Abstract:

The frequency characteristics of self-resonating water jet determine the impact effect of jets under submerged conditions. Obtaining pressure pulsation signals of jets is significant to investigate frequency characteristics of self-resonating water jet. Usually, the pressure pulsation signals are obtained by some indirect method, such as erosion experiments and striking target tests. However, frequency characteristics of self-resonating water jet are analyzed experimentally by directly measuring flow pressure pulsation in a jet nozzle’s cavity. Through comparative analysis, it is proved that the spectrum characteristics of self-resonating water jet can be effectively obtained by collecting pressure signal in the cavity directly. This method has significant advantages over traditional striking target test for less random disturbance and more clear spectrum. Based on this experimental method, resonance frequency of the self-resonating water jet is obtained by spectrum analysis. Furthermore, a series of experiments are carried out to investigate the effects of flow parameters on the spectrum characteristics of jets. The experiment results show that the resonance frequency of the self-resonating water jet is not the direct amplification of disturbance frequency of inflow, and the disturbance frequency of inflow has little effect on jet resonance frequency. However, inflow velocity could greatly affect jet resonance frequency. With the increase of inflow velocity, the resonance frequency of jet and its amplitudes significantly increase. This demonstrates that the increase of inflow velocity can effectively improve the oscillation characteristics of self-resonating water jet.

Key words: pulsating flow, resonance frequency, signal analysis, self-resonating water jet