Applies To
Product(s):	AutoPIPE
Version(s):	ALL;
Environment:	N/A
Area:	Analysis
Original Author:	Bentley Technical Support Group
Date Logged & Current Version	Feb. 2017 11.00.00.22

Problem:

What are the criterion for generating a forcing function (i.e. new TIH file) at a point along the fluid transient path in AutoPIPE?

Solution:

Use the following procedure:

1. 1. One TIH function for the start point of the transient.

   2. One TIH function for every bend point along the path (this is typically the farthest point on the bend along the transient. If the fluid transient path is along the segment direction then this would be the far (F) point, otherwise it is the near (N) point). The force direction is along the bend tangent with orientation depending on the sign of the pressure rise specified.

   3. One TIH function for every kink point ( a kink is a change in pipe direction of more than 5 degrees).

   4. One TIH function for every point where a change in inside pipe diameter of more than 15 percent (|D2-D1|/D1 > 0.15), where D1 is the upstream diameter (This is the point closer to the source point) and D2 is the downstream diameter along the transient path.

   5. One TIH function at every flow rate change.

   6. One TIH function at every pipe segment change.

   7. Only one TIH function can be generated per point (e.g. flow and direction change can happen at a single point, but only one TIH is generated for the point).

Note: If there is a reducer element, the forcing function will be applied at the far end of the reducer (relative to wave propagation). When no reducer is found the forcing function will be applied at the following point downstream of the point where pipe size actually changes. A reducer element is recommended for this reason.

See Also

"Fluid Transient"

Bentley AutoPIPE