滴灌湿润比的解析设计

Determination of wetted percentage of tricke irrigation system

湿润比的计算是滴灌系统设计的重要内容本文根据湿润比的合理定义，按照实际单个滴头下湿润体的形状，首次提出了相应当量湿润直径（面积）的概念，导出了现在国内广泛使用的湿润比计算公式的理论基础和实际应用时应满足的严密条件，分析了已往国内滴灌湿润比设计与理论值间的误差．文中提出了用地表湿润面积（直径）进行湿润比计算的方法，这个方法将大大方便实际应用．根据湿润比的计算公式提出了设计湿润比的若干方法：滴头布置（量）；设计滴头流量．由滴头下湿润宽度与时间的关系及湿润土体的形状，首次提出并验证了湿润宽度与时间关系函数的经验常数间应满足的约束条件首次提出了进行湿润比有理设计的方法，可用了计算湿润范围不达计划湿润深度时湿润比的计算方法，湿润范围超出计划湿润深度时湿润比及渗漏湿润土体、渗漏水量的计算方法由实验所得结果，给出了多种条件下设计湿润比的例子．

Based on a reasonable definition of wetted percentage and the actual wetting patterns created by an isolated trickler, a concept of equilibrium wetted diameter or area' is proposed. Meanwhile, the theoretical basis of the wetted percentage formulae now being widely used in China and its restrictions in practical application are described. For simplification, wetted area at ground surface is suggested to be an important parameter in determning wetted percentage. The determination of trickler number and their distribution are given as an example. A rational method is developed to determine the wetted percentage in the case of wetting front not exceeding the expected irrigation depth and that in the case of wetting front exceeding the expected irrigation depth. Experimental study of wetting front created by an isolated dripper enables the estimation of coefficients of the time dependent functions for wetting distances. Finally, pratical examples are given to illustrate the procedures of wetted percentage determination.