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首页> 外文期刊>Coastal engineering >Alongshore fluid motions in the swash zone of a sandy and gravel beach
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Alongshore fluid motions in the swash zone of a sandy and gravel beach

机译：沙滩和砾石滩冲积带的近岸流体运动

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摘要

Field experiments were conducted on a low-gradient, high-energy sandy beach (True Vert, France) and a steep, low-energy gravel beach (Slapton, UK) to examine alongshore-directed currents within the swash zone. At True Vert, data were collected over 33 tidal cycles with offshore significant wave heights of 1 -4 m and periods of 5-12 s. At Slapton data were collected during 12 tides with wave heights of 0.3-1 m and periods of 4-9 s. The swash motion was predominantly at infragravity frequencies at True Vert and incident frequencies at Slapton.During selected tides, strong alongshore currents of the same order of magnitude as the cross-shore flows were a consistent feature of both swash zones; however, while the cross-shore flows were saw-toothed with a distinct flow reversal, the alongshore flows were unidirectional and continuous. On the sand beach, alongshore momentum was adverted into the swash from the surf zone by standing long-wave motion resulting in the strongest flows in the lower swash. In contrast on the gravel beach, highly oblique uprush directly forced the longshore-directed motions and resulted in strong flow velocities in the upper swash. On the sandy beach, the cross- and longshore boundary layers were consistently different with strong vertical shear during the uprush for the cross-shore and during the backwash for the alongshore flows. A logarithmic profile better fitted the longshore flows during the backwash, compared to during the uprush for the cross-shore flows, and enabled the drag coefficient to be computed. The alongshore drag coefficient was C_(d,v)= 10~(-3) and of the same order as for the cross-shore, but was generally larger during the backwash compared to the uprush. Sediment transport efficiency during the backwash is potentially enhanced by longshore-directed swash flows. Significant bed shear stress is maintained throughout that cross-shore flow reversal enabling down-slope transport earlier in the swash cycle.
机译：在低坡度，高能量的沙滩（法国真尔特）和陡峭的，低能量的砾石海滩（英国，Slapton）上进行了野外实验，以检查斜流区内的沿岸定向水流。在True Vert，在33个潮汐周期中收集了数据，海上重要波高为1 -4 m，周期为5-12 s。在Slapton，在12个潮汐期间收集数据，波高为0.3-1 m，周期为4-9 s。斜流主要发生在真垂直的次重力频率和斯拉普顿的入射频率。在选定的潮汐中，两个斜流区的一致特征是沿岸水流强度与跨岸水流数量级相同。然而，尽管跨岸水流呈锯齿状且有明显的逆流，但沿岸水流却是单向连续的。在沙滩上，近海动量通过站立的长波运动从冲浪带被转化为冲积层，导致下部冲积层的流量最大。与之相反，在砾石滩上，高度倾斜的上冲直接迫使沿岸运动，并导致上斜流的强劲流速。在沙滩上，跨岸和长岸边界层始终不同，在跨岸上升期和沿岸水流反冲洗期间，垂直切变强。与跨岸水流的上冲期相比，对流剖面与对流期间的对数曲线更好地拟合了长岸流，并能够计算出阻力系数。沿岸阻力系数为C_（d，v）= 10〜（-3），与跨岸阻力系数相同，但反冲过程中与上冲相比通常更大。沿岸导向的斜流有可能提高反冲洗过程中的泥沙输送效率。在整个跨岸水流逆转过程中都保持了明显的地层剪切应力，从而使得在斜流循环的早期可以进行下坡运输。

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  • 来源
    《Coastal engineering》 |2011年第8期|p.690-705|共16页
  • 作者

    Martin J. Austin; Gerd Masselink; Paul E. Russell; Ian L Turner; Chris E. Blenkinsopp;

  • 作者单位

    School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK;

    School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK;

    School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK;

    Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales, Sydney, Australia;

    Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales, Sydney, Australia;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Swash zone; Longshore current; Drag coefficient; Sediment transport; Field experiment;

    机译：冲积带;长流;阻力系数;泥沙输移;田间试验;

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