期刊
APPLIED ACOUSTICS
卷 66, 期 6, 页码 607-624出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.apacoust.2004.02.005
关键词
porous materials; tortuosity; porosity; granular materials; characteristic lengths
类别
资金
- Engineering and Physical Sciences Research Council [GR/S42071/01, GR/S58935/01] Funding Source: researchfish
An acoustic method for obtaining the tortuosity, and porosity of thick samples of rigid porous materials consisting of large (>1 mm) grains or fibres is proposed. The method uses pulses with central frequencies close to 12 kHz and an approximate bandwidth of between 3 and 20 kHz. In this frequency range, inertial rather than viscous or scattering effects dominate sound propagation in large pores. This allows application of the high frequency limit of the equivalent fluid model. Both reflected and transmitted signals are used in the measurements. Tortuosity is deduced from the high frequency limit of the phase speed (obtained from transmission data) and porosity is obtained from the high frequency limit of the reflection coefficient once the tortuosity is known. The method is shown to give good results in the cases where significant scattering does not occur until frequencies much higher than the upper limit of the pulse bandwidth. Apart from its applicability to samples with several centimetres thickness, the method needs only one set of measurements with the sample to deduce both tortuosity and porosity. In principle the method can be used also to estimate characteristic lengths. However, the errors are found to be larger and the results less consistent than for tortuosity. (C) 2004 Elsevier Ltd. All rights reserved.
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