Calculation Of Local Head Loss In Labyrinth Channel

As so far,the drip irrigation technology is one of the most efficient water-saving irrigation technologies,which is recognized in the world.Since the birth of drip irrigation technology,the drip irrigation technology is becoming more and more mature with the more than seventy-years' development and improvement.With the accelerating of agricultural-modernization process,and the rising of shortage of water resources,the exploitation and research of drip irrigation is becoming more and more important.Emitter is the most critical component in drip irrigation system,while the labyrinth-channel emitters are widely applied in all kinds of drip irrigation system for such advantages as high hydraulic performance,simple manufacturing process,low manufacture cost,a certain degree of pressure compensating,which become the more representative and one of the most potential for development in various emitter types.Since our country imports the fist set of drip irrigation system from Mexico in 1974,the exploitation and develop of emitters mainly rely on introduce and copy.Some scholars introduce the rapid prototyping and manufacturing technique to the exploitation and develop of emitter since 2001,which shorten the R&D cycle for more than 2/3.If we can calculate the head loss of water in the labyrinth-channel emitters on the stage of design like the design and calculation in ordinary pipeline,which is expected to further shorten the R&D cycle.To this end,we need to construct the formula between the head loss of water in the labyrinth-channel emitter and the structure parameters of the labyrinth-channel emitter.However,the determination of energy loss in the labyrinth-channel emitter mainly relies on the experiment and numerical simulation method,which makes a certain extent inconvenience to the exploitation and develop of emitter.Based on this issue,this passage carried out the study on the structure parameters and water head loss of trapezoidal labyrinth-channel(tooth angle is 30 o,45o,60o),dental shape labyrinth-channel(tooth angle is 30 o,45o,60o),rectangular labyrinth-channel(tooth varies is 0,1times,4times of width of flow path),triangular labyrinth-channel(tooth angle is 30o),which analyzed the relationship between the head loss of water in the labyrinth-channel emitter and the structure parameters of the labyrinth-channel emitter,which determined the calculation method of head loss in labyrinth channel,which constructed the head loss calculation formula in labyrinth channel.In this paper,several conclusions were obtained as follows:(1)Different types of trapezoidal labyrinth-channel,dental shape labyrinth channel,rectangular labyrinth channel and triangular labyrinth channel can obtained by change the structure parameters based on the trapezoidal labyrinth channel basic type.(2)The basic structure of control parameters of labyrinth channel as follows: the channel unit number N,the channel depth D,the tooth varies J,dental angle ?,the height of dental h,the dental tooth width c,which can determine the only type of channel.(3)The laws between the frictional head loss coefficient and Reynolds number in pony-size,rectangular cross-section straight flow channel are similar to the Nicholas' s test results: When Re<416,the flow regime is laminar flow;when 416<Re<1068,the flow regime is unstable flow;when 1068<Re<1445,the flow regime is hydraulically smooth zero of turbulent flow;when Re>1445,the flow regime is fully turbulent flow.The critical Reynolds number for flow regime transition in straight flow channel is 10 times of that in labyrinth channel.(4)The head loss in labyrinth channel Conform to the law of linear superposition,and the major proportion in local head loss,while the frictional head loss only accounts for small proportion,the maximum ratio is not more than 24.2%.(5)The head loss coefficients ? of trapezoidal labyrinth-channel,dental shape labyrinth channel,triangular labyrinth channel can be expressed as a function of the tooth angle?,while the head loss coefficients ? of rectangular labyrinth channel can be expressed as a function of tooth varies J and tooth height h.In the relative error analysis,the error of water head loss calculated by the formula is not more than 10%.