Applies To Product(s): AutoPIPE, Version(s): 2004, XM, & V8i Environment: N/A Area: modeling Subarea: Original Author: Bentley Technical Support Group Problem: Provide details about modeling SLUG flow in AutoPIPE Answer: 1. Modeling Slug flow is covered in one of our offical AutoPIPE trainging classes in detail. Please contact your Account Manager for training options and pricing. 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 historyanalysis? 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. See Also Bentley AutoPIPE External Links Bentley Technical Support KnowledgeBase Bentley LEARN Server Comments or Corrections? Bentley's Technical Support Group requests that you please submit any comments you have on this Wiki article to the "Comments" area below. THANK YOU!
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