# A Review on the Erosion Mechanism in Cavitating Jets and Their Industrial Applications
## 4 Industrial Applications of Cavitating Jets  
### Jet Hydrodynamics for Cleaning Applications  
[PERSON] et al. [67] introduced a new method based on the cavitation effect to assist soft abrasive flow (SAF) processing. The fluid used for high-speed soft abrasive flow has a low viscosity. The conventional SAF processing method is widely used due to its ability to avoid material damage. However, these SAF methods suffer from long polishing times and low efficiency. To address these issues, it was proposed to add a cavitation effect to assist the soft abrasive flow polishing. It was shown that the SAF with cavitation has a significantly shorter processing time and better polishing quality. There are two types of nozzles which are applied in hydrodynamic cleaning industry. The first type utilizes the maximum technologically possible discharge coefficient. In this case, the jet's destructive property is mostly characterized by hydrodynamic jet impact. Usually, such nozzle design is close to a de Laval nozzle. The second type of nozzle utilizes the cavitation effect and minimizes the discharge coefficient. This can be achieved by manufacturing and installation of impact sharp edges inside the nozzle, which generate more cavitation bubbles. [PERSON] et al. [33] performed erosion tests using nozzles of type one (Figure 14). The discharge coefficient was around 0.8. Aluminum plates were used in these experiments, with an exposure time of 60 min, an upstream pressure of 20 MPa, and a distance to the target of 66 mm. Other parameters are shown in Table 3 and Figure 14. Erosion results for three nozzles' configurations are shown in Figure 15, which illustrates that the 60\({}^{\circ}\) nozzle has the best erosion efficiency. [PERSON] and [PERSON] [68] used the nozzles of the second type. The nozzle used in this study is shown in Figure 16a. The discharge coefficient in this case was 0.6 which is lower than in [33]. Most of the experiments were conducted at 9.9 MPa inside the system, and the ambient pressure was varied from 0.14 to 0.40 MPa. Circular plates of aluminum alloy (A5056 BD) were used in erosion experiments. The erosion pattern for \"nozzle B\" is shown in Figure 16b. Impinging cavitation clouds collapse on the target causing ring damage on the specimen. When the standoff distance is short (10 mm; Yamaguchi and Shimizu [68]), a deeply eroded ring-like valley is also formed in the region near the center. In [33], the mass loss was measured at the end of each experiment for various stand-off distances. High water-based fluid of chemical solution type (HWBF) and tap water were used as test liquids. For \"nozzle A\", the mass loss for ambient pressures of 0.14, 0.20, 0.30, and 0.40 MPa had maximum values at standoff distances of 25-27.5, 20-22.5, 20, and 17.5 mm, respectively. For ambient pressures of 0.4 and 0.20 MPa, the mass losses had local maximums at 12.5 and 10 mm, respectively. The maximum mass loss for \"nozzle A\" was 150 mg after 2 h of exposure to the cavitating jet. From the experiments conducted at a standoff distance of 10-22.5 mm using \"nozzle B\", the mass loss had a maximum at a standoff distance of 20 mm and a local maximum at 12.5 mm for an ambient pressure of 0.14 MPa. When the downstream pressure is equal to or larger than 0.20 MPa, the mass loss had a maximum at a standoff distance of 10 mm. The maximum mass loss for \"nozzle B\" was 70 mg after 2 h of exposure to the cavitating jet. It was also shown that, in general, the mass loss with tap water was smaller than that in HWBF with the same operating conditions. The effect of high weight polymer on cavitation erosion was also described by authors. [PERSON] and [PERSON] [69] reported that the erosion rates increased when replacing water with polyacrylamide. In [70], it was shown that underwater jet cutting was significantly improved by polymer additions to the jet fluid. In [71], it was observed that the cavitation bubbles in the drag reducing polymer solution appeared larger than those in pure water.