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NEW SIMPLIFIED OPTIMIZATION TECHNIQUES FOR IRRIGATION SYSTEMS

During the last 40-year various "high tech" technologies with various applications in agriculture have been developed rapidly, however, the rate of improvement of the irrigation output per piece of land remains very low.

Most of the suggested technologies that are still impractical either because they are very complex to study and implementat or because of the persistence of farmers to apply the old-fashioned agricultural practices.

John D. Valiantzas, Professor of the Agricultural University of Athens, in a series of research work, proposes new simplified hydraulic analysis and optimization methods for different types of irrigation systems.

The proposed solutions by Prof. J. D. Valiantzas, combine two criteria: a) adequate accuracy for practical applications and b) simplicity, in order to address the excessive requirements of complex and multiplex solutions leading to the failure of their implementation.

Agricultural water management

SIMPLIFICATION OF DARCY-WEISBACH EQUATION

As far as the pipe-water flow design under pressure is concerned, the majority of researchers believes that the high precision equation which calculates energy loss due to friction, i.e. the Darcy-Weisbach, has got mainly an academic interest because of its difficulty of actual implementation. Therefore, many of them select simpler, purely empirical, methods for calculating losses, with significant limitations and reduced accuracy such as the equations of Hazen-Williams & Manning. The popularity of these equations is based on their simplicity, since the main pipe flow parameters - the water supply and the diameter - are directly connected to the losses through a simple power equation.

In the current research work, as a first step, a new simple equation for the calculation of water loss is suggested in the form of power equation. Its power is limited, however, to the range of full-tracheal turbulence flow only. Additionally, the equation expands with a generalized effect to all three turbulence flow regimes. The equation suggested, has the form of power equation with its exponent depending on the absolute roughness of the pipe. The equation has dimensional analysis and provides sufficient accuracy for practical routine applications in Hydraulic Engineering and Mechanics of Irrigation. A correction coefficient is inserted in order to change the kinematic viscosity with temperature. The usefulness of the simplified equation is apparent in the case of optimizing networks with pump as well as for various applications in irrigation systems. It can be easily adapted to different complex models of hydraulic analysis, optimization and hydraulic parameters identification of piping.

Environmental & Water Resources Institute (EWRI)




The research paper of Professor John D. Valiantzas: “Explicit Power Formula for the Darcy - Weisbach Pipe Flow equation: Application in Optimal Pipeline Design”, was published in the international Journal of Irrigation and Drainage Engineering, ASCE (τ.134 (4):454-461, 2008) and was awarded the best paper award of the year 2010 by “EWRI” committee of ASCE.

Furthermore, Professor John D. Valiantzia won the best “Discussion Paper” in 2006 for the: Valiantzas J.D. “Discussion of Equivalent Friction Factor Method for Hydraulic Calculation in Irrigation Laterals” Journal of Irrigation and Drainage Engineering, ASCE, 130(4), 339-340, 2004.

AGRICULTURAL UNIVERSITY OF ATHENS

John D. Valiantzas, Professor of the Department of Natural Resources Management and Agricultural Engineering, Division of Water Resources Management, AUA.

http://wrm.aua.gr/DIVISION/Valiantzas/Valiantzas.htm