| Micro-irrigation is a high efficient and water-saving irrigation technology. Emitter is one of the key components of micro-irrigation system. Structural characteristics of internal flow passage are directly related to emitter's performance and micro-irrigation system's quality. Therefore, research on internal flow field of micro channel in micro-irrigation emitter has important significance to optimization design of internal flow passage's structural and performance improvement of emitter.Using Micro-PIV technique, inflow field were measured in straight and jagged micro-channels with cross section of 600μm×600μm and 800μm×800μm under the conditions of the Reynolds number of 80-300. Clear images of particles were obtained by combining Mini:YAG double pulse laser,14-digit grey scale CCD camera, 10x microscope,3μm fluorescence tracer particles and light filtering lens allowing 610nm red light permeation. Using image processing techniques, Flow field streamlined diagrams,velocity vector distribution map and velocity cloud chart were obtained under all kinds of flow conditions. The influence of Brownian motion was eliminated through the average of obtained images. Flow field distribution of micro channel was obtained by the ensemble cross-correlation algorithm. Experiments exposed that the wall roughness of micro channel has a greater effect on internal flow field. The smaller the size of micro channel was, the greater the wall roughness affected. There existed a low speed vortex cavity at the swerving inside with a complete vortex in three jagged micro-channels. However, there existed a smaller scale low speed vortex cavity with a vortex at the left vertex of flat-jagged micro-channel. Furthermore, there are two vortexes, big intact vortex and superposition vortex on the jag peak of cusp-jagged micro-channel, and compared with the former, and the latter is lower speed, converse and unsteady. The impure substance in low-speed region is prone to deposit and block, hence the structure of micro-channels could be altered.The essay utilized "Fluent" numerical analytic computing software to design the optimum micro-scales flowing simulating plan. The designing adopted micro-scales affect manipulating approaches setting wall roughness element and the porous medium simulating wall roughness element. By utilization of standard k-εmodel, RNG k-εmodel, realizable k-εmodel, standard k-ωmodel and sst k-ωmodel provided by Fluent software, the experiment executed relatively numerical simulations on the rectangle cross section micro-scales water flowing with section size of 600μm×600μm and 800μm×800μm in the case of Re=100 and Re=300. The comparison of velocity field computed from various numerical analyses and the fitting degree of Micro-PIV experimental outcome was done. The results showed that better flow field of micro channel could be obtained by the optimum case that designing case via the porous medium simulating wall roughness element under the solution of realizable k-s. Thickness of the porous medium was set by wall roughness element of micro channel. Viscous resistance coefficient and inertial resistance coefficient were calculated by fluid state and resistance within the porous medium.Using recommend numerical simulating method of flow field of micro channel, internal flow field of micro channel in micro-irrigation emitter was numerical simulated in three jagged micro-channels under the conditions of the Reynolds number of 100 and 300. By the comparison of velocity field computed from various numerical analyses and the fitting degree of Micro-PIV experimental outcome, we can concluded that this numerical simulating method of micro channel was suitable for the calculation of complex internal flow field of micro channel. Using recommend numerical simulating method of flow field of micro channel, further emitter models in three jagged micro-channels were built under the conditions of the Reynolds number of 100,200 and 300. The analysis and evaluation of results were got at the aspects of distribution of recirculation zone of internal flow field of micro channel, different flow channel scales, pressure drop under the conditions of different Reynolds number, fluid index and flow coefficient. The results showed that cusp-jagged micro-channels had advantages in performance as internal channel of micro-irrigation emitter. However, the impure substance in low-speed region is prone to deposit and block. Partial structure of cusp-jagged micro-channels should be modificated. Considering the reduction of low-speed region and the increase of flow resistance, two rehabilitation programs were built of cusp-jagged micro-channels in micro-irrigation emitter. One of them was to rake cut tooth tip and the other was to cut tooth tip by circular arc. Base on micro channel in micro-irrigation emitter after transformation, numerical model was built and internal flow field was calculated. By evaluation and analysis of results, conclusion could be reached that flow channel structure after transformation improved the performance of micro-irrigation emitter.
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