Y-Junction
Use this feature to specify additional losses due to irreversible turbulent friction in a Y-junction, which can act as a split or a merger. The pressure drop is calculated according to
,
where Kf is a loss factor. Alternately, specify the pressure drop as a user-defined expression.
Figure 2-3: A Y-junction with local pressure indications.
The Y-junction can only be applied to a point that is connected to exactly two side branches and one main branch. The angle between each of the side branches and main must be equal, and must not be 120 degrees. See Figure 2-3. If these conditions are not met, use an n-way junction. The flow can go in either direction through each of the main branches and the side branch.
The automatic search for Y-junction points is possible. If you want to use this option, clear the Manual control of selections check box, the selections will be replaced by the automatic ones. If you want to modify the selection, select Manual control of selections again.
Friction Specification
The Loss coefficients options allows you to enter a value or expression for the Loss coefficient main branch Kside for the energy loss between side and junction and the Loss coefficient side branch Kmain for the energy loss between the main branch and junction (the default is 1.2). Both are dimensionless numbers. See Figure 2-3. The respective pressure losses are calculated as
.
For Nonisothermal Pipe Flow and Reacting Pipe Flow interface interfaces, the respective pressure drops are calculated as
.
The advantage of using loss coefficients is that they are readily available in engineering tables and textbooks.
Use the Pressure drops option to specify a value or expression for the pressure drop explicitly for each branch respectively:
Side 1 is the main pipe segment that has the lower index of the two in the selection list (for example, see the list in Pipe Properties).
Advanced Settings
The angle tolerance is used to specify the tolerance to a geometry not being a perfect Y. Increase the tolerance if you get an error message but accept the geometry even if does not fulfill the requirements for an Y-shape.
Constraint Settings
To display this section, click the Show More Options button () and select Advanced Physics Options.