COMPUTATION OF ENERGY-DISSIPATION IN TRANSIENT FLOW

A new model for the computation of unsteady friction losses in transie nt flow is developed and verified in this study. The energy dissipatio n in transient how is estimated from the instantaneous velocity profil es. The ratio of the energy dissipation at any instant and the energy dissipation obtained by assuming quasi-steady conditions defines the e nergy dissipation factor. This is a nondimensional, time-varying param eter that modifies the friction term in the transient how governing eq uations. The model was verified for laminar and turbulent flows and th e comparison of measured and computed pressure heads shows excellent a greement. This model can be adapted to an existing transient program t hat uses the well-known method of characteristics for the solution of the continuity and momentum equations.