EVALUATING PRESSURE LOSSES IN DRIP-IRRIGATION LINES

In this paper an experimental investigation was carried out to deduce an evaluating procedure of local losses due to the protrusion of emitt er barbs into the how in drip-irrigation lines. Local losses correspon ding to different pipe-on line emitter systems were measured for diffe rent Reynolds number values. Each pipe-emitter system was characterize d by an obstruction index (OI) summarizing the reduction of cross-sect ional area of the pipe due to the emitter connection. A power relation ship between a characteristic value of the alpha coefficient, expressi ng the local losses amount as a fraction of the kinetic height, and th e corresponding OI index was deduced. Two evaluating procedures of OI were also compared: an analysis of photographs of the connections obta ined by dissecting the pipe at the emitters and the use of a caliper t o measure emitter protrusion dimensions. Only the first procedure make s it possible to obtain an estimating criterion of the alpha coefficie nt because it takes into account both the characteristics of the emitt er connection and the deformation of the pipe surrounding the stem.