Study And Numerical Simulation Of Soil Hydrothermal Content In Double Membrane Greenhouse In Arid And Cold Area Of North China

Solar greenhouse is the basic facility of protected agriculture.It is widely used in northern China for producing fruits and vegetables through winter with no or little heating.Greenhouse makes up for the shortcoming that the northern region of our country cannot grow fruits and vegetables in winter,and realizes the ability to grow vegetables all the year round "summer vegetables in winter,south vegetables in north" to meet the needs of consumers.It is the most important facility agriculture in the northern region.Soil temperature and humidity in solar greenhouse play a crucial role in crop growth in arid and cold regions of north China.Solar greenhouse is a semi-closed structure,composed of soil-crop-air,each part of its climate is different,but there is a coupling effect.In this thesis,the current figure of Inner Mongolia agricultural university of science and technology park double membrane as the sunlight greenhouse experiment in greenhouse,in the sunlight greenhouse celery crop canopy is studied under different growth height daily variation law of soil temperature,moisture content,as well as the crop canopy formed after day and night the crop canopy internal temperature and humidity and soil moisture content of internal temperature of the spatial distribution characteristics are analyzed,and establish the CFD numerical model,the simulation of crop canopy and soil temperature field at the top and bottom.The results show that:(1)With the increase of canopy height,the decrease time of soil temperature lagged in both east-west and north-south directions.The decrease time of soil temperature under 1.0m canopy was 1.5 hours later than that under 0.4m canopy,and the fluctuation range of diurnal variation of soil water content became smaller.The maximum and minimum temperature difference in the east-west span and the north-south span is about 11℃.The difference between the lowest and highest water content in the east-west span is nearly 9%,while the difference between the south and north is 3%.(2)When the celery canopy reached1.0m,the temperature and humidity inside the canopy as well as the soil temperature and moisture content showed a big difference,which showed that the temperature at the top of the canopy was higher than the temperature at the bottom at 11:00 in the daytime,while the humidity was the opposite.The distribution trend of soil temperature and moisture content is similar to that of temperature and moisture at the bottom of canopy.At 1:00 PM at night,the humidity at the top of the canopy was greater than that at the bottom of the canopy,and the temperature was vice versa.The soil temperature increases with the deepening of the soil layer,and the water content is evenly distributed with little difference between the soil layers.(3)CFD method was used to simulate the crop canopy area and soil surface as porous media in solar greenhouse.The simulation results showed that the error was small compared with the measured results,and the model was effective and feasible.The numerical model can effectively characterize the temperature distribution of crop canopy and soil surface layer under canopy.