流动反转现象影响土壤内流场和温度场研究

Effects of flow reversal on soil flow field and temperature field

中文关键词: 三维模型  含水土壤  流动反转  自然对流  孔隙率

英文关键词: three-dimensional model  soil containing water  flow inversion  natural convection  porosity

中文摘要:

      为了保持植物内营养成份,使植物快速进入休眠状态,以含水土壤作为研究对象,采用数值计算方法,构造水的物性方程组,建立三维模型,采用有限容积法进行数值求解,分析土壤在不同高温壁面、不同Ra数以及不同孔隙率条件下的流动反转现象。研究结果表明：含水土壤在3.98℃时水密度最大,土壤影响在3.98℃时水密度最大； 在3.98℃时出现流动反转现象,此时流场和温度场均以中心呈轴对称；流动反转现象不会由于Ra数大小的变化而变化,变化的只是流动的剧烈程度；在流动反转现象下,高温壁面的平均努谢尔特数与孔隙率存在非线性关系,其最小值出现在0.65左右。

英文摘要:

      In order to keep the plant nutrients and make the plant quickly enter a dormant state, taking soil containing water as the research object and considering the water properties, a three-dimensional model is numerically solved by the finite volume method to study the soil flow reversal phenomenon in different high temperature wall, different Ra numbers and different porosity. The results show that the water density of the soil containing water is the highest at 3.98℃, and the soil density is the largest when the soil temperature is 3.98℃. Flow reversal phenomenon occurs at 3.98℃, and the flow field and temperature field are in axisymmetric center. Flow reversal does not varies withRayleigh, and only the intensity of flow changes with it. In the flow reversal phenomenon, a nonlinear relationship exists between the average Nusselt number at high temperature wall and the porosity, and the minimum value appears at about 0.65.