Turbulent kinetic energy and self-sustaining tones: Experimental study of a rectangular impinging jet using high Speed 3D tomographic Particle Image Velocimetry

Abstract : Impinging jets are widely used in ventilation systems to improve the mixing and diffusion of airflows. When a rectangular jet hits a slotted plate, an acoustic disturbance can be generated and self-sustained tones produced. Few studies have looked at the Turbulent Kinetic Energy (TKE) produced by the aerodynamic field in such configurations and in the presence of self-sustaining tones. The aim of this work is to investigate the energy transfer between the aerodynamic and acoustic fields generated in a rectangular jet impinging on a slotted plate. The present paper methodology is based on experimental data measurements using 3D tomographic Particle Image Velocimetry (PIV) technique and microphones. It was found that the spectrum of the TKE for Re=5294 (configuration of self-sustained tones) is fRe=5294=148Hzwhich is smaller than that of the acoustic signal F0,Re=5294=164Hz.A negative peak of correlation CRe=5294≈−0.24is obtained between the acoustic signal and TKE for Re=5294.These results may lead to conclude that the acoustic cycle should be covered by the TKE period and the two signals of both fields are in opposition of phase in order to obtain an optimal configuration for energy transfer