Wave Breaking Induced by Opposing Currents in Submerged Vegetation Canopies
Wave Breaking Induced by Opposing Currents in Submerged Vegetation Canopies
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DOI：
10.1029/2021wr031121
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发表时间：
2022-03
影响因子：
5.4
通讯作者：
Z. Hu;S. Lian;T. Zitman;H. Wang;Z. He;H. Wei;L. Ren;W. Uijttewaal;T. Suzuki
中科院分区：
文献类型：
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作者：
Z. Hu;S. Lian;T. Zitman;H. Wang;Z. He;H. Wei;L. Ren;W. Uijttewaal;T. Suzuki
植被冠层的波高衰减通常都归因于植被施加的阻力，而其他潜在的耗散过程往往被忽略。以往的研究发现，在没有植被的情况下，相反的水流可以引起波浪破碎，大大增加耗散。目前尚不清楚类似的过程是否也可能发生在植被冠层中。我们进行了系统的水槽实验，表明在植被流中可以发生反向水流的波浪破碎，但只有在植被顶部上方有切变水流的淹没冠层中才会发生。随后，我们建立了一个新的分析模型来理解和评估下层植被层的阻力诱导耗散和上层自由层的电流诱导断裂的贡献。在模型中应用了一种新的通用阻力系数关系来量化不同电流波组合下的阻力诱导耗散。结果表明，反向电流引起的分断占总耗散的重要部分（高达87%），导致耗散大大高于随流情况。在不同的淹没比和较小的反流条件下，淹没植被区都可能发生断裂。这表明在真实的植被场中也可能发生类似的破坏过程。本研究揭示和量化了以往未见报道的电流诱导破波过程，有助于提高我们对植被在野外条件下的消波能力的认识。
Wave height attenuation in vegetation canopies is often all attributed to the drag force exerted by vegetation, whereas other potential dissipation process is often neglected. Previous studies without vegetation have found that opposing currents can induce wave breaking and greatly increase dissipation. It is not clear if similar process may also occur in vegetation canopies. We conducted systematic flume experiments to show that wave breaking in opposing currents can occur in vegetated flows, but only in submerged canopies with shear currents above vegetation top. Subsequently, we developed a new analytical model to understand and assess the contribution of both drag‐induced dissipation in the lower vegetation layer and current‐induced breaking in the upper free layer. A new generic drag coefficient relation was applied in the model to quantify drag‐induced dissipation with various current‐wave combinations. It shows that breaking induced by opposing currents constitutes an essential part (up to 87%) of the total dissipation, which leads to considerably higher dissipation than the cases with following currents. Breaking can occur with various submergence ratios and with small opposing currents in the submerged vegetation field. It indicates that similar breaking process is likely to occur in real vegetation fields. The present study reveals and quantifies the current‐induced wave breaking process that has not been reported before, which can improve our understanding of vegetation wave dissipation capacity in field conditions.