

1985 ◽  
Vol 50 ◽  
Author(s):  
J-E. Andersson ◽  
O. Persson
Keyword(s):  
Steady State ◽  
Hydraulic Conductivity ◽  
Flow Pattern ◽  
Transient Analysis ◽  
Crystalline Rock ◽  
Steady State Analysis ◽  
Single Hole ◽  
The Mean ◽  
Transient Methods ◽  
State Analysis

AbstractThe results from a large number of single-hole packer tests in crystalline rock from three test sites in Sweden have been analysed statistically. Average hydraulic conductivity values for 25 m long test intervals along boreholes with a maximal length of about 700 m are used in this study. A comparison between steady state and transient analysis of the same test data has been performed.The mean vaule of the hydraulic conductivity determined from steady state analysis was found to be about two to three times higher compared to transient analysis. However, in some cases the steady state analysis resulted in 10 to 20 times higher values compared to the transient analysis. Such divergence between the two analysis methods may be caused by deviations from the assumed flow pattern, borehole skin effects and influence of hydraulic boundaries.

scholarly journals Investigation in terms of digestive values, silages quality and nutrient content of the using pomegranate pomace in the ensiling of apple pomace with high moisture contents

2018 ◽  
Vol 46 (1) ◽  
pp. 1233-1241 ◽  
Author(s):  
Kanber Kara ◽  
Berrin Kocaoglu Guclu ◽  
Erol Baytok ◽  
Eray Aktug ◽  
Fatma Karakas Oguz ◽  
...  
Keyword(s):  
Nutrient Content ◽  
Apple Pomace ◽  
High Moisture ◽  
Moisture Contents

Numerical and experimental study of steady-state CO2 and inert gas washout

1988 ◽  
Vol 64 (3) ◽  
pp. 1022-1029 ◽  
Author(s):  
P. W. Scherer ◽  
S. Gobran ◽  
S. J. Aukburg ◽  
J. E. Baumgardner ◽  
R. Bartkowski ◽  
...  
Keyword(s):  
Steady State ◽  
Diffusion Equation ◽  
Tidal Volume ◽  
Sulfur Hexafluoride ◽  
Source Term ◽  
Gas Diffusion ◽  
Inert Gases ◽  
Phase Iii ◽  
Distributed Source ◽  
Single Path

The predictions of a single-path trumpet-bell numerical model of steady-state CO2 and infused He and sulfur hexafluoride (SF6) washout were compared with experimental measurements on healthy human volunteers. The mathematical model used was a numerical solution of the classic airway convention-diffusion equation with the addition of a distributed source term at the alveolar end. In the human studies, a static sampling technique was used to measure the exhaled concentrations and phase III slopes of CO2, He, and SF6 during the intravenous infusion of saline saturated with a mixture of the two inert gases. We found good agreement between the experimentally determined normalized slopes (phase III slope divided by mixed expired concentration) and the numerically determined normalized slopes in the model with no free parameters other than the physiological ones of upper airway dead space, tidal volume, breathing frequency, and breathing pattern (sinusoidal). We conclude 1) that the single-path (Weibel) trumpet-bell anatomic model used in conjunction with the airway convection-diffusion equation with a distributed source term is adequate to describe the steady-state lung washout of CO2 and infused He and SF6 in normal lungs and 2) that the interfacial area separating the tidal volume fron from the functional residual capacity gas, through which gas diffusion into the moving tidal volume occurs, exerts a major effect on the normalized slopes of phase III.

Analysis of transient behaviour of certain processes with return to a central state

1983 ◽  
Vol 20 (01) ◽  
pp. 61-70
Author(s):  
Peter G. Buckholtz ◽  
L. Lorne Campbell ◽  
Ross D. Milbourne ◽  
M. T. Wasan
Keyword(s):  
Probability Distribution ◽  
Diffusion Equation ◽  
Diffusion Approximation ◽  
Cash Management ◽  
Central State ◽  
Transient Behaviour ◽  
Management Problems ◽  
Transient Probability ◽  
Birth Death

In economics, cash management problems may be modelled by birth-death processes which reset to central states when a boundary is reached. The nature of the transient behaviour of the probability distribution of such processes symmetric about a central state is investigated. A diffusion approximation of such processes is given and the transient probability behaviour derived from the diffusion equation.

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