Saturation parameter, hysteresis


Attributes: ASAT [-] (initial saturation), USAT [-] (zone number for Van-Genuchten-parameter, vertical- and 3D models only)

The flow computation with the module SITRA contains three different parameter combinations for the residual saturation (Sres), the reciprocal of the water inlet pressure (a = 1/pe), the pore size distribution index (n) and specific parameters in the function of the relative k-value (l). The determination of the soil (sand, silt or clay) depends on the assigned permeability. For the calculation, the corresponding soil parameters are used:

 

K-value [m/s]

Sres

a

n

l

Soil type

> 9.81*e-4

0.2

1.4*e-3

1.5

0.5

Sand

9.81*e-4 bis 9.81*e-7

0.4

2.5*e-4

1.35

0.5

Silt

< 9.81*e-7

0.9

1.25*e-4

1.3

0.5

Clay

 

For the reason of numerical stability from these functions calculated K-values are limited down to 1.e-2 m/s.

Should other classes as the set parameters been used the definition has to be based on soil areas (element areas):

Then the attribute USAT assigns to each element in an area, which should be obtain a certain parameter combination, a zone identification number.

Each of these zone identification numbers uniquely identifies a set of Van Genuchten parameters. USAT needs to be fully defined. If the attribute USAT is assigned to all elements the parameters can be modified in SPRING with Attributes Special features van-Genuchten parameters. The following dialog box appears:

 


Input of new defined van-Genuchten parameter

 

The parameters are stored in the model file in the following format:

Van Genuchten Parameter:

1 0.400000 0.000250 1.350000 0.010000 0.500000 1.000000

Hysteresis-Parameter:

1 0.400000 0.000250 1.350000 0.010000 0.000000 1.000000

 

The subsequent assignment of the attribute USAT in 3D models is performed automatically in the model checking.

For the flow and transport calculation in consideration of unsaturated circumstances for each element the saturation at the beginning (ASAT) can be defined. Then it is possible to choose that the initial value for the initial pressure is calculated by the saturation at the beginning. ASAT must be completely defined. In 3D-modells the later seizure if necessary executed in DADIA automatically.

For the definition of the Van-Genuchten parameters must the area defined with names for which the particular parameter set should obtain. Also USAT must completely defined.

The subsequent assignment for 3D models is performed automatically in the model checking.