Water hammer analyses for high temperature and high pressure nuclear power piping have commonly overlooked temperature dependent fluid compressibility and two way fluid structure interaction (FSI) effects. This paper proposes a two way FSI numerical method for compressible fluids that accounts for temperature effects. Based on the Tait equation of state, temperature-dependent modified models for fluid density and wave speed are developed, and the three-dimensional (3-D) two-way coupling framework between computational fluid dynamics (CFD) and structural mechanics is established in ANSYS Workbench. The Reservoir Pipe Valve system is considered at the system pressure of 6 MPa, and the transient water hammer responses predicted by rigid wall and elastic wall models are compared at 50 °C, 150 °C, and 250 °C. The results show that increasing temperatures substantially reduces the bulk modulus of water, resulting in that the wave speed in an elastic wall at 250 °C is 32.07% lower than that at 50 °C. Compared with the conventional rigid wall model, elastic wall deformation further attenuates pressure impact, decreasing the pressure wave peak by approximately 14.16% at 50 °C. This attenuation effect weakens with increasing temperature, with a reduction of 4.96% at 250 °C. Ultimately, the proposed two way coupling method provides a more accurate numerical approach for the transient structural integrity assessment of nuclear power piping.

Fluid structure interaction (FSI); Water hammer; Tait equation of state; Compressible fluid