宽尾墩—跌坎消力池脉动压强试验研究

Experimental investigation on fluctuating pressure of drop stilling basin with flaring gate pier

宽尾墩与跌坎消力池联合消能使跌坎消力池内的水力参数更加复杂,研究消力池底板的脉动压强特性对宽尾墩体型设计具有参考作用.基于模型试验研究5种收缩比(a=0.38;0.44;0.50;0.56;0.62)Y型宽尾墩与跌坎消力池联合消能下消力池的脉动压强特性.试验结果表明:脉动压强峰峰值可以达到设计水头的1.03~1.36倍,收缩比的减小可以削减峰峰值,消除跌坎后的负压;消力池底板脉动压强均方根沿程呈现单峰与双峰型,最大脉动压强系数出现在跌坎之后,减小收缩比使消力池主要脉动消能区域增大前移,最大脉动压强系数降低;脉动压强概率密度基本符合正态分布,存在正偏与负偏现象,水流速度偏向底板为正,偏离时为负;消力池底板脉动压强主要由10 Hz以内的低频脉动组成,随着收缩比的减小,消力池前端的脉动能量增大,后端脉动能量减小.

The combined energy dissipation of the flaring gate pier and the drop stilling basin makes the hydraulic parameters more complicated.The study of the fluctuating pressure characteristics of the stilling basin floor has a reference effect on the shape design of the flaring gate pier.Based on the model test,the fluctuating pressure characteristics of the stilling basin under the combined energy dissipation of Y-shaped flaring gate pier and drop stilling basin with five contraction ratios(a=0.38;0.44;0.50;0.56;0.62)were studied.The results showed that the peak-to-peak value of fluctuating pressure could reach 1.03~1.36 times of the design head,and the decrease of the contraction ratio could reduce the peak-to-peak value and eliminate the negative pressure after the drop.The root mean square of the fluctuating pressure of the stilling basin bottom plate showed a single peak or a double peak along the way.The maximum fluctuating pressure coefficient appeared after the drop sill.Reduc-ing the contraction ratio made the main fluctuating energy dissipation area of the stilling basin increase and move forward,and the maximum fluctuating pressure coefficient decreased.The probability density of fluctuating pressure basically conformed to the normal distribution,and there were positive and negative biases.When the water flow velocity was biased towards the bot-tom plate,the distribution was positive,and on the contrary,it was negative.The fluctuating pressure of the stilling basin floor was mainly composed of low-frequency pulsations within 10 Hz.As the contraction ratio decreased,the pulsating energy in-creased in the front section of the stilling basin and decreased in the rear.