Toward the Development of a Comprehensive Nuclear System Analysis Code Based on Two-Fluid Model: Starting with an Isentropic Approach

In the complex field of nuclear reactor design and analysis, there is a continuous need for sophisticated computational models that can accurately capture the diverse and challenging thermal hydraulic phenomena during steady-state and transient conditions. This research sets the stage for the development of a comprehensive system analysis code for nuclear reactor thermal hydraulic design, starting with a fully implicit isentropic two-fluid model with four governing equations. The computational methodology for this model incorporated the Advection Upstream Splitting Method scheme with a staggered grid arrangement. The nonlinear system of governing equations was solved implicitly by employing Newton’s method while a numerical Jacobian matrix was calculated for the derivative terms, enhancing the stability and efficiency of the solution process. The performance of the model was assessed using three classical two-phase benchmark problems: water faucet problem, oscillating manometer problem, and air–water phase separation problem. The validation results indicate a reliable and accurate prediction of the model. Consequently, the successful development and validation of current two-fluid isentropic model provide a solid foundation for the future development of a comprehensive nuclear system analysis code based on the two-fluid model.