Hydraulic Of The Flow Path In A Gradual Shrinking And Sudden Enlarging Channel

Emitters is an important part in a drip irrigation system.The flow path design is the key technology for emitters.To reveal the hydraulic of water in its path,a new structure of flow path with tapered following a sudden enlargement was put forward.An orthogonal experiment under three factors and three levels was built.Three experimental factors are flow passage as triangle,circle and streamline,the size of the narrowest section and the size ratio.A CFD model was established and fluent was adopted to carry on the numerical simulating the inner water flow field within the structure.The internal flow field was studied under different orthogonal test.Influences of all above factors were analyzed under the discharge and energy and its head-loss in the different cross-section along the channel.In a taper vertical with sharp-edged structure,results show that: 1)All factors impact on the flow rate under the 10 m head.Ratio of shape factors influence its discharge significant,while the other has no obviously effect.Flow capacity can be written as a multiple linear regression equation of the above parameters.2)Flow index is between 0.494~ 0.509 with such a reducing and sudden enlargement structure.Three factors of tests have influence on the flow index.From large to small is size ratio,shape,the narrowest distance.But none all of them are reached significant level.3)The Reynolds number is between 614 and 6915.The range of local head loss coefficient is from 2.1 to 10.6.In a repeat taper vertical with sharp-edged structure: 1)All factors impact on the flow rate under the 10 m head.Ratio of shape factors influence its discharge significant,while the other has no obviously effect.Flow capacity can be written as a multiple linear regression equation of the above parameters.2)Flow index is between 0.506 ~ 0.525 with such a repeat reducing and sudden enlargement structure.Three factors of tests have influence on the flow index.From large to small is size ratio,the narrowest distance,shape.All of them are reached significant level.3)An enlarged emitter model was designed according to hydraulic engineering model principle,which was used for exploring hydraulic similarity between the original model and the enlarged model,similarity of the two is better.Outlet pressure distribution of flow passage in the first five and the last two pressure at the exit of the match.