A Hybrid Solution Method for the Two-Phase Fluid Flow Equations

This paper will present a hybrid solution algorithm for the two-phase flow equations coupled to wall heat conduction. The partial differential equations in the physical model are the same as in RELAP5. The hybrid solution algorithm couples two solution methods, the solution method currently employed by RELAP5 and an implicitly balanced solution method. The RELAP5 solution method provides a fast solution that is “close” to the correct solution. The implicitly balanced solution method provides an accurate solution that is very stable. The resulting hybrid solution method is both fast and accurate. Results will be presented that show the hybrid solution method is more accurate than the RELAP5 solution method for the same size time step. In addition, results will be presented that show when accuracy and CPU time are considered simultaneously that there are ranges when the hybrid solution algorithm is preferred over the RELAP5 solution method.