An Investigation of the Genaration Mechanism of Discrete Frequency Noise Relating to the Large Scaled Turbulent Organized Structures and Its Noise Control

大型湍流组织结构离散频率噪声产生机制及其噪声控制研究

基本信息

批准号：
09650210
负责人：
TANAKA Shuji
金额：
$ 2.11万
依托单位：
Toyota Technological Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Flow fields around a two-dimensional flat plate aerofoil emitting discrete frequency noise in a uniform flow have been determined, and the generation mechanism of the noise has been studied.Frequency analysis as well as phase-locked averaging technique were used for determination of flow fields. The wake velocity fields were obtained with I-type and X-type hotwire probes and the fluctuating pressure on the aerofoil surface was measured with small-sized semiconductor pressure transducers mounted in the aerofoil, whereas the sound level of emitted noise were artificially modified by inserting a circular cylinder with a small diameter in the near wake region. The flow details, such as organized structures in a turbulent wake flow as well as fluctuating pressures on the aerofoil surface, have been analyzed quantitatively, from which the generating mechanism of discrete frequency noise has been studied relating to the larged scaled organized structures in a turbulent wake.Clear coherent organized structures in a turbulent wake are confirmed in every case. The sound source of discrete frequency noise are distributed in a narrow region restricted near the traihing edge of the aerofoil. It has been quantitatively confirmed that the sound sources are generated from the fluctuating pressures due to the fluctuating velocities on the aerofoil induced from the turbulent organized structures in the wake. The span-wise correlations of the organized structures in the turbulent wake have a dominant effect on the sound pressure level of the discrete frequency noise.The calibratrion of the sound intensity mesuring system has been made, which shows that the location of the sound source can be determined within the accuracy of 1mm in the three-dimensional space.

已经确定了均匀流动中发射离散频率噪声周围的流场，并研究了噪声的产生机理。频率分析以及相锁定的平均平均技术用于确定流场。使用I型和X型热孔探针获得了唤醒速度场，并用安装在空气装饰机中的小尺寸半导体压力换能器测量了气压表面上的波动压力，而通过将圆形圆柱插入圆形圆形区域，可以将声音水平插入空气固定材料中，而将声音水平与小尾灯插入附近的循环效果。流动细节，例如湍流唤醒流中的有组织的结构以及驾驶表面上的波动压力，已经进行了数量分析，已经研究了离散频率噪声的生成机制，与湍流唤醒中的较大缩放的有组织结构有关。在每种情况下，在湍流唤醒中确认了湍流唤醒中的有组织结构。离散频率噪声的声源分布在狭窄区域，该区域受到限制的螺旋装置，在空气层的Traihing边缘附近。已定量证实，声源是由于在湍流有组织的结构引起的气压上波动的速度而产生的，这是由于波动的压力而产生的。湍流尾流中有组织结构的跨度相关性对离散频率噪声的声压水平具有主要作用。声音强度进行修饰系统的校准率已经建立，这表明可以在三维空间中确定声源的位置在1mm的精度内确定。