The flow characteristics of cavitation water jets with different nozzle structures

A new type of self-excited oscillating cavitation nozzle was proposed, and numerical simulations of the self-excited oscillating nozzle (SEON), organ pipe nozzle (OPN), and column nozzle (CN) were carried out by using the large eddy simulation model and Zwart–Gerber–Belamri (ZGB) cavitation model in this work. The attached-wall flow mechanism of automatic switching in the cavity of the oscillating cavitation nozzle was revealed, and significant differences in the jet mixing capacity and jet impact characteristics of different nozzle structures were found. When the inlet pressure is lower than 10 MPa, the SEON nozzle shows better impact characteristics than the traditional OPN and CN jet nozzles. However, the OPN has the highest peak velocity at the axial point, and the radial kinetic energy dissipation is less; As the jet develops downstream, the SEON structure has a high intensity of streamwise vortex and a large area of spanwise vortex disturbance, while the OPN and CN nozzles show a more centralized vortex structure and the cavitation cloud morphology. Energy coherent structures of larger size were obtained by dynamic modal decomposition, indicating that the SEON nozzle produces better cavitation and dispersion. This study aims to provide guidance for the selection of jet nozzles with different performance parameters in various engineering fields.