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Biblioteca(s): 
Embrapa Agropecuária Oeste. 
Data corrente: 
21/09/2006 
Data da última atualização: 
21/09/2006 
Autoria: 
HOFFMANN, M. R. 
Título: 
Macroscopic equations for flow in unsaturated porous media. 
Ano de publicação: 
2003 
Fonte/Imprenta: 
2003. 
Páginas: 
123 f. 
Idioma: 
Inglês 
Notas: 
Thesis (Doctor)  Wageningen University, Wageningen. 
Conteúdo: 
This dissertation describes averaging of microscale flow equations to obtain a consistent description of liquid flow in unsaturated porous media on the macroscale. It introduces a new method of averaging the pressure term and a unit cell model capable of describing unsaturated flow. Starting from the description of liquid flow through individual pores, a macroscopic equation for flow of a liquid in a porous medium in the presence of a gas is derived. The flow is directly influenced by phase interfaces, i.e. solidliquid or gasliquid. By including these pore scale phenomena in a continuum description of fluid transport in porous media, equations for liquid flow on the macroscale are obtained.
The unit cell model is based on a simplified geometric representation of a porous medium. It allows for the modeling of the important characteristics of a porous medium for unsaturate flow. Through the use of volume averaging and direct integration macroscale momentum and mass balance equations are derived from the microscale momentum and mass balance equations, resulting in a novel form of the macroscale pressure term. The macroscale flow of liquids in unsaturated porous media can be written proportional to a driving force, which is proportional to the difference of the inverse area averaged liquid pressures across an averaging volume. In principle the flow is driven by gradients in liquid pressure, but due to nonlinear coupling between capillary forces and liquid pressure the driving force becomes nonlinear. Two dynamic terms were derived by simplifying the flow dynamics in a porous medium. They remain to be tested quantitatively and still have considerable uncertainty concerning their exact form and/or magnitude.
Comparison of the newly proposed macroscale equations with the BuckinghamDarcy equation shows that, using reasonable assumptions, the newly proposed macroscale equations can be written in a form similar to the BuckinghamDarcy equation. The newly proposed macroscale equations are compared to an experimet and satisfactory agreement between experiment and calculations was observed. MenosThis dissertation describes averaging of microscale flow equations to obtain a consistent description of liquid flow in unsaturated porous media on the macroscale. It introduces a new method of averaging the pressure term and a unit cell model capable of describing unsaturated flow. Starting from the description of liquid flow through individual pores, a macroscopic equation for flow of a liquid in a porous medium in the presence of a gas is derived. The flow is directly influenced by phase interfaces, i.e. solidliquid or gasliquid. By including these pore scale phenomena in a continuum description of fluid transport in porous media, equations for liquid flow on the macroscale are obtained.
The unit cell model is based on a simplified geometric representation of a porous medium. It allows for the modeling of the important characteristics of a porous medium for unsaturate flow. Through the use of volume averaging and direct integration macroscale momentum and mass balance equations are derived from the microscale momentum and mass balance equations, resulting in a novel form of the macroscale pressure term. The macroscale flow of liquids in unsaturated porous media can be written proportional to a driving force, which is proportional to the difference of the inverse area averaged liquid pressures across an averaging volume. In principle the flow is driven by gradients in liquid pressure, but due to nonlinear coupling between capillary forces and liquid pressure the driving ... Mostrar Tudo 
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LEADER 02484nam a2200133 a 4500 001 1253241 005 20060921 008 2003 bl uuuu m 00u1 u #d 100 1 $aHOFFMANN, M. R. 245 $aMacroscopic equations for flow in unsaturated porous media. 260 $a2003.$c2003 300 $a123 f. 500 $aThesis (Doctor)  Wageningen University, Wageningen. 520 $aThis dissertation describes averaging of microscale flow equations to obtain a consistent description of liquid flow in unsaturated porous media on the macroscale. It introduces a new method of averaging the pressure term and a unit cell model capable of describing unsaturated flow. Starting from the description of liquid flow through individual pores, a macroscopic equation for flow of a liquid in a porous medium in the presence of a gas is derived. The flow is directly influenced by phase interfaces, i.e. solidliquid or gasliquid. By including these pore scale phenomena in a continuum description of fluid transport in porous media, equations for liquid flow on the macroscale are obtained. The unit cell model is based on a simplified geometric representation of a porous medium. It allows for the modeling of the important characteristics of a porous medium for unsaturate flow. Through the use of volume averaging and direct integration macroscale momentum and mass balance equations are derived from the microscale momentum and mass balance equations, resulting in a novel form of the macroscale pressure term. The macroscale flow of liquids in unsaturated porous media can be written proportional to a driving force, which is proportional to the difference of the inverse area averaged liquid pressures across an averaging volume. In principle the flow is driven by gradients in liquid pressure, but due to nonlinear coupling between capillary forces and liquid pressure the driving force becomes nonlinear. Two dynamic terms were derived by simplifying the flow dynamics in a porous medium. They remain to be tested quantitatively and still have considerable uncertainty concerning their exact form and/or magnitude. Comparison of the newly proposed macroscale equations with the BuckinghamDarcy equation shows that, using reasonable assumptions, the newly proposed macroscale equations can be written in a form similar to the BuckinghamDarcy equation. The newly proposed macroscale equations are compared to an experimet and satisfactory agreement between experiment and calculations was observed.
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Embrapa Agropecuária Oeste (CPAO) 

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