Erosion characteristics of dual cavitating waterjet under an unsubmerged environment

To improve the erosion performance of cavitating waterjet under an unsubmerged environment, dual cavitating waterjet, which is created by generating shear cavitation and separation cavitation in the jet beam, was first proposed in this study. The shear cavitation was produced by concentric high-speed and low-speed waterjets, and the separation cavitation was generated by an embedded central body. The morphology characteristics of the erosion region and the effects of non-dimension standoff distance (NSD), high-speed waterjet pressure (PH), and low-speed nozzle diameter (dL) on the erosion characteristics of pure aluminum Al1060 specimens impacted by the dual cavitating waterjet were investigated. The flow field at the nozzle outlet was also numerically studied. The results show that the erosion region is typically circular in shape and mainly composed of 3 parts, which are the center hole, the low damage region, and the shear cavitation ring. The center hole is always much deeper than the shear cavitation ring. The mass loss of the specimen first increases and then decreases with the increase in NSD. The waterjet has a better erosion effect when the PH increases, and the peripheral low-speed waterjet has a better effect on the artificial submerged environment when dL = 20 mm. The maximum mass loss is 58.1 mg at NSD of 14 when PH is 30 MPa and dL is 20 mm. This study provides a new type of waterjet generating effective cavitation under an unsubmerged environment, which could promote the applications of a cavitating waterjet.