Hydraulic Modeling of Venturi Injector by Means of CFD

The Venturi injector is the chemigation device in pressurized watering systems which causes the biggest head losses. However it is an economic and robust system, largely used in the fertirrigation of small and medium size farms. The typical way of assembly is in parallel to the main pipe, being necessary negative pressures (below the atmospheric one) in the throat of the Venturi. Using Computational Fluid dynamics techniques (CFD), the hydraulic behavior of Venturis has been analyzed. These analyses have been carried out by means of the program FLUENT that uses finite differences theory. The results obtained in the computer process have been validated with real values, measured in an experimental setup. In this experimental setup Venturis of different geometries has been tested, with a range of pressures from 0.1 to 0.4 kPa, and typical flow-rates in irrigation systems. The experimental results and those obtained with FLUENT are very similar, with differences below 5% in the pressures in the entrance and throat of the Venturi.. The proximity of the values obtained with the numerical method to those tested is enough as to analyze new geometries with the computer, and to manufacture only the appropriate ones.