台阶式溢洪道滑掠流时均压强影响因素分析

Factors Affecting Time-averaged Pressure of Skimming Flow in Stepped Spillways

由于台阶式溢洪道结构特殊,流态复杂,对台阶式溢洪道压强并未取得一致性的研究成果。对多个台阶式溢洪道滑掠流时均压强资料进行分析,探讨来流流量、掺气、台阶尺寸、溢洪道坡度等对台阶式溢洪道时均压强的影响。分析结果表明:单宽流量大,时均压强变大;掺气可有效降低正压时均压力并增加负压值;台阶尺寸对台阶式溢洪道的影响较为复杂,台阶尺寸较小,且坡度较缓时竖直面压强呈中间小、两头大分布,坡度较大时具有2个压力极小值,位于竖直面底部和顶部,台阶尺寸较大时竖直面压强自下而上呈减小趋势;坡度增加,台阶式溢洪道压强变化幅度增大。

As stepped spillway has special structure and complex flow patterns,researches on the pressure in stepped spillway are not consistent. In view of this,we investigate into the effects of flow discharge,air entrainment,step size and spillway＇s slope gradient on the distribution of time-averaged pressure through analysing the pressure data of skimming flow in several stepped spillways. Results reveal that big discharge per unit width leads to big time-averaged pressure. Air entrainment could effectively reduce positive time-averaged pressure and increase negative pressure. Effect of the step size is complicated： when the step size is small with gentle slope,pressure is small in the middle but large on both ends in vertical plane of the step; when step size is small with steep slope,minimum pressure occurs on the bottom and top of step in vertical plane; while when the step size is large,pressure decreases from the bottom to the top,and pressure variation intensifies with the increase of slope gradient.