A Review of Acoustic Absorption Mechanisms of Nanoscopic Fibres

Advances in nanotechnology have provided acoustic researchers with a number of new materials with nanofibres and nanopores that can potentially be implemented as an acoustic porous absorber. The molecular behaviour of these new nanoscopic materials may have a significant influence on their sound absorption; in addition, their properties could play an important role in reducing the absorber thickness compared to the currently available materials. However, the absorption mechanisms of nanoscopic fibres are not fully understood and the application of numerical and analytical modelling methods to this problem is still at an early stage. This paper presents a review of numerical methods which have been implemented for various microand nano-scale analyses of relevance to the acoustics of nanofibres. The review is focused mainly on the application of non-continuum particle based approaches such as the Lattice Boltzmann Method (LBM) and the Direct Simulation Monte Carlo (DSMC) method, since it is expected that the flow behaviour for nanoscopic fibres will be in transition regime (where molecular mean free path is comparable to characteristic dimension) due to the high Knudsen number. The acoustic absorption mechanisms are thus likely to deviate from the continuum phenomena and modelling approaches applicable to flow associated with larger scale fibres. It is intended that this review will provide an overview of the potentially applicable approaches for the exploration of acoustic absorption mechanisms of nanoscopic fibres.