现有泥沙理论的不足和改进——扩散模型和费克定律适用性的讨论  

A comment on the defect of sediment theory __a discussion on the suitability of the diffusion model and the Fick′s law

作　　者：刘大有[1] 

机构地区：[1]中国科学院力学研究所

出　　处：《泥沙研究》1996年第3期39-45,共7页Journal of Sediment Research

摘　　要：描写混合物运动可以采用单流体模型、扩散模型和双流体模型，本文简要介绍了这三种模型，并作了比较，指出：单流体模型方程少、求解简单，但解中包含的信息量少；后两种模型包含的信息量相等，由于扩散模型方程组可从双流体模型方程组引入某种近似后推导出来，它的求解比双流体模型方程组简单，但包含一定的误差．本文分析了这种误差与运动介质物性的关系，给出了扩散模型的适用范围，说明了为什么对于气体混合物常用单流体模型或扩散模型，而对于气－固混合物大多采用双流体模型．液－固混合物性质介于上述两种混合物之间，扩散模型对于它基本上适用，但并不完全适用．扩散模型中的扩散速度表达式，常根据费克定律给出．本文指出了费克定律的局限性，并把它与泥沙运动力学目前遇到的困难联系起来，由此说明采用更一般的扩散速度表达式的必要性．One fluid model, diffusion model and two fluid model can be used to describe the motion of mixtures. By introducing these three models and comparing them with each other, it should be pointed out that the one fluid model has fewer motion equations and hence can be easilier solved, but there are less informations in the solution. The latter two models contain equal amount of information. Since the motion equations of the diffusion model can be deduced from that of the two fluid model by introducing some approximate assumptions, a certain error is involved in it while it can be easilier solved than the two fluid model. The relationship between the error and the physical properties of the moving media has been analysed and the application range of the diffusion model has been given in this paper. It has been explained why the one fluid model and the diffusion model are often used for mixed gas and the two fluid model is used for gas particle mixture. The property of liquid particle mixture lies between the two kinds of mixture above and the diffusion model is basically, but not completely suitable to it. In the diffusion model, the diffusion velocity is often expressed according to the well known Fick′s law. It should be pointed out that the application of the Fick′s law is conditional and the difficulties met in sediment mechanics nowdays are contacted with these limitations, hence it is necessary to introduce a more general expression of the diffusion velocity. \ \

关 键 词：单流体模型 双流体模型 扩散理论 费克定律 泥沙理论 泥沙运动 

分 类 号：TV14[水利工程—水力学及河流动力学]