HydroGeoSphere/Dual Continuum (Saturated)
Default Dual-Continuum Saturated Flow PropertiesEdit
Unless you modify the default values, all dual-continuum zones (and elements) in the domain will be assigned the default properties which are listed in Table 5.7. These values are representative of a sand:
Parameter | Value | Unit |
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Name | Default Sand | - |
Hydraulic conductivity terms: | - | - |
7.438 × 10^{−5} | m s^{−1} | |
7.438 × 10^{−5} | m s^{−1} | |
7.438 × 10^{−5} | m s^{−1} | |
Specific storage | 1.0 × 10^{−4} | m^{−1} |
Porosity | 0.375 | - |
Volume fraction of porous medium | 0.01 | - |
Unsaturated flow relation type | Pseudo-soil | - |
Note that the default state of the hydraulic conductivity tensor ( in Equation 2.17) is that it is isotropic. It should also be noted that for dual continua, off-diagonal terms are not considered.
You can use the general methods and instructions outlined in Section 5.8.1 to modify the default distribution of saturated dual-continuum properties.
As was the case for the instructions which modify porous medium properties, the following instructions also have a scope of operation, the only difference being that they would appear in the .dprops file instead of the .mprops file.
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K isotropicEdit
Scope: .grok .dprops
- kval Hydraulic conductivity [L T^{−1}].
Assign an isotropic hydraulic conductivity (i.e. = = ).
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K anisotropicEdit
Scope: .grok .dprops
- kvalx, kvaly, kvalz Hydraulic conductivities [L T^{−1}] in the x-, y- and z-directions respectively.
Assigns anisotropic hydraulic conductivities.
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Specific storageEdit
Scope: .grok .dprops
- val Specific storage [L^{−1}], , but defined in a similar way to in Equation 2.10.
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PorosityEdit
Scope: .grok .dprops
- val Porosity [L^{3} L^{−3}], in Equation 2.16.
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Volume fraction dual mediumEdit
Scope: .dprops
- val Volume fraction [L^{3} L^{−3}], in Equation 2.16.
The volume fractions of the dual medium and porous medium always add up to 1.0.
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First-order fluid exchange coefficientEdit
Scope: .dprops
- val First-order fluid exchange rate, in Equation 2.69.
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Interface kEdit
Scope: .dprops
- val Interface hydraulic conductivity [L T^{−1}], in Equation 2.69.
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Convert pm k to macropore kEdit
Scope: .dprops
- val Porous medium background hydraulic conductivity .
We can express the bulk hydraulic conductivity of a dual-continuum as the sum of the porous media and fracture components:
- (Equation 5.11)
where is the volume fraction [L^{3} L^{−3}] in Equation 2.16.
If we assume that the observed (porous medium) hydraulic conductivity is equal to , and supply an educated guess for , we can rearrange the equation and calculate as:
- (Equation 5.12)
For all elements in the currently chosen dual zones, the porous medium hydraulic conductivity is replaced by and the fracture hydraulic conductivity is set equal to the calculated value.
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