Effects of feeding pipe diameter on the performance of a jet-driven Helmholtz oscillator generating pulsed waterjets

Self-excited oscillation pulsed waterjet (SOPW) can take advantage of water hammer effect by generating discrete water slugs with large pressure oscillations. To further improve its efficiency, the performance of a jet-driven Helmholtz oscillator generating SOPWs was experimentally studied with feeding pipe diameter being considered. The axial pressure oscillations of the jets against the chamber length and standoff distance under four pump pressures were analyzed. It was found that feeding pipe diameter greatly affects the pressure oscillations. This dramatically depends on the pump pressure and is mainly caused by the wave and acoustic interactions in the oscillator. Feeding pipe which induces the maximum peak is the one that results in the minimum amplitude, and vice versa. Moreover, feeding pipe of diameter of 25 mm makes the amplitude fluctuate more violently at lower pump pressures. Further investigations related to the interactions of feeding pipe, hydroacoustic waves, and vorticities in shear layer should be performed.