| Slope farmland occupies an important position in cultivated land resources in China.Ensuring crop growth on sloping farmland is of great significance to the survival and development of people in hilly and mountainous areas.However,due to the thin soil layer and poor water retention of sloping land,crops on sloping land are susceptible to drought,which often results in large yield reduction due to insufficient water supply.Sprinkler irrigation,as a new irrigation method,has the advantages of saving water,increasing production,saving labor and strong adaptability to terrain,and is often used for slope irrigation.However,problems such as uneven water distribution and poor irrigation quality exist in slope sprinkler irrigation,which were mostly solved by changing the deflection angle of the standpipe and the form of spray nozzle in the past,but this problem has not been solved very well due to limited means.Therefore,the pulsating water pressure supply technology is applied to sprinkler irrigation on sloping land.According to the characteristics of topographical gradient,the amount of water obtained at each point in the spraying area changes regularly with the time of irrigation through the alternation of working pressure of sprinkler head.By the superposition of water obtained unevenly at each point,the overall water distribution in the spraying area is relatively uniform,thus overcoming the influence of topographical gradient on the irrigation quality zone.Adverse effects.In order to provide practical parameters for the design of sprinkler irrigation system on dynamic hydraulic slope land,this paper takes R5000 rainbird sprinkler used in irrigation as the research object,combines experimental analysis with numerical simulation to study the distribution law of droplet diameter and energy intensity of sprinkler irrigation on pulsating hydraulic slope land,and preliminarily obtains the following conclusions:(1)The influence of pulsating water pressure on spray head range and spray intensity is analyzed.Pressure and amplitude have obvious effects on spray nozzle range.Spray nozzle range and wetted area of single spray nozzle increase with the increase of basic water pressure and amplitude.The shape of wetted area of single spray nozzle transits from cock-centered to round.Water quantity on the uphill direction is more concentrated and water quantity on the downhill direction is thinner.The influence of the change of pulsating pressure foundation pressure and amplitude on the uniformity is not obvious.(2)Distribution characteristics of sprinkler droplets on pulsating hydraulic slope were revealed.By comparing the droplet diameter and energy intensity distribution under different calculation methods with the measured values,the volume weighting method is determinedas the calculation method of droplet diameter in this paper.The influence of different gradients and pressures on the droplet distribution and the relationship between the droplet speed and the angle of droplet to the ground and the droplet diameter under dynamic water pressure are analyzed.The results show that the diameter of water droplets increases with the increase of range,while the influence of pulsating water pressure on the diameter of water droplets decreases with the increase of slope;the diameter distribution of water droplets is more dispersed under dynamic water pressure;the average speed of water droplets increases logarithmically with the diameter of water droplets;the frequency of water droplets falling vertically is significantly related to the distance from the spray head,and the diameter of water droplets falling vertically is smaller;and the pressure mode has a significant influence on angle.The relationship with diameter had no significant effect.Through statistical regression,the relationship between droplet speed,landing angle and droplet diameter under dynamic water pressure is established.(3)The distribution law of pulsating hydraulic slope spraying water droplet kinetic energy intensity is clarified,and a calculation model of dynamic hydraulic slope single spraying head spraying water droplet kinetic energy intensity is proposed.Based on the distribution law of water droplet diameter on different gradients,the mathematical relationship between water droplet diameter,water droplet ground speed and gradient was established.Combining with the data of spray water volume distribution on sloping land,a calculation model of pulsating water pressure single spray head spray water droplet kinetic energy intensity on sloping land was proposed preliminarily,and the correctness of the model was verified by tests.The above model was used to study the distribution of kinetic energy intensity of single spray head spraying water droplets on different slopes.The results show that near the nozzle,the value of kinetic energy intensity increases with the increase of slope,and the maximum value of kinetic energy intensity generally appears at the end of range.Uphill direction,with the increase of slope,the kinetic energy intensity at the same distance from the nozzle increases.In downhill direction,the kinetic energy intensity at the same distance from the nozzle decreases with the increase of slope. |
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