AEROACOUSTICS ANALYSIS OF TRAILING EDGE INCLUDING POROSITY EFFECTS

Resumo

Trailing edge noise on rigid surfaces is a significant source of sound in aircraft. In order to minimize

the sound radiated by a process involving acoustic waves, the present article investigates the effects of trail-
ing edge noise generation on rigid semi - infinite and porous plates. For this purpose, the Boundary Element

Method is employed to solve the Helmholtz equation, subject to boundary conditions that seek to model the
vibration and porosity effects of the plates. The study is developed for a two-dimensional problem, in which
the incident source of noise generation was a lateral quadrupole, positioned at the trailing edge. In this paper
the lateral quadrupole represents a turbulent vortex in the boundary layer of the plate, according considerations
presented in the literature. Initially, the study verified the acoustical directivity for the rigid plate with the wave
numbers k = 0.1, 1, 5 and 10. In a second moment, the directives for the porous plate with k = 0.1 and 10 were
analyzed. From the results it was found that because the sides of the porous plate have opposite phases, the
pressure variation on the surface of the plate opposes pressure in the region above it causing noise reduction. It
was also found that the porosity effect causes noise reduction more effectively at low wave numbers.