Simulations of single- and two-phase shock tubes and gravity-driven wave problems with the RELAP-7 nuclear reactor system analysis code

This work presents an assessment of the capabilities of RELAP-7, the next-generation nuclear reactor system code, to solve single- and two-phase flows developing shock tubes and gravity waves. RELAP-7 is based on a seven-equation two-phase flow model with distinct phasic pressures. It is well established that these hyperbolic conservation laws can develop shocks and discontinuities thus requiring a stabilization numerical method. The all-Mach flow Entropy Viscosity Method (EVM) is now employed in RELAP-7 as a viscous stabilization approach. This paper briefly describes implementation of the EVM and uses open-literature test cases that exhibit pressure and gravity waves to show that the entropy viscosity method performs adequately for these single- and two-phase cases.