Investigating on the Orifices Outflow with Different Diameters and Envelops in the Subsurface Irrigation System

The use of appropriate emitters, such as perforated-pipe in the subsurface irrigation system, improves the efficiency of these systems. In present study, the best hydrodynamic conditions of the permeation environment, optimal hydraulic conditions of the orifice, and interaction between the orifice hydraulic and the surrounding environment are investigated. For this purpose, the conditions of flow and outflow resistance of the 16 mm polyethylene pipe with 1, 2.5, 5, 8 and 10 mm orifice were conducted in two modes (with and without geotextile cover) in a clay soil and 12 mm gravel in the pressure 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and 2 atmospheres are investigated. The experimental results were compared with two-way ANOVA and the characteristic curves of different orifices were fitted with pressures in all experiments.
The range of the values of R2 and the power of the discharge-pressure equation was Obtained 99% -93% and 0.41-0.63, respectively. The experimental results showed, using gravel around the buried orifice in the soil in all the diameters reduced the flow resistance, increased water outflow of the orifices and increased flow turbulence, conversely, using the geotextile increased the flow resistance and it was observed that in the 1 and 2.5 mm orifices, geotextile envelopment in soil and gravel have significant difference with the normal state. Based on the results of the use of 1 mm orifice in all environments and 2.5 mm orifice in the soil environment with or without the geotextile cover, had the best performance and other orifices are not recommended