阶梯形丁坝是常见的航道整治建筑物,天然河道中的水流多为非恒定流,非恒定流作用下的阶梯形丁坝局部冲刷特性研究,对丁坝结构设计和水毁防护等具有重要意义。采用自回归马尔柯夫模型,将天然来流过程概化为波谷起冲和波峰起冲2种情况,基于平面二维水流泥沙数学模型,探讨非恒定流作用下的阶梯形丁坝局部冲刷特性。结果表明:① 不同流量过程下,坝后主流区和回流区的流速均随上游来流量的变化而变化,波谷起冲时主流区随冲刷历时的增加逐渐分为2个区域,而波峰起冲时主流区在初期便被分为2个区域。② 受主流区变化和冲坑后方淤积区的共同影响,波谷起冲时的冲坑下游边界向下游凸起后回缩,波峰起冲时的冲坑边界向坑内收缩后扩散到下游,坝头最大冲深较恒定流条件可增加25.5%~54.3%。③ 如采用一级丁坝长度Ld1表征冲坑尺度,6 h冲刷历时中,波谷起冲时冲坑长度、宽度最大值分别可达9.2Ld1和2Ld1,波峰起冲时则分别可达11.3Ld1和2.1Ld1。
Abstract
The flow in natural river is mostly unsteady flow. Researching the local scour characteristics of step-shaped spur dike, a common waterway regulation structure, under the action of unsteady flow is of great significance to spur dike structure design and protection against flood damage. In the present research, the local scour characteristics of step-shaped spur dike under unsteady flow were discussed by establishing a 2-D mathematical model of flow and sediment. The natural inflow process was simplified as trough and peak inflow processes by using autoregressive Markov model. Research results demonstrated that the flow velocity in the main flow area and the recirculation area behind the spur dike changed with the upstream flow regardless of different discharge processes. The main flow area in trough inflow process gradually divided into two regions along with time, while in peak inflow process into two regions in the early stage. Influenced by the change of the main flow area and the siltation area behind the scour pit, the downstream boundary of the scour pit protruded towards the downstream and then retracted in trough inflow process, while in peak inflow process, the boundary of the scour pit shrank into the pit and then diffused to the downstream. The maximum scour depth at dam head can increase by 25.5%-54.3% compared with that in constant flow condition. Ld1, the length of the first-step spur dike, was used to characterize the scour pit scale; during the 6-hour scouring, the maximum length and width of the scour pit can reach 9.2Ld1 and 2Ld1 respectively in trough inflow process, and 11.3Ld1 and 2.1Ld1 respectively in peak inflow process.
关键词
阶梯形丁坝 /
非恒定流 /
自回归马尔柯夫模型 /
局部冲刷 /
冲坑尺度
Key words
step-shaped spur dike /
unsteady flow /
autoregressive Markov Model /
local scour /
scour pit scale
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
参考文献
[1] 钟 亮,孙建云,刘珺洁,等. 阶梯形丁坝下游回流规律分析[J]. 水利水运工程学报,2017(5):9-17.
[2] 樊书刚,朱代臣,何艳军,等. 三峡水库变动回水区胡家滩滩段阶梯状整治建筑物设计方案[J]. 水运工程,2016(1):134-138,157.
[3] 范雪梅,余 敏,王春华,等. 阶梯型潜丁坝纵断面结构型式优化研究[J]. 中国水运(下半月),2019,19(6):141-143.
[4] 武永新,王建家,苑希民. 丁坝工程冲刷与防护措施研究综述[J]. 自然灾害学报,2020,29(1):1-10.
[5] 潘军峰,冯民权,郑邦民,等. 丁坝绕流及局部冲刷坑二维数值模拟[J]. 四川大学学报(工程科学版),2005,37(1):15-18.
[6] BEY A,FARUQUE M A,BALACHANDAR R.Two-dimensional Scour Hole Problem: Role of Fluid Structures[J]. Journal of Hydraulic Engineering,2007,133(4):414-430.
[7] ZHANG Hao, NAKAGAWA H, KAWAIKE K, et al. Experiment and Simulation of Turbulent Flow in Local Scour Around a Spur Dyke[J]. International Journal of Sediment Research, 2009, 24(1): 33-45.
[8] KUHNLE R, ALONSO C. Flow Near a Model Spur Dike with a Fixed Scoured Bed[J]. International Journal of Sediment Research, 2013, 28(3): 349-357.
[9] 彭 静,玉井信行,河原能久. 丁坝坝头冲淤的三维数值模拟[J]. 泥沙研究,2002(1):25-29.
[10] PANDEY M, AHMAD Z, SHARMA P K. Estimation of Maximum Scour Depth Near a Spur Dike[J]. Canadian Journal of Civil Engineering, 2016, 43(3): 270-278.
[11] 张 立,孙忠克,徐东坡. 丁坝局部冲刷坑形态演变及冲刷平衡临界条件[J]. 水利学报,2017,48(5):545-550.
[12] 宁 健,李国栋,马 淼. 河宽缩窄率对河床冲刷形态影响数值模拟研究[J]. 水力发电学报,2017,36(8):43-49.
[13] 喻 涛,王平义,陈 里,等. 非恒定流作用下丁坝局部冲刷研究[J]. 四川大学学报(工程科学版),2014,46(3):31-36.
[14] 钟 亮,王振志,王 舒,等. 非淹没复式断面丁坝区的流速分布规律[J]. 长江科学院院报,2018,35(6):60-66.
[15] 丁晶晶,陆彦,陆永军. 台阶式丁坝水动力特性及防冲效应[J]. 水利水运工程学报,2014(5):67-74.
[16] 喻 涛. 非恒定流条件下丁坝水力特性及冲刷机理研究[D]. 重庆:重庆交通大学,2013.
[17] 姜 彤. 阶梯形丁坝局部冲刷特性数值模拟研究[D]. 重庆:重庆交通大学,2020.
[18] 陈稚聪,黑鹏飞,丁 翔. 丁坝回流分区机理及回流尺度流量试验研究[J]. 水科学进展,2008,19(5):613-617.
基金
重庆市基础科学与前沿技术研究项目(cstc2017jcyjAX0278);重庆交通大学大学生创新创业训练计划项目(202010618002)
PDF(3764 KB)
