Numerical Investigation of Flow Characteristics in a Novel Triple-Feedback Fluidic Oscillator

This study uses a three-dimensional unsteady Reynolds-averaged Navier–Stokes (shear stress transport [Formula: see text]) model to compare a newly developed triple-feedback fluidic oscillator (TFO) with a conventional double-feedback oscillator (DFO), focusing on external sweeping performance and the TFO driving mechanism. The DFO shows canonical left–right switching, leading to a time-averaged jet with unilateral stretching and a biased footprint. In contrast, the TFO undergoes clockwise three-direction switching within one cycle and crosses the outlet center three times, producing an almost omnidirectional mean field with improved spatial coverage and higher central mean velocity. Over [Formula: see text], the TFO Strouhal number remains nearly constant, indicating stable oscillation. The TFO cycle is decomposed into three stages: separation-vortex growth, midsection stabilization, and downstream stabilization with dissipation. The vortex forms along the inclined wall to trigger deflection, remains quasi-stable with the primary jet, then convects downstream and dissipates to recenter the jet and initiate the next switch. Time-resolved resultant-momentum flux analysis shows synchronous modulation between feedback-exit momentum flux and mixing-chamber inlet velocity and a three-lobed polar trajectory, supporting a momentum-coupled deflection mechanism.