Interaction Between a Crossflow and a Spatially Oscillating Jet at Various Angles

Abstract

The quasi-time-resolved flowfields of spatially oscillating jets emitted by fluidic oscillators at various installation angles, velocity ratios, and oscillation frequencies are examined experimentally. The velocity fields are acquired plane by plane using a stereoscopic particle image velocimetry system. Dominant streamwise vortices are identified and found to prevail downstream. The flowfield at a given velocity ratio is independent of the oscillation frequency because velocity ratio and Strouhal number are proportional. For small Strouhal numbers, the flowfield behaves similar to that of a vortex generating jet. For higher Strouhal numbers, the crossflow experiences a steady, wide-spread jet. When the skew angle decreases, one of the former two dominating vortices diminishes until at a skew angle of 45 deg one vortex dominates the flowfield. At a skew angle of 0 deg (i.e., the plane spanned by the oscillating jet is parallel to the crossflow), the jet penetration is comparable to that of a steady jet, and a pair of co-existing, counter-rotating vortices is identified. When changing the inclination angle, the flow features in the far field reduce to two dominant streamwise vortices whose spanwise effect increases when the inclination angle decreases. Additionally, the Strouhal number effects are shifted toward higher Strouhal numbers.