应用斜坎改善弯道流态的可行性研究

Feasibility of using oblique ridges to improve flow pattern of curved channel

【目的】基于模型试验对使用斜坎改善泄洪洞弯道流态的可行性进行研究,为同类工程提供参考。【方法】在泄洪洞弯道段沿程分别布置5道3种形式的斜坎(高0.35m矩形斜坎、高0.25m矩形斜坎及高0.25m梯形斜坎),对3种工程措施下弯道的水流流态、水面超高、流速和压强分布进行量测,通过流态优劣和流速、压强分布的合理性对比,对其改善流态的可行性进行研究。【结果】3种形式的斜坎均能有效消除弯道水面超高,改善流态,但矩形斜坎的改善效果优于梯形斜坎。布置0.35m矩形斜坎可使弯道最大水面超高减小至2.70m,但局部出现水面击打洞顶现象;布置0.25m矩形斜坎和0.25m梯形斜坎后,弯道水面超高分别减小至3.42和4.21m,且无击打洞顶现象,但压强量测均出现极大负压。【结论】对于已建工程,斜坎对消减弯道水面超高、改善水流流态非常适用,且矩形斜坎优于梯形斜坎;但在高速水流工况下,斜坎坎顶、坎后及坎后侧壁会出现负压,为避免出现负压,建议将斜坎应用于低速水流弯道。

【Objective】The feasibility of using oblique ridges to improve flow pattern of spillway tunnel was investigated to provide reference for similar projects.【Method】Five channels of oblique ridges belonging to three types（rectangle oblique ridges with heights of 0.35 mand 0.25 m,and trapezoid oblique ridge with height of 0.25m）were set along the curved section of spillway tunnel.The flow pattern,ultra-height and distribution of velocity and press were measured and the feasibility was analyzed based on comparison.【Result】All three types of oblique ridges were useful to eliminate the ultra-height and improve the channel flow pattern.The pattern of rectangle oblique ridges was better than the trapezoid ones.Using oblique ridges with height of 0.35 mreduced the ultra-height to 2.70 m,but the flow hit the roof at some parts.Using rectangle oblique ridges or trapezoid oblique ridges with height of 0.25 mreduced the ultra-height to 3.42 m and 4.21 mwithout hitting to the roof,but they could cause negative pressure.【Conclusion】Oblique ridges could eliminate the ultra-height and improve the flow pattern for constructed projects,and rectangle oblique ridges were superior to trapezoid ridges.However,under the high velocity flow,negative pressurecould appear in the roof,back and side of oblique ridges.It is suggested to use oblique ridges for low velocity flow.