Three-dimensional flow breakup characteristics of a circular jet with different nozzle geometries

Abstract

The Reynolds-averaged Navier–Stokes (RANS), large eddy simulation (LES), and coupled level set-volume of fluid (CLSVOF) methods were used to numerically investigate the breakup characteristics of three-dimensional unsteady circular jets. The jet breakup lengths and initial amplitudes of the surface waves of the jets from nozzles with different geometries were measured in a high-speed photography (HSP) experiment. The numerical model showed the formation, development, and variation of the jet flow structure. The circumferential and sinusoidal waves on the jet surface were captured by a high-speed camera, and the entrainment effect of the jet was studied with LES. The time-averaged velocity distribution fields were clarified with LES; the breakup of the liquid band structure and formation of droplets led to irregular changes in the droplet velocities, which indicates that the LES of the jet breakup was close to the actual situation. The relative errors between the simulation and experimental values for the breakup length and initial amplitude of the surface waves of the jet were less than 10%, which confirms that LES and CLSVOF can accurately and feasibly extract the details of circular jet breakup characteristics under intermediate- and low-pressure conditions. • Breakup characteristics of 3D unsteady circular jets numerically simulated. • Different methods compared with jet breakup length and initial surface wave amplitude. • Large-eddy simulation method showed good agreement with experimental results. • Results can be used to characterise intermediate-pressure jets for irrigation systems.