Effects of air-injection pressure and nozzle diameter on flow and cavitation characteristics of aerated submerged waterjet

Abstract

The present study aims to elucidate flow and cavitation characteristics of the aerated submerged waterjet. A numerical study is conducted using the method incorporating the large eddy simulation (LES) and Schnerr-Sauer cavitation models. The numerical scheme is validated through an experimental work of visualizing cavitation clouds in submerged waterjet. With two nozzles of 2.0 and 4.0 mm in diameter, evolution of cavitation clouds is illustrated and compared under non-aeration and different air-injection pressures. The results show that cavitation intensity and air-injection pressure are not monotonically related. For the nozzle of 4.0 mm in diameter, the cavitation volume fraction reaches its maximum at an air-injection pressure of 0.3 MPa and declines drastically with further increasing the air-injection pressure. The shedding frequency of cavitation clouds varies inversely with the air-injection pressure. When increasing air-injection pressure, vortex structures remain similar for the nozzle of 2.0 mm in diameter, while for the larger nozzle, long and straight vortex structures prevail. Integrity of vorticity rings attenuates continuously with increasing air-injection pressure. The conclusions are expected to shed light on the mechanisms underlying cavitation evolution and inter-phase interactions in the aerated submerged waterjet.