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Tsunami-like flow induced force on the structure: Prediction formulae for the horizontal force in quasi-steady flow phase
Coastal Engineering ( IF 4.4 ) Pub Date : 2021-06-09 , DOI: 10.1016/j.coastaleng.2021.103938
S. Harish , V. Sriram , Holger Schüttrumpf , S.A. Sannasiraj

Destruction of the structures in coastal areas due to an extreme coastal event like a tsunami necessitates the deeper understanding of flow behaviour to improve the design guidelines. The characteristics of inland propagating tsunami surge or bore consist of an initial aerated surge or bore tip followed by the gradual increase in water depth (quasi-steady flow phase). During the bore interaction, the structure initially experiences an impulsive pressure, bore pressure followed by quasi-static pressure (quasi-steady flow phase) depending on the ratio of the structure obstruction width to flow channel width (b/W), incoming bore Froude number (Fr), the shape of the structure, and the orientation of structure to the direction of flow. From field surveys and video observations during the 2004 Indian Ocean Tsunami and the 2011 Tohoku tsunami, the structure failure during the quasi-steady state of tsunami flow is found to be predominant. Also, most of the literature in the past focused on the interaction of bore on a single structure in which the flow channelling effect (b/W) is not considered. Thus, the present experimental study gives a detailed insight into the b/W and Fr effect in the force acting on the rectangular structure during the quasi-steady flow of tsunami-like events. To estimate the hydrodynamic force in the quasi-steady flow phase, we have adopted the hydrostatic force equation by incorporating bore height at the structure front (hf) and bore height at the structure back (hr). A simplified semi-analytical method is proposed based on conservation of mass and momentum to estimate the force on the rectangular structures. This approach of force estimation is showed to reasonably predict experimental force-time history. Since design guidelines use the hydrodynamic drag force equation for force estimation, the present study also provides the drag force coefficient (Cd) for b/W > 0.2 and Fr between 0.6 and 2. Along with the consideration of Fr and b/W, the study attempted to provide a closed-form set of equations to the quasi-static force, which helps designers with a convenient force determination method.



中文翻译:

结构上的类海啸流致力:准稳态流动相水平力的预测公式

由于海啸等极端沿海事件导致沿海地区结构的破坏,需要更深入地了解流动行为以改进设计准则。内陆传播海啸浪涌或钻孔的特征包括初始曝气浪涌或钻孔尖端,随后水深逐渐增加(准稳态流动阶段)​​。在孔相互作用期间,该结构最初经历脉冲压力,孔压力随后是准静态压力(准稳态流动阶段)​​,这取决于结构障碍宽度与流道宽度的比率(b/W))、流入孔弗劳德数 (Fr)、结构形状以及结构相对于流动方向的方向。从 2004 年印度洋海啸和 2011 年东北海啸期间的实地调查和视频观察,发现海啸流准稳态期间的结构破坏占主导地位。此外,过去的大多数文献都集中在未考虑流道效应 ( b/W )的单个结构上的孔的相互作用。因此,本实验研究详细了解了黑白在类海啸事件的准稳态流动期间作用在矩形结构上的力中的 Fr 效应。为了估计准稳态流动阶段的流体动力,我们采用了流体静力方程,其中结合了结构前部的孔高 ( h f ) 和结构后部的孔高 ( h r )。提出了一种基于质量和动量守恒的简化半解析方法来估计矩形结构上的力。这种力估计方法被证明可以合理地预测实验力-时间历程。由于设计指南使用流体动力阻力方程进行力估计,因此本研究还提供了阻力系数 ( C d )b/W  > 0.2 和 Fr 介于 0.6 和 2 之间。在考虑 Fr 和b/W 的同时,该研究试图为准静态力提供一组封闭形式的方程,这有助于设计人员方便地确定力方法。

更新日期:2021-06-28
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