MODELING OF 2-PHASE BLOWDOWN FROM PIPELINES .1. A HYPERBOLIC MODEL-BASED ON VARIATIONAL-PRINCIPLES

In this paper, Geurst's variational principle for bubbly how is extend ed to generalised multicomponent two-phase dispersions. The present va riational principle allows both phases to be compressible in deriving the momentum equations. A mixture energy equation is obtained using No ether's invariant theorem and is shown to be comparable with the avera ging formulation. The hyperbolicity of the equations is achieved by fo rcing the flow to be marginally stable. Under the marginally stable co ndition, all the information related to the structure of the flow is f ound to be embedded in an inertial coupling constant and an expression for this constant is obtained based on critical flow data. The margin ally stability model gives correct sonic characteristics up to void fr actions of 0.8. The clearly defined sonic characteristics make possibl e the rigorous determination of the critical flow condition for rapid depressurisation of pipelines.