Variation law of subsurface drip irrigation emitter flow rate and response to infiltration cavity in two types of soils
The influence of infiltration cavity on the emitter flow rate and soil water potential of subsur-face drip irrigation was studied by using a soil tank experiment and numerical simulations.The variation of soil back pressure and emitter flow rate during the irrigation process in clay and loamy sandy soil was compared.The cavity radius at the outlet of the emitter was inverted,and a calculation model for the cavity radius in clay was established.The results show that under the same conditions,the emitter flow rate in loamy sandy soil is larger than that of clay,but the variation amplitude is smal-ler than that of clay.The back pressure of soil in loamy sandy soil increases with time,while the soil back pressure in clay decreases with time.There is no inevitable relationship between the variation of emitter flow rate and the soil back pressure due to the influence of cavity.In the simulation,the radius of the infiltration cavity of loamy sandy soil can be taken as a small value or be considered to be the same as the emitter outlet radius.The radius of the cavity in clay increases with the increase of emitter nominal flow rate and soil bulk density.Compared with the constant value,the cavity radius obtained in this study can improve the accuracy of the current formulas in solving the emitter flow rate and soil back pressure.The fitted empirical model of cavity radius can be used for the hydraulic design of sub-surface drip irrigation and provide a basis for the setting of boundary conditions for the numerical simu-lation of soil water infiltration.
subsurface drip irrigationemitter flow ratesoil back pressurecavityclayloamy sandy soil
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