黄河上游大柳树-沙坡头河段河床变形数值模拟

A Numerical Simulation of the Upper Yellow River Bed Deformation in Daliushu-Shapotou Section

对黄河宁夏境内具有连续弯道的大柳树-沙坡头河段的泥沙运移及河床变形等进行了平面二维数值模拟研究.建立了修正的平面二维RNGk-ε紊流泥沙数学模型,其中水流模块采用修正的RNGk-ε紊流模型,泥沙模块采用全沙模型,考虑了不同粒径组悬移质和推移质运移对河床变形的影响。数值模拟结果与实测结果比较吻合。表明该模型可以用于模拟具有连续弯道的多沙河流泥沙运移及河床演变过程;在4种典型工况下分别进行了数值模拟,研究了不同水沙条件对水沙运移及河床变形的影响;吸取了关于泥沙数学模型中水流模块和泥沙模块的耦合式算法和分离式算法的优点,建立了一种半耦合算法,其计算量比耦合式算法大大减小,计算精度上比分离式算法要高。

2-D numerical simulation is conducted for the upper Yellow River flow from Daliushu to Shapotou to study sediment transportation and river-bed deformation. Modified 2-D RNG κ-εturbulence sediment model, which consists of flow and sediment modules,is established. Modified 2-D RNG κ-ε turbulence model is adopted for the flow module, and total load model is adopted for the sediment module. In the total load model, both the bed deformations caused by various fractions of particle size of suspended load and bed load are considered. The numerical results are well consistent with the measured data, indicating that the model can be used to simulate sediment transport and bed deformation in silt-laden rivers with continuous bends. Numerical simulations are conducted in four typical cases to study the influence of silt-discharge condition to the sediment transportation and bed deformation. In addition, on the basis of the coupled and separated algorithms about flow and sediment modules, a semi-coupled algorithm is established, which needs less calculation time rhan the coupled algorithm, and is more accurate than the separate algorithm.