Modeling Multiphase Flow in Variably Saturated Media. For: BAE 558 By: Kate Burlingame 5/7/07. Introduction.
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For: BAE 558
By: Kate Burlingame
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There are two major types of NAPLs: those that are less dense than water (LNAPL’s), and those that are denser than water (DNAPLs). This property of the NAPL is of primary importance in predicting the behavior of the NAPL, as DNAPLs will continue to sink below the porous media until reaching an impermeable layer. LNAPLs, on the other hand, will float on top of water found in the soil matrix or aquifer. Also, while LNAPLs will travel in the direction of the slope of the water table, DNAPLs will travel with the slope of the lower boundary of material in a soil. DNAPLs deposit a greater fraction of free product to the aquifer.
Viscosity quantifies the internal energy of an object and describes how rapidly a liquid flows over a surface (Simmons, 2003). Viscosity, therefore, will act as a resistive force to the wetting front progression. It is important to note that viscosity is a function of temperature, and therefore the rate at which the liquid flows is dependent upon the temperature of the soil and atmosphere.
Interfacial Tension, or surface tension, is the potential energy associated with the area of contact between two liquids. These forces are important in fluid flow in both the horizontal and vertical directions.
Vapor pressure is indicative of a liquid's evaporation rate. Volatile substances are substances that have a high vapor pressure at normal temperatures, and therefore evaporate easily. This is an important factor in determining not only how the NAPL will behave in the vadose zone, but also in determining remediation techniques for the site. For example, a volatile substance responds more readily to soil vapor extraction than a non-volatile substance.
This soil property describes how much moisture is retained in the soil for a given pressure.
Porosity is the ratio of the volume of voids in a soil compared to the volume of the soil. This property determines the amount of water, NAPL, or gas that a soil may imbibe and retain.
The permeability and hydraulic conductivity of a soil describes the ability of that soil to transport a fluid.
The slope of the surface that the spill occurs on plays a fundamental role in determining the direction and magnitude of the spill.
The soil texture, including grain size distribution, has a key influence on many properties of the soil.
Results at 47cm and 37 cm elevations: