《表3 尖频噪声频率：雷诺数对机翼尾缘噪声的影响（英文）》

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《雷诺数对机翼尾缘噪声的影响（英文）》

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Figure 4shows the PSD results，in which thefrequency f*is normalized by the chord length and the freestream velocity.The amplitude is normalized by its maximum value.It can be seen that for the low Reynolds number cases，only one single tone dominates the acoustic spectrum.As the angle of attack increases，the single tone displays a higherfrequency harmonic for the R1A4 case.For the moderate Reynolds number cases，discrete frequencies imposed on humps are identified，similar to the observation of Arbey and Bataille[4]and Desquesnes，Terracol，and Sagaut[8].At zero angle of attack case（R5A0）there is only one hump in the spectrum.For the other two cases（R5A2and R5A4），two humps are observed.The second hump is illustrated with a dashed rectangular frame.After conducting a careful inspection，it confirms that the second hump is not the higher-frequency harmonic of the first one.The two humps in the spectrum are related to different noise sources，which will be discussed in following sections.The tonal frequencies fnas well as the primary frequency fn*in the spectra of the six cases are listed in Table 3.The primary frequency fn*in the moderate Reynolds number cases equals fn which has the highest power spectral energy ineach hump，following Arbey and Bataille’s[4]approach.