分流比及取水角度对弯道引水口水流流场的影响

摘要

以引水工程中引水口"护岸防沙"问题为研究背景,探究干渠与引水支渠分流比变化以及取水角度变化对弯道引水口水流流场的影响,为弯道引水工程中的堤岸防护、减少泥沙淤积提供参考依据.基于雷诺方程和有限体积法建立弯道水流运动三维数学模型,并利用物理模型试验进行验证,结果表明该数学模型能够较好的模拟弯道引水口附近水流形态和流速分布.利用该模型模拟多种分流比工况、若干取水角度下的弯道水流运动,分析引水口附近平面流速分布、口门断面流速分布以及引水口上游分水宽度的变化.结果表明:引水口附近平面均值流速分布为V中间层>V近表层>V近底层,口门断面流速峰值位于断面上唇中下部,试验流量为30L·s-1的情况下,该区域最大流速可达0.25m·s-1,故实际工程中应对引水口上唇中下部重点进行防护.当分流比η<0.42时,分水宽度呈现d表0.42时,分水宽度呈现d表>d中>d底.取水角度为60°~90°情况下,取水口附近流速较小,平面均值流速不足0.10m·s-1,取水角为钝角时取水口附近流速峰值达0.22m·s-1.分流比过小或取水角度过大,支槽右壁均易形成回流区,为减小回流区面积,避免淤沙过多,应尽量选取较小的取水角度,并根据支渠的需水量,合理确定分流比.%Using the "bank revetment and sand prevention" problem of diversion port in diversion projects as a background, the diversion ratio change of trunk canal and branch canal, and the influence of water intake angle change on flow field of diversion port in cruve have been studied, which gives a reference to embankment protection and sediment reduction in diversion works. Based on reynolds equation and finite volume method, three-dimensional mathematical model of water movement in curve was established and proved by physical model test. The results showed the mathematical model could be used to simulate the flow pattern and velocity distribution near the curve inlet. By using the model, water movement in curve under various split ratio conditions with several water intake angles was simulated. And the velocity distribution near diversion port and diversion port gate was studied as well as the change of water width in diversion port upstream. The results showed that the mean velocity distribution on slicing plane beside diversion port gate was V intermediate layer>V near-surface layer>V near-bot om layer. The velocity of middle and lower part at the top of diversion port was the highest. In the case of the flow rate at 30 L·s-1, the maximum flow velocity in the area was up to 0.25 m·s-1, so the middle and lower part at the top of diversion port should be given prevention in practical engineering. When the split ratio η < 0.42 and the water wildth shows dsurface < dmiddle < dbot om,η > 0.42, the water wildth showed dsurface> dmiddle >dbotom. When water intake angle was between 60°-90°, the flow velocity near the nozzle was small and the plane mean velocity was less than 0.10 m·s-1. While the intake angle was an obtuse angle, peak velocity near the intake was up to 0.22 m·s-1. Because the split ratio was too small or the diversion port angle was too large, circulation zone may be formed easily in the right wall of trough. To reduce recirculation zone and avoid too much sediment, a smaller diversion port angle should be chosen, and the split ratio can be determined reasonably according to the water demand of banch canal.