Engineering Assumptions

AFT Impulse is based on the following fundamental fluid mechanics assumptions:

  • Liquid-phase flow only

    • Entire system is wet (100% liquid full)

    • AFT Impulse is not meant for analysis of two-phase flow

  • One dimensional flow

  • Fluid properties remain constant during transient

    • Non-condensable gas release and dissolution is negligible

    • Wavespeed remains constant

    • No chemical reactions

    • Fluid density is not affected by pressure waves in the system

  • Vapor pockets formed during transient cavitation in pipes are considered point-volumes at section boundaries, and do not move

    • AFT Impulse is limited in its ability to model sustained cavitation and two-phase flow. The accuracy of results will be reduced when sustained two-phase flow conditions exist. Small cavitation volumes over short durations are handled with good accuracy.

  • Additional assumptions exist for particular modeling components and features, discussed where relevant