Simulation of Interaction between Air Flow Field and Soil Seedbed Covering on Whole Plastic Film Mulching on Double Ridges

Abstract

To further improve the quality of film mulching soil on whole plastic film mulching on double ridges, rationally cover soil on the film surface, reduce dust, and explore the interaction between soil on the film surface and airflow, the annual mean wind speed of 1.32m/s, annual mean maximum wind speed of 18.07m/s, and monthly mean top wind speed of 26.5m/s in 52986 meteorological observation station of Lintao County, Dingxi City, Gansu Province in recent 30 years were used as simulation data source. Based on the experience of farmers, the minimum, middle and maximum values in the range of 0°~90° were the planting bed directions of whole plastic film mulching on double ridges, and three whole plastic-film planting bed models, T1(0°), T2(45°) and T3(90°), were established, respectively. Using CFD-DEM gas-solid coupling technology, the interaction mechanism of the wide large airflow field at different wind speeds and direction of membrane double dealt with all kinds of bed was got, and combining with the influence of solar radiation energy, cultivated land utilization of double-membrane dealt with all kinds of bed on the building, the building method was optimized, finally, the field validation test was carried out. The analysis result of the soil surface flow field showed that when the air velocity was constant, the maximum air velocity on the surface of the horizontal belt was T3, T1, and T2 in descending order, and the difference between the air velocity and the standard air velocity on the prominent ridge surface was T3, T1, and T2 in descending order. The analysis of soil covering the process of seedbed showed that when the air velocity was constant, the influence degree of seedbed and soil particles on airflow was T3, T1, and T2 in descending order, and the influence degree of airflow on particles was T3, T1, and T2 in descending order. Therefore, it can be seen that the air velocity of the T3 model seedbed and soil covering surface was the largest, which was affected by airflow, and the movement distance of film covering surface was the largest, which was easy to form dust. At the same time, the film covering the intersection point on a prominent ridge surface was easy to penetrate the airflow, causing film uncovering phenomenon in solid wind, affecting crop growth and endangering economic benefits. The optimized seedbed construction method should follow the principles of minimum soil cover displacement, maximum solar radiation energy, the fastest construction efficiency, the south slope (sunny slope) cultivated land priority, north south direction cultivated land priority, the priority model was T1, T2 and T3. Field test results showed that when the air velocity was 2.77m/s and the wind direction was north, the average pass rate of seedbed was T2, T1, and T3 from large to small, the film mulling efficiency, the utilization rate of cultivated land and the occupancy rate of lighting area were T1, T3, and T2 from large to small. The test results were entirely consistent with the simulation results, which mutually verified the reliability of the model.

Keywords: northwest arid area, whole plastic film mulching on double ridges, seedbed covered with soil, membrane flow field  interaction process, CFD-DEM