Numerical investigation of airfoil self-noise reduction by addition of trailing edge serrations

Jones, L.E. and Sandberg, R.D. (2010) Numerical investigation of airfoil self-noise reduction by addition of trailing edge serrations. 16th AIAA/CEAS Aeroacoustics Conference, , Stockholm, Sweden. 06 - 08 Jun 2010. 23 pp .

Record type: Conference or Workshop Item (Paper)

Abstract

DNS of the flow around a NACA-0012 airfoil are conducted, employing an immersed
boundary method to represent flat-plate trailing-edge extensions both with and without
serrations. Properties of the turbulent boundary layer convecting over the trailing-edge
are similar for all cases. For cases with serrations, the trailing-edge noise produced by the
flow over the airfoil is observed to decrease in amplitude, and the frequency interval over
which the noise reduction occurs differs depending on the serration length. The trailing-
edge noise appears otherwise largely unaffected by the serrations in terms of its directivity
and spanwise coherence. The hydrodynamic behaviour in the vicinity of the trailing-edge
extensions is investigated. The streamwise discontinuity imparted upon the turbulent flow
by the straight trailing-edge can clearly be observed in statistical quantities, whereas for
the serrated case no spanwise-homogeneous discontinuities are observed. The turbulent
flow through the serrations promotes the development of horshoe vortices originating at
the serrations themselves, which appear to promote a more rapid mixing within the airfoil
wake.

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