Infiltration Characteristics And Numerical Simulation Under Hole Single Line Irrigation With Biogas Slurry

Biogas slurry contains water-soluble and nutritive components,and it is one of the effective fertilizers.And the application of biogas slurry in a reasonable way can obviously improve the physical and chemical properties of the soil,improve the ability of soil water conservation and fertilizer,and can effectively solve the problem of water shortage.In this paper,according to the irrigation methods of hole irrigation,combined with laboratory tests,theoretical studies and numerical simulations,the characteristics of one-way intersection infiltration,influencing factors,and infiltration characteristics of water-biogas slurry mixture are studied.The main conclusions are:?1?The cumulative infiltration volume per unit area for both interference infiltration and free infiltration increased with time,and the cumulative infiltration volume per unit area of one-way intersection infiltration and free infiltration of double-hole irrigation in water-biogas slurry mixture is less than that of the water irrigation under the same conditions.Under different bulk density conditions in the infiltration model,the coefficients shows:K_1.35>K_1.40,the index shows;?_1.35>?_1.40;Under different irrigation hole diameter conditions in the infiltration model,the coefficients shows:K_3cm>K_5cm>K_7cm,the index shows?_3cm>?_5cm>?_7cm.Under different biogas slurry ratio conditions in the infiltration model,the coefficients shows:K_{1 4:}<K_{1 6:}<K_1:8,the index shows?_1:4<?_1:6<?_{1 8:}.And the cumulative infiltration volume per unit area at the same time point shows:I_1.35>I_1.40,I_3cm>I_5cm>I_7cm,I_1:4<I_1:6<I_{1 8:}.?2?After the intersection,the increment of cumulative infiltration volume per unit area of the interference infiltration is less than that of the free infiltration under the same conditions,and the interference infiltration has the effect of reducing infiltration;Through the establishment of the model of infiltration reduction,the regression analysis method is used to analyze the variance of the coefficients of the infiltration model,and the relationship between the amount of seepage reduction and the hole diameter D and the mixture ratio C of the biogas slurry is established.?3?The distance before the intersection of the horizontal wet front and the vertical wet front increased with the increase of time,and the relationship with time corresponds to the power function relationship.The intersection infiltration and free infiltration wetting body shape are consistent before the intersection,and can be described by the semi-elliptic equation.Wet front speed shows:V_??>V_??.Run-forward distance in the same time period shows:S_??>S_???.After the intersection,in the horizontal direction,the vertical wetting front distance of 12.5cm shows:S_????>S_????.The distance of the wet front in different density conditions in the same period of time for the one-way intersection infiltration of the water slurry mixture shows:S_1.35>S_{1.4 0}.In the power function model with vertical wetting front,the coefficient increases and the exponent decreases.The coefficient and exponent of the power function model in the horizontal humid front are reduced.In the same time period,the migration distance of the wetting front of the intersection infiltration with different hole diameters shows:S_3cm<S_5cm<S_7cm.The coefficient and exponent increase in the power function model of the vertical wetting front increased,but the coefficient increased and the exponent decreased in the horizontal power front model,the migration distance of wetting front for single hole intersection of different biogas slurry proportions in the same time period shows:S_1:4<S_1:6<S_{1 8:},the coefficient and exponent decreases in the power function model of the vertical wetting front increases,but the coefficient decreased and the exponent increased in the horizontal power front model,?4?After the infiltration,the water content value becomes smaller as the position is far from the hole,and the relationship with the vertex of the hole center conforms to the model:?=Mr^N+?₀.The water content in the intersection area of intersection infiltrates is greater than that of free infiltration.The water content of the infiltration of clean water is higher than the infiltration of the biogas slurry.When the bulk density becomes larger,the water content of the whole wetted body decreased,and it decreased with the increase of hole diameter and biogas slurry ratio.?5?The highest value of total nitrogen content in soil with biogas slurry infiltration is near the hole,and the total nitrogen content decreased with the position far from the hole,and changed significantly in the unconverged area,and the rate of change in the intersection area became slower,and there is a slight increase.The maximum soil total nitrogen content after infiltration in clean water appears near the wet front,and the total nitrogen content in other locations is lower than the soil background value.As the soil bulk density increased,the total nitrogen content increased near the hole and in the upper region of the intersection,but the total nitrogen content near the wet front decreased;And when the diameter of the hole increases,the total nitrogen content in the vicinity of the hole and in the upper area of the intersection decreased,but the total nitrogen content near the wet front increased;When the proportion of the biogas slurry in the mixture increased,the total nitrogen content increased.?6?Among the influencing factors of biogas slurry infiltration,the ratio of biogas slurry has the greatest impact.?7?The hole infiltration model was established by using COMSOL Multiphysics,and a numerical simulation study on the hole infiltration test was conducted under laboratory conditions.By simulating the infiltration test of water and biogas slurry under the depth of 10cm hole depth under the conditions of double holes,the measured values and simulated values of wetting front migration distance and soil moisture content in wet soil were compared.The results showed that the mean value of absolute error of vertical wetting front,horizontal wetting front and soil moisture content were3.46%,3.94%and 4.87%,respectively.The degree of anastomosis is good,and the accuracy of the model is high,which indicates that the model is reasonable.Therefore,using COMSOL Multiphysics can accurately describe the movement in the process of infiltration of water and biogas slurry in the hole.