Numerical simulation of self-oscillating pulsed jet nozzle

Abstract

This paper investigates effects of velocity and pressure fluctuation at the outlet of a self-excited oscillating water jet nozzle. First, a three-dimensional model of the self-excited oscillating nozzle is established for modal analysis, which identifies two favorable modes with corresponding natural frequencies of 268 Hz and 500 Hz. Subsequently, using the Transient Structural and Fluent modules in Workbench, a three-dimensional fluid-structure interaction model of the self-excited oscillating nozzle system is created. Different initial velocities are applied at the nozzle inlet, inlet along with disturbances at various frequencies of the velocity. Finally, a bidirectional fluid-structure coupling simulation is conducted on the model. Research findings indicate that significant velocity and pressure fluctuations occur at the outlet when the applied disturbance velocity frequency matches the natural frequencies of the nozzle system identified in the modal analysis, specifically 268 and 500 Hz. The best fluctuation effect is observed when the disturbance velocity frequency is 500 Hz, with the velocity fluctuation amplitude approximately 1.9 times that of 268 Hz and 7.4 times that without the disturbance velocity. Similarly, the pressure fluctuation amplitude is approximately 1.8 times that of 268 Hz and 7.2 times that without the disturbance velocity.