Abstract

The scour and flow field patterns with accumulation of debris around bridge piers are completely different due to the reduction of flow area and the increase in depth average velocity. Accordingly, the risks of bridge piers failure are increased due to the evolution of scour depth. This paper aims to analyse the effect of rectangular debris accumulation around single and dual cylindrical piers on river bed morphology in three dimensional simulation under clear water conditions. An experimental and numerical investigations were conducted to implement computational fluid dynamic (CFD) models that reveal the influence debris accumulation on the characteristics of scour hole and the increase in depth average velocity. The large eddy simulation model (LES) was coupled with three morphological models (Meyer-Peter, and Muller; Van Rijn model, and Nielsen) to assess the performance of simulation and produce efficient CFD morphological models. It was found that coupling of LES turbulence model and Nielsen morphological model yield best agreement with measured scour depth and scour hole characteristics according to the indication of statistical analysis, while the under prediction was noted for other models. As compared with temporal scour development and scour hole morphology of experiments of this study, good agreement was achieved for implemented CFD morphological models for single pier and dual piers with debris accumulation for (6.2 and 16.6% obstructed area to the flow area) respectively. According to the indications of this study, the increase in depth average velocity due to debris accumulation can be ranged from 26 to 44% and from 17 to 41% during the first ten minutes of accumulation around single and dual piers respectively. More consideration should be taken to mitigate bridge piers from debris accumulation.

中文翻译：

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基于 CFD 的模型用于估计由于杂物堆积引起的圆柱形桥墩附近河床形态特征

摘要

由于流动面积的减少和深度平均速度的增加，桥墩周围杂物堆积的冲刷和流场模式完全不同。因此，由于冲刷深度的演变，桥墩失效的风险增加。本文旨在通过三维模拟在清水条件下分析单柱和双柱墩周围矩形碎片堆积对河床形态的影响。进行了实验和数值研究以实施计算流体动力学 (CFD) 模型，该模型揭示了碎屑堆积对冲刷孔特征和深度平均速度增加的影响。大涡模拟模型 (LES) 与三个形态模型（Meyer-Peter 和 Muller；Van Rijn 模型、和 Nielsen）来评估模拟的性能并生成高效的 CFD 形态模型。统计分析表明，LES湍流模型与Nielsen形态学模型的耦合与实测冲刷深度和冲刷孔特征的一致性最好，而其他模型预测不足。与本研究实验的时间冲刷发展和冲刷孔形态相比，单墩和双墩的 CFD 形态模型分别为（6.2% 和 16.6% 的流动区阻塞面积）具有良好的一致性。根据本研究的迹象，在单墩和双墩周围堆积的前十分钟内，由于碎片堆积导致的深度平均速度增加范围分别为 26% 至 44% 和 17% 至 41%。应该更多地考虑减轻桥墩堆积的碎片。