井窖风场特征的CFD模拟与验证

为明确井窖内部空气受外界气流的影响及井窖维持适宜水热条件的机制,通过建立未移栽作物条件下井窖的三维数值模拟模型,利用CFD计算流体力学软件分析在1.50、2.70和3.90m/s近地表风速条件下,对井窖内部空气流速和流向进行数值模拟计算,并进行试验验证。模拟试验结果表明:近地表风速设为1.50、2.70和3.90m/s时,模拟的井窖纵切面平均空气流速分别为0.25、0.48和0.72m/s,井窖内的平均空气流速较近地表下降81.54%~83.34%;近地表风向由右向左时,井窖内纵切面的空气呈逆时针流动。验证试验结果表明:井窖内空气流速与地表风速成线性相关,模拟方程为y=0.220 9 x-0.176(R2=0.925 3);近地表风速为2.70m/s时,井窖内实测空气流速为0.42m/s,模拟值为0.48m/s。井窖内部空气受外界大气扰动较弱,减少热量和水分向外散失,有利于保持烟苗生长适宜的水热条件。

CFD simulation and verification of wind field characteristic in transplanting hole

In order to clarify the mechanism of suitable water and heat conditions in transplanting hole,this study analyzed the effects of the wind speed near the soil surface on air velocity in the transplanting hole.Based on the three-dimensional numerical simulation model of transplanting hole under the condition of no crops planted,CFD software was used to simulate the internal airflow in the transplanting hole at 1.50,2.70 and 3.90 m/s,respectively.The flow velocity was verified by experimental test.The simulation results showed that the average air speed of the longitudinal section was 0.25,0.48 and 0.72 m/s,respectively,when the wind speeds near the soil surface were 1.50,2.70 and 3.90 m/s.In general,the average air velocity in the transplanting hole was reduced by 81.54% to 83.34%.When the wind direction near the soil surface was from right to left,the air in the vertical section of the transplanting hole was counterclockwise.The verification results showed that there was a positive linear correlation between the air velocity in the transplanting hole and the wind speed near the soil surface,and this linear fitting equation was y=0.220 9x-0.176 (R²=0.925 3).When the wind speed near the soil surface was 2.70 m/s,the air flow rate was 0.42 m/s by measurement and was 0.48 m/s by simulation in the transplanting hole of well-cellar style transplanting,respectively.The dispersed heat and moisture from the transplanting hole were decreased due to small atmospheric disturbances from the soil surface,which contributed to the maintenance of the suitable water and heat conditions for the growth of tobacco seedlings.