不同丁坝间距对水流特性的影响研究

Study on the Effect of Different Spur Dike Spacing on Water Flow Characteristics

丁坝具有束窄水流、防冲减淤的作用,坝头附近流场呈三维紊动特性使河道受到强烈冲刷。在实际工程中,丁坝大多以丁坝群形式布设,丁坝间距直接影响绕流流场和局部冲刷,合理的丁坝间距,不仅节约成本,还能使丁坝群功能优化。选取不同丁坝间距并拟定5种对比方案,建立三维紊流数学模型,基于计算流体力学数值模拟方法,采用RNG k-ε湍流模型,模拟非淹没型直立正挑薄壁丁坝群对水流特性的影响。通过改变丁坝间距,分析不同丁坝间距对水位、流速、流态、回流区长度的影响。结果表明:随着丁坝间距的减小,坝下游水位下降变缓,坝间距为1 m时,分界线沿着坝首与河岸平行;丁坝间距与丁坝长度的比值在15~7.5时,最下游丁坝回流长度随丁坝间距的减小而减小;丁坝间距与丁坝长度的比值在7.5~5时,最下游丁坝回流长度随丁坝间距的减小而基本不变。对丁坝间距及数量进行适当调整,可有效改善局部冲刷和回流区长度。

The spur dikes can narrow water flows,prevent erosion and reduce silt.The three-dimensional turbulence of the flow field near the dike head causes the river bank to be strongly scoured.In practice,the spur dikes are placed in groups,and the space between the dikes directly affects the flow field and local scouring.A reasonable spacing not only saves cost but also optimizes the function.This paper selected different spur-dike spacing and 5 comparison schemes to establish a three-dimensional turbulent flow mathematical model.Based on the numerical simulation method of computational fluid dynamics,the RNG k-εturbulence model was used to simulate the effect of non-inundated upright vertical thin-walled spur-dike on the flow characteristics.By varying the spacing,the effects of different dike spacing on water level,flow velocity,flow regime,and length of re-circulation zone were analyzed.The results show that the water level downstream of the dikes decreases slowly as the spacing narrows,and the dividing line is parallel to the river bank along the dike head when the spacing is 1 meter.The length of the re-circulation zone of the most downstream decreases with the decrease of spacing when the ratio of the spacing to the length is between 15 to 7.5;while the length of the re-circulation zone of the most downstream remains the same when the ratio of that is between 7.5 to 5.Appropriate adjustment of the spacing and number of spur dikes can effectively improve the local scour and length of re-circulation zone.