Abstract: Pipe wall vibration process is simulated in this work using the CFD method with a dynamic mesh technique, and influence caused by pressure fluctuation of the flow in the pipe system is examined. A numerical model is developed that can overcome the defects in traditional forced vibration analysis－the closure problem in applying constant pressure boundary conditions and the overdetermined equations of the system. From the propagation characteristics of water hammers, the principle of mass conservation, and the barotropic relation between the density and pressure of water, a theoretical solution of pressure fluctuation magnitudes caused by pipe wall vibration is derived; superposition characteristics of pressure fluctuation are analyzed, along with the influence of domain parameters on pressure fluctuation magnitude. The simulation results indicate that once pipe wall vibration reaches a frequency of hundreds of Hertz, even with a magnitude as small as tens of microns, it may induce several meters of water-column pressure fluctuation, possibly leading to significant effects. And the amplitude of superimposed pressure fluctuation is less than twice the original one when the superposition characteristics of a reflected wave is considered. The calculations using our formula agree well with the CFD simulations, showing the same variation trends.

Key words: computational fluid dynamics, dynamic mesh, pipe wall vibration, pressure fluctuation, hydraulic vibration, forced vibration