沙尘起动初期近地面浓度分布数值模拟研究

摘要/Abstract

摘要： 对沙尘事件发生初始阶段近地面空间的风沙运动进行了数值模拟研究。考虑固相的剪切黏性、总体黏性、气固相间动量交换、升力等,建立了一个二维气固两相流动数学模型。采用Fluent流体力学软件,进行数值计算。对一组风洞实验数据进行了模拟计算,验证了本模型和计算方法的正确性。研究区域高500 m、长1 000 m。近地层风速廓线采用指数式。沙尘粒度分布用R-R分布;粒径5~150 μm。模拟计算得出近地层内不同风速、沙粒直径的风沙速度及沙尘体积浓度空间分布。结果表明,沙尘起动初期分为发展壮大、回落、稳定3个阶段。沙尘卷起的发展段长度、沙尘卷扬高度及浓度分布曲线形状,均随沙粒和入口风速而明显变化。到达稳定阶段,沙尘浓度沿高度的分布表现为,近地面存在一个均匀的浓度层,即饱和层,其浓度、高度取决于风速和沙粒粒径;饱和层以上沙尘浓度呈指数衰减。

关键词: 风沙运动, 气固两相流, 数值模拟

Abstract: A numerical simulation method is used to investigate the wind-blown sand near the surface at the early entrainment stage. Taking into account the shear and bulk viscosity, the inter- phase momentum exchange, the lift force, etc., a two-dimension mathematic model is developed for gas-solid two-phase flow. Numerical calculations are carried out using Fluent software. The model and its algorithm are verified by simulating blown sand transport in a wind tunnel. The region simulated is 1 000 m long and 500 m high. An exponential function is taken as the vertical profile of wind velocity. An R-R function is adopted to describe the distribution of dust volume fraction, and their diameters are 5~150 μm. The velocities of wind and grains, the spatial distribution of grains volume concentration are obtained from the calculation results. It is shown that the suspension layer can be divided into three sections: developing, declining and steadying. The length of the developing section, the height of suspension layer and the shape of sand concentration profile change with particle size and characteristic velocity of wind.There is a clear band of uniformly saturated sand concentration in the suspension layer immediately above the surface. Its dust concentration and height depend upon particle size and wind velocity. Above the saturated layer, the sand concentration decreases exponentially with an increase in height.

Key words: wind-blown sand, gas-solid two-phase flow, numerical simulation

中图分类号:

X169

李荫堂;佘园元;孟海燕. 沙尘起动初期近地面浓度分布数值模拟研究[J]. 中国沙漠, 2010, 30(3): 492-497.

LI Yin-tang;SHE Yuan-yuan;MENG Hai-yan. Numerical Simulation of the Near-surface Particle Concentration at the Early Stage of Blown Sand Emission[J]. JOURNAL OF DESERT RESEARCH, 2010, 30(3): 492-497.

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