仿鱼体柔性变形运动流噪声特性研究

Research on the Characteristics of Flow Noise Induced by Fish-like Flexible Deformation Motion

鱼类游动具有低噪声、高效率等特点,鱼体摆动可抽象并表征为壁面的柔性变形运动。柔性变形将诱导产生复杂的涡系流场结构,其流噪声的形成机理及特性在很大程度上有别于常规问题。以美国国家航空咨询委员会开发的NACA0012翼型为研究对象,考虑流噪声计算的需求,建立可模拟柔性变形的数值模型。基于声类比理论获得其流噪声特性,揭示柔性变形对流噪声的影响机制,获得流噪声辐射场指向性。结果表明:柔性变形运动诱发的复杂涡系流场演变是流噪声的主要来源;不同方位下流噪声总声压级随距离的增加均呈衰减趋势;在柔性变形壁面正上方和正下方,辐射噪声达到极值,噪声指向与偶极子声源的辐射场特性最为相似。

Fish swimming has the characteristics of low noise, high efficiency, and the swing of fish body can be abstracted as a flexible wall deformation motion. Flexible deformation can induce a complex vortex structure in the flow field, of which the flow noise formation mechanism and characteristics are different from the conventional problems in a large extent. The NACA0012 airfoil developed by National Advisory Committee for Aeronautics is used as the research object. Considering the demand of flow noise calcula- tion, a numerical model based on the acoustic analogy theory is set up to simulate the flexible deforma- tion, revealing the mechanism of the effect of the flexible deformation on noise characteristics, and radia- tion directivity of flow noise is obtained. The results indicate that the complex vortex structure evolution induced by flexible deformation is the major source of flow noise ; the total sound pressure levels at different orientations decrease with the increase in distance; the total sound pressure level tends to be maximum just above and below the flexible deformation wall, and the noise radiation directivity is most similar to the radiation directivity of a dipole source.