Development and verification of 3D single-phase water hammer code based on finite volume method

• Based on a finite volume framework, an innovative pseudo-two-phase conceptualization was proposed for single-phase water hammer simulation. • The two-fluid three-equation model was employed to calculate single-phase water hammer phenomena. • A three-dimensional single-phase water hammer pressure wave propagation calculating code was developed. • The proposed model and algorithm were verified by using simple cases from one-dimensional to three-dimensional. Water hammer has always been one of the most important thermal safety issues in nuclear power plants. The resulting pressure waves exhibit pronounced multi-dimensional propagation characteristics, particularly in structurally complex regions. However, traditional one-dimensional analysis methods have inherent limitations in this regard. Furthermore, conventional numerical approaches such as the method of characteristics (MOC) suffer from several limitations, including low computational efficiency, significant numerical dissipation, and limited applicability to complex grid systems. In response, a simplified “pseudo-two-phase” two-fluid three-equation model has been established in this study based on the finite volume method (FVM). On this basis, a three-dimensional analysis code for single-phase water hammer pressure wave propagation was developed. The core of this code is a time-step segmentation algorithm with pressure iteration, which effectively enhances the convergence and stability of the pressure–velocity coupling solution. To preliminarily verify the validity of the code, simulations were conducted successively on the one-dimensional single-phase water shock tube benchmark case, the pressure wave propagation in a two-dimensional case, and in a three-dimensional case. In the one-dimensional benchmark, superior accuracy in capturing pressure discontinuities was demonstrated by the proposed code when compared to the RELAP5 code and the Lax-Friedrichs scheme, achieving a maximum error of only 0.9% relative to the analytical solution. In the multi-dimensional verification, key physical processes, including wave propagation, reflection, and superposition, were successfully captured by the new code. The evolution of the pressure field showed good agreement with the results obtained from ANSYS Fluent, with maximum relative errors of 4% and 8.5% observed for the two-dimensional and three-dimensional cases, respectively. The relevant research results can provide some theoretical and methodological support for the analysis and evaluation of water hammers in nuclear power plant reactors.