Cross-Section Curve
By default, tanks are treated as having a circular shape with a constant cross section described by its diameter. If the tank has a constant cross section that is not circular, the user can select Non-circular and specify the cross sectional area. If the user selects Variable Area, it is necessary to provide a depth to volume table.
In a variable area tank, the cross-sectional geometry varies between the minimum and maximum operating elevations. A depth-to-volume ratio table is used to define the cross sectional geometry of the tank.
To Define the Cross Section of a Variable Area Tank
- Select the tank in the Drawing View.
- In the Properties window, click the Section menu and select the Variable Area section type.
- Click the ellipsis button (...) in the Cross-Section Curve field.
- In the Cross-Section Curve dialog that appears, enter a series of points describing the storage characteristics of the tank. For example, at 0.1 of the total depth (depth ratio = 0.1) the tank stores 0.014 of the total active volume (volume ratio = 0.014). At 0.2 of the total depth the tank stores 0. 028 of the total active volume (0.2, 0.028), and so on.