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首页> 外文学位 >In-flight receptivity experiments on a 30-degree swept-wing using micron-sized discrete roughness elements.
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In-flight receptivity experiments on a 30-degree swept-wing using micron-sized discrete roughness elements.

机译：使用微米级离散粗糙度元件在30度后掠翼上进行机上接受性实验。

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摘要

One of the last remaining challenges preventing the laminarization of swept-wings is the control of unstable crossflow vortices. In low-disturbance environments the transition from laminar to turbulent flow on the swept-wing initially takes the path of receptivity, where surface roughness or disturbances in the environment introduce short-wavelength disturbances into the boundary layer. This is followed by development and linear growth of stationary crossflow vortices that modify the mean flow, changing the stability characteristics of the boundary layer. Finally, breakdown to turbulence occurs over a short length scale due to the high-frequency secondary instability. The receptivity mechanism is the least understood, yet holds the most promise for providing a laminar flow control strategy. Results of a 3-year flight test program focused on receptivity measurements and laminar flow control on a 30-degree swept-wing are presented. A swept-wing test article was mounted on the port wing of a Cessna O-2A aircraft and operated at a chord Reynolds number of 6.5 to 7.5 million. Spanwise-periodic, micron-sized discrete roughness elements were applied at the leading edge of the swept-wing in order to excite the most unstable crossflow wavelength and promote early boundary-layer transition. An infrared camera was used to detect boundary-layer transition due to changes in leading-edge roughness. Combined with the IR camera, a new technique of calibrating surface-mounted hotfilms was developed for making disturbance-amplitude measurements downstream of modulated roughness heights. This technique proved to be effective at measuring disturbance amplitudes and can be applied in future tests where instrumentation is limited. Furthermore, laminar flow control was performed with subcritically-spaced roughness. A 100% increase in the region of laminar flow was achieved for some of the conditions tested here.
机译：防止后掠翼分层的最后一项挑战是控制不稳定的错流涡流。在低干扰环境中，后掠机翼上的从层流到湍流的过渡最初采用接受路径，其中表面粗糙度或环境中的干扰将短波干扰引入边界层。随后是固定横流涡流的发展和线性增长，这些涡流改变了平均流量，改变了边界层的稳定性。最后，由于高频二次不稳定性，在短的长度范围内发生了湍流破坏。接受性机制了解最少，但最有希望提供层流控制策略。介绍了一项为期3年的飞行测试程序的结果，该程序侧重于30度后掠机翼的接受度测量和层流控制。一架后掠翼测试物品被安装在塞斯纳O-2A飞机的左翼，并且雷诺数为6.5至750万。为了激发最不稳定的错流波长并促进早期边界层过渡，在扫掠机翼的前缘应用了跨度周期，微米大小的离散粗糙度元素。使用红外热像仪检测由于前沿粗糙度变化而引起的边界层过渡。结合红外相机，开发了一种校准表面安装热膜的新技术，用于在调制粗糙度高度的下游进行干扰幅度测量。事实证明，该技术可有效地测量干扰幅度，并且可用于将来仪器受限的测试中。此外，以亚临界间隔的粗糙度进行层流控制。对于此处测试的某些条件，层流区域实现了100％的增加。

著录项

  • 作者

    Carpenter, Andrew Lee.;

  • 作者单位

    Texas A&M University.;

  • 授予单位 Texas A&M University.;
  • 学科 Engineering Aerospace.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 226 p.
  • 总页数 226
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 航空、航天技术的研究与探索;
  • 关键词

  • 入库时间 2022-08-17 11:38:27

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