Modeling and analysis of two-phase, flow-induced instabilities using two-fluid model

Two-phase flow instabilities are known to occur in various two-phase flow systems. The hydrodynamic oscillations caused by such instabilities not only affect normal operation of a system but may also cause damage to system components. Because of the practical importance of the instability issue, especially in boiling water nuclear reactor (BWR) technology, several models and computer codes have been developed to date for the analysis of flow-induced oscillations in boiling channels and systems.;The purpose of this thesis is to present a complete new tool for the analysis of flow-induced instabilities in boiling water nuclear rectors, and boiling systems in general, using a one-dimensional two-fluid model of two-phase flow. This new model combines the linear frequency-domain methodology and the direct time-domain integration method of full nonlinear equations. The time-domain model has been compared against the frequency-domain model for stable and marginally stable cases and, then, used to investigate the response of unstable systems.;Extensive model testing and validations have been performed. The steady-state results show excellent agreement against the experimental data. Various new observations have been made in regard to modes of instability and modeling assumptions. The advantages have been shown by using a two-fluid model to analyze flow-induced instabilities.