Experiments on flow noise generation in simple exhaust geometries

摘要

Aerodynamic sound generation in mufflers has become a major concern for exhaust manufacturers, mainly in high-performance engines running at high speed, in which the contribution to overall noise from aerodynamic sources generated by the flow inside the muffler may even surpass the acoustic attenuation effect for which they are designed. Therefore, it would be convenient to gain some insight into the mechanisms by which a given geometrical arrangement may give rise to the generation of flow noise, so that a compromise may be sought between acoustic attenuation and flow noise production. In this paper, a series of experiments with geometries of increasing complexity is designed and performed in an attempt to account for the different mechanisms present in practice and their interactions. The final objective is to obtain some order-of-magnitude arguments regarding the expectable flow noise levels associated with a given geometry at given running conditions, and to check the applicability of usual scaling laws to measurements representative of current industrial practice. [References: 32]