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A new experimental approach to study helicopter blade-vortex interaction noise.

机译：研究直升机叶片涡旋相互作用噪声的新实验方法。

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摘要

A unique and novel experimental approach has been developed to study the aerodynamics and acoustics of the helicopter Blade-Vortex Interaction in a controlled hover environment. This is achieved by having a non-lifting single-bladed rotor with a rigid hub interact with a carefully controlled gust disturbance that replicates the essential characteristics of the vortex velocity. This experimental approach termed the Blade-Controlled Disturbance-Interaction or the BCDI, decouples the rotor parameters from the charactersitics of the incident disturbance velocity, thus providing an ideal setup for studying the blade's aerodynamics and acoustic response in detail. Moreover, the angle of interaction between the disturbance field and the rotor blade can be controlled by orienting the gust, providing the ability to study both parallel and oblique interactions. The noise data was recorded at thirty different microphone locations.;A series of experiments at various rotor tip Mach numbers and interaction angles, replicating many of the conditions of helicopter BVI, were performed. The results show that the the directionality of the BVI noise is strongly determined by the interaction angle. A small change in interaction angle results in the radiation of noise over a larger azimuthal area compared to the parallel interaction. Moreover, as the interaction becomes more oblique, the peak noise elevation angle approaches closer to the rotor plane.;A linear unsteady lifting-line aerodynamic theory (corrected for chord-wise non-compactness) was used to estimate the blade aerodynamics during the interaction and hence the radiated noise. Although the theory under-predicted the noise levels for most of the cases, and did not replicate exactly the general pulse shape, the general directionality trends were predicted reasonably well. The theory was used to separate the contribution to the acoustics, from different spanwise blade sections, providing significant insights into the phasing mechanism of BVI noise.
机译：已经开发出一种独特而新颖的实验方法来研究在受控悬停环境中直升机叶片涡旋相互作用的空气动力学和声学特性。这是通过使具有刚性轮毂的非提升式单叶片转子与精心控制的阵风扰动相互作用来实现的，该阵风扰动复制了涡旋速度的基本特征。这种称为叶片控制扰动相互作用或BCDI的实验方法将转子参数与入射扰动速度的特征分离，从而为详细研究叶片的空气动力学和声学响应提供了理想的设置。而且，扰动场和转子叶片之间的相互作用角度可以通过定向阵风来控制，从而能够研究平行和倾斜相互作用。噪声数据记录在30个不同的麦克风位置。进行了一系列在不同旋翼尖端马赫数和相互作用角的实验，复制了直升机BVI的许多条件。结果表明，BVI噪声的方向性强烈取决于相互作用角。与平行相互作用相比，相互作用角的小变化会导致在较大的方位角区域上辐射噪声。此外，随着相互作用的增加，峰值噪声仰角更接近于转子平面。；线性非稳态提升线空气动力学理论（针对弦向非紧凑性进行了校正）用于评估相互作用期间的叶片空气动力学从而产生辐射噪声尽管该理论在大多数情况下低估了噪声水平，并且没有精确地复制一般的脉冲形状，但是可以很好地预测一般的方向性趋势。该理论被用来从不同的翼展方向叶片部分中分离出对声学的贡献，从而为BVI噪声的相位机制提供了重要的见识。

著录项

  • 作者

    Koushik, Sudarshan N.;

  • 作者单位

    University of Maryland, College Park.;

  • 授予单位 University of Maryland, College Park.;
  • 学科 Engineering Aerospace.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 225 p.
  • 总页数 225
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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