To create an object, see “Creating, Selecting, and Editing Objects in GoPhast” (p. 17). When the object is complete, the Object Properties dialog box will appear (fig. 24). The Object Properties dialog box is also used to edit the properties of existing objects by double clicking on them or selecting Object|Edit Selected Object(s) or by using the “Show or Hide Objects Dialog Box” (p. 57).
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Figure 24. Object Properties dialog box |
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The Object properties dialog box is a tabbed dialog box with 2 to 4 visible tabs. The Properties and Data Sets tabs are visible for all objects. If the object in question is evaluated at nodes and only one object is being edited, an additional tab, Boundary Conditions, is visible. If only one object is being edited, the Vertices tab will be visible.
Evaluated at: When objects are used to assign values to data sets, the formula for the object can be evaluated either at the grid nodes or at the element centers. The choice helps determine for which data sets the object can set values. If an object is evaluated at elements, it can be used to set the values of a data set that is evaluated at elements. If an object is evaluated at nodes, it can be used to set the values of a data set that is evaluated at nodes.
Name: Each object is assigned a name. By default, when an object is created, it is assigned a unique name. However, object names are not required to be unique. The user can edit the name of an object if only one object is being edited. Object names are useful for identifying particular objects. For example, The View|Go To… menu item (p. 60) allows the user to move the view of the model so that a particular object is visible in the field of view by selecting the name of the object.
Names of selected objects: displays the names of all the objects that are being edited. The names can not be edited in the list.
Use to set grid element size and Grid element size: If the Use to set grid element size checkbox is checked, the value in the Grid element size edit box is used to help define the extent and node spacing of the grid. See “Using Objects to Specify the Grid” on p. 17 for more information.
Color object line, Color object interior, Set object line color, and Set object fill color: If desired, the lines and interiors of objects can be colored. These checkboxes and buttons allow the user to specify how the object will be colored. If one of the checkboxes is checked, the corresponding button becomes enabled. The user can then click the button to select the color used for the boundary line or interior of the object.
Set values of enclosed elements\nodes, Set values of intersected elements\nodes, and Set values of elements\nodes by interpolation: An object can be used to assign the values to a data set in any of the three ways indicated by these three checkboxes. If none of these checkboxes is checked and the Use to set grid element size checkbox is also not checked, the object can not affect the model in any way. The user is warned of this problem when clicking the OK button and given a chance to check one of the checkboxes.
The Set values of enclosed elements\nodes check box is used to specify that the object will be used to set the values of data sets or boundary conditions of nodes or of elements whose centers are inside the object. In the case of objects with a single associated third-dimension formula, a node or element is considered to be in the interior of the object if its center is inside the plan view of the object and the cell around the node or the element is intersected by the object in the third dimension (fig. 25).
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Figure 25. Elements affected by object with "Set values of enclosed elements” check box (shown in red) in top and front views. |
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The Set values of intersected elements\nodes check box is used to specify that the object will be used to set the values of data sets or boundary conditions of elements intersected by the object or of nodes whose cells are intersected by the object.
The Set values of elements\nodes by interpolation check box is used to specify that the object will be used to set the values of data sets (but not boundary conditions, p. 54) of elements or nodes by interpolation. The interpolation method is specified in the Data Sets dialog box (see p. 39). Interpolation only applies to two-dimensional data sets.
Associated third-dimension formulas: An object can have zero, one, or two associated third-dimension formulas. If an object has zero associated third-dimension formulas, it is a 2D object and can only be used to set the values of 2D data sets. If it has one or two associated third-dimension formulas, it is a 3D object and can be used to set the values of both 2D and 3D data sets. The third-dimension formulas set the position of the object in the dimension perpendicular to the one in which the object has been drawn. For example, if an object is drawn on the top view of the model, its third-dimension formula(s) set its position on the Z axis. An example of using the third-dimension formula for defining the properties of a geologic unit with an irregular upper and lower surface has been presented earlier in “Assigning Values to Data Sets” on p. 9.
X-, Y-, or Z-coordinate: The Z coordinate formula sets the Z coordinate of the object as a function of position for objects that have one associated third-dimension formula. For objects drawn on the side and front views of the model, the corresponding formula sets the X or Y coordinate respectively.
Higher X-, Y-, or Z-coordinate and Lower X-, Y-, or Z-coordinate: The Higher Z-coordinate and Lower Z-coordinate formulas sets the Z coordinates of the object as a function of position for objects that have two associated third-dimension formula. For objects drawn on the side and front views of the model, the corresponding formulas set the X or Y coordinates respectively.
The Data Sets tab is used to specify which data sets will be affected by an object and the formulas used to set the value for each data set. Alternatively, the interpolation mechanism built into PHAST can be used to specify the values that will be assigned for a particular object.
The main part of the Data Sets tab is made up of a table with three columns: Name, Affects, and Formula. Each row of the table represents a separate data set. If a data set is not being used in the current model, its name is written in italics and a light gray background is used for its cells. Under the “Affects” column, there is a checkbox for each data set. Only those data sets whose values can be set by the current object have their checkboxes enabled. The user can change which data sets can have their values set by changing their choices for “Evaluated At” and “Associated third-dimension formulas” on the Properties tab. Once the user has checked the checkbox for a data set under the Affects column, the user can enter a formula for the object or check the checkbox near the bottom of the tab labeled Use PHAST interpolation. PHAST interpolation is only applied to cells or elements enclosed or intersected by an object not to cells or elements that are assigned by interpolation among objects. When interpolating among objects, the formula for the object is always used even if PHAST style interpolation is used when assigning values to enclosed or intersected cells. See “PHAST-Style Interpolation” on p. 23 for more information.
The Boundary Conditions tab is used to assign boundary conditions with an object. Because all the boundary conditions in PHAST are assigned at nodes, the Boundary Conditions tab is only visible when the object is evaluated at nodes. In addition, the 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, Specified Solution, 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.
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 right side of the dialog box, the user can specify data related to the type of boundary condition that is being specified. All of the different types of boundary conditions include a table that specifies how the boundary varies with time. One of the columns in the table specifies when the boundary condition changes. The first time is required to be zero so it can not 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 GoPhast. GoPhast synthesizes all the times throughout the model and combines them correctly to create the PHAST input file.
All of the boundary conditions have parameters that vary with time. These time-varying parameters are specified in the table. The user can specify a formula for any of these parameters. If PHAST allows PHAST-style interpolation (see p. 23) to be used with the a parameter, a column of check boxes 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 left side 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 Leaky, River, and Well boundaries, additional information is required by PHAST, and which is specified on the right side of the dialog box. 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 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 (see p. 43).
If only one object is being edited, the Vertices tab will be visible. On it, the user can adjust the positions of vertices of the object by entering new values for their X and Y coordinates. If the coordinates that are entered in the Vertices tab are invalid in some way, all changes to the vertex coordinates will be ignored. The coordinates are invalid if they cause the object to cross itself. It is impossible to add or delete vertices on the Vertices tab. Tools described in the section entitled “Editing Objects” on p. 21 allow the user to add and delete vertices.