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Turbulence measurements in high-speed wind tunnels using focusing laser differential interferometry.

机译：使用聚焦激光微分干涉术测量高速风洞中的湍流。

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摘要

Characterization of freestream disturbances and their effect on laminar boundary layer transition is of great importance in high-speed wind tunnel testing, where significant differences between the behavior of scale-model and free-flight transition have long been noted. However, the methods traditionally used to perform this characterization in low-speed flows present significant difficulties when applied to supersonic and especially hypersonic wind tunnels. The design and theory of a focusing laser differential interferometer (FLDI) instrument, originally invented by Smeets at the Institut Saint-Louis in the 1970s and used recently by Parziale in the CalTech T5 shock tunnel, is presented. It is a relatively-simple, non-imaging common-path interferometer for measuring refractive signals from transition and turbulence, and it has a unique ability to look through facility windows, ignore sidewall boundary-layers and vibration, and concentrate only on the refractive signal near a pair of sharp beam foci in the core flow. The instrument's low cost and ease of implementation make it a promising alternative to traditional hot-wire anemometry and particle-based methods for turbulence characterization. Benchtop experiments using a turbulent supersonic air jet demonstrate its focusing ability, frequency response, unwanted signal rejection, and ease of use. The instrument is used to optically interrogate the flow in the Penn State University Supersonic Wind Tunnel and USAF AEDC Hypervelocity Tunnel 9 for measurement of the overall intensity and spectra of freestream disturbances. Precise characterization of the strength and spectral content of the disturbances provides insight into their nature and potential effect upon boundary layer transition. A special feature of the FLDI instrument used here is the replacement of traditional fixed Wollaston prisms with variable Sanderson prisms for laser-beam separation and recombination.
机译：在高速风洞测试中，自由流扰动及其对层流边界层过渡的影响的表征非常重要，长期以来，人们一直注意到比例模型行为与自由飞行过渡之间的显着差异。然而，传统上用于低速流中进行此表征的方法在应用于超音速尤其是超音速风洞时会遇到很大的困难。介绍了聚焦激光差分干涉仪（FLDI）仪器的设计和原理，该仪器最初由Smeets在1970年代圣路易斯研究所发明，最近被Parziale在CalTech T5冲击隧道中使用。它是一种相对简单的非成像共路径干涉仪，用于测量来自过渡和湍流的折射信号，并且具有独特的能力，可以透过设施窗口查看，忽略侧壁边界层和振动，并且仅关注折射信号在岩心流中靠近一对尖锐的光束焦点。该仪器的低成本和易用性使其成为传统热线风速仪和基于粒子的湍流表征方法的有希望的替代品。使用湍流超音速喷气机进行的台式实验证明了其聚焦能力，频率响应，不想要的信号抑制以及易用性。该仪器用于光学检查宾夕法尼亚州立大学超音速风洞和美国空军AEDC超高速隧道9中的流动，以测量总强度和自由流干扰谱。干扰强度和频谱含量的精确表征可提供对干扰性质和对边界层过渡的潜在影响的深入了解。这里使用的FLDI仪器的一个特殊功能是用可变的Sanderson棱镜代替传统的固定Wollaston棱镜，以进行激光束分离和重组。

著录项

  • 作者

    Fulghum, Matthew R.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Mechanical engineering.;Optics.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 252 p.
  • 总页数 252
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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