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A Study on Axisymmetric Cavity Flows in Supersonic Flow

机译：超音速流中轴对称腔流的研究

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摘要

The research presented in this dissertation focuses on understanding and passively controlling the unsteadiness of the flow that occurs in cavity flows. Flow passing over a cavity generates turbulent structures that result in pressure fluctuations in the cavity that exhibits itself as noise at selected tonal frequencies. The unsteadiness and the presence of the turbulent structures can be strong enough to damage the equipment that is stored in these cavities. Understanding the flow unsteadiness and determining the means to control it is an important research area that has been undertaken over the past several decades. High speed cavity flow presents several problems when used in practical applications. At lower speeds, vibrations can be controlled with ramps and/or flaps; however, there is a current need to provide a better understanding of supersonic flow around a cavity to allow future aircraft to release payload at high speed. Most of the previous research on cavity flows has been done on rectangular cavities and has provided guidelines for determining dominant frequencies and other flow properties over a cavity. This project focuses on understanding the flow unsteadiness in more of a basic configuration, namely over an axisymmetric cavity, to eliminate the effects of the side walls on the flow development. Such research is scarce in the literature, although it is a building block in understanding the nature of the cavity flows.;The results of the current research agree well with the previous research conducted on rectangular cavities. The measured tonal frequencies match the predicted Rossiter modes that are well defined for rectangular cavities. The pressure data obtained at the cavity walls has shown a decrease in sound pressure levels at the various tonal frequencies when the cavity is lengthened.;It is also shown that replacing the back wall of the cavity with a half-height wall results in both positive and negative effects to the tonal frequencies. At the front wall pressure fluctuations are reduced at all cavity lengths; however, the rear wall shows significant increase in pressure fluctuations for the medium and large cavity lengths.
机译：本文的研究重点是了解和被动控制腔内流动中的流动不稳定性。流过腔体的气流会产生湍流结构，从而导致腔体中的压力波动，并在选定的音调频率上表现为噪声。湍流结构的不稳定性和存在强度可能足以损坏存储在这些型腔中的设备。在过去的几十年中，了解流量不稳定并确定控制流量的方法是一个重要的研究领域。当在实际应用中使用时，高速腔流带来了几个问题。在较低的速度下，可以通过斜坡和/或襟翼控制振动。然而，当前需要更好地理解围绕腔的超音速流动，以允许未来的飞机以高速释放有效载荷。以前大多数关于腔体流动的研究都是在矩形腔体上完成的，并为确定腔体上的主导频率和其他流动特性提供了指导。该项目着重于在基本构造上（即在轴对称腔上）了解流动的不稳定性，以消除侧壁对流动发展的影响。尽管这是了解空腔流动性质的基础，但在文献中却很少见。；当前的研究结果与以前对矩形空腔进行的研究非常吻合。测得的音调频率与为矩形腔定义的Rosseter预测模式匹配。在腔壁处获得的压力数据表明，当腔体加长时，在各种音调频率下声压级都会降低;还表明，用半高壁代替腔体的后壁会导致两个正值对音调频率的负面影响。在前壁，所有腔长的压力波动都减小了。然而，对于中型和大型腔体，后壁的压力波动显着增加。

著录项

  • 作者

    Brooker, Brian Tyler.;

  • 作者单位

    The University of Alabama.;

  • 授予单位 The University of Alabama.;
  • 学科 Aerospace engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 167 p.
  • 总页数 167
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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