The Screen junction type requires two connecting pipes. This junction type allows you to model the irrecoverable loss that occurs through a screen, mesh, or filter flow restriction. It also allows you to specify loss factors as a function of a flow parameter.

The Screen Properties Window follows the first of the two basic Properties Window formats, displaying the connecting pipes in a fixed format. The Screen junction does not have an explicit flow direction; it adopts a flow direction from the connecting pipes.

AFT Fathom provides four standard screen types for your use:

• Sharp-edged perforated plate

• Round-edged perforated plate

• Circular wire screen

• Silk thread screen

The loss factors for these screens are taken from handbook values. In addition to the standard screens that AFT Fathom provides, you may enter your own custom screen loss factor that is consistent with the application.

When you select Resistance Curve in the Loss Model section on the Loss Model tab, the Screen Properties window makes additional features available. Using these features, you can input pressure drops that vary with flow. To enter this information, you can specify polynomial constants, fit a curve to available data, or use interpolated x-y data.

When a variable loss is specified, AFT Fathom modifies the loss factor in the Solver to agree with the solution. You can choose any of the optional flow and pressure parameters provided, and you can specify the most convenient units.

An optional input in the Screen Properties Window is the Restricted Flow Area. This parameter describes the effective area restriction in the screen. This is done for the purpose of assessing cavitation. In most cases, information on the size of the restricted area must be obtained from handbook or test data.