
	Applies To

	Product(s):	AutoPIPE,
	Version(s):	ALL
	Environment:	N/A
	Area:	modeling
	Original Author:	Bentley Technical Support Group

Problem:

Provide details about modeling SLUG flow in AutoPIPE

Solution:

1. Modeling Slug flow is covered in one of our official AutoPIPE training classes in detail. Please contact your Account Manager for training options and pricing.

Slug Flow Analysis V11, Practice Workbook (v. TRNC02988-1/0001)

a. Page 9 of the document, step 3, the user is asked to open the Time History Location Command. The user must create this file using one of the methods mentioned below:

i. Manually fill out the Time History Location dialog as needed.

ii. Manually create with Text editor application

A time history load file may also be constructed as an external, ASCII text file using any text editor software. Refer to AutoPIPE help for instructions in "Creating an ASCII Time History Load File (THL)"

iii. Semi automatic create and manual modify

Using the Fluid transient module, generate a transient that follows the intended path. The will automatically generate 65% of the information needed. Next navigate to the folder containing the model and open the THL file with any text editor. For each row with a node point delete, from column 72 to the end of the row. Also, after the last row of node points, delete all line to the end of the file

Example:

Finally, with the THL file opened in a text editor, insert rows as needed (ex. A01 N, A04 N, A06 N, and A09 N) while being mindful of the TIP file setting, scale, direction, and time.

Example:

2. You can find some time history examples in the online help under:

Help> Contents> Modeling approaches> example systems:
Water hammer(Time history) example (ap50sr1.dat)
Steam relief (time history) example (apham1.dat)

3. We do not have a procedure for equivalent static analysis. The ZPA option in time history attempts to do an approximate static analysis by applying peak forces to better capture reactions for rigid supports. The fluid transient load generator (Load> fluid transient) will show the peak forces due to valve closure or steam hammer for every two consecutive pipe bends. these can be used in a static analysis if needed.

For example, model apham1.dat, the file W1.THL is shown below. The first force is 1428 lbs applied at valve location C12. The force is larger for longer legs The leg length corresponding to 1428 lbs is 23 ft.. These forces can be applied as static loads under a User case if needed.

W1.THL from Apham1.dat example model: POINT TIH FILE SCALE DX DY DZ TIME(sec) FORCE(lbf) LENGTH(ft) VEL.(in/sec) C12 W1C12 1.000 0.000 0.000 1.000 0.005000 1428.57 23.00 -48.97 C10 N W1C10N 1.000 1.000 0.000 0.000 0.010522 5341.61 86.00 -48.97 C05 N W1C05N 1.000 0.000-1.000 0.000 0.031169 496.89 8.00 -48.97 C04 N W1C04N 1.000 1.000 0.000 0.000 0.033090 1987.58 32.00 -48.97 C01 N W1C01N 1.000 0.000 1.000 0.000 0.040773 360.25 5.80 -48.97

4. Why is there a force at the near and far points of a bend in slug analysis but not in the Load> Time history analysis?

When doing time history analysis you would need forces at both near and far point or else resolve these at the midpoint of the bend.

If you are performing static analysis, placing forces at both ends would cause the main force to cancel and that would not be appropriate. For example the force on the far end of one bend and near end of the next bend would be equal and opposite. This is not true in time history analysis as there is a phase between these forces. So the approach of applying forces at the near point only (i.e. along the flow direction) for static analysis is reasonable.

Note: The ZPA option in time history can sometimes be conservative as it applies the peak dynamic forces at the same time.

03. Modeling Slug flow in AutoPIPE

Problem:

Solution:

See Also