Some problems of water flow pattern and compensation mechanism for micro-irrigation emitters

Hydraulic calculation of micro-irrigation emitters is important for pipeline engineering design. Classified basis of water flow pattern and the flow condition of pressure pipes, the differences of the operating head of drip?emitters and frictional head loss flow modification, and water temperature modification of dripper discharge were studied. Then the reason for flow stance index x＜0.5 observed in hydraulic measured data of inelasticity elements was analyzed, and the method of area compensation was proposed. Results show that: 1) it’s wrong that the water flow pattern in pressure pipes based on Nituradse’s experimental results were applied in hydraulic calculation of micro-irrigation emitters except for microtubule drippers; 2) water temperature modification of drippers should be done for flow stance index?x=1, not for x≤0.5 not because flow state is at drag square area but because loss of pipes are presented as local loss and not for 1＞x＞0.5 respectively. The hydraulic relationship at different water temperature can be got by hydraulic experiments at corresponding water temperature for drippers of 1＞x＞0.5; 3) the way of classifying water flow pattern of drippers should be abandoned because this way just suitable for microtubule drippers cannot be applied for others; and 4) the reason for x＜0.5 of is area compensation effect, which means the area of passage decreased with water head increased, because of rapid changes for flow channel boundary and a positive correlation between the flow inertia and the water head.