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首页> 外文学位 >Turbulent plane jets: Impingement, instability and interaction with surface gravity waves.
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Turbulent plane jets: Impingement, instability and interaction with surface gravity waves.

机译：湍流平面射流：撞击，不稳定性以及与表面重力波的相互作用。

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摘要

For better understanding of the turbulent jet, especially in a wave environment, experiments were conducted in this study to investigate (1) the impingement of the plane jet onto a free surface; (2) the propagation of surface waves in current shear layers generated by the plane jet; (3) the interaction of turbulent plane jet with progressive waves; (4) the coherent structures of turbulent plane jet; and (5) the instability of turbulent plane jet.;In the experiment on wave-current interaction, the wave number was measured with a wave height gauge moving along the wave propagation direction. The waves were measured in an environment of currents, which were generated by the plane jets. In the upstream of the plane jets, the wave number first increases in the velocity-dominated current region and then decreases in the vorticity-dominated current region.;Plane jets in wave environments were observed to have the same flow regimes as in a stagnant ambient, i.e., ZFE, ZEF, ZSI and ZHJ. The self-similar feature in ZEF with a wider spreading of a plane jet was found in a wave environment. Wave-induced velocities u&d15;i, wave-associated mean stresses u&d15;iu&d15; j and wave-induced turbulent Reynolds stresses are r&d15;ij obtained with a phase average scheme. The results show that the wave-induced flow field is dominated by the fundamental mode and the contribution from harmonic is negligible. The amplitude of the fundamental mode of w&d15;,r&d15; ww and r&d15;uu, denoted by w, rˆww and rˆuu and the wave-associated normal mean stress w&d15;w&d15; have similar twin-peak distributions, indicating maximum energy transfer at about half-velocity location eta = +/-0.16. There is an about 180° phase shift across the plane jets for the phase of the fundamental mode of w&d15;,r&d15; ww and r&d15;uu, denoted by qw&d5;, qr&d5; ww and qr&d5;ww .;Coherent vortex structures were observed in the plane jets when the progressive surface waves were imposed, even though no coherent vortex structures are shown in a stagnant ambient. The flow visualizations also show the plane jets are stable for H/d = 130 even though surface waves are imposed.;Experiments on turbulent plane jets impinging onto a free surface in a stagnant ambient at a water depth of H/d = 130 show the existence of four flow regimes in a plane jet: the zone of flow establishment (ZFE), the zone of established flow (ZEF), the zone of surface impingement (ZSI) and the zone of horizontal jet (ZHJ).;Plane jets become unstable to exhibit a flapping motion when the jet exit velocity exceeds a critical velocity W0cr. The flapping frequency f is found to be inversely proportional to the square root of water depth H and the critical jet exit velocity to be linearly proportional to H. (Abstract shortened by UMI.)
机译：为了更好地理解湍流射流，特别是在波浪环境中，本研究进行了实验以研究（1）平面射流对自由表面的撞击； （2）平面射流产生的电流剪切层中表面波的传播； （3）湍流平面射流与渐进波的相互作用； （4）湍流平面射流的相干结构； （5）湍流平面射流的不稳定性。在波流相互作用实验中，用波高计沿波传播方向测量波数。这些波是在由喷气飞机产生的电流环境中测量的。在平面射流的上游，波数首先在速度主导的电流区域中增加，然后在涡度主导的电流区域中减小。;观察到波浪环境中的平面射流具有与停滞的环境相同的流态，即ZFE，ZEF，ZSI和ZHJ。在波浪环境中发现了ZEF中的自相似特征，其中平面射流的传播范围更广。波浪引起的速度u＆d15; i，与波浪相关的平均应力u＆d15; iu＆d15;用相位平均方案获得j和波浪引起的湍流雷诺应力。结果表明，波诱导的流场以基本模式为主，而谐波的贡献可忽略不计。 w＆d15;，r＆d15;的基本模式的振幅ww和r＆d15; uu，用w，rˆww和rˆuu表示，以及与波相关的法向平均应力w＆d15; w＆d15;具有相似的双峰分布，表明在大约一半速度位置eta = +/- 0.16处的最大能量传递。对于w＆d15;，r＆d15;的基本模式的相位，整个平面射流之间存在大约180°的相移。 ww和r＆d15; uu，分别用qw＆d5;，qr＆d5;当施加渐进的表面波时，即使在停滞的环境中未显示出相干的涡旋结构，在平面射流中也观察到了相干的涡旋结构。流动的可视化结果还显示，即使施加了表面波，平面射流在H / d = 130的情况下也是稳定的。在H / d = 130水深的停滞环境中撞击到自由表面的湍流平面射流的实验表明平面射流中存在四个流态：流动建立区域（ZFE），建立流动区域（ZEF），表面撞击区域（ZSI）和水平射流区域（ZHJ）。当射流出口速度超过临界速度W0cr时，它不稳定以表现出拍打运动。发现拍打频率f与水深H的平方根成反比，而临界射流出口速度与H成线性比例。（摘要由UMI缩短）。

著录项

  • 作者

    Kuang, Jun.;

  • 作者单位

    Hong Kong University of Science and Technology (Hong Kong).;

  • 授予单位 Hong Kong University of Science and Technology (Hong Kong).;
  • 学科 Hydrology.;Physical Oceanography.;Physics Fluid and Plasma.
  • 学位 Ph.D.
  • 年度 1999
  • 页码 205 p.
  • 总页数 205
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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