灌溉输水管道沟槽减阻研究

Research on Drag Reduction of Irrigation Delivery Pipeline

【目的】探索沟槽结构对灌溉输水管道的减阻作用。【方法】采用SA与RNG k-?湍流模型,模拟分析了沟槽在湍流流动中的减阻效果,并与Bechert的试验结果进行了对比;采用RNG k-?湍流模型对灌溉输水管道开展了0.1~1 mm尺度下的V形沟槽减阻研究;采用LES湍流模型对沟槽减阻机理进行了探索。【结果】(1)相较于SA湍流模型,RNG k-?湍流模型的计算结果与Bechert的试验结果相比误差更小,为4.6%,即RNG k-?湍流模型计算精确度更高;(2)夹角为60°的V形沟槽,当沟槽边长为0.5 mm时对灌溉输水管道具有最佳减阻效果,减阻率为7.17%,对应无量纲沟槽间距s+=15.2,无量纲沟槽尺寸lg+=10;(3)沟槽中存在很小的涡旋,这些小涡旋可能是沟槽在湍流中具有减阻作用的原因之一。【结论】夹角为60°的V形沟槽对灌溉输水管道的最佳减阻效果为7.17%。

[Objective] Explore the drag reduction effect of riblet structure on the irrigation pipeline. [Method] The drag reduction effect of the riblet in the turbulent flow was simulated by SA and RNG κ-ε turbulence model, and compared with the results of Bechert＇ s test, then the RNG κ-ε turbulence model was used to analyze the V- shaped riblet drag reduction at the scale of 0.1~1 mm for the irrigation pipeline, finally the LES turbulence model was used to explore the drag mechanism of the riblet structure. [Result] Compared with the SA turbulence mod- el, the RNG k-e turbulence model had the smaller error compared with the Bechert＇ s test result, which was 4.6%, in other word, the RNG k-e turbulence model was more accurate. For a V-shaped riblet with the angle of 60~ , when the riblet length was 0.5 mm, it had the best drag reduction effect on the irrigation pipeline, the drag reduction rate was 7.17%, corresponding to the dimensionless pitch st was 15.2, and dimensionless riblet size l＋8 was 10. There were small vortices in the riblets that might be one of the causes of the drag reduction in the turbulence. [Conclusion] The best drag reduction effect of the V-shaped riblet with an angle of 60° for the irrigation pipelines was 7.17%.