Experimental Investigation of Cavity Dynamics in Convergent-Divergent Nozzle in Sheet Mode

The present experimental study focuses on hydrodynamic cavitation in a transparent horizontal convergent-divergent nozzle. In the experimental section, flow first occurs through a nozzle with a half convergent angle of 21° and then a divergent angle of 8° to exit. The static pressure and the flow rate are varied to achieve different cavitation numbers in sheet mode. Pressure fluctuations are measured at three different locations in the test section of the nozzle and analyzed. Images of the cavities at the throat section are captured, and the average cavity length is measured for all cavitation numbers in sheet mode. The cavity dynamics variation with time is analyzed with the help of image captured using a high-speed camera. The study confirms that the cavitation number and average cavity length are exponentially inversely proportional. Pressure fluctuations and their corresponding frequency are obtained for the different stages of cavitation. The experimental findings show that the sheet cavitation stage is the most turbulent and the magnitude of pressure fluctuations gets smaller as the cavity volume increases.