Abstract
As a reaction to the increasing noise pollution, caused by the expansion of airports close to residential areas, porous trailing edges are investigated to reduce the aeroacoustic noise produced by flow around the airframe. Besides mechanical and acoustical investigations of porous materials, the fouling behavior of promising materials is an important aspect to estimate the performance in long-term use. For this study, two sintered fiber felts were selected for a long-term fouling experiment where the development of the flow resistivity and accumulation of dirt was observed. Based on 3D structural characterizations obtained from X-ray tomography of the initial materials, acoustic models (Biot and Johnson–Champoux–Allard) in the frame of the transfer matrix method were applied to the sintered fiber felts. Flow resistivity measurements and the measurements of the absorption coefficient in an impedance tube are the basis for a fouling model for sintered fiber felts. The contribution will conclude with recommendations concerning the modeling of pollution processes of porous materials.
Highlights
The constant exposure to noise affects physical health and can cause insomnia
Mounted on trailing edges of airplane wings, the porous materials are exposed to dirt, which is expected to accumulate in the pores during service
After the last flow resistivity measurements, small circular samples were punched out of the bigger samples used for flow resistivity measurements to measure the absorption coefficient using an impedance tube
Summary
The constant exposure to noise affects physical health and can cause insomnia. Especially in areas close to airports, this has become a serious problem. Due to a rising number of flights, it is about to become even more serious Facing this problem, the noise reduction of commercial aircrafts has become important in engineering. Mounted on trailing edges of airplane wings, the porous materials are exposed to dirt, which is expected to accumulate in the pores during service. This would change the size and shape of the pores as well as the porosity, and, as a consequence, affect the aeroacoustic performance. As the porous material is carefully chosen to reduce the noise of specific phenomena, the affect of dirt must be known. A gradient based optimization algorithm is used to identify missing parameters that are mainly the viscous and the thermal length of the material
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