露天堆场防风抑尘网后湍流结构及抑尘效率的数值模拟

建立了开放性露天堆场周围空气流动的三维数学物理模型,选择应用标准k-ε紊流模型进行了静态流场的数值模拟;分析了典型棱形堆迎风面、平顶面和背风面周围空气的湍流结构和表面受力特性;基于流场数据揭示了防风抑尘网不同孔隙率下空气动力学结构的分布规律.结果显示:物料堆平顶面剪切力随孔隙率增大而增大;料堆迎风面在孔隙率较小时出现局部涡流,表面剪切力方向向下,孔隙率较大时,网后空气垂直方向压差作用显著,表面剪切力方向向上;背风面始终处于回流区,表面剪切力和回流点数随孔隙率大小变化不显著.综合流场结构和受力分布可得最佳孔隙率为0.2~0.4.该研究中对物料堆逐个表面进行空气动力学模拟可以避免由于剪切力方向不同产生矢量抵消而带来的计算失真.

Numerical simulation of turbulence structure and sheltering effect behind porous fences in open storage piles

This paper was conducted to predict the turbulence structure and sheltering effect behind porous fences in open storage piles. The numerical simulation of the three dimensional static flow field was performed applying the standard k-ε turbulence model; the airflow characteristics and the shear stress distribution on the windward side, flat top surface and leeward side of a typical prismatic material stack were analyzed; and the distribution of the aerodynamic structure of each surface of the storage pile was revealed based on the data of flow field for the porous fence with different porosity. Results indicated that the shear force on the flat top surface increased with increasing porosity, exhibited litter change with unfenced conditions. Regarding the windward side of the storage piles, a re-circulating flow in the region between the fence and the pile at low porosities and the shear force acted downward along the windward face, but rather, the shear force acted upward along the windward side at high porosities. Since the leeward side was always in the backflow region, the shear force on the prismatic leeside changed little with increasing porosity. The numerical predictions showed the porous fence with porosity between 0.2and 0.4was found to be the optimum. Through the aerodynamic simulation of each surface of the storage pile, the computation distortion caused by vector offset out of different directions of the shear force can be avoided.