The ability to understand and manage the performance of hydraulic control valves is important in many automatic and manual industrial processes. The use of computational fluid dynamics (CFD) aids in the design of such valves by inexpensively providing insight into flow patterns, potential noise sources, and cavitation. Applications of CFD to study the performance of complex three-dimensional (3D) valves, such as poppet, spool, and butterfly valves, are becoming more common. Still, validation and accuracy remain an issue. The Reynolds-averaged Navier–Stokes equations were solved numerically using the commercial CFD package FLUENT V6.2 to assess the effect of geometry on the performance of a 3D control valve. The influence of the turbulence model and of a cavitation model was also investigated. Comparisons were made to experimental data when available. The 3D model of the valve was constructed by decomposing the valve into several subdomains. Agreement between the numerical predictions and measurements of flow pressure was less than 6% for all cases studied. Passive flow control, designed to minimize vortical structures at the piston exit and reduce potential cavitation, noise, and vibrations, was achieved by geometric smoothing. In addition, these changes helped to increase Cv and reduce the area affected by cavitation as it is related to the jet shape originated at the valve throat. The importance of accounting for full 3D geometry effects in modeling and optimizing control valve performance was demonstrated via CFD. This is particularly important in the vicinity of the piston. It is worth noting that the original geometry resulted in a lower Cv with higher velocity magnitude within the valve, whereas after smoothing Cv increased and served to delay cavitation inception.
Cavitation is a phenomenon that can be present in several agro-forestry applications such as irrigation pressure-reducing valves, sprinkler orifices or even in the flow through xylem vessels inside plants. In the present research, numerical predictions of cavitation in a series of orifices, nozzles and venturis were compared to experimental measurements to show the possibilities and performances of the new cavitation model in the commercial Computational Fluid Dynamics (CFD) code FLUENT V6.1. A flashing study is also presented for the nozzle case. Model predictions for the orifice cases accurately capture cavitation inception and its influence on the orifice discharge coefficient. However, when an unsteady flow is modeled, the cavitation phenomenon is not simulated properly and leads to a steady situation. In general, the new cavitation model in FLUENT V6.1 provides very reliable simulation for easy geometries when steady flow is assumed.
This work focuses on the situation of the technological transition to new technologies in drip irrigation in the Valencian Community (Spain). The study covers the last decade with data from interviews to managers of Irrigation Communities in 2010 and 2018. We analyze the main technological problems in seven topics: (i) Catchment & Pumping; (ii) Storage & Regulation; (iii) Treatment & Filtering; (iv) Transport & Distribution; (v) Maneuver, Regulation & Protection; (vi) Automation; (vii) Theft and Vandalism. We also have researched the influence of the performance of the Automation system, the presence of a technician in the Irrigation Community and the use of sensors or climatic data. Results show that problems related to technological maintenance of filtering systems or automation are very common and important and they are more important in large Irrigation Communities. We have also observed that mostly large ICs are using sensors or climatic data for their irrigation schedule. We can conclude that their current situation is focused in the daily maintenance of technological problems, inherited from the first modernization processes at the beginning of 21st century. Hence, they are far away from a second stage of modernization or the smart irrigation pushed by the new advances on technology.
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