非定常表面压力的使用远程麦克风探头测量
Summary
Here, we present a protocol to measure, with high spatial resolution, the unsteady surface pressure in turbulent flows. This method demonstrates the construction of a remote microphone probe (RMP) and the determination of its frequency-dependent, complex transfer function. An analytical determination of the dynamic response is presented and validated.
Abstract
Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various characteristic length scales can result in pressure fluctuations over a wide frequency range. This property of turbulence requires sensing devices to have sufficient sensitivity over a wide range of frequencies. Furthermore, the small characteristic length scales of turbulent structures require small sensing areas and the ability to place the sensors in very close proximity to each other. The complex geometries of the solid bodies, often including large surface curvatures or discontinuities, require the probe to have the ability to be set up in very limited spaces. The development of a remote microphone probe, which is inexpensive, consistent, and repeatable, is described in the present communication. It allows for the measurement of pressure fluctuations with high spatial resolution and dynamic response over a wide range of frequencies. The probe is small enough to be placed within the interior of typical wind tunnel models. The remote microphone probe includes a small, rigid, and hollow tube that penetrates the model surface to form the sensing area. This tube is connected to a standard microphone, at some distance away from the surface, using a “T” junction. An experimental method is introduced to determine the dynamic response of the remote microphone probe. In addition, an analytical method for determining the dynamic response is described. The analytical method can be applied in the design stage to determine the dimensions and properties of the RMP components.
Introduction
物体表面的流体流动通常会导致不稳定和动荡是导致不稳定的表面压力（USP）。流引起的响声和振动往往这个不稳定的直接结果。由散热风扇，螺旋桨，和风力涡轮机产生的辐射声是由相关的USP 1来源为主。的美国专利中湍流的空间和时间特性的测定一般都需要以预测的辐射声音。
美国专利的统计特性中的自动谱密度的形式一般是给定，二点交叉谱密度，和空间相关函数2,3。可以根据不同的应用而变化所需要的频率响应。在许多风洞应用，10kHz至20kHz的响应是足够的。湍流运动的小尺度通常需要感测区域和传感器间距小于1毫米。
EXTEnsive实验研究，以获得湍流诱发压力波动已进行。一个直接的方法是使用嵌入式安装嵌入式传感器。这种方法通常采用的麦克风大型阵列，因为每个传感器只能测量在一个离散点的压力波动。在该方法中使用的典型的传感器是压电换能器，通过高奇4建议。压电式传感器的阵列可以是昂贵的，和测量的频率范围通常是小于10千赫兹。
直接表面安装的麦克风通常用作便宜的USP传感器5。麦克风具有高灵敏度，这是低速流动的显着的益处。然而，这也导致了传感器饱和的风险时的压力大振幅的波动都存在。这种方法是不适合用于大曲率的不连续性，或几何形状过于薄，以包含整个传感器表面。
<p class="“jove_content”">获得的光谱和空间信息的间接方法是使用薄膜齐平安装到一个表面6。的时间和空间依赖性振动运动进行测量，然后转换为表面用膜的已知机械性能的压力的统计信息。此方法需要仔细的设计，实施和膜的动态响应的精确校准。另外，该振动测量设备，如激光多普勒振动计，是昂贵的。最后，这种方法只能适用于平面。压敏涂料（PSP）是可用于测量不稳定的表面压力的另一种技术。这种技术需要在透明聚合物粘合剂，这将导致内的分子，因为它们是由特定波长的光照射被激发到更高的能态到待涂覆的表面。随着分子进行氧淬火，能量再在成比例的氧分压的速率，导致发光是成反比的表面压力7租用光。相比麦克风时到PSP方法的主要缺点是在测量的相对低的灵敏度。这限制了PSP相对高速流动的应用。
本通信描述了美国专利，它使用一个远程麦克风探针（RMP）的方法。这种方法首先由英格伦和Richards 8所述。的概念使用连接到表面压力抽头具有中空管的标准微型麦克风。在模型表面上的不稳定压力将行进到在声波的形式油管。管用作“波导”，以允许麦克风，其垂直地安装在管道，以测量声波。波浪然后继续到另一个管足够长，以消除大振幅声řeflections。
英格伦和Richards通过应用和贝赫9 Tijdeman概述确定RMP的动态响应的分析方法。 Perrenes和罗杰·10利用的RMP来衡量过度高扬程设备二维机翼表面的压力。他们开发了一种探针与被连接到一个27厘米长的刚性管经由两个单独的步骤的变化从0.7毫米膨胀至2.5mm表面的直径为0.5mm的毛细管。每一步的变化引起所述管的声阻抗相对大的变化。勒克莱尔和Bohineust 11研究湍流边界层下的墙壁压场。他们使用了一种直径恒定的贼法牧，由弗兰佐尼和Elliott 12的建议。然而，动态响应是只在一个有限的频率范围内足够高。 Arguillat 等人 13设计的制冷剂管理学习发送到车厢内部的噪声。他们测试各个管进行压力变动的麦克风。 Yang等人 14通过使用管道传递函数的方法，它类似于本报告中介绍的方法校正油管失真。 Hoarau 等 15研究了分离区下游的墙压迹。他们设计的RMP有恒定的内径和油管是完全非刚性。
根据先前的研究中，表面压力测量用的RMP获得的精确度主要依赖于该涉及的表面压力到麦克风压力探针的频率依赖传递函数的确定。下面的章节将描述一个贼法牧的几何形状，既简单又有效。实验和分析方法将被引入并为了准确地确定制冷剂管理的动态响应验证。该分析模型允许一个贼法牧为Optimized在设计阶段对潜在的广泛的应用范围。
的RMP可以用于在宽的频率范围内测量压力的波动。相对较高的空间分辨率可以提供在空间上分布的不稳定压力场16的特性的详细信息。作为探针小，制冷剂管理可以用来测量在复杂几何形状，如大曲率或有限间距17压力波动。此外，连接表面抽头和麦克风传感器管可以在麦克风减小感应压力波动的幅度。因此，RMP传感器的几何形状和参数的合理设计产生获得相对于嵌入式安装，直接将话筒模型表面时有显著较少限制USP特征的方法。
制冷剂管理的RMPThe一般结构的结构图1中示出</strong>的信息。制冷剂管理由一个管从模型表面导致的膨胀部，并从该扩大部分延伸到第二管的“摇篮”。然后，第三管被连接到充当消声终止。摇篮是用于房屋麦克风和管连接的机械加工的塑料部件。制冷剂管理结构的细节可以为各种实验条件进行调整。第二，大径管的目的是允许的相对笨重的麦克风和支架进一步来自USP测量点被放置而不显著降低测量灵敏度。如果它不是必要该第二管可被消除，并扩大部分可以建在摇篮。消声终止制成的软塑料，这是大约2到3米的长度。
对于本演示中，贼法牧的设计是为表面压力波动的测量浊度下优化ulent 如图2所示边界层没有流向压力梯度，该第二管被淘汰了。观察到所述第一管的两种不同长度的影响。第一管从不锈钢制成具有0.5mm的内径和0.81毫米的外径。第一管的长度分别为5.35和10.40厘米分别。扩大部分，将其掺入支架的入口的内径，为0.5mm，和出口的内径为1.25毫米，这是相同的耗散终止的内径。扩大部分的角为7°。有在直径1.25毫米托架为了平稳地展开部与消声终止连接的孔。传感区域通过一个垂直0.75毫米孔连接到1.25毫米的孔。
Protocol
Representative Results
Discussion
The measurement of USP in wind tunnel experiments is needed for many applications related to aeroacoustics and flow-induced vibrations. Compared to existing methods, such as flush-mounted imbedded sensors, PSP, or vibrated membranes, the method described here allows for accurate measurements with a high sensitivity to large-magnitude fluctuation over a wide range of frequencies. More importantly, it also provides a method for USP measurements using a small sensing area that minimizes the spatial averaging effects describ…
Declarações
The authors have nothing to disclose.
Acknowledgements
This research was made possible through funding from the U.S. Office of Naval Research under Grant No. N000141210337, Deborah Nalchajian and Ronald Joslin.
Materials
| Microphone | ACO Pacific (http://www.acopacific.com/) | 7016 | Used to measure the sound pressure and calibrate the RMP as a reference. |
| Microphone | Knowles (http://www.knowles.com/eng) | FG-23629-C36 | Used to measure the pressure fluctuation as a part of the RMP. |
| Microbore Tubing | Saint-gobain (http://www.biopharm.saint-gobain.com/en/index.asp) | Tygon ND 100-80 | Used to dissipate the sound waves as a dissipation termination. |
| Hypodermic Tubing | MicroGroup (http://www.microgroup.com/) | 304H21RW | Used to connect the surface tap and allow the surface pressure fluctuation to convect to the microphone in the RMP in the form of sound. |
| Hypodermic Tubing | MicroGroup (http://www.microgroup.com/) | 304H14H | Used to reduce the dissipative effect and allow the surface pressure fluctuation to convect to the microphone in the RMP in the form of sound. |
| plexiglass | Plaskolite (http://www.plaskolite.com/) | 1X76204A | Used to make cradles which can connect the tubing and the microphone for the RMP. |
| Data acquisition chassis | National Instruments (http://www.ni.com/) | PXI-1006 | For data acquisition. |
| Data acquisition channel | National Instruments (http://www.ni.com/) | PXI-4472 | For data acquisiton. |
| Function generator | thinkSRS (http://www.thinksrs.com/) | DS360 | To generate white noise signal. |
| Pistonphone | B&K (http://www.bksv.com/) | 4228 | To generate sine waves with constant frequency which will be used to calibrate the reference microphone. |
| Loudspeaker | Mackie (http://www.mackie.com/index.html) | HD1531 | Used to convert the electrical white noise signal into sound. It is the sound source for calibrating the RMP. |
| MatLab | Mathworks (http://www.mathworks.com/) | Used to process experimental data. | |
| LabVIEW | National Instruments (http://www.ni.com/) | Used control the hardware for data acquisition and record the data. |
Referências
- Blake, W. K. Mechanics of Flow-induced sound and vibration. Academic Press, Orlando, FL (1986).
- Schloemer, H. Effects of pressure gradients on turbulent-boundary-layer wall-pressurefluctuations. J Acoust Soc Am., 42 (1), 93 – 113 (1967).
- Willmarth, W., Wooldridge, C. Measurements of fluctuating pressure at wall beneath a thick turbulent boundary layer, J Fluid Mech., 14 (2), 187-210 (1962).
- Gautschi, G. Piezoelectric Sensorics: Force, Strain, Pressure, Acceleration and Acoustic Emission Sensors, Materials and Amplifiers. Springer Berlin (2002).
- Blake, W. K. A statistical description of pressure and velocity fields at the trailing edges of a flat strut. David W. Taylor Naval Ship Research and Development Center – Report 4241. (1975).
- Huettenbrink, K. B. Lasers in Otorhinolaryngology. Thieme (2005).
- Bell, J. H., Schairer, E. T., Hand, L. A., Mehta, R. D. Surface Pressure Measurement using Luminescent Coatings. Annu Rev Fluid Mech., 33,155-205 (2001).
- Englund, D., Richards, W. The infinite line pressure probe. ISA Transactions., 24 (2), 11-19 (1985).
- Bergh, H.,Tijdeman, H. Theoretical and Experimental Results for the Dynamic Response of Pressure Measuring Systems. NRL Report TR F 238., National Aero-and Astronautical Research Inst., Amsterdam (1965).
- Perennes, S., Roger, M. Aerodynamic noise of a two-dimensional wing with high-lift devices. 4th AIAA/CEAS Aeroacoustics Conference., 98-2338, Toulouse (1998).
- Leclercq, D., Bohineust, X. Investigation and modeling of the wall pressure field beneath a turbulent boundary layer at low and medium frequencies. J Sound Vibrat., 257 (3), 477-501 (2002).
- Franzoni, L. P., Elliott, C. M. An innovative design of a probe-tube attachment for a half in. microphone. JASA . 104, 2903-2910 (1998).
- Arguillat, B., Ricot, D., Robert, G. and Bailly, C. Measurements of the wavenumber-frequency spectrum of wall pressure fluctuations under turbulent flows. In Collection of Technical Papers – 11th AIAA/CEAS Aeroacoustics Conference., 1,722-739 (2005).
- Yang, H., Sims-Williams, D., He, L. Unsteady pressure measurement with correction on tubing distortion. Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines, 521-529. Springer Berlin (2006).
- Hoarau, C., Boree, J., Laumonier, J., Gervais, Y. Analysis of the wall pressure trace downstream of a separated region using extended proper orthogonal decomposition. Phys Fluids., 18 (5), 055107 (2006).
- Bilka, M. J., Paluta, M. R., Silver, J. C. Spatial correlation of measured unsteady surface pressure behind a backward-facing step. EXIF., 56 (2),doi:10.1007/s00348-015-1897-7 (2015).
- Probsting, S., Gupta, A., Scarano, F., Guan, Y., Morris, S. C. Tomographic PIV for Beveled Trailing Edge Aeroacoustics. 20'th' AIAA/CEAS Aeroacoustics Conference, AIAA Paper. 2014-3301, (2014).
- Wong, G. Microphones and Their Calibration. Springer Handbook of Acoustics (2007).
- Bendat, J. S., Piersol, A. G. Random data: analysis and measurement procedures. John Wiley & Sons, New York, NY, 2nd edition (1986).
- Goody, M. Empirical spectral model of surface pressure fluctuations. Am Instit Aero Astronaut., 42 (9), 1788-1794 (2004).
- Corcos, G. M. Resolution of pressure in turbulence. J Acoust Soc Am., 35 (2), 192-199 (1963).
- Tijdeman, H. On the propagation of sound waves in cylindrical tubes. J Sound Vibrat., 39 (1), 1-33 (1975).
- Iberall, A. S. Attenuation of oscillatory pressures in instrument lines. J Res Natl Bureau Stand ., 45 (1), 85-108 (1950).
- Zwikker, C. Kosten, C. Sound Absorbing Materials. Amsterdam: Elsevier (1949).
