Acoustic Emissions of Semi-Permeable Trailing Edge Serrations

An experimental study of airfoil instability tonal noise with trailing edge serrations

This paper presents an experimental study of the effect of trailing edge serrations on airfoil instability noise. Detailed aeroacoustic measurements are presented of the noise radiated by an NACA-0012 airfoil with trailing edge serrations in a low to moderate speed flow under acoustical free field conditions. The existence of a separated boundary layer near the trailing edge of the airfoil at a...

AIAA 99-0231 Simulation of Acoustic Scattering from a Trailing Edge

Three model problems were examined to assess the diiculties involved in using a hybrid scheme coupling ow computation with the the Ffowcs Williams and Hawkings equation to predict noise generated by v ortices passing over a sharp edge. The results indicate that the Ffowcs Williams and Hawkings equation correctly propagates the acoustic signals when provided with accurate ow information on the i...

Statistical Estimation of Turbulent Trailing Edge Noise

A new computational aeroacoustic model suitable for the prediction of turbulent airfoil trailing edge noise is presented. The method (known as the RANS based Statistical Noise Model or RSNM) combines numerically generated, mean turbulence information with a Green’s function for a semi-infinite half-plane to generate a far-field acoustic auto-spectrum. As a preliminary application of the method,...

Computation of trailing-edge noise at low Mach number using LES and acoustic analogy

Morphological Variations of Leading-Edge Serrations in Owls (Strigiformes)

BACKGROUND Owls have developed serrations, comb-like structures, along the leading edge of their wings. Serrations were investigated from a morphological and a mechanical point of view, but were not yet quantitatively compared for different species. Such a comparative investigation of serrations from species of different sizes and activity patterns may provide new information about the function...