Circular cylinders with soft porous cover for flow noise reduction

Circular cylinders with soft porous cover for flow noise reduction The use of porous materials is one of several approaches to passively control or minimize the generation of flow noise. In order to investigate the possible reduction of noise from struts and other protruding parts (for example components of the landing gear or pantographs), acoustic measurements were taken in a small aeroacoustic wind tunnel on a set of circular cylinders with a soft porous cover. The aim of this study was to identify those materials that result in the best noise reduction, which refers to both tonal noise and broadband noise. The porous covers were characterized by their air flow resistivity, a parameter describing the permeability of an open-porous material. The results show that materials with low air flow resistivities lead to a noticeable flow noise reduction. Thereby, the main effect of the porous cylinder covers is that the spectral peak of the aeolian tone due to vortex shedding appears much narrower, but is not suppressed completely. Based on the measurement results, a basic model for the estimation of the total peak level of the aeolian tone was derived. In addition to the minimization of the vortex shedding noise, a reduction of broadband noise can be observed, especially at higher Reynolds numbers. The noise reduction increases with decreasing air flow resistivity of the porous covers, which means that materials that are highly permeable to air result in the best noise reduction. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Circular cylinders with soft porous cover for flow noise reduction

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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2016 by Springer-Verlag Berlin Heidelberg
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-016-2119-7
Publisher site
See Article on Publisher Site

Abstract

The use of porous materials is one of several approaches to passively control or minimize the generation of flow noise. In order to investigate the possible reduction of noise from struts and other protruding parts (for example components of the landing gear or pantographs), acoustic measurements were taken in a small aeroacoustic wind tunnel on a set of circular cylinders with a soft porous cover. The aim of this study was to identify those materials that result in the best noise reduction, which refers to both tonal noise and broadband noise. The porous covers were characterized by their air flow resistivity, a parameter describing the permeability of an open-porous material. The results show that materials with low air flow resistivities lead to a noticeable flow noise reduction. Thereby, the main effect of the porous cylinder covers is that the spectral peak of the aeolian tone due to vortex shedding appears much narrower, but is not suppressed completely. Based on the measurement results, a basic model for the estimation of the total peak level of the aeolian tone was derived. In addition to the minimization of the vortex shedding noise, a reduction of broadband noise can be observed, especially at higher Reynolds numbers. The noise reduction increases with decreasing air flow resistivity of the porous covers, which means that materials that are highly permeable to air result in the best noise reduction.

Journal

Experiments in FluidsSpringer Journals

Published: Feb 17, 2016

References

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