Estudo experimental da hidroacústica de bordos de fuga flexíveis

Abstract

This work has as main objective to analyse experimentally the influence of the effects of the flexibility in the sound emissions of extensions of trailing edge in aeronautical structures. For this, an experimental apparatus installed in a cavitation tunnel was used, whose working fluid is water. Flow was studied around a rigid NACA 0012 profile with interchangeable trailing edge extensions. As extensions two flat metal plates with different thicknesses were used, and therefore, different values of flexural stiffness. The purpose of such tests is to obtain high Reynolds numbers, low Mach numbers and high fluid-structure loading factors (associated to the ratio of fluid to solid den- sity). With it is possible to accentuate the fluid-structural interactions and to capture these effects through hydrophone installed in acoustic chamber in the section of tests. This analysis allows to make comparisons of the experimental results with the theory of acoustic analogy. Increasing the flexibility of the trailing edge, according to this theory, reduces aeroacoustic and hydroacoustic emissions. However, the experimental results obtained show the opposite effect: the more flexible trailing edge led to a greater sound radiation. The results suggest that there is significant variation of the turbulence due to the effect of the trailing edge vibrations; a possible increase in turbulent kinetic energy due to surface vibration could explain the results obtained.