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(Theta). 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(Theta) function. F(Theta) 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(Theta) functions were then calculated in each soil. The proposed F(Theta) function was compared with the limiting F(Theta) 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(Theta) for all soil types.