Unsteady PSP Technique for Measuring Naturally-Disturbed Periodic Phenomena
Unsteady PSP Technique for Measuring Naturally-Disturbed Periodic Phenomena
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DOI：
10.2514/6.2010-307
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发表时间：
2010-01
期刊：
影响因子：
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通讯作者：
Daisuke Yorita;H. Nagai;K. Asai;T. Narumi
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文献类型：
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作者：
Daisuke Yorita;H. Nagai;K. Asai;T. Narumi
为了理解非定常流动现象，测量高空间分辨率的时间分辨压力变化是很重要的。压敏涂料(PSP)具有提供高分辨率压力图像的能力，但其信噪比(SNR)不足以分析低速流动中的非定常流动结构。在周期性流动现象的PSP测量中，通常采用锁相法，但这种方法很难应用于含有振幅和相位自然扰动的非定常流动。为了解决这一问题，我们提出了一种新型的锁相方法，即利用经过带通滤波和信号微分等信号调理技术处理的触发信号对非定常压力场图像进行锁相。利用模拟信号验证了该方法的有效性，并应用于三维方柱模型的低速风洞试验。结果表明，由于卡门旋涡的周期性脱落，方柱侧面的非定常压力场是时间分辨的。侧壁下部的脉动压力较大，与压力传感器的数据吻合较好。
To understand unsteady flow phenomena, it is important to measure time-resolved pressure variations with high spatial resolution. Pressure Sensitive Paint (PSP) has a capability of providing high-resolution pressure images, but the Signal-to-Noise Ratio (SNR) is not high enough to analyze unsteady flow structures in low-speed flow. The phase-lock method is often applied to PSP measurement of periodic flow phenomena, but it is difficult to apply this technique to unsteady flow containing natural disturbances in amplitude and phase. To solve this problem, we propose a new type of phase-lock method in which images of unsteady pressure field are phase-locked using a trigger signal processed with signal conditioning techniques such as band-pass filtering and signal differentiation. The effectiveness of this method was verified using simulated signal and applied to low-speed wind tunnel testing of a 3-D square cylinder model. As a result, we could obtain time-resolved unsteady pressure field on the side of the square cylinder due to periodic Karman vortex shedding. The fluctuating pressures were found to be high at the lower part of the side wall, that is in good agreement with the pressure transducers data.