# A Study of Cavitation Erosion in Artificial Submerged Water Jets
## 1 Introduction
[PERSON] [10] conducted erosion tests and measured the impact load of bubble collapse using a standard cavitation liquid injector. The incubation period was evaluated based on the cumulative damage rule by measuring the cavitation impact load acting on the specimen surface. The development of the cavitation cloud is closely linked to the water jet erosion process. To date, numerous experimental studies have been conducted on cavitation jets. However, cavitation jets are characterized by intense turbulent flow, typically occurring in regions of higher speed and lower pressure. The cavitation effect involves complex inter-phase interactions, making it challenging to capture detailed information using conventional experimental methods. With the rapid development of computational fluid dynamics (CFD), numerical simulation has emerged as an important approach for studying the characteristics of cavitation jets [11; 12; 13]. Numerical simulations offer the ability to visualize flow structures that may not be observable experimentally and capture intricate flow details, prompting many researchers to conduct extensive studies on cavitation jets using computational methods. For instance, [PERSON] [14] applied computational fluid dynamics methods to optimize nozzle geometry. The optimized parameters led to a 9.41% increase in the axial maximum vapor fraction at a depth of 50 m underwater, significantly enhancing the cavitation effect. [PERSON] et al. [15] investigated submerged cavitation jets in a narrow cylindrical bore under different back pressure conditions. The results indicated that, for a given pressure boundary, the impact force increases with the spacing of the target plate. Furthermore, the influence of spacing on the impact force diminishes as the target plate moves farther away. [PERSON] et al. [16] studied the effects of various structural parameters on the cavitation effect and compared the numerical simulation results with experimental findings. Their research demonstrated that increasing the length and diameter of the resonator promotes cavitation occurrence and enhances the structural stability of the flow domain. When performing numerical simulations, the choice of turbulence model significantly impacts the accuracy of the results. The Reynolds-averaged Navier-Stokes (RANS) method may not yield accurate simulation results, particularly when dealing with the unsteady behavior of cavitation effects [17]. The Large Eddy Simulation (LES) method has been employed to simulate cavitation effects around hydrofoils or provide high-resolution turbulence simulations within nozzles [18]. However, the computational requirements of the LES method limit its industrial applicability. To strike a balance between computational resources and accuracy, a hybrid approach combining the RANS method and LES method has been utilized for simulating cavitation effects, such as the Scale-Adaptive Simulation (SBES) model, which can capture the instability and periodicity of cavitation clouds [19]. Moreover, the SBES model can capture more turbulent details when simulating super-cavitation flows generated by high-speed submerged water [20]. However, most of the literature on cavitation water jets predominantly focuses on theoretical studies and engineering applications conducted under submerged conditions. In comparison, artificial submerged cavitation water jets have received relatively limited research attention [21; 22]. Accurately predicting the periodic distribution pattern of cavitation clouds and cavitation erosion in artificially submerged cavitation water jets remains a challenging task. Several researchers have tried to produce an artificially submerged jet in the air by injecting a high-speed water jet into a concentric low-speed water jet for cutting rocks or cleaning. However, the aspect of the cavitating jet in the air was not clear [23; 24; 25]. The objective of this study is to investigate the cavitation erosion characteristics of artificially submerged cavitation water jets.