缓变曲线改善120°弯道水沙运动的三维数值模拟

人工河道的弯道段大多曲率单一，水流动力轴线的曲率与弯道曲率难以匹配，导致了流固分离和弯道二次流的产生。针对弯道曲率突变问题，引入两种插有缓变曲线的弯道形式，研究缓变曲线对120°弯道水沙特性的影响和流态的改善。运用MIKE 3水动力模型和泥沙输移模型对单曲线弯道、缓圆缓弯道和对称凸弯道进行数值模拟，对比分析不同弯道型式在冲刷和定床两种工况下的近底流速、水面横比降和超高、弯道环流和河床冲淤变形。研究结果表明：插有缓变曲线的两种弯道可以遏制弯道中水体湍动的发展，改善120°弯道水流的流态，能够有效减小弯道凹岸冲刷、凸岸淤积的现象，缓解河床的冲淤变形。

Improvement on flow and sediment transport by transition curves in 120° channel bend and its 3-D numerical simulations

The curvature of an artificial open channel bend is mostly a constant that is hardly to be matched by the curvature of flow dynamic axis, thereby causing a separation of fluid and solid and the formation of secondary flow. This study adopts two types of transition curves connecting a circular bend section to plane walls at its inlet and outlet in modification of an artificial 120?-turn open channel bend with abrupt curvature changes, and examines the improvement of its flow and sediment transport condition. For this purpose, the MIKE 3 FM hydrodynamic and sediment transport model is used to simulate the 3-D bend flows, focusing on comparison of near bed velocity, variation in water surface, secondary flow, and bed topography between the bends with and without wall transition curves. Results reveal that the transition curve modification is effective in significantly suppressing the development of turbulences in the bend and reducing concave bank erosion and convex bank sediment deposition.