自動車のフロントピラー及びドアミラーにおける空力騒音の発生メカニズムについて

摘要

流れによる音の発生メカニズムについては，rnLighthillのアナロジーを始め，多くの研究が行われてrnきた．powellは流体音の音源が渦の変化である理論をrn提唱し，Curleは物体がある場合，音の発生が物体表rn面の圧力変動に支配されることを示した．%The mechanism of aerodynamic noise generated from front pillar and door mirror of production automobile has been investigated by applying experiment and numerical simulation. In the simulation, the flow filed was firstly analyzed by Finite Differential Method (FDM) with 3rd-order upwind scheme, then Powell's acoustic analogy was applied to evaluate the acoustic source. Furthermore, the velocity fluctuation and acoustic source were clarified by the use of experiment. It is found that the interaction between vortices separated from front-pillar and door mirror results in the instability of boundary layer, which induces the aerodynamic noise near side window. As a result, controlling the separation vortices from front-pillar and door-mirror is the key point to reduce the aerodynamic noise of automobile.