Design Of Fractal Flow Path For Emitters And Experiment Study And Modeling On Its Fluid Mechanism

The emitter is one of the crucial devices in a drip irrigation system which is used to dissipate pressure and to discharge water at a constant rate by dissipating energy when the pressured water flows through its internal narrow and long path structure or micro-orifice. In some foreign countries, such as in Israel, there have been mature design theories) production workmanship, and adequate application experience. Now the design of emitters in China is only in its preliminary stage of introduction and imitation. Up to now, there has been no domestic trickle irrigation emitter with self-owned intellectual property right that possesses both good anti-blocking property and good hydraulic performances. The main reason behind this situation is lack of the guidance by flow path design theories, which is not beneficial for serialization of emitters. Some famous international companies, have their own design institutes of trickle irrigation emitters. But the theories and methods for designing flow paths have been strictly confidential and the research papers on flow path of emitters with the function of practical guidance have seldom been published. In this dissertation, Fractal theory, Digital Particle Image Velocimetry (DPIV), Planar Laser-induced Fluorescence (PLIF), Computational Fluid Dynamics (CFD), and hydraulics performance experiments were combined to design new flow path of emitters.With high-speed development of modern cyber-technology, synthesizing the CAD (Computer Aided Design) and CFD has been the development trend for designing hydro-machines. By thoroughly analyzing the process of emitters design, the platform for designing drip irrigation fractal flow path emitter was formed with CAD/CFD software cooperation technologies and plane model. It was explored to measure the geometric parameters of the flow path by means of combining high-precision microscope and AutoCAD technology, and the two-dimensional model was constructed via the technology of line incision with electric spark.In this study, fractal flow path was designed with Koch and Minkowski curves to shape the boundary, and the full-turbulence design of flow path was realized. The results of path analysis showed that the cross-sectional area and length of the flow path were the primary factors affecting the flux coefficient of drip irrigation emitter. The exponent of emitter was independent with respect to parameters of the flow path, and main with respect to the structural form of the flow path. The results of dimension analysis and turbulent pipe flow theory showed that the Reynolds number Re had low effect on the flow path friction coefficientλ, which could be ignored. Friction coefficientλ was linearly increasing with augmenting of Ra /Ln , and the pressure loss was descending with linearity rules along the flow path, and the head losses due to continuous dentiform cell was equaled.It is creative that the Digital Particle Image Velocimetry sytem was conformed based on changing the CCD camera lens with microscope object lens, and the fluorescent particle was excogitated in this study. The problems of the inconsistency between digital image resolution andareas and the image noises were settled successfully. The non-intrusive and whole-field velocity measurement for velocity within the drip irrigation emitter flow path was realized in the world. The result showed that the flow regime was turbulent in labyrinth and fractal flow path under pressure Of 1.0-15.0m. The complex boundaries and curved structure within labyrinth paths of emitters facilitated the transformation of the flow from laminar flow into turbulent flow. The critical Reynolds number within the small labyrinth paths of emitters was smaller than that within the normal dimension paths. And there were some stagnant areas (including the low velocity areas) in the fractal flow path.The average velocity magnitude, distributing vorticity magnitude, magnitude and distributing of high speed areas and second flow ones, and the turbulence intensity distribution within the three typical column labyrin...