HydroGeoSphere/Channel Flow

Channel domains, can be set up using the following instructions, as outlined in Section 2.3.2.4 and in Equation 2.65.

Default Channel Properties

Unless the user modifies the default values, all channel zones in the domain will be assigned the default properties. The default values, Table 5.10, can be and are recommended to be modified to fit the model application.

Table 5.10: Default Values for Channel Properties

Parameter	Value	Unit
Shape	Rectangle	m
Width	1	m
Manning’s Friction Coefficient	0.0548	m−1/3 s
River Bank Height	1	m
Streambed Thickness	0.001	m
Steambed Conductivity	1 × 10−4	m

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Example Channel Flow Instructions

As an example, the following set of instructions, with prefix.cprops file Figure 5.14, could be inserted into the prefix.grok file to produce a channel:

use domain type
channel

properties file
prefixl.cprops

clear chosen segments
choose segments polyline
2
0.0  10.0  20.0
100.0  10.0  10.0

new zone
1

clear chosen zones
choose zone number
1

read properties
channel one

clear chosen nodes
choose nodes all
initial head surface elevation

clear chosen nodes
choose node
0.0  10.0  20.0

create node set
inlet_node

boundary condition
    type
    head

    name
    inlet_node_flux

    node set
    inlet_node

    time value table
    0.0  20.0001
    end
end

clear chosen nodes
choose node
100.0  10.0  10.0

create node set
outlet_node

boundary condition
    type
    channel critical depth

    name
    cd_outlet_node

    node set
    outlet_node
end

clear chosen nodes
choose nodes top block
0.0 99.5
9.0 11.
0.0 20.

create node set
internal_node

boundary condition
    type
    flux nodal

    name
    internal_flux

    node set
    internal_node

    time value table
    0.0  0.601818e-2
    end
end

The channel domain example opens the property file prefix.cprops, shown in Figure 5.14, and creates a 1 m wide channel. The channel one properties are read into grok.

!------------------------------------------
channel one

type rectangle
1.0

friction
0.01

rill storage height
0.001

obstruction storage height
0.0

streambed thickness
0.3

streambed conductivity
1.0e-4

bank height
1.0

end

Figure 5.14: Sample channel domain property file prefix.cprops

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Dual nodes for channel flow

Scope: .grok

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

• • •

Type rectangle

Scope: .grok .cprops

1. ChanWidth Channel Width [L].

The width of the rectangular channel.

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Type trapezoid

Scope: .grok .cprops

1. ChanWidth Channel Width [L].
2. ChanTrapBankAngle Channel Bank Angle [degree].

The width of the bottom of the trapezoidal channel and the angle of the bank from the vertical line.

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Type circle

Scope: .grok .cprops

1. ChanRadius Channel Radius [L].

The radius of the circular channel.

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Type general

Scope: .grok .cprops

1. nChanTab The number of water depth values in the table.
2. i=1, nChanTab, ChanTabD, ChanTabAF, ChanTabWP, ChanTabTW Tables for water depth, area of flow, wetted perimeter, and top width.

A tabular form of data can be used to specify the area of flow, wetted perimeter, and top width for given depth values.

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Friction

Scope: .grok .cprops

1. ChanFrictn Manning friction for the channel.

Manning friction coefficient for the zone chosen.

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Rill storage height

Scope: .grok .cprops

1. ChanRillStor Channel rill storage height.

A minimum water depth required for flow.

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Obstruction storage height

Scope: .grok .cprops

1. ChanOnstructStor Channel obstruction storage height.

Obstruction storage height.

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Streambed thickness

Scope: .grok .cprops

1. ChanStrmBedThick Thickness of streambed.

Streambed thickness that defines the coupling between channel and subsurface.

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Streambed conductivity

Scope: .grok .cprops

1. ChanStrmBedK Hydraulic conductivity of streambed.

Streambed hyarulic conductivity together with thickness to define the coupling conductance between channel and subsurface.

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Bank height

Scope: .grok .cprops

1. ChanBankHeight Height of river bank.

River bank height to define the interaction between the channel and overland flow domains.

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