丁坝绕流流场及局部冲刷三维数值模拟研究

3D numerical simulation for flow and local scour around spur dike

精确模拟丁坝附近流场信息,预测冲刷形态对丁坝的设计和安全运行具有重要的意义。本文采用一种基于多相流模式的悬移质输沙与传统推移质输沙相结合的模型模拟丁坝局部流场与冲刷过程,而河床变形则通过填充层体积份数的变化来模拟,VOF法处理自由面。泥沙冲刷侵蚀模型主要分为三个模块:悬移质漂流模块、泥沙挟带模块以及推移质输运模块,通过模拟在水流作用下的泥沙运动来预测泥沙侵蚀、对流扩散以及沉积等过程,同时考虑床面坡度对泥沙输运以及临界希尔兹数的影响。模拟得到了丁坝附近局部流场、地形冲淤变化以及冲刷坑形态等,并把计算结果与试验资料进行了对比分析,二者吻合较好,证明该模型能够很好地反映丁坝附近流场信息和床面变形特征。

Accurately simulation of flow field around spur dike and predicting scouring shape has great significance for the design and safe operation of spur dike. Based on multiphase flow model of suspended load sediment transport and the traditional model of bed load transport combining, the paper simulates local flow field and scour process. The riverbed deformation is simulated by changing packed bed volume, while VOF method to deal with free surface. Sediment scour and erosion model include three models： suspended sediment drift model, sediment entrainment model and bed load transport model. We simulate sediment transport to predict erosion, adveetion diffusion and deposition process, while considering the impact of bed surface slope and critical Shields numbers for the sediment transport. The obtained results include detailed flow field around spur dike, deposi- tion and erosion changes and scour hole terrain morphology. The numerical results agree well with experiment data. It shows that the model can well reflect flow field and riverbed deformation characteristics around spur dike.