Flow behaviors and velocity fields of non-oscillating and transversely oscillating jets

Abstract The near-field flow characteristics and jet fluid dispersion properties of non-oscillating and transversely oscillating jets issued from a fluidic oscillator were studied experimentally. A V-shaped fluidic oscillator was designed to induce transverse jet oscillations by merging two bifurcated alternatively issuing side jets. The characteristic flow patterns, evolution processes, velocities, vorticities, turbulence intensities and jet fluid dispersion capabilities in the median plane of the jets were examined. The characteristic flow patterns were obtained using laser-light-sheet-assisted smoke flow visualization method. The flow velocities were measured using particle image velocimetry. The jet fluid dispersion properties were analysed using tracer gas detection method. The non-oscillating jet was axial momentum-dominated—the axial momentum of the jet was limited within a narrow region around the central axis and was significantly larger than the transverse momentum. Therefore, the transverse velocities and vorticities were small and the dispersion of the jet fluid was relatively low. The transversely oscillating jets meandered in the near-field so the flow patterns presented a violent breakup of vortical flow structures and large transverse widths. The streamlines expanded transversely outwards and caused a part of the axial momentum to transfer towards the transverse direction. The vorticities and transverse velocities were increased and the axial velocities were decreased, so the dispersion of jet fluid was augmented in the transversely oscillating jets.