基于水渗流和热对流传导耦合模型的冻土热量传输

Heat Transfer in Frozen Soil Based on Coupling Model of Water Flow and Heat Convection Conduction

冻土作为气候系统的一部分,是气候变化的重要指示因子。冻土的冻融过程,对地-气间的能量-水分传输、植被的生长状况和碳循环等具有重要的影响。采用数值模拟方法,分析了冻土冻融过程中伴随的热量传输,直观地呈现了能量和渗水在土壤中的传输过程。通过冻土热传导模型和流体流动模型耦合,采用有限元素法Comsol Multiphysics多物理场耦合软件系统,实现了速度与温度协同响应及对冻土冻融过程影响的模拟。模拟结果直观反映了在理想条件下,冻土冻融过程中温度场与速度场的变化:一方面,在土壤冻融过程中,温度场和速度场是相互作用的,并且其变化对土壤冻融过程起着至关重要的作用;另一方面,比较冻土的冻结过程与融化过程,冻结过程更难于发生且需要更加苛刻的条件。为此,可以间接地认为,永久冻土一旦退化便很难恢复,并且也将进一步加速环境的改变,从而形成恶性循环。

As a part of climate system,frozen soil is an important indicative factor of climate change. Freezingthawing processes of frozen soil have the significant effects on the energy-water transfer,vegetation growth and carbon cycle between ground and atmosphere. In this study,the numerical simulation was used to analyze the heat transfer processes accompanied with soil freezing-thawing processes and to intuitively model the transfer processes of energy and water penetration in soil. The cooperative response of velocity and temperature and its effect on the simulation of freezing-thawing process of frozen soil were achieved by coupling the heat conduction model of frozen soil and fluid flow model and by using the finite element analysis software COMSOL Metaphysics. The simulated results displayed intuitively the changes of temperature field and velocity field in the freezing-thawing processes of frozen soil under ideal conditions. On the one hand,temperature field and velocity field were interactive in the freezingthawing processes of frozen soil,and their changes were crucial in the freezing-thawing processes of frozen soil. On the other hand,it was difficult to occur freezing process compared with thawing process. Therefore,it is considered that it is difficult to restore permafrost once its degradation occurs,the environmental change would further be accelerated,and a vicious cycle occurs.