Prediction of Wetting Front Movement During One‐Dimensional Infiltration into Soils

Kao, Cindy S.; Hunt, James R.

doi:10.1029/95wr02974

Cited by 44 publications

(40 citation statements)

References 45 publications

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“…The NAPL retention behavior can then be connected with entirely fundamental physical parameters. Kao and Hunt (1996) further reinforce this concept that a capillary pore-scale viewpoint can be employed to explain NAPL movement, requiring only a minimum of phenomenological parameters. McBride et al (1992) also showed how the relative absorption behavior of NAPL can be compared using a simple capillary model.…”

Section: Spill Disappearancesupporting

confidence: 56%

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Status of Models for Land Surface Spills of Nonaqueous Liquids

Simmons¹,

Knell²

2003

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Executive SummaryThis report describes the status of models for predicting the spreading behavior of nonaqueous phase liquids (NAPLs) when spilled on land. NAPLs are liquids other than water and are commonly immiscible with water. Examples include diesel fuel, brake fluid, transmission fluid, and many chemical solvents. If there are adequate models available to describe spills, hydrologists can determine how the size of a spill relates to the amount spilled and how long it persists. Further, remote sensors can then be used to detect the presence of a spill on land.A NAPL spill area can often be detected by remote sensing of its vapors with infrared spectroscopy, for a period after a spill. The opportunity for sensing NAPLs having low volatility, however, may depend on the possibility of detecting directly the liquid phase, or adsorbed material, on the surface of a land spill area. Therefore, a NAPL spill model is useful to predict how large an area is produced by a spill of a certain amount and how long it remains visible for remote sensing. Only one land spill model, a simplified screening type, for NAPL spreading was found after searching the scientific literature. This model was built for the U.S. Environmental Protection Agency. It uses the theory of gravity currents from fluid dynamics to represent spill spreading, and it applies the Green-Ampt sharp front model to describe the concurrent infiltration of NAPL into the ground. This spreading model also considers component-wise evaporation of volatile petroleum liquids, but it does not treat drainage away from the surface after a spill. Predicting the drainage just beneath the surface is a critical capability for determining whether remote sensors can detect the liquid phase of a NAPL near the surface after a spill.An exact solution to the problem of coupling a gravity current of viscous liquid to its simultaneous infiltration into a porous medium was found. It derives from fluid dynamics and can be used as a paradigm for spill spreading on a flat ideally smooth surface. Test calculations of this gravity current theory revealed that the spreading area is strongly controlled by the release rate of a spill and by the subsurface permeability. A more realistic prediction of spreading under less ideal situations, however, must consider the roughness of the land surface.This report outlines the processes and mechanisms that control spill mechanics on a porous surface. It also defines physical parameters and lists sources of their values required by mathematical theory for spill phenomena. The key parameters are: iv Liquid properties: density, viscosity, interfacial tension, and vapor pressure Land properties: soil-water retention curve, permeability, surface slope, and roughness.To build a more general model for NAPL spreading over the land, two existing modeling capabilities for overland flow and multiphase subsurface flow of NAPL must be coupled. The two flow theories that must be mathematically coupled are: Saint Venant fluid dynamical equations for overland flo...

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Section: Spill Disappearancesupporting

confidence: 56%

“…A more extensive and updated explanation of this subject is given by Dullien (1992). Kao and Hunt (1996) provide a useful table of values related to particle sizes. The information is sufficient to cover a great variety of granular porous media.…”

Section: Intrinsic Permeabilitymentioning

confidence: 99%

Status of Models for Land Surface Spills of Nonaqueous Liquids

Simmons¹,

Knell²

2003

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“…The higher sorptivity of the fracture surface zone of each rock was qualitatively revealed in the imbibition experiments conducted such that water enters directly into both the surface zone and bulk matrix (as in Figure 2a Results of the imbibition experiments on the highly waterwettable ceramics showed no significant differences in the B parameter relative to the mean value of 0.5 (Figure 7), indicating that scale effects were not responsible for discrepancies between measured and calculated permeabilities. The fact that values of B = 0.5 were obtained for these fused matrix ceramics also suggests that this parameter is not strongly specific to pore geometry, since the data used by Kao and Hunt [1996] were all from granular porous media. Thus wettability appears to be the most general potential limitation of using (5b).…”

Section: Resultsmentioning

confidence: 94%

Surface‐zone flow along unsaturated rock fractures

Tokunaga¹,

Wan²

2001

Water Resources Research

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Abstract. Although fractures in rock are well recognized as pathways for fast percolation of water, processes which permit fast flow along unsaturated fracture pathways remain to be identified and understood. Earlier aperture-based models of flow in partially saturated fractures permit fast flow only through a continuous network of locally saturated segments. Film flow was recently identified as a mechanism capable of sustaining fast flow along truly unsaturated fractures when the matric potential is very close to zero. Another mechanism for fast flow along unsaturated fractures is introduced in this study, "surfacezone flow," which can be important when the permeability of the rock along fractures (fracture skin) is significantly greater than that of the bulk rock matrix. In such systems the fracture surface zone provides low resistance pathways through which fast flow (relative to the bulk matrix rock) can occur, even when the fractures are at very low water saturation. Initial experimental tests of surface-zone fast flow were performed. Surfacezone fast imbibition of water was measured on a welded tuff and a rhyolite. However, because (1) imbibition rates are also strongly influenced by rock wettability, (2) these initially air-dry rocks exhibited finite contact angles upon exposure to water, and (3) we lack methods to reliably measure permeabilities of thin regions on rock surfaces, quantification of permeability contrasts was not possible in these initial tests.

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“…Le facteur de forme p est tel que 0 < p < 1 (HAVERKAMP et ai, 1994) mais p devrait être constant pour des milieux poreux à structures similaires (CINDY et JAMES, 1996). D'ailleurs HAVERKAMP et al (1994), SMETTEM et al (1995) ont pris, pour des sols limono-sableux et sablo-limoneux (Redlands) respectivement P = 0,56 et p = 0,60.…”

Section: -Approche Théoriqueunclassified

Prédiction de la profondeur de sol humidifié sous goutteur

Hammami¹,

Maâlej²

2005

rseau

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SUMMARYIn trickle irrigation, the wetted soil volume fraction (P) is a fundamental parameter for both network design and irrigation scheduling. However, methods used to détermine such parameter (P) are still limited and unaccurate. Further, numerical models established for predicting wetted soil volume (or bulb) dimensions remain onerous, complex, expensive, and therefore hardly used.Expérimental and numerical results performed on water infiltration from point source on the soil surface show a close relationship between the horizontal and vertical bulb dimensions. This study which was based on continuity and cumulative infiltration équa-tions allowed to establish a new and simple équation for predicting wetted soil depth. This équation enables, knowing initial and wetting front water content and K(h f ) (soil hydraulic conductivity on the wetting front), to calculate the front depth Zf(t) beneath a point source with only measuring the front radius Rf(t) on the soil surface. The established équation vérifies physical conditions of axisymmetric water infiltration into the soil.The established équation was tested by performing trials on two différent soil types and three discharge rates. Two différent procédures were simultaneously used for determining Rj(t) and Zf(t). i) observing bulb dimensions évolution on the soil surface and along the symmetry axis. ii) R{(t) and Zf(t)values were inferred from the horizontal and vertical suction profiles respectively.

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Prediction of Wetting Front Movement During One‐Dimensional Infiltration into Soils

Cited by 44 publications

References 45 publications

Status of Models for Land Surface Spills of Nonaqueous Liquids

Status of Models for Land Surface Spills of Nonaqueous Liquids

Surface‐zone flow along unsaturated rock fractures

Prédiction de la profondeur de sol humidifié sous goutteur

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