Self-Excited Oscillations of Wiping Air Knives Part II: Suppression of Jet Oscillation

Planar jets impinging upon a rigid surface exhibit large-scale oscillations and produce high-intensity tonal noise. These phenomena are due to an aeroacoustic feedback mechanism discussed in the first paper in this three paper series. This paper is part of an experimental investigation into the interaction of multiple impinging planar jets. An experimental facility of two auxiliary planar jets placed at an inclined angle either side of a planar impinging jet is used to examine the effect of auxiliary jet velocity on the aeroacoustic feedback mechanism of the centre jet. It is found that auxiliary jets of sufficiently high velocity can eliminate the oscillations of the planar jet. Particle Image Velocimetry (PIV) images and Proper Orthogonal Decomposition (POD) analysis confirm that the auxiliary jets have stabilized the planar jet and eliminated the large vortical structures. Static and dynamic pressure measurements performed in the presence of the auxiliary jets show an increase in the stagnation pressure at the plate along with a reduction in the fluctuating pressure.