Chris Evangelides

Estimation of soil moisture profile and diffusivity using simple laboratory procedures.

Diffusivity is one of the main soil hydraulic properties. It is a critical parameter for the prediction of water transport within the vadose zone. The aim of this research was to generate the soil moisture profile from very simple measurements such as sorptivity, distance of the wetting font in transformed coordinates, and initial and final water contents. The objective was to use a complex empirical function with three constants to generate the transformed soil moisture profile by treating the whole process as an optimization problem. The required conditions are that the constants of the empirical function are computed so that the analytically computed sorptivity agrees with the experimental one, and at the beginning and at the end of the transformed soil moisture profile, the water content is the final and the initial correspondingly. Once an analytic function for the transformed soil moisture profile is determined, then diffusivity is calculated analytically. As an added verification of the accuracy of the analytic diffusivity function produced by this method, diffusivity results were used as input in Philips semianalytic method to verify that the transformed soil moisture profiles can be regenerated. Integral continuity is preserved throughout the process.

FLUX-SATURATION RELATIONSHIP FOR UNSATURATED HORIZONTAL FLOW

The prediction of unsaturated flow is a never-ending quest for many scientists. Many methods exist with their corresponding advantages and disadvantages, such as semianalytic, finite difference, finite element, finite control volume, and flux-saturation. The last one, even though it belongs to the semianalytic group, is very interesting due to its simplicity and the way it approaches the physical problem. During laboratory research, a new intuitive monoparametric fitting function was used for F(Θ). The purpose of this research was to examine the range of variation of the new fitting function coefficient and the feasibility to replace it with a constant. A series of experiments was carried out on horizontal absorption under constant-head conditions, using three different soil types, to measure their F(Θ) function. F(Θ) values were also obtained for four other soils, using different methods. The soils that were examined were characterized from silt to sand, according to the textural triangle of the United States Department of Agriculture. Actual F(Θ) functions were then calculated in each soil. The proposed F(Θ) function was compared with the limiting F(Θ) function for linear and Dirac soil and with preexisting ones. The results were satisfactory both in shape and in quantity, leading to a new expression for F(Θ) for all soil types.

Explicit Approximate Analytical Solution of the Horizontal Diffusion Equation

Abstract The solution of unsaturated flow is a never-ending quest for many scientists. Many methods exist with their corresponding advantages and disadvantages, such as semianalytic methods, finite difference and finite element methods, finite control volume method, and flux concentration method. This article produces an improved approximate analytical solution for nonlinear diffusion, in terms of the Boltzmann similarity variable, that has the advantages of being explicit, accurate, and relatively simple to evaluate. It is assumed that the diffusivity can be described with an exponential function, the profiles of soil water content are of finite extent, the concentration at the boundaries is constant, and the reduced flux of Philip (1973) is of the form of Vauclin and Haverkamp (1985). The proposed explicit approximate analytical solution has the Boltzmann transformation as the dependent variable and the soil water moisture as the independent variable. The solution is presented in normalized form as a function of normalized diffusivity and normalized soil moisture. It is tested with 12 soils and shows an excellent agreement with Philip’s method.

Data for moisture measurements during vertical absorption in building porous materials such as brick and limestone

This article contains the datasets obtained from experiments in laboratory related to moisture propagation in building porous materials. The datasets contain moisture measurements and corresponding time measurements during vertical infiltration experiment in brick and limestone samples. Moisture measurements were carried out using a γ-ray device and water volume absorption was recorded by a computer controlled digital scale.

A fuzzy set approach of an analytical solution of non-steady two-dimensional drainage

A new analytical solution for soil water two-dimensional movement to an orthogonal mesh of parallel drains is presented, as an extended case of the one-dimensional flow problem of the same nature. An equation is provided, that gives the profile of the water surface as well as the volume that has passed through the drains at a given time moment. Non-dimensional profiles of the piezometric surface are given for various values of time and space parameters. The water volume versus time derived from the respective equation is in very good accordance with the volume derived from surface profile integration. We also explore the possibility to solve this problem by using the fuzzy set approach, to cope with the uncertainties of the hydraulic parameters. Triangular fuzzy numbers are used to represent the hydraulic conductivity of the soil as well as the storativity of the aquifer. The drained water volume derived from the fuzzy set after defuzification, approaches the one calculated by the analytical solution, included in the interval of presumption level @a=0.8.

A simplified equation for two-dimensional drainage

In this paper a new analytical solution for soil-water two-dimensional movement to an orthogonal mesh of parallel drains is presented, as an extended case of the one-dimensional flow problem of the same nature. An equation is provided that gives the profile of the water surface as well as the volume that has passed through the drains at a given time. A simplified form of the equation is presented, which provides very good results for time values higher than a certain level. Non-dimensional profiles of the piezometric surface are given for various values of time and space parameters. The water volume versus time derived from the respective equation accords well with the volume derived from surface profile integration.