The Flow Boundary Condition Editor is shown in Figure 1. For flow BC's the Flow Assignment BC’s the Cell by Cell Options frame has several useful functions. The Edit button to allow allows the user to edit the associated time series. The All buttons next to the fields in this subframe allow the user to quickly assign all the boundary cells in the current group to the parameter specified in the adjacent field. For example, pressing the All next to the Flow Table field shown in in Figure 1 would set the flow series number for all cells in the US Flow flow group to the current Flood Flow “NC Q50” table settings. If the user has an input flow series for a river that requires distributing the river flow across several cells, the single time series of flow can be specified in the Flow Table. The and the Factor can then be set to split the flow appropriately among the cells. The Dist Factors button automatically sets the Factor based on each cell volumevolumes. A constant inflow can also be distributed in a similar manner by using the Distribute Dist Flow button . The user sets a value in next to the Constant Flow field. This constant flow will then be added to the time series for the flow table for this cell.
The Flow Assignment Cell by Cell Options frame also provides the Apply Flow Files button which allows access to quite a specialized option. This feature is predominantly used in wetting and drying models and is designed to handle the case where there is flow coming into a river with a flood plain. During low flow conditions the flow will go only into the channel, whereas in high flow conditions the flow should be distributed across the flood plain. Selecting the Apply Flow Files button displays a form where the user may browse to Flow and Head files. These are a flow table for total flow and a rating curve respectively. In this way the user can , allowing the user to import flow with the flow files to build a cell by cell variable inflow series. . This feature is predominantly used in wetting and drying models.
The user interface for boundary conditions has a uniquely designed editor with drop down menus for concentration table assignment to flow tables. When the user selects Flow Table as shown in Figure 1, they can use drop - down menu items to link flow tables with concentration tables. As with earlier versions of EFDC_Explorer, the concentrations specified in the Constant Concentrations frame are only used with constant flows. If specifying Specifying a constant salinity concentration of 5 ppt in the Constant Concentrations frame but with zero constant flow, even when if the boundary has flows assigned via a time series, the salinity input to the model will be zero. If using a time series for flows, the user must use a time series to assign salinitysalinities, even if they are constant. Note that the water column concentration settings, for both time series and constant, are fixed for all cells for the same group.
The Momentum Options frame for the flow boundaries provides the user with more control over how EFDC handles momentum flux on the cell faces. The options now include:
- Inflow Momentum Flux Ignored (default option)
- Momentum Flux on West U Face
- Momentum Flux on South V Face
- Momentum Flux on East U Face
- Momentum Flux on North V Face
The Flow Multiplier Switch subframe provides a drop-down box with a number of options, from normal inflow to various lateral inflow/outflow options. Constant concentrations and time variable Concentration Tables may also be edited from this frame.
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Figure 1 Boundary condition settings – Flow boundary.