防风网扬尘庇护区湍流流场模拟数值边界条件

Numerical boundary conditions for simulation of turbulent flow field in the shielding zone behind windbreaks

防风网后方存在复杂的湍流结构,通过耗散能量、降低风速形成扬尘庇护区。数值风洞是研究防风网流场结构及预测堆场扬尘的重要方法,由于涉及复杂的大气边界层及多孔介质边界问题,建立高精度的数值风洞目前仍是计算流体的难题。通过一系列数值模拟并与物理实验对比分析,研究了影响防风网数值风洞模拟精度的3个边界条件,即紊流入流边界、地面粗糙边界和多孔介质边界。结果表明:计算域入流紊动强度对风场结构模拟结果具有较大影响,紊动不足能够造成高达50%以上的虚假庇护长度;数值风洞地面粗糙高度通过壁面函数影响流场结构,对防风网抑尘效应有较大影响;防风网阻风效果可利用多孔跳跃介质边界模型实现,模型中惯性阻力系数对模拟结果有较大影响,应根据风压损失系数、防风网厚度和雷诺数设定。

There is a complex turbulence structure behind the windbreak, where a dust refuge will be formed by energy dissipation and wind speed reduction. The numerical wind tunnel is an important method to study the flow field structure of the windbreak and predict the dust in the yard. Due to the complex atmospheric boundary and porous boundary conditions, the establishment of high-precision numerical wind tunnels is still a computational fluid challenge. Through a series of numerical simulations and comparison with physical experiments, three boundary conditions, such as turbulent inflow boundary, rough surface boundary and porous media boundary, were studied, which could affect wind tunnel numerical wind tunnel simulation accuracy. The results show that the turbulence intensity of inflow in computational domain has a relatively high effect on the simulation results of wind farm structure. The lack of turbulence can lead to a false refuge length of up to 50%. In numerical wind tunnel, the roughness height affects the structure of flow field through the wall function, which has a great impact on the dust suppression effect of the windbreak. The wind blocking effect of the windbreak can be simulated by using the porous jumping medium boundary model. The inertial resistance factor in the model has a great influence on the simulation results, and it should be set according to the wind pressure loss coefficient, windbreak thickness and Reynolds number.