圆柱桥墩绕流的数值模拟研究

发布时间：2019-04-11 08:35

【摘要】：圆柱绕流一直是众多理论分析,实验研究及数值模拟的对象,但是由于圆柱周围三维水流的复杂性,迄今对该流动现象物理本质的理解仍是不完整的,特别是对于圆柱绕流流态与圆柱桥墩周围冲刷的关系问题,尚未形成系统的理论研究。本文利用Flow-3D流体力学数值模拟软件,研究圆柱桥墩绕流流场特征和桥墩冲刷特点,探索圆柱绕流和冲刷之间的关系,以期为圆柱桥墩绕流及冲刷研究提供理论依据和新的研究思路。论文运用Flow 3D软件模拟了单圆柱桥墩绕流特性以及河床冲刷,获得了圆柱桥墩绕流流场分布及河床冲刷特征。结果发现,①圆柱桥墩二维流场分布特征为靠近两侧,由于水槽边壁的影响,水流流速都有所降低,桥墩前由于桥墩对水流的阻挡作用使得水流流速减小趋于零,桥墩过后随着流程的增加流场变得平顺而稳定;②初始流速增大墩前绕流向桥墩附近集中绕流范围减小,墩后尾流影响范围增大;③初始流速为37cm/s时,二维平面流速的最大值达到42.3cm/s,其它两个初始流速下的二维流速分布也具有相同的规律,其中最大值分别为流速34.4cm/s、22.2cm/s,三维流速分量中纵向流速是最大的,其他两个方向的流速分量较小但主要影响着流速的偏移方向。论文模拟了不同顺水桥墩布置方式下桥墩绕流特征,分别从水流结构、流速分布、冲刷地形进行分析,结果表明,①两排10桥墩轴向与水流方向成不同角度的直线均匀的布置,彼此之间必然会相互影响,靠近上游的桥墩影响靠近下游桥墩的水流结构,60°布置时冲深最大位置位于前排2#墩处,t=4s时其值为7.66 cm,t=6s时其值为11.27cm,冲刷深度随时间的增加而增大,直到最后达到冲淤平衡;②当桥墩90°布置时,1~5#圆柱的流速具有明显的对称性,中间3#桥墩前的冲刷范围最小。而30°布置时,则发现1#桥墩前的流速值明显高于其它4个桥墩,且有逐次递减的趋势,斜向分散布置减少了桥墩的阻水作用。0°布置时则是靠近左岸的一排桥墩冲刷较严重,30°时1#和5#桥墩的冲刷较其他桥墩严重,60°布置时2#和4#墩前的冲刷范围较大。总的来说,通过此次实验研究,运用Flow 3D软件模拟了桥墩绕流,将得到的结果与实际测试结果进行了对比,成功结合数值模拟以及实际实验两种研究方法,研究分析了水流分布的特性和河床冲刷变形的情况,亦能为日后类似的研究提供参考。
[Abstract]:The flow around a cylinder has always been the object of many theoretical analyses, experimental studies and numerical simulations. However, due to the complexity of the three-dimensional flow around the cylinder, the understanding of the physical nature of the flow phenomenon is still incomplete. In particular, there is no systematic theoretical study on the relationship between the flow around the cylinder and the scour around the cylindrical piers. In this paper, the characteristics of the flow field around the cylindrical pier and the scour characteristics of the pier are studied by using the numerical simulation software of Flow-3D fluid dynamics, and the relationship between the flow around the cylinder and the scour is explored. In order to provide theoretical basis and new research ideas for the study of flow around cylindrical piers and scour. In this paper, the flow around a single cylindrical pier and the scour of the river bed are simulated by using Flow 3D software, and the distribution of the flow field around the pier and the scour characteristics of the river bed are obtained. The results show that: (1) the two-dimensional flow field of the cylindrical pier is close to the two sides, the velocity of flow decreases due to the influence of the side wall of the tank, and the velocity decreases to zero because of the blocking effect of the pier on the flow in front of the pier. After the pier, the flow field becomes smooth and stable with the increase of the flow. (2) when the initial velocity increases, the range of concentrated flow around the pier in front of the pier decreases and the influence range of wake on the back of the pier increases; 3 when the initial velocity is 37cm/s, the maximum velocity of two-dimensional plane reaches 42.3 cm / s, and the two-dimensional velocity distribution of the other two initial velocity has the same law, in which the maximum velocity is 34.4cm / s and 22.2 cm / s, respectively. The longitudinal velocity is the largest in the three-dimensional velocity component. The other two directions have a smaller velocity component but mainly affect the migration direction of the velocity. In this paper, the characteristics of flow around piers under different arrangement modes of water-bearing piers are simulated and analyzed from the aspects of water flow structure, velocity distribution and scour topography. The results show that 1 two rows of 10 piers are arranged in a straight line with different angles between the axial direction and the direction of water flow, and the results are as follows: 1. The pier close to the upstream affects the water flow structure near the downstream pier. The maximum depth of the pier at 60 掳is located at the front row of pier 2, and the maximum value is 11.27 cm at 7.66 cm,t=6s for t ~ (2) 4s, and the water flow structure of the pier near the downstream pier is affected by the bridge pier near the upstream of the pier at 60 掳. The scour depth increases with the increase of time until the scouring and silting balance is finally reached. (2) when the piers are arranged at 90 掳, the velocity of 1 ~ 5 # cylinder has obvious symmetry, and the scour range in front of the middle 3 # pier is the smallest. At 30 掳arrangement, it is found that the flow velocity in front of 1 # pier is obviously higher than that of the other 4 piers, and there is a trend of decreasing gradually, and the oblique dispersion arrangement reduces the water resistance of the pier, and the scour of a row of piers near the left bank is more serious in the 0 掳arrangement, and the flow velocity in front of the pier is obviously higher than that of the other 4 piers. The scour of 1 # and 5 # piers at 30 掳is more serious than that of other piers, and the scour range in front of 2 # and 4 # piers at 60 掳arrangement is larger than that of other piers. In general, through this experimental study, the flow around the pier is simulated by using Flow 3D software. The results obtained are compared with the actual test results, and the two research methods are successfully combined with numerical simulation and practical experiment. The characteristics of the flow distribution and the scour deformation of the river bed are studied and analyzed, which can be used as a reference for similar research in the future.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U442.3

【相似文献】