An investigation of the abrasive water jet with an emphasis on the oblique impact of abrasive particles on the target plate is performed. Ultra-high jet pressure necessitates a close examination of the phenomena featured by small spatial and temporal scales. The effect of oblique impact is assessed from both numerical and practical aspects. Numerical simulation, implemented using the commercial code LS-DYNA, allows a detailed inspection of transient stress wave propagation inside the target plate. And impact experiments facilitate a qualitative description of resultant footprints of oblique water jet. Different incident angles of abrasive particles are adopted and a comparison is thereby unfolded. The results indicate that rebound, embedding, and penetration of single abrasive particle are three representative final operation states. Adjacent to the abrasive particle, the response of the target plate to oblique impact is reflected by von Mises stress distribution and plate deformation as well. Oblique impact arouses non-symmetrical stress wave distributions and distinct unbalanced node displacements at the two sides of the abrasive particle. As for the target plate, global surface morphology is in accordance with predicted effects. The most favorable surface roughness is not associated with vertical impact, and it hinges upon the selection of standoff distance. Furthermore, variation of surface roughness with incident angle is not monotonous.

Recent industrial applications have unfolded a promising prospect for submerged water jet. Apart from widely acknowledged water jet properties, submerged water jet is characterized by the formation and complex evolution of cavitation bubbles. These bubbles not just alter the flow behavior of submerged water jet but also pose a profound effect upon impinged solid surface. At low jet pressures, some conclusions associated with submerged water jet have been acquired, while studies at high jet pressures have rarely been reported. From today’s view, both numerical and experimental approaches manifest apparent limitations in the presence of high-pressure submerged water jet. Consequently, validation of numerical results cannot be implemented conveniently due to lack of relevant experimental results. The major purpose of the present study is to explore cavitation features in submerged water jets with jet pressures of 120 and 150 MPa. Numerical techniques are utilized to locate cavitation zone in submerged water jet stream and to delineate cavities as well. Meanwhile, velocity distribution in the jet stream is obtained to calculate jet kinetic energy. Under submerged conditions, bubbles disperse rapidly in ambient water and therefore impede the penetration of incident light. Thus submerged water jet stream cannot be distinguished accurately. Such a difficulty encountered in optical flow measurement and flow visualization for submerged water jet seems insurmountable. Thus experimental efforts are devoted to an interpretation of cavitation effect through examining surface morphology features of the solid sample impinged by submerged water jet. And these features are obtained quantitatively using an optical profiling system. The results show that the occurrence of cavitation depends largely on the shear effect between fluid layers with different velocity magnitudes. Annular cavity shape is typical for submerged water jets. The existence of cavitation can be maintained within a limited streamwise distance from the nozzle. Furthermore, different jet pressures result in considerably different cavitation severity and effective streamwise lengths of cavity. According to the footprints on the impinged sample surface, it can be concluded that the impingement effect is ascribed to both cavitation effect and jet kinetic energy. The footprint produced on the target surface is in accordance with that predicted with numerical techniques in terms of size and shape. Several important aspects associated with the cavitation phenomenon in the submerged water jet are clarified in the present study.