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Experimental and theoretical investigations of synthetic jets.

机译：合成射流的实验和理论研究。

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摘要

A synthetic jet is a type of a fully pulsatile jet that results from the formation and interaction of vortex rings or pairs. This study addresses the need for a simple model of the time average spatial evolution of a synthetic jet.;First, the external flow field of round and rectangular orifice synthetic jets in a quiescent environment are studied using hot-wire anemometry. The similitude exhibited by synthetic jets and continuous steady jets leads to the hypothesis that a synthetic jet may be modeled as a continuous turbulent jet using self-similarity analysis, with the replacement of the eddy viscosity of a turbulent continuous jet with that associated with a synthetic jet. The experiments validate this hypothesis, further showing that the eddy viscosity of the synthetic jet is larger than an equivalent turbulent jet. The effect of the critical actuator parameters on the synthetic jet are assessed with the goal of clarifying the pertinent scaling laws of the flow field.;Next, a round synthetic jet operating in a background flow parallel to the jet axis is examined. An integral model of a continuous jet in a co-flow is shown to be applicable to synthetic jets in a co-flow, through the use of an empirically determined spreading rate in a quiescent environment. The solutions for the spreading and velocity decay show good agreement with experiments.;Finally, a wall jet induced by the impingement of a round synthetic jet normal to a wall is experimentally investigated. The manner of spreading and decay of the jet, as well as the evolution of the time average velocity profiles are investigated. The synthetic wall jet is observed to be dominated by vortical structures associated with the actuator driving frequency and harmonics. The effect of increasing the actuator driving amplitude on the flow field, is the widening of the outer layer. For the actuator conditions investigated, neither laminar nor fully turbulent analytical solutions are shown to be amenable to modeling the synthetic wall jets. A fully empirical form is resorted to, so as to accommodate for the transitional and unsteady nature of the synthetic wall jet.
机译：合成射流是一种完全脉动的射流，由涡流环或涡流环或涡流环的形成和相互作用引起。这项研究满足了对合成射流时间平均空间演化的简单模型的需求。首先，使用热线风速仪研究了静态环境下圆形和矩形孔口合成射流的外部流场。合成射流和连续稳态射流表现出的相似性导致这样一个假设：可以使用自相似性分析将合成射流建模为连续湍流射流，并用与合成相关的湍流连续射流代替涡流粘度喷射。实验证实了这一假设，进一步表明，合成射流的涡流粘度大于等效的湍流射流。评估关键致动器参数对合成射流的影响，目的是弄清流场的相关缩放定律。接下来，研究在平行于射流轴的背景流中运行的圆形合成射流。通过使用根据经验确定的静态环境中的扩散速率，显示出并流中连续射流的积分模型适用于并流中的合成射流。扩散和速度衰减的解与实验结果吻合良好。最后，对圆形合成射流撞击壁而产生的壁射流进行了实验研究。研究了射流的扩散和衰减方式以及时间平均速度分布的演变。观察到合成壁射流由与致动器驱动频率和谐波相关的旋涡结构所主导。增加致动器驱动振幅对流场的影响是外层的加宽。对于所研究的执行器条件，层流和完全湍流的解析解决方案均未显示可用于模拟合成壁射流。采取完全经验形式，以适应合成壁射流的过渡和不稳定特性。

著录项

  • 作者

    Krishnan, Gopi.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Engineering Aerospace.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 157 p.
  • 总页数 157
  • 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;机械、仪表工业;
  • 关键词

  • 入库时间 2022-08-17 11:38:27

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