Gate

Overview:

Gates are sites that present a barrier or control on flow. A gate may have an arbitrary number of associated hydraulic devices (pipes and weirs), each of which may be operated independently to control flow.

The Gates View is primarily for specifying the physical properties of the gate and some simple operating modes. Gates that are operated simply can be completely specified in this table. Much more elaborate controls are possible using Gate Time Series and Operating Rules, and in addition to manipulating the hydraulic devices you can completely uninstall the gate.

GATE

The Gate table defines the name and connectivity of the gate. Gates are a top-level layered table.

Field Descriptions

NAME

Name of the gate. This is the identifier of the gate used elsewhere to refer to the gate.

FROM_OBJ

Type (channel/reservoir) of the water body to which the gate is attached. Gates are always connected from a water body to a node. This column is a picklist that is also connected to the Name/no. column.

FROM_IDENTIFIER

Identifier (channel number or reservoir name) of the water body to which the gate is attached.

TO_NODE

Node to which gate is attached.

Table Info

Identifier:

NAME

Parent Table:

GATE

Include Block:

GRID

GATE_WEIR_DEVICE

This table lists hydraulic structures that exist at the gate site to control flow that resemble weirs or rectangular conduits. In this table, the user specifies physical properties of the device as well as default operations. Both employ the following formulas depending on whether the water surface is higher on the water body or node side of the gate:

Q = nC_{op_to}C_toA(z_wb, p) sqrt[ 2g(z_wb - z_node) ] ... z_wb > z_node

Q = nC_{op_from}C_fromA(z_node, p) sqrt[ 2g(z_node - z_wb) ] ... z_wb \< z_node

Where:

n is the number of duplicate devices>
C_{op_to} and C_{op_to} are operating coefficient representing controls such as flap gates
C_to and C_from are coefficients representing the hydraulic efficiency of the gate
A is the area of flow depending on higher water surface and position p
g is gravity and
z_wb and z_node are the water surface elevations at the water body and node (node surface is assessed by means of a reference channel that has no gates attached to it).

Please see usage notes below

Field Descriptions

GATE_NAME

Name of the gate this device in which the device is located.

DEVICE

Name of the device.

NDUPLICATE

Number of exact duplicates, such as a number of similar pipes in parallel. Parameters such as width apply to a single one of the duplicates.

WIDTH

Maximum width of the device (radius of a pipe, width of a weir).

ELEV

Invert elevation or weir crest.

HEIGHT

Height of the device from the invert elevation. This can be used to represent the height of rectangular flashboards or of a radial gate. If the surface goes above this height, flow will be submerged. Use NA for an open top. If you click in an NA column, you will see that it is encoded using a large number, but you should only use 'NA' or a real height.

CF_FROM_NODE

Flow coefficient of the gate (0 \< Cto \<= 1.0) describing the efficiency of the gate from node to water body. This parameter is the physical coefficient of flow. It should never be zero and should not be used to describe a control structure or operation such as flap gates or gate openings.

CF_TO_NODE

Same as CF_FROM_NODE, but for the direction from water body to node.

DEFAULT_OP

Default operation mode. The gate operation is a "magic" parameter between 0.0 and 1.0 that modulates gate flow. Operating coefficients can be used to represent flap gates, fractions of duplicates operating or other physical controls. The default ops are simple on this table are like initial conditions -- if you want more sophisticated control you will need to use a Gate Time Series or Operating Rule. Nevertheless, the defaults are enough to represent structures that are fully open or closed or operated unidirectionally. Here is how the default operation mode will affect the operating coefficient:

gate_open

C_{op_to}=1.0; C_{op_from}=1.0;

gate_close

C_{op_to}=0.0; C_{op_from}=0.0;

unidir_to

C_{op_to}=1.0; C_{op_from}=0.0;

unidir_from

C_{op_to}=0.0; C_{op_from}=1.0;

Table Info

Identifier:

GATE_NAME, DEVICE

Parent Table:

GATE

Parent Identifier:

GATE_NAME

Include Block:

GRID

GATE_PIPE_DEVICE

This table lists pipes at the gate site. In this table, the user specifies physical properties of the device as well as default operations.

Field Descriptions

GATE_NAME

Name of the gate this device in which the device is located;

DEVICE

Name of the device.

NDUPLICATE

Number of exact duplicates, such as a number of similar pipes in parallel. Parameters such as width apply to a single one of the duplicates.

RADIUS

Maximum width of the device (radius of a pipe, width of a weir).

ELEV

Invert elevation or weir crest.

CF_FROM_NODE

Flow coefficient of the gate (0 \< Cto \<= 1.0) describing the efficiency of the gate from node to water body. This parameter is the physical coefficient of flow. It should never be zero and should not be used to describe a control structure or operation such as flap gates or gate openings.

CF_TO_NODE

Same as CF_FROM_NODE, but for the direction from water body to node.

DEFAULT_OP

Default operation mode. The gate operation is a "magic" parameter between 0.0 and 1.0 that modulates gate flow. Operating coefficients can be used to represent flap gates, fractions of duplicates operating or other physical controls. The default ops are simple on this table are like initial conditions -- if you want more sophisticated control you will need to use a Gate Time Series or Operating Rule. Nevertheless, the defaults are enough to represent structures that are fully open or closed or operated unidirectionally. Here is how the default operation mode will affect the operating coefficient:

gate_open

C_{op_to}=1.0; C_{op_from}=1.0;

gate_close

C_{op_to}=0.0; C_{op_from}=0.0;

unidir_to

C_{op_to}=1.0; C_{op_from}=0.0;

unidir_from

C_{op_to}=0.0; C_{op_from}=1.0;

Table Info

Identifier:

GATE_NAME, DEVICE

Parent Table:

GATE

Parent Identifier:

GATE_NAME

Include Block:

GRID

Several types of time series and operational controls can be placed on gates

At least one channel at every node must be ungated.
Gates can be removed using an operation rule that sets the gates install variable to zero. Gates that are uninstalled behave like normal nodes with equal water surface constraints between them. Operations and time series that manipulate the device operating coefficients and positions will be applied, but the devices will be totally ignored in computations to determine flow. flow.
Gates can be controlled by a number of variables that are time-varying and controlled by time series or operating rules:

install
- Install applies to the whole gate, not individual devices. When the gate is uninstalled (install=0) the gate ceases to exist, none of its devices are applied (although the continue to exist in the background). The gate is totally replaced by an equal-stage compatibility condition.
op_to_node
- Operating coefficient in the direction from water body to node.
op_from_node
- Operating coefficient in the direction from node to water body.
op
- Operating coefficient in both directions. This is just a convenience combo of the individual to/from node versions. It is write-only in operating rules, because it combines two variables and there is no single value that can be read.
position
- Physical operating position whose interpretation depends on the Position Control setting of the gate device. This is now deprecated in favor of more direct manipulation of things like gate elevation.
elev
- Weir crest or pipe invert elevation. This can represent evolution over time or a bottom-operating structure.
width
- Weir width or pipe radius. This usually represents evolution over time.
height
- Weir gate height, width of a flashboard. This can represent evolution over time or a top-operating structure like a radial gate.