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Coupling between free-surface fluctuations, velocity fluctuations and turbulent Reynolds stresses during the upstream propagation of positive surges, bores and compression waves

机译:在正涌动,孔和压缩波的上游传播过程中,自由表面波动,速度波动和雷诺湍流应力之间的耦合

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摘要

In open channel, canals and rivers, a rapid increase in flow depth will induce a positive surge, also called bore or compression wave. The positive surge is a translating hydraulic jump. Herein new experiments were conducted in a large-size rectangular channel to characterise the unsteady turbulent properties, including the coupling between free-surface and velocity fluctuations. Experiments were repeated 25 times and the data analyses yielded the instantaneous median and instantaneous fluctuations of free-surface elevation, velocities and turbulent Reynolds stresses. The passage of the surge front was associated with large free-surface fluctuations, comparable to those observed in stationary hydraulic jumps, coupled with large instantaneous velocity fluctuations. The bore propagation was associated with large turbulent Reynolds stresses and instantaneous shear stress fluctuations, during the passage of the surge. A broad range of shear stress levels was observed underneath the bore front, with the probability density of the tangential stresses distributed normally and the normal stresses distributed in a skewed single-mode fashion. Maxima in normal and tangential stresses were observed shortly after the passage of a breaking bore roller toe. The maximum Reynolds stresses occurred after the occurrence of the maximum free-surface fluctuations, and this time lag implied some interaction between the free-surface fluctuations and shear stress fluctuations beneath the surge front, and possibly some causal effect.
机译:在明渠,运河和河流中,流量深度的迅速增加将引起正涌动,也称为钻孔或压缩波。正浪涌是平移的液压跳跃。在本文中,在大型矩形通道中进行了新的实验,以表征不稳定的湍流特性,包括自由表面和速度波动之间的耦合。实验重复了25次,数据分析得出了自由表面高程,速度和湍流雷诺应力的瞬时中值和瞬时波动。喘振前沿的通过与较大的自由表面波动相关,与在固定液压跳跃中观察到的波动相当,并具有较大的瞬时速度波动。在浪涌通过期间,孔的传播与大的雷诺湍流应力和瞬时切应力波动有关。在钻孔前部下方观察到很大范围的切应力水平,切向应力的概率密度正态分布,而法向应力以偏斜单模方式分布。破孔的脚趾通过后不久,观察到法向和切向应力的最大值。最大雷诺应力出现在最大自由表面波动发生之后,并且这个时间滞后暗示了自由表面波动和浪涌前沿下方的切应力波动之间存在一些相互作用,并可能有一定的因果关系。

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  • 作者

    Xinqian Leng; Hubert Chanson;

  • 作者单位
  • 年度 2015
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  • 原文格式 PDF
  • 正文语种 eng
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