HydroGeoSphere/Tile Drains

Tile drains, as outlined in Section 2.3.2.3, can be set up using the following instructions. Currently, this option requires that the system be variably-saturated.

Default Tile Drain Properties

The default tile drain values, Table 5.9, can be and are recommended to be modified to fit the model application.

Table 5.9: Default Values for Tile Drain Properties

Parameter	Value	Unit
Screen Radius	1 × 10−5	m
Coupled Conductivity	7.438 × 10−5	m s−1
Coupled Length	1 × 10−4	m
Coupled Scheme	Shared	-
Tile Drain Type	Hagen-Poiseuille	-
Manning's Friction Coefficient	0.0548	m−1/3 s
Hazen Williams Coefficient	130	m0.37 s−1

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Example Tile Drain Instructions

As an example, the following set of instructions, with prefix.tprops file Figure 5.13, could be inserted into the prefix.grok file to produce a horizontal tile drain:

use domain type
tile

properties file
prefix.tprops

clear chosen segments
choose segments polyline !Screen interval
2
15. 1. 2.
15. 29. 2.

new zone
1

clear chosen zones
choose zone number
1

read properties
tile one

clear chosen nodes
choose node !Tile drain intake
15. 15. 2.

create node set
tile

boundary condition
    type
    flux nodal

    name
    tile one

    node set
    tile

    time value table
    0.0  -2                            !Pumping duration and rate
    end
end

The tile domain example opens the property file prefix.tprops, shown in Figure 5.13, and creates a 28 m long screen between (15, 1, 2) and (15, 29, 2) with a pump intake located at (15, 15, 2). The tile one properties are read into grok and a steady pumping rate is set at -2 m³ s⁻¹.

!------------------------------------------
tile one

radius
0.0108

!Coupling length and conductivity for dual node approach
coupling length
1.0e-4

coupling conductivity
.0023

!Infilled tiled drain with properties from the mprops file
infilled
Porous medium

end

Figure 5.13: Sample tile drain domain property file prefix.tprops

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Radius

Scope: .grok .wprops

1. TileScreenRadius Tile drain screen radius [L].

The radius of the screen interval of the tile drain.

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Infilled

Scope: .grok .wprops

This command should be included in the input file for an infilled tile drain.

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Hagen Poiseuille

Scope: .grok .wprops

This command should be included in the input for the Hagen Poiseuille flow option.

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Hazen Williams

Scope: .grok .wprops

This command should be included in the input file for the Hazen Williams flow option.

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Manning

Scope: .grok .wprops

This command should be included in the input file for the Manning flow option.

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Friction

Scope: .grok .wprops

1. tile_friction Manning’s friction for tile drains.

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Hazen Williams coefficient

Scope: .grok .wprops

1. tile_hw_coeffient Hazen-Williams coefficient for tile drains.

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Dual nodes for tiles

Scope: .grok .wprops

This instruction causes the tile drain flow scheme to use dual node approach.

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Coupling conductivity

Scope: .grok .wprops

1. TilePropsCplCond Coupling conductivity for tile [L T⁻¹].

Coupling conductivity parameter only required for the dual node approach for tile drains.

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Coupling length

Scope: .grok .wprops

1. TilePropsCplLngth Coupling length for tile drain [L].

Coupling length parameter only required for the dual node approach for tile drains.

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