Journal of Fluid Mechanics

Papers

Aerodynamic noise from a poroelastic edge with implications for the silent flight of owls

Justin W. Jaworskia1 c1 and N. Peakea1

a1 Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK

Abstract

The interaction of a turbulent eddy with a semi-infinite poroelastic edge is examined with respect to the effects of both elasticity and porosity on the efficiency of aerodynamic noise generation. The scattering problem is solved using the Wiener–Hopf technique to identify the scaling dependence of the resulting aerodynamic noise on plate and flow properties, including the dependence on a characteristic flow velocity . Special attention is paid to the limiting cases of porous-rigid and impermeable–elastic plate conditions. Asymptotic analysis of these special cases reveals parametric limits where the far-field acoustic power scales like for a porous edge, and a new finite range of behaviour is found for an elastic edge, to be compared with the well-known dependence for a rigid impermeable edge. Further numerical results attempt to address how trailing-edge noise may be mitigated by porosity and flexibility and seek to deepen the understanding of how owls hunt in acoustic stealth.

(Received December 04 2012)

(Revised February 28 2013)

(Accepted March 04 2013)

(Online publication April 16 2013)

Key words

  • aeroacoustics;
  • flow–structure interactions;
  • swimming/flying

Correspondence

c1 Email address for correspondence: J.W.Jaworski@damtp.cam.ac.uk

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