Hydraulic Structures - BC

Hydraulic Structures - BC#Figure 1 displays the Hydraulic Structure Boundary Conditions form. In this form the user can create or edit hydraulic structures boundary group, assign the appropriate HS equations, as well as defining a flow series for the structure. A model will typically be configured to use grid masks to prevent flow except where the hydraulic structure is located, with the structure allowing flow across the mask.

Figure 1. Hydraulic Structure Boundary Conditions form.

In Boundary Condition Group frame, the user can enter the Group Name, or select from drop-down menus the appropriate Flow Control Type, Time Control and Flow Multiplier

In the Flow Control Type drop-down menu there a range of options based on rating curves or equations. In the case of the sluice gate, combinations of these to support rule-based and time variable control of the gate. Hydraulic structure flow options currently comprise:

Upstream Elevation Whole Channel Rating
Upstream Depth
Elevation Difference
Elevation Difference with Flow Accelerations
US and DS Elevations
Upstream Depth with Low Chord
Elevation Difference with Low Chord
Equation: Culvert
Equation: Sluice Gate
Equation: Weir

The details of how to configure and use the equation-based structures and flow table based hydraulic structures are described in the Flow Derived Hydraulic Structures section.

The Time Control drop-down menu is only enabled when the sluice gate option in Flow Control Type is selected. The options available in this menu are as summarized in the table below

Name

Meaning

Uncontrolled Structure	The hydraulic structure is uncontrollable type. The previous method of flow computational using lookup table or equation will be used
Controlled using Time-Series	The operation of the hydraulic structure is controlled using a time-series which defines the changes with time of gate openings or rating curves
Controlled based on Upstream Elevation	The operation of the hydraulic structure is controlled using control rules defined based on water surface elevation at an upstream location. This location can be different from the upstream cell of the structure.
Controlled based on Head Difference	The operation of the hydraulic structure is controlled using control rules defined based on the difference of water surface elevations at two locations upstream and downstream of the structure. These locations can be different from the upstream and downstream cells of the structure.

The user can also sets boundary Flow Multiplier options in the Boundary Condition Group frame. The drop-down menu allows selection from the following equations for the boundary flow multiplier, where q(h) are unit discharges and need to be multiplied by a dimension:

The user may also input the cell downstream from hydraulic structure in the Downstream I and J boxes. The length "L", bottom elevation and initial depth are all displayed for the downstream cell.

In the Rating Table/Flow Lookup Table frame shown in Figure 1 allows the user to set the head for each table. After the user has selected the table number, the All button applies the current flow table setting for cells in the current group. The user may also enter an Head Offset which will apply an offset to the result as described in the Head Lookup Table Equations frame.