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灌溉支管注1的沿程水头损失可表达为总流量、管径长度注2都相同的但无沿程出流的另一根相关供水管的沿程水头损失乘一个小于一的系数。克里斯琴森于1942年首先采用此系数,并称它为多口系数F。目前通行的多口系数F对支管上的喷头总数有很密切的关系。若令相关供水管长度延伸到灌溉地块的边界,就可对多口系数F进行修正。这样的相关供水管,称为修正的相关供水管。当多口系数F根据这种修正的相关供水管或修正的多口系数来计算时,如喷头数多于五、修正的多口系数Fm的数值实际上为一常数。采用修正多口系数Fm,将使实际中支管沿程水头损失的计算工作简化。本文提出了牵引式拖管系统和时针式喷灌系统支管的修正多口系数Fm。
The head loss along irrigation branch note 1 may be expressed as the total flow, multiplied by a factor less than one along the head loss of the other associated supply pipe with the same diameter but equal length. Christianson first adopted this coefficient in 1942 and called it a multi-port coefficient F. The prevailing multi-port coefficient F on the total number of branches on the nozzle has a very close relationship. If the relevant water supply pipe length is extended to the boundary of irrigation plots, the multi-port coefficient F can be amended. Such related water pipes are called correlative water pipes. When the multi-port coefficient F is calculated on the basis of this modified relevant water supply pipe or modified multi-port coefficient, if the number of sprinklers is more than five, the corrected multi-port coefficient Fm is actually a constant value. The correction of the multi-port coefficient Fm will simplify the calculation of the actual head-branch loss along the branch pipe. In this paper, a modified multi-port coefficient Fm is proposed for the trailing draft tube system and the branch pipe of the hourglass sprinkler system.