initial water pressure meaning in English

初始水压

( 4 ) through the hydraulic property experiment of micro - hole lateral pipes of simple sdi in air , it was found that the average pressure of 60 mitre length lateral pipes was at the position of per 40o / o ~ ~ ~ 50 % of the effectual pipe length from the fist micro - hole , major pressure - loss was occurred at the ahead part of half pipe . the pressure uniformity reduced with orifice aperture ? increasing , and the relationship between pressure uniformity and initial water pressure was poor . running under the initial water pressure of 1 . 5 meter , the discharge uniformity reduced with orifice aperture ? increasing , and when the orifice aperture smaller than or equal 1 . 0mm , irrigation uniformity could achieve above 0 . 6
（ 3 ）通过对空气介质中简易地下滴灌的微孔毛管试验研究发现： 60m管长的毛管平均压力水头的位置基本上在距第一孔口的有效管长40 - 45的地方；大部分水头损失发生在毛管的前半部分；压力均匀度随孔径的增大而减小，但与初始工作水头关系不密切；在1 . 5m以下的工作压力下运行，沿程出流均匀度随孔径的增大而降低，当孔径不大于1 . 0mm时，灌水均匀度可以达到60以上；当孔径大于等于1 . 2mm时，灌水均匀度低于50 。