冬季田间水热状况的数值模拟

根据土壤冻结过程中水热迁移的基本方程，推导了土壤水热耦合方程，改进了冻结条件下土壤水热迁移问题的求解方法。用该模型模拟了室内土柱冻结试验，模拟结果与试验结果吻合较好，同时计算速度较快。根据地表能量平衡原理、微气象学理论，建立了冻结条件下土壤蒸发模型，将其作为土壤水热迁移的上边界条件，模拟了北京永乐店试验站冬小麦试区１９９５～１９９６年越冬期（１９９５．１２．０１～１９９６．０２．２９共３个月）土壤的冻融过程，模拟结果与实测值基本符合。在模拟过程中，采用有限差分法求解土壤水热运动方程，水、热方程的上边界分别为第二、三类边界。根据模拟结果，分析了越冬期土壤水热状况的变化规律

Numerical Simulation of Soil Moisture and Thermal Regime in Winter

Based on the basic equations of simutaneous soil water and heat transfer during soil freezing and thawing, the coupled equation of water heat is educed.The model is used to simulate a freezing experiment,and the result compares favorably with the experiment result. According to the soil surface energy budget method and micrometeorology theory, the soil evaporation model under freezing condition is established. Using this model as the upper boundary of simutaneous water and heat transfer, the freezing and thawing process from 1995.12.01 to 1996.02.29 in Beijing is simulated.The simulated and observed values for soil water storage and temperature show the same trend. In the above simulations,the finite difference scheme is used to solve the soil water and heat equations, and the Neumann and Cauchy condition are introduced for the upper boundary of moisture and heat transfer, respectively. Based on the simulations, the dynamic change of soil moisture and heat is analyzed.