Erosion characteristics and mechanism of the self-resonating cavitating jet impacting aluminum specimens under the confining pressure conditions

In order to study the effects of the confining pressure on the erosion characteristics of the self-resonating cavitating jet under wellbore and deep-water conditions, experiments are conducted on aluminum specimens impinged by the organ pipe cavitation nozzle and the conical nozzle with the confining pressure in the range 0 MPa–10.0 MPa. Meanwhile, through the numerical simulation of the collapsing process of the cavitation bubble and the noise test, the cavitation erosion mechanism is analyzed. The experimental results show that the optimal standoff distance and the confining pressure can be obtained for the maximum erosion quantities, and the optimal standoff distance is 5 to 7 times greater than the equivalent nozzle outlet diameter and the confining pressure is about 2.0 MPa. Under the same conditions, the erosion caused by the cavitation nozzle is up to 2 times larger than that caused by the conical nozzle. According to the numerical simulation and the noise test, the cavitation erosion on the aluminum specimens is mostly caused by mechanical forces due to the high-frequency pressure pulse generated during the collapse of cavitation bubbles, while just a small part is caused by micro-jets.