丁坝长度对弯道水力特性影响的数值模拟研究

Numerical simulation for the effect of spur dike lengths on the hydraulic characteristics of the bend

于河道弯折处设置丁坝后,其水流特征显著改变,为探究该问题,采用RNG k-ε湍流模型及VOF模型对60°弯道内的单丁坝绕流进行了三维数值模拟,模拟中分别计算了设置3种丁坝的工况(模型单丁坝的长度分别为0. 15、0. 25、0. 35m)。基于数值计算的结果,重点对弯道流场结构、断面流速分布、湍流特征参数和液面特性等进行了分析探讨。研究表明:水流流经无丁坝的弯道,会对凹岸产生冲刷,凸岸造成淤积;丁坝的布设,加剧了凹、凸两岸的流速不均匀性,削弱了对凹岸的冲刷,调整了水面横比降;当丁坝长度增长,混流区的尺度变大,流体湍动能以及湍流黏度的强度和作用范围随之变大;在坝后流动分离区域,湍动能呈现最大值,在坝后旋涡中心区域,湍流黏度呈现最大值。

The hydraulic characteristics significantly changes if build a spur dike on the river bend. To solve this problem,a 3D numerical model using the RNG k-ε turbulence model coupled with the Volume of Fluid( VOF) model was conducted to predict the flow characteristics around a single spur dike within the 60° corner bend. The modelling considered three kinds of spur dike model length( 0. 15 m,0. 25 m,and 0. 35 m) and analyzed the flow field structure,cross-section velocity distribution,turbulence characteristic parameters and liquid surface characteristics. It is found that water flowing through the river bend without spur dike will wash the concave bank and cause deposition on the convex bank. The spur dike aggravates the inhomogeneity of flow velocity between the concave and convex banks,weakens the scouring on the concave bank and adjusts the horizontal drop of water surface. As the spur dike length increases,the dimension of backflow area increases,then the strength and action range of turbulent kinetic energy and turbulent viscosity also become larger and larger. The maximum turbulent kinetic energy appears in the flow separation area behind the dam,and the maximum turbulent viscosity appears near the vortex center behind the dam.