自由出流状态下矩形薄壁堰流量公式的实验研究与理论分析

Experimental Study and Theoretical Analysis of Discharge Formulae for Free Flow over Rectangular Sharp-Crested Weirs

为确定精度,对矩形薄壁堰在自由出流状态下的流量特性进行了实验研究,依据水位-流量关系对典型的流量公式进行了分析和评价。结果表明,Vatankhah提出的基于雷诺数的流量公式精度最高,E_(±4)=100%(误差≤?4%的计算值所占的百分比),平均绝对误差|E|_(m)=0.88%。在基于收缩率(b B)的流量系数公式中,Bijankhan和Mahdavi Mazdeh提出的通用公式具有最高的精度,完全收缩堰精度为E_(±4)=100%、|E|_(m)=0.91%,部分收缩堰精度为E_(±4)=94.64%、|E|_(m)=1.60%。由Gharahjeh等提出的堰流速公式也具有相对较高的精度,完全收缩堰精度为E_(±4)=98.41%、|E|_(m)=1.34%,部分收缩堰精度为E_(±4)=91.07%、|E|_(m)=1.91%。研究肯定了由Aydin等提出的堰流速理论并且表明堰流速是描述矩形薄壁堰流量的一个重要参数,可以被用来很好地描述矩形薄壁堰过堰流量。

Laboratory experiments were carried out to investigate the discharge characteristics and accuracy of discharge formulas of rectangular sharp-crested weirs under free flow condition.The performances of available discharge formulas have been evaluated by using the experimental data sets of present and previous studies.Error statistics of our experimental data indicate that the discharge formula in terms of weir Reynolds number proposed by Vatankhah gives the highest accuracy among the existing slit weir equations,with E_(±4)=100%(i.e.percent error less than or equal to±4) and a mean absolute error|E|_(m)Mazdeh shows the highest accuracy among the re=0.88%.The fullrange discharge equation presented by Bijankhan and Mahdavi lationships in terms of weir contraction ratio,with E_(±4)=100%,|E|_(m)=0.91% for slit weirs and,E_(±4)=94.64%,|E|_(m)=1.60%for partially contracted weirs,respectively.The weir velocity formulae suggested by Gharahjeh et al.exhibit the relatively better performance,with E_(±4)=98.41%,|E|_(m)s study confirm=1.34%for slit weirs and,E_(±4)=91.07%,|E|_(m)the weir velocity approach presented by Aydin e=1.91% for contracted weirs,respectively.Statistical results of thit al.and show that,the weir velocity is a predominant quantity for rectangular sharp-crested weirs,unique characteristics of the weir velocity curves make it more suitable for expressing the discharges.