T型丁坝对90°弯道水力特性影响的大涡模拟研究

Study on Effects of T-Spur-Dikes on Flow Characteristics in 90° Bend Channel by Large Eddy Simulation

为了解决实际河流弯道中水流对凹岸冲刷严重而凸岸泥沙淤积的问题,有必要对弯道中布设了丁坝后的水力特性进行研究。采用气液两相流大涡模型模拟90°弯道明渠增设了丁坝后的水流水力特性。通过比较弯道纵向流速模拟值与试验值,结果吻合较好,得出大涡模型是模拟弯道水流水力特性的有效方法;通过分析弯道处水平面和不同弯转角度横断面的流速和流场分布规律,得出弯道环流的流态特征,即靠近凸岸的近底面处较凹岸近水面处存在较大的二次流强度;在弯道中布设丁坝后可有有效的消除弯道环流,而且T形丁坝无论是在改善弯道水流流态方面还是在自身安全性上都有更大的优越性。

In order to solve the problems of river erosion at concave bank and of sediment deposition at convex bank in actual bend rivers, the 3D hydraulic characteristics of bend channel with spur-dikes must be studied. The gas-liquid two-phase large eddy model was used to numerically simulate the hydraulic characteristics of flow in a 90° bend channel with a spur-dike. Comparisons of the simulated longitudinal velocity with the experimental data show a good agreement, which indicates that the large eddy model is an effective way to study the hydraulic characteristics of bend channels. The analysis of the distribution of velocity and flow fields on different horizontal plans, and on cross-sections of different bending angles,shows that the intensity of circulation near the concave bank is larger than that near the convex bank as a result of the secondary flow, and also shows that the spur-dike can effectively eliminate the circulation in the bend channel, and that the T-shaped groin has more advantages of improving the flow patterns of bend channels and of its own security.