The following Detailed Tee/Wye junctions have a different automatic orientation than defined on the Workspace

A Caution message in AFT Impulse

Full Message Text

The following Detailed Tee/Wye junctions have a different automatic orientation than defined on the Workspace:

Tee/Wye: J1, J2, J3, J4, J5, J6, J7, J8, J9, J10 and X more junctions. See the Model Diagnostics window for more information.

Explanation

The listed Tee/Wye junctions are using the Detailed Loss Model with the Arrangement Type set to "Auto", however, the automatic pipe orientation saved for the Tee/Wye Properties window is not consistent with the current orientation on the Workspace. For the K factors to be calculated correctly, the connections for pipes A, B, and C must be defined correctly. For example, on a 90 degree Tee, the branching flow pipe (C) in the Tee/Wye Properties window must match the intended branching pipe on the Workspace. If the branching pipe C was switched with the straight run pipe B, then the K factors would be switched. This can give incorrect results which may propagate through the model and compound with other Tee/Wye junctions since the Detailed Loss Model is dependent on flows and pressures.

A full list of the affected junctions can be found on the Model Diagnostics window (Tools menu > Model Diagnostics > Junctions > Tee/Wye > "Tee orientation inconsistent to workspace?").

Required Action

First, it is recommended to align the pipes on the Workspace in a way that resembles the true geometric orientation of the junction as depicted by either the 2D or Isometric grid. If there is a 90 degree angle, draw the pipes in a way that depicts this in the proper way. Furthermore, point the pipe Reference Positive Flow Direction towards the expected flow direction. The Auto Arrangement Type will utilize the directions and angles between each pipe when attempting to automatically configure the pipe connections. Therefore, following these modeling practices can increase the success rate of properly identifying and applying the K factors to the correct pipes. The tips below can be used to help quickly apply these principles:

  • The pipe direction can be switched by using the Reverse Pipe Direction icon on the Workspace Toolbar or using the F3 keyboard shortcut.

  • Display the Workspace Grid and enable Snap to Grid from the Arrange menu.

  • Rotate the Tee/Wye junction icon such that it is consistent with the pipes by right-clicking the icon and selecting either "Auto-rotate Icon" or "Customize Icon".

Next, open each Tee/Wye Properties window listed in the Caution message or in the Model Diagnostics window, configure and verify the proper pipe connections, click OK, and re-run the model. If needed, the Arrangement Type can be switched to "User" to guarantee that the junction retains the proper configuration.

If the losses due to the Tees/Wyes are negligible compared to the total system pressure drop, the user can consider switching to the Simple Loss Model which assumes the junction is lossless. This would be equivalent to morphing the junction into a Branch.