Cavitation loading and erosion produced by a cavitating jet
The aim of the project is to investigate the detail of cavitation loading and erosion process using a submerged jet cavitation technique. Large size cavitating jet apparatus in the University of Nottingham was used with an long orifice nozzle and experiments were carried out using tap water as a test liquid with upstream pressure ranging from 8D-120bar. Distribution of the mean pressure, cavity clouds and cavitation damage on a specimen have been obtained and their mutual relation was discussed. Effects of pressures and stand off distances on the characteristics of the erosion produced by the cavitating jet were studied and the results were compared with previous investigations. These include not only the weight loss but also the size of the damage and the jet length both related with the optimum stand off distance. Indentations on soft aluminium produced by the cavitating jet were investigated. Their size distributions were obtained for various pressures and stand off distances. Variations of the total number and the average size of indentations with stand off distance were also presented. The cavitation loading pulses were successfully measured by a novel piezoelectric pressure transducer using PYDF polymer and the pulse height measurement system, both of which were developed in the present project. During the process to determine the size of the sensitive area of the transducer, its effect on the pulse height was found. Then, the loading pressure was estimated from the pulse height and the indentation size distribution. The value estimated is around 2GPa and compared with results of the other investigators using similar method with different, vibratory and water tunnel, cavitation facilities. All of them show the similar magnitude. Good correlations of the indentation counting and the pulse height analysis with erosion results were obtained in terms of the intensity of cavitation loading. Simple calibration apparatus for the pressure transducer which utilises a pencil lead break.