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RADIATED SOUND AND TURBULENT MOTIONS IN A BLUNT TRAILING EDGE FLOW FIELD

Daniel W. Shannon
Center for Flow Physics and Control Department of Aerospace and Mechanical Enginerring, University of Notre Dame Notre Dame, Indiana 46556, USA

Scott C. Morris
Department of Aerospace and Mechanical Engineering University of Notre Dame 110 Hessert Laboratory, Notre Dame, IN 46556 USA

Thomas J. Mueller
Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556

Résumé

The dipole sound produced by edge scattering of pressure fluctuations at a trailing edge is most often an undesirable effect in turbomachinery and control surface flows. The ability to model the flow mechanisms associated with the production of trailing edge acoustics is important for the quiet design of such devices. The objective of the present research was to experimentally measure flow field and acoustic variables to develop an understanding of the mechanisms that generate trailing edge noise. These measurements facilitated the study of the causal relationships between the turbulent flow field, unsteady surface pressure, and radiated farfield acoustics. Experimental methods used in this paper include Particle Image Velocimetry (PIV), unsteady surface pressure, and far field acoustic pressure. The model investigated had an asymmetric 45° beveled trailing edge. Reynolds number ranging from 1.2×l06 to 1.9×l06. It was found the small scale turbulent motions in the vicinity of the trailing edge were modulated by a large scale von Karman wake instibili-ties. This dependance of the broadband sound created by these motions on the "phase" of the wake instability was observed.