In order to estimate cavitation erosion rate in hydraulic machinery the erosion resistance of materials can be investigated using a cavitating jet apparatus, standardized by ASTM G134. As the jet aggressivity is affected by the nozzle outlet geometry, this should also be considered to obtain reliable erosion tests. In this paper, we investigated the effects of the nozzle outlet geometry on the aggressivity of the cavitating jet by erosion tests, impact force measurements, and high-speed movie observations. The effect of Strouhal number, defined by the shedding frequency of the cavitation cloud, the width of the cavitating region, and the jet velocity, was also studied. The aggressivity of the cavitating jet peaked at a certain nozzle outlet bore, D, and outlet length, L. It was found that the Strouhal number, St, is 0.17 at the optimum D and L, even though the nozzle throat diameter d and injection pressure p1 were different. It was also revealed that the frequency of the large cavitation impact is closely related to the shedding frequency of the cavitation cloud.
ASJC Scopus subject areas
- Mechanics of Materials
- Mechanical Engineering
- Fluid Flow and Transfer Processes