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首页> 外文期刊>Journal of Physical Oceanography >Cyclonic Spirals in Tidally Accelerating Bottom Boundary Layers in the Zhujiang (Pearl River) Estuary
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Cyclonic Spirals in Tidally Accelerating Bottom Boundary Layers in the Zhujiang (Pearl River) Estuary

机译：珠江口潮汐加速底部边界层的旋流螺旋

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摘要

A velocity spiral in the tidally accelerating bottom boundary layer (BBL) was defined as a directional shear of the prevailing flow with the elevation and the tidal phase. However, so far there is no information on the spiral for the oscillatory BBL flows or a valid explanation for its origin, life history, and persistence. To investigate this rotating current in the tidally accelerating BBL flow, the authors performed instrumented tripod observations in the tidally energetic Zhujiang (Pearl River) estuary. The tidal BBL flows may fall into three distinct regimes: (i) the quasi-steady phase in the peak tide; (ii) the accelerating-decelerating phase at the slack tide; and (iii) the transition between (i) and (ii), when a cyclonic spiral occurs only in the early-late ebb. The subcritical spiral, denned by a Froude number of the oscillatory BBL flow, may be analytically examined by unsteady linearized turbulent BBL equations. The spiral is formed under the momentum balance between local acceleration and bottom friction, independent of stratification conditions. The spiral consists of the "diffusive" and oscillatory boundary layers in the streamwise and spanwise direction, respectively. The streamwise spiral presents an exponential degradation (growth) in the decelerating (accelerating) ebb, indicating its limited life history over a tidal cycle. The transient in bottom stresses induced by the growth or the degradation of the spiral may be the mechanism for sediment trapping in the very little bed friction in the tidal estuary.
机译：潮汐加速底部边界层（BBL）中的速度螺旋定义为主要水流随高度和潮汐相的方向剪切。但是，到目前为止，还没有关于振荡BBL流的螺旋的信息，也没有关于其起源，生活史和持久性的有效解释。为了研究潮汐加速BBL流中的旋转电流，作者在潮汐充满活力的珠江（珠江）河口进行了仪器化的三脚架观测。潮汐水流可能分为三个不同的状态：（i）潮汐潮汐的准稳态阶段； （ii）松弛潮时的加速-减速阶段； （iii）（i）和（ii）之间的过渡，当气旋螺旋仅发生在早期晚期。由不稳定的BBL流动的弗洛德数定义的亚临界螺旋可以通过不稳定的线性化BBL方程来分析地检查。螺旋线是在局部加速度和底部摩擦力之间的动量平衡下形成的，与分层条件无关。螺旋线分别由沿流向和跨度方向的“扩散”边界层和振荡边界层组成。流向螺旋形在减速（加速）退潮中呈指数下降（增长），表明其在潮汐循环中的寿命有限。由螺旋线的生长或退化引起的底部应力的瞬态可能是潮汐河口极小的床层摩擦中泥沙被捕集的机制。

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  • 来源
    《Journal of Physical Oceanography》 |2011年第6期|p.1209-1226|共18页
  • 作者

    Jiaxue Wu; Huan Liu; Jie Ren; Junjie Deng;

  • 作者单位

    The Center for Coastal Ocean Science and Technology, School of Marine Sciences, Sun Yat-sen University, Guangzhou, 510275 Guangdong, China;

    The Center for Coastal Ocean Science and Technology, School of Marine Sciences, and School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, China;

    The Center for Coastal Ocean Science and Technology, School of Marine Sciences, Sun Yat-sen University, Guangzhou, China;

    The Center for Coastal Ocean Science and Technology, School of Marine Sciences, Sun Yat-sen University, Guangzhou, China;

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