台阶形式对阶梯溢洪道水力学特性的影响研究

The Effects of Step Configurations on the Hydraulic Properties of Stepped Spillways

大单宽流量下,阶梯溢洪道存在消能率较低、空化空蚀等问题。尽管前人对台阶尺寸、布置方式进行了相关研究,但鲜有涉及台阶形式本身。基于此,结合mixture方法,采用Realizable k-ε模型对几种新型阶梯溢洪道进行了数值模拟研究,对比分析了其流场特性、旋涡结构、掺气浓度、压强分布等。结果表明:设置尾坎不仅可降低主流流速,也能增加台阶上旋涡尺度和范围;各体形掺气浓度均呈“S”形分布,但是设置尾坎和调整台阶面均不能改善掺气效果,常规阶梯体形平均掺气浓度最高;坎式阶梯溢洪道台阶面上压强呈“凹”形分布,当台阶面上无尾坎时,台阶水平面上压强呈“S”形分布;设置尾坎和上翘台阶面均能增加台阶竖直面压强,但台阶面向下倾斜将使得负压区范围增加;设置尾坎和上翘台阶面均能增加紊动能耗散率,向下倾斜台阶面则相反;此外,坎式阶梯体形消能率比常规体形高约10%,上翘台阶面提高约6%,但向下倾斜台阶面使得消能率降低约10%。

At large unit discharges, low-energy dissipation rate and cavitation damage are common problems in stepped spillways, and relevant studies have been conducted to address these issues by investigating the size and layout of the steps, with little focus on the step configurations. Therefore, the current paper aims at examining the effects of step configurations on the flow field, vortex structure, air concentration and pressure distribution by using Realizable k-ε model for mixture flows. The simulated results suggest: Installing pool weirs can decrease the interfacial velocity and increase the vortex intensity. The air concentrations for all cases presented S-shaped variations, but step modifications cannot improve the aeration performance compared with the traditional configuration. The pressure distributions on the horizontal step surfaces of the configurations with pool weirs illustrated U-shaped variations, while the pressure distributions display S-shaped variations for the flat stepped models. Installing pool weirs and upward inclining step faces can increase the pressures on the vertical surfaces, but downward inclining the steps increases the areas with negative pressures. Compared with the conventional model, the energy dissipation rate for pooled stepped spillway and upward inclined stepped spillway are respectively 10% and 6% higher. However, the case with downward inclined steps shows a 10% decrease.