PHAST Boundary Conditions Tab

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The PHAST Boundary Conditions tab is on the Object Properties dialog box.

The PHAST Boundary Conditions tab is used to assign boundary conditions for a PHAST model with an object. Because all the boundary conditions in PHAST are assigned at nodes, the PHAST Boundary Conditions tab is only visible when the object is evaluated at nodes. In addition, the PHAST Boundary Conditions tab is only visible if a single object is being edited. To apply a boundary condition using an object, select the type of boundary condition to apply from the list of radio buttons. The choices are None, Specified head, Flux boundary, Leaky boundary, River boundary, and Well boundary. River and Well boundary conditions can only be used with objects drawn on the top view of the model. In addition Rivers can only be used with polyline objects and Wells can only be used with point objects. If the boundary applies to only one face of a cell such as a flux boundary, it will be applied to the face of the cell on which the object is drawn. For example, if an object was drawn on the top view of the model, any boundaries associated with that object will be on a horizontal cell surface.

All of the different types of boundary conditions include a table that specifies how the boundary varies with time. For each boundary, the user specifies the number of times that the boundary condition values are specified in the edit box labeled Number of times. On the bottom part of the dialog box, the user can specify data related to the type of boundary condition that is being specified. One of the columns in the table specifies when the boundary condition changes. The first time is required to be zero so it cannot be edited. The user must specify each of the other times when the boundary condition changes. The times that are specified do not need to be the same as those specified elsewhere in ModelMuse. ModelMuse synthesizes all the times throughout the model and combines them to create the PHAST input file.

The user can specify a formula for any of the time-varying parameters. If PHAST allows PHAST-style interpolation to be used with the a parameter, a column of checkboxes will be next to the parameter in the table with a heading indicating that the parameter can be interpolated. To use PHAST-style interpolation, check the checkbox for PHAST-style interpolation for the parameter and specify the interpolation direction distances and values using the radio buttons and edit boxes on the upper, right portion of the dialog box. If a boundary condition has more than one parameter that varies with time and the parameters do not change at the same times, the user may leave some values blank. A value may be left blank if PHAST-style interpolation is not used and the parameter has been specified at an earlier time. A time-varying parameter must always be specified for time zero.

For Specifed head, Leaky, River, and Well boundaries, additional non-time-varying information is required by PHAST. This information is specified on the bottom part of the dialog box. For a Specified head boundary, the user must specify whether the boundary also has a specified solution or an associated solution. For a Leaky boundary, Hydraulic conductivity and Thickness must be specified. For a River boundary, a River name, Hydraulic conductivity, Width, Depth, and Bed thickness must be specified. For a Well, a Name, Diameter, the open intervals in the well, and the method of allocating pumpage among the open intervals must be specified. In addition, if the open intervals are specified by using depths rather than elevations, a Land surface datum must be specified. Some of these data can be specified by using formulas. If so, a button (labeled Edit F()…) is provided next to the edit box in which the formula is specified. Clicking the button will call up the Formula Editor.

In the table containing the times, double-clicking on a cell in the table for a time will cause a drop down list of the times defined in the PHAST Time Control dialog box to appear. Double-clicking on a cell for a formula will cause a button labeled F() to appear. Clicking this button will cause to Formula Editor to appear so that the formula can be edited.