Study On The Uniformity For Sprinkler Irrigation And Droplets Kinetic Energy On Sloping Land

Slope farmland is the production land which the masses of hilly and mountainous areas depend on for survival and development.However,because of the influence of terrain slope for a long time,the soil of slope farmland in our country has the characteristics of drought,barren,thin and coarse in different degrees,often makes the crops on sloping farmland reduced drastically due to insufficient water demand,which will affect the economic benefit.Therefore,it is very important to select a reasonable irrigation method to irrigate crops on sloping land in time,and sprinkler irrigation as a new water-saving and high-efficiency irrigation technology has the advantages of saving labor,saving water and adapting to terrain conditions,is one of the common methods of slope irrigation.The uniformity for sprinkler irrigation and the kinetic energy of droplets are the important indexes to evaluate the quality of sprinkler irrigation system,and many scholars have studied it in the past,but the research on sloping land is relatively few.In order to provide practical parameters for the design of sprinkler irrigation system on sloping land,this paper took the Rainbird LF1200 sprinkler used in farmland irrigation as the research object.Through the combination of experimental analysis and numerical simulation,the uniformity for sprinkler irrigation and the kinetic energy of droplets were studied.The main research contents and conclusions are as follows:(1)the effect of terrain slope on water distribution,sprinkler range,and water application uniformity of the sprinkler were analyzed.The results show that the water distribution curve was roughly “heart-shape” on slope,and the water had the trend of focusing on the upslope with the increased of the slope.Sprinkler range decreased on the upslope and increased on the downslope as the slope increased.Sprinkler operating pressure and spacing had a significant influence on irrigation uniformity.The impact of sprinkler operating pressure was more significant than that of sprinkler spacing,and the influence of sprinkler spacing was more significant than that of terrain slope under the experimental condition.Additionally,for the convenience of sprinkler irrigation system design on sloping land,a formula for computing the sprinkler range on sloping land was put forward by the theoretical derivation.(2)It is difficult to measure water distribution for sprinkler irrigation on sloping land.Based on the formula for calculating sprinkler range on sloping land,according to the principle of water balance along spray direction,a calculated model for transforming sprinkler water distribution from the flat ground into sloping land was proposed and validated by an experiment.The effects of sprinkler layout,sprinkler spacing,operating pressure and slope on sprinkler water distribution on sloping land were analyzed using the model.The results show that water distribution for the sprinkler triangular arrangement was more uniform than that for square layout,and the combined sprinkler irrigation water application uniformity for the sprinkler triangular arrangement was slightly higher than that for the square layout.The combined sprinkler irrigation water application uniformity decreased as sprinkler spacing increased.When the sprinkler was operating at low pressure,the combined sprinkler irrigation water application uniformity was relatively low,and the low uniformity could not meet the requirement of sprinkler irrigation uniformity.The combined sprinkler irrigation water application uniformity increased as sprinkler pressure increased.The effect of slope on water distribution and the combined sprinkler irrigation water application uniformity was insignificant within a certain slope.(3)The diameter and velocity of spray droplet on different slopes under no wind were measured by Two-dimensional Video Disdrometer.The change regularities of average droplet diameter and its cumulative frequency along spray direction under different slopes were studied.The relationship between the average droplet diameter,velocity and slope were established.Based on the calculation method of water distribution,the model for calculating droplet kinetic energy intensity distribution of sprinkler irrigation on sloping land without wind was proposed.The model was validated by experiment.The Rainbird LF1200 sprinkler was selected as the research object,the influences of sprinkler layout,spacing,and slope on the kinetic energy intensity distribution of combined sprinkler were mainly analyzed by the model.The results showed that droplet kinetic energy intensity distribution uniformity and the proportion of the high-value area of kinetic energy intensity were both decreasing as the sprinkler spacing increasing.The effect of slope on kinetic energy intensity distribution was insignificant.Sprinklers layout with triangular lattice was useful to decrease kinetic energy intensity of the sprinkler on sloping land.(4)If the Rainbird LF1200 sprinkler is used for designing sprinkler irrigation system on sloping land,the sprinkler spacing is recommended as 0.8 times of the spraying range on flat ground with the triangular lattice layout,the sprinkler operating pressure should be 300 kpa,and the slope of less than 0.15,considering the impact of the uniformity for sprinkler irrigation and the kinetic energy of droplets simultaneously.