典型断面渠道临界水深计算

系统总结了明渠特征水深研究领域的计算方法,评价了各方法的特点;为了优选出典型断面渠道临界水深简捷、通用、精度高、适用范围广的显式计算公式,通过定义包含典型断面几何要素及流量的量纲为一的参数,将目前成果中临界水深的显式计算公式用定义量纲为一的参数进行统一表达,并对其进行简捷性、精度及适用范围的综合评价比较,优选出梯形、圆形、弧底梯形、普通城门洞形、马蹄形等5种典型断面渠道临界水深的显式计算公式;对标准城门洞形断面的临界水深应用最优一致逼近原理,提出以幂函数形式分段表达的新显式计算公式．误差分析表明,在工程常用范围内,由推荐的显式公式所计算的6种典型断面的临界水深,其最大相对误差均小于1％,满足工程设计对精度的要求．该研究可为典型断面排灌渠道的设计及水力计算提供参考．

Calculation of water critical depth in channels with common shapes

The existing methods for calculating critical depths of open channels were summarized and their characters have been clarified.In order to identify simple,universal,accurate explicit equations for calculating the critical depth in open channels with typical cross-sections,two dimensionless variables related to channel cross-section geometry and discharge were defined.Then,those explicit equations available for five sorts of open channels with typical cross-sections in literature were expressed by the dimensionless variables,thus the most appropriate ones could be selected by comparing their complexity,accuracy and application range.Also,by applying the best approximations algorithm,a new explicit equation expressed as a series of piecewise power functions was developed for the open-channel with standard city-gate cross-section.For the new equations,the results of error analyses indicate that all the maximum relative errors in critical depth are less than 1% in the channel normal application range.The results of the study may provide a reference for the design and hydraulic calculations of ty-pical open channels applied in drainage and irrigation.