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Numerical Simulation Analysis Of The Hydraulic Characteristics Of The Dual-inner-teeth Rectangular Labyrinth Channel Emitter

Posted on:2017-02-27Degree:MasterType:Thesis
Country:ChinaCandidate:L JinFull Text:PDF
GTID:2283330503957479Subject:Hydraulic engineering
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Numerical simulation analysis of the hydraulic characteristics of the dual-inner-teeth rectangular labyrinth channel emitterThe Water resource is irreplaceable natural resources for human survival and social development. Although China has abundant reserves of water resources, its per capita water resources occupancy volume is extremely low,which makes China a one of the countries which have serious water shortage.China’s irrigation technology is relatively backward, but the amount of water used for agricultural irrigation is very large, which results in that China’s water shortage is becoming more and more serious. As a result, it is imperative to promote water-saving irrigation technology.In recent years, the drip irrigation has been rapidly developing because of its higher water utilization ratio and strong adaptive capacity to the environment.At present, the energy dissipation of frequently-used labyrinth channel emitter is achieved by the increased loss caused by those constantly crooked channels and the head loss is related to the velocity head. In order to increase the head loss and obtain a relatively larger velocity head, the cross-sectional area of the emitter channel should be reduced so that the anti-clogging performance of theemitter will be degraded. This paper suggests to add the internal tooth in the rectangular labyrinth channel which is frequently used at present to increase the head loss. In this way, the cross-sectional area of the emitter channel will be duly increased, the anti-clogging performance of the channel will be improved and a dual-inner-teeth rectangular labyrinth channel emitter will be formed in the end. So far, there is literally no literature of this aspect.This paper uses CFD which is a fluid dynamics software to simulate the water flow movement conditions of the dual-inner-teeth rectangular labyrinth channel emitter and the rectangular labyrinth channel emitter which is frequently used at present under 8 water heads with different pressures, extracts its velocity vector chart and conducts the computational analysis about the emitter’s head loss coefficient, discharge coefficient, fluid state index,pressure-flow relationship and the pressure-Reynolds number relationship. It also compares the hydraulic performances of the dual-inner-teeth rectangular labyrinth channel emitter and the rectangular labyrinth channel emitter which is frequently used at present from these above-mentioned aspects, analyzes the influences of the internal tooth’s height and space width on the hydraulic performance of the dual-inner-teeth rectangular labyrinth channel emitter and compares the hydraulic performances of the dual-inner-teeth rectangular labyrinth channel emitters whose internal teeth are at different locations to provide the reference basis for further research and development of the emitter.Through the numerical simulation and analysis, the following conclusions are reached:1) The fluid state index of the dual-inner-teeth rectangular labyrinth channel emitter is generally less than that of the commonly-used rectangular labyrinth emitter, which indicates that after forming the dual-inner-teeth rectangular labyrinth channel emitter by adding the internal tooth into the commonly-used rectangular labyrinth emitter, its irrigation uniformity degree is increased and the hydraulic performance is improved.2) In channels of commonly-used rectangular labyrinth emitters, the fluid state index of the dual-inner-teeth rectangular labyrinth channel emitter which is formed by adding the internal tooth into the vortex-free area at the horizontal position is less than that of the same emitter which is formed by adding the internal tooth into the vortex area at the horizontal position, which indicates that the emitter which is formed by adding the internal tooth into the horizontal vortex-free area of the commonly-used rectangular labyrinth emitter possesses higher irrigation uniformity degree and better hydraulic performances than that which is formed by adding the internal tooth into the vortex area.3) The dual-inner-teeth rectangular labyrinth channel emitter’s head loss coefficient variation is positively correlated with its internal tooth’s height variation and is negatively correlated with its internal tooth’s space width variation. When the internal tooth’s space width is small, this emitter’s head loss coefficient is sensitive to its internal tooth’s height variation; otherwise, it is relatively insensitive. When internal tooth’s height is greater, the internal tooth’s space width has larger influences on this emitter’s head loss coefficient;otherwise, its influences are relatively less.4) The dual-inner-teeth rectangular labyrinth channel emitter’s discharge variation is positively correlated with its pressure head’s variation; it is negatively correlated with its internal tooth’s height variation and is positively correlated with its internal tooth’s space width variation; the discharge coefficient is negatively correlated with the internal tooth’s height and is positively correlated with the internal tooth’s space width. Along with the enlargement of the internal tooth’s height, the fluid state index presents a clear trend which first decreases and then increases. However, along with the variations of the internal tooth’s space width, the above index presents an unapparent trend.5) Along with the enlargement of the internal tooth’s height, the vortex which is formed in the corner of the emitter is becoming more and more obvious,its area is becoming larger and larger and it has improved energy dissipation effects. However, the variations of the internal tooth’s space width have less influence on the vortex of the dual-inner-teeth rectangular labyrinth channel emitter. The peak flow rate in the channel of the above emitter is generally lowered along with the enlargement of the internal tooth’s height. Variations of the internal tooth’s space width have unapparent influences on the water velocity in the emitter’s channels.
Keywords/Search Tags:labyrinth channel, internal tooth, numerical simulation, hydraulic performance, emitter
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