Sound propagation in composite micro-tubes with surface-mounted fibrous roughness elements

The influence of surface roughness such as short fibers on sound propagation in cylindrical micro-tubes is investigated, both theoretically and numerically. Based on the calculated velocity and temperature fields, a theoretical model is developed to evaluate the sound propagation performance of composite micro-tubes containing periodical fibrous surface roughness elements. Finite element models are developed to validate the theoretical model, with good agreements achieved. The sound propagation performance of micro-tubes with surface roughness is compared with that of micro-tubes without surface roughness, with the influence of roughness geometry on sound propagation systematically investigated. Surface roughness can dramatically increase the sound energy consumed by viscous effect and decrease the sound energy consumed by thermal effect, resulting enlarged sound absorption.