In most of industrial applications, rotating machines are operated in presence of ducts or nearby obstacles as for cooling fans placed on the back of a cooling unit or aircraft Environmental Control Systems (ECS) fans located in ducts. The acoustic scattering by surrounding surfaces should be then taken into account in addition to the free-field acoustic radiation. The present paper proposes to combine an extension of Amiet's theory for trailing-edge noise with a BEM solver. The method is validated on a fan test case, investigated experimentally at the Universite de Sherbrooke, in which an automotive fan is located in a duct used as complementary scattering surface. The necessary inputs for Amiet's theory are obtained using a scale-resolved simulation of the test setup, from which the trailing-edge wall-pressure spectra at different positions along the blade span are directly extracted. The comparison of the experimental results with the numerical method proves the necessity to take surrounding surfaces as scattering objects into account.
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机译：在大多数工业应用中，旋转机械在存在管道或附近障碍物的情况下运行，例如放置在冷却装置背面的冷却风扇或位于管道中的飞机环境控制系统（ECS）风扇。除自由场声辐射外，还应考虑到周围表面的声散射。本文提出将Amiet理论的后缘噪声扩展与BEM求解器结合起来。该方法在Universite de Sherbrooke进行的风扇测试案例中得到了验证，该案例中，汽车风扇位于用作互补散射面的风道中。 Amiet理论的必要输入是通过对测试装置进行比例解析的模拟获得的，从中可以直接提取沿叶片跨度的不同位置处的后缘壁压力谱。实验结果与数值方法的比较证明了有必要将周围的表面作为散射对象。
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