Coherent Disturbance Structures and Bed Topography Responses in Large Depth-to-Width Ratio River Bends With Constant Curvatures
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摘要: 蜿蜒河流床面形态既是其复杂动力结构响应的结果,同时也是决定河流进一步演化方向的重要因素.以蜿蜒河流中一种典型的大深宽比河湾为背景,探索其动力结构与床面响应的关系,将黏性不可压缩流体方程、泥沙输移方程和床面变形方程耦合,通过摄动方法求解床面响应,分析床面形态变化特性.研究成果显示在水流二维扰动作用下,河道中浅滩深槽呈现规则响应.当弯曲度等于0时,床面响应形态围绕河道中轴线基本呈反对称分布;当弯曲度不等于0时,床面响应形态呈不对称分布,中轴线向凹岸偏移.该文给出了由Reynolds(雷诺)数、扰动波数、床面形态增减率等构成的床面响应发展趋势稳定关系的判别方法.Abstract: The bed topography is the result of the dynamic response of a complex meandering river system, and is an important factor influencing the further river development. Based on meandering rivers characterized by large depth-to-width ratios, the relation between the hydraulic structure and the bed topography was explored. The flow characteristics and bed topography responses were discussed through coupling of the N-S equations, the sediment transport equations as well as the bed deformation equations, and with the perturbation method. Research results show that shallows and deep grooves present regular responses under the effects of 2D flow disturbances. For a zero curvature, the bed topography shows an anti-symmetric distribution about the channel centerline; while for a non-zero curvature, the channel centerline deviates toward the concave bank. Finally, the criteria for the judgement on the stability of the bed topography influenced by the Reynolds number, the disturbance wave number and the decay ratio of the bed topography, are given.
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