Large-scale oscillating jet reconstruction and flow performance under confined inlet conditions

To enable jet oscillation in existing industrial impinging nozzles while retaining circular supply pipes, a large-scale fluidic oscillator equipped with a spindle-shaped flow disturbance element was proposed. The mechanisms of oscillation failure and reconstruction under confined inlet conditions were clarified, and the influence of disturbance element geometry on jet flow performance was systematically evaluated through numerical simulations. The results indicated that: (1) under the confined inlet condition, excessive centerline velocity weakened the vertical pressure difference in the mixing chamber and suppressed feedback recirculation and alternating vortical evolution, resulting in oscillation failure. (2) The disturbance element redistributed the inlet flow, increased the near-wall velocity, and re-established the vertical pressure difference and feedback recirculation, thereby restoring stable periodic oscillation. Although the Reynolds number decreased from 1.23 × 104 for the failed NFO to 1.11 × 104 for the reconstructed ICFO, the ICFO achieved a Strouhal number of 0.046. (3) The vertical blockage ratio β had the strongest influence on flow performance, and the maximum overall sweep angle of 60.51° was obtained at β = 0.35. This study advanced the understanding of oscillating jet dynamics under confined inlet conditions and provided a basis for the application of oscillating jets in novel industrial jetting technologies.