Theory Analysis and CFD Simulation of the Pressure Wave Generator

Abstract

In a pressure wave generator mainly consisting of a stator and a rotor with several valve blocks, pressure waves are generated by the continuous shear perturbation of fluids. In this paper, theory analysis of pressure wave generated in water hammer principle was conducted. Then a simplified CFD model of a pressure wave generator connecting the upstream and downstream pipes was established, and the grid and the time step independence tests were carried out. Generating process of controllable pressure waves in pipe flows was simulated, and the frequency and amplitude characteristics were obtained. The results suggest that pressure waves in upstream and downstream pipes have the similar shapes of approximate sinusoidal waveform and opposite phase. Pressure is inversely proportional to the first order derivative of x-velocity at a certain position, which is in good agreement with theoretical analysis; pressure wave amplitude increases with an increment of the rotational frequency of the rotor at the beginning of the pressure wave generator operation, but reaches the maximum amplitude in an optimal frequency when the generator is in stable operation, which means there exists a transition process for the generator. The critical frequency related to the first characteristics time can be applied to avoid the waveform distortion.