Experimental and numerical simulations to examine the mechanism of nozzle geometry affecting cavitation water jets

Abstract

The geometry of the cavitation nozzle is the major determinant of the cavitation process and cleaning effect. To better service the cleaning industry, it is necessary to understand the process by which nozzle geometry impacts cavitation. This research uses experimental flow visualization and large eddy simulation (LES) to study the cavitation effects of three different nozzle configurations (Cylindrical, organ-pipe and converging–diverging nozzles). The shedding frequency of the cavitation cloud was determined through power spectrum analysis (PSD). The collapse range of the cavitation cloud produced was measured using the frame difference technique (FDM). A cleaning experiment was carried out to remove the tube scale with the aim of assessing the performance of the nozzle. The findings indicate that under the impact of the re-entrant jet, the cavitation cloud was distorted and fractured, and large shear stresses were produced at the fracture sites. The cylindrical nozzle creates a flow field with more vapour, velocity, and Reynolds stress than the other two nozzles. The findings from the cleaning experiments indicate that the utilization of appropriate nozzle geometry and an optimal standoff distance can significantly enhance the efficiency of tube descaling. This paper can help choose the right nozzle geometry and standoff distance for the cavitation water jet cleaning process, offer crucial technical support for the efficient cleaning within tubes.