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Effect of turbulent structures on the riverbank erosion due to tidal influence: A case study from the Rupnarayan River, eastern India
Journal of Earth System Science ( IF 1.9 ) Pub Date : 2021-03-30 , DOI: 10.1007/s12040-021-01554-w
Vikas Kumar Das , Koustuv Debnath , Sayahnya Roy , Krishnendu Barman , Sunil Hansda , Bijoy Singha Mazumder

Abstract

For understanding the sediment removal mechanism from the bank face, field measurements of the dominating turbulent flow structures under the influence of flood and ebb tide were carried out at the middle reach 98 km upstream of the mouth of Rupnarayan River, India where the bank erosion activity was highly dynamic. Measurement of the three-dimensional temporal variation of velocity was carried out using a 16-MHz Micro-ADV during the transition period of flood to ebb tide. Results from the present field study depict that during the transition of the onset of the ebb tide, the velocity field showed reduced values that gradually acquired negative values at the near bank region. This manifested the existence of an anti-clock circulation during flood tide and clock-wise circulation during ebb tide at the near bank flow field. It was also pertinent that the velocity gradient during ebb tide was greater as compared to the velocity gradient during flood tide. Accordingly, the turbulent bursting analysis revealed that the ejection and sweep events were prominent during ebb tide resulting in the dislodgement of sediment from the bank face at a larger rate. Further, the similarity of the wavelet patterns revealed that a good correlation existed between the stream-wise and transverse velocity component during ebb tide that enhanced the erosion process during the ebb tide event.

Research highlights

  • The velocity gradient was greater during ebb tide than during flood tide.

  • Flow-circulation is clockwise during ebb tide and anti-clockwise during flood tide.

  • Bursting structures reveal the dominance of ejection and sweep events during ebb tide.

  • The entrained sediment particles are transported with ebb current.

  • The entrained sediment is deposited at the lower reach causing rapid sedimentation.



中文翻译:

潮汐影响下湍流结构对河岸侵蚀的影响:以印度东部鲁普纳拉扬河为例

摘要

为了了解河床面的泥沙清除机理,在印度鲁普纳拉扬河河口上游98 km的中游进行了洪水和退潮影响下主要湍流结构的现场测量。充满活力。在洪水到退潮的过渡期间,使用16-MHz Micro-ADV来测量速度的三维时间变化。当前现场研究的结果表明,在退潮开始过渡期间,速度场显示出减小的值,并逐渐在近岸区域获得负值。这表明在近岸流场中,在洪潮期间存在逆时针环流,而在退潮期间则存在顺时针环流。与此相关的是,退潮时的速度梯度比洪潮时的速度梯度大。因此,湍流爆发分析表明,在退潮期间喷水和掠水事件非常明显,导致沉积物以较大的速度从河岸面上脱落。此外,小波模式的相似性表明,在退潮期间流向和横向速度分量之间存在良好的相关性,从而增强了退潮事件期间的侵蚀过程。湍流爆破分析表明,在退潮期间喷水和掠水事件非常明显,导致沉积物以较大的速度从河岸面上脱落。此外,小波模式的相似性表明,在退潮期间流向和横向速度分量之间存在良好的相关性,从而增强了退潮事件期间的侵蚀过程。湍流爆破分析表明,在退潮期间喷水和掠水事件非常明显,导致沉积物以较大的速度从河岸面上脱落。此外,小波模式的相似性表明,在退潮期间流向和横向速度分量之间存在良好的相关性,从而增强了退潮事件期间的侵蚀过程。

研究重点

  • 退潮期间的速度梯度大于洪潮期间的速度梯度。

  • 潮汐流在退潮时为顺时针,潮汐流时为逆时针。

  • 爆裂结构揭示了退潮期间弹射和横扫事件的优势。

  • 夹带的沉积物颗粒随着退潮而被运输。

  • 夹带的沉积物沉积在下游,导致快速沉积。

更新日期:2021-03-30
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