Detection of small-amplitude periodic surface pressure fluctuation by pressure-sensitive paint measurements using frequency-domain methods
Detection of small-amplitude periodic surface pressure fluctuation by pressure-sensitive paint measurements using frequency-domain methods
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DOI：
10.1007/s00348-018-2550-z
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发表时间：
2018-05
影响因子：
2.4
通讯作者：
T. Noda;K. Nakakita;Masaki Wakahara;M. Kameda
中科院分区：
文献类型：
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作者：
T. Noda;K. Nakakita;Masaki Wakahara;M. Kameda
压敏漆图像测量技术是分析低速气流中物体表面非定常压力场的有效手段。在这项研究中，由于音调后缘（TE）噪声的二维NACA 0012翼型的表面压力脉动定量检测使用多孔阳极氧化铝PSP（AA-PSP）。使用12位高速互补金属氧化物半导体（CMOS）相机捕获PSP在蓝色激光二极管照射下的发射。使用标准的基于强度的方法将捕获图像的强度转换为压力。为了提高非稳态PSP数据的信噪比，对三种基于快速傅里叶变换（FFT）的图像处理方法进行了测试。除了两个基本的FFT技术（全数据和合奏平均FFT），使用的相干输出功率（COP），其中涉及的PSP数据和使用逐点声级计测量的信号之间的互相关的技术进行了测试。初步测试表明，随机光子散粒噪声占主导地位的强度波动捕获的PSP发射高于200赫兹。通过分析以10 kfps记录的40，960个连续PSP图像，成功测量了与TE噪声相关的压力波动，TE噪声的主频率约为940 Hz。利用功率谱的定量验证表明，COP技术是识别与TE噪声直接相关的压力波动的最有效方法。当使用COP而不使用另一个风关数据时，可以以10 Pa的分辨率（振幅为4 Pa）区分功率差。由于背景噪声的消除不充分，所以不能通过总体平均FFT来实现该分辨率。
Image measurement using pressure-sensitive paint (PSP) is an effective tool for analyzing the unsteady pressure field on the surface of a body in a low-speed air flow, which is associated with wind noise. In this study, the surface pressure fluctuation due to the tonal trailing edge (TE) noise for a two-dimensional NACA 0012 airfoil was quantitatively detected using a porous anodized aluminum PSP (AA-PSP). The emission from the PSP upon illumination by a blue laser diode was captured using a 12-bit high-speed complementary metal-oxide-semiconductor (CMOS) camera. The intensities of the captured images were converted to pressures using a standard intensity-based method. Three image-processing methods based on the fast Fourier transform (FFT) were tested to determine their efficiency in improving the signal-to-noise ratio (SNR) of the unsteady PSP data. In addition to two fundamental FFT techniques (the full data and ensemble averaging FFTs), a technique using the coherent output power (COP), which involves the cross correlation between the PSP data and the signal measured using a pointwise sound-level meter, was tested. Preliminary tests indicated that random photon shot noise dominates the intensity fluctuations in the captured PSP emissions above 200 Hz. Pressure fluctuations associated with the TE noise, whose dominant frequency is approximately 940 Hz, were successfully measured by analyzing 40,960 sequential PSP images recorded at 10 kfps. Quantitative validation using the power spectrum indicates that the COP technique is the most effective method of identification of the pressure fluctuation directly related to TE noise. It is possible to distinguish power differences with a resolution of 10 Pa(4 Pa in amplitude) when the COP was employed without use of another wind-off data. This resolution cannot be achieved by the ensemble averaging FFT because of an insufficient elimination of the background noise.