树冠流动阻力风洞试验与数值模拟

Wind Tunnel Experiment and Numerical Simulation of Canopy Flow Resistance

为深入分析树冠结构形态参数和风速对树冠流动阻力的影响,通过风洞试验和数值模拟对5种具有典型形态特征的树种(荷花木兰、桂花、枫香树、樟树及腊梅)的流动阻力进行研究,探讨树冠叶面积指数(leaf area index,LAI)和风速对树冠流动阻力的影响规律。通过对试验数据进行多元回归分析,得到5种树冠流动压力损失与叶面积指数和风速的多元关系表达式。将树冠视为多孔介质,并由试验所得树冠流动阻力确定多孔介质流动的黏性和惯性阻力系数。采用计算流体动力学(computational fluid dynamics,CFD)进行数值模拟,结果表明,忽略多孔介质内部的速度流态分布时,多孔介质区域模型可较好地描述树冠流动压力损失,且树冠流动压降模拟结果与试验结果吻合较好。

To deeply analyze the influence of canopy structure parameters and wind speed on canopy flow resistance,we studied the flow resistance of five typical morphological species of magnolia,osmanthus fragrans,sweet gum,cinnamomum camphora and wintersweet by wind tunnel test and numerical simulation.The effect of leaf area index(LAI)and wind speed on canopy flow resistance was explored.The multivariate relationship expressions of flow stress loss,LAI and wind speed of five kinds of leaves were obtained through multivariate regression analysis.The canopy was regarded as a porous medium,and the viscous and inertia resistance coefficients of the porous medium flow were determined by the canopy flow resistance obtained by experiment.The numerical simulation was carried out by computational fluid dynamics(CFD).It shows that the porous medium model can describe the pressure loss of canopy flow and the simulation results of flow pressure drop agree well with the experimental ones,when the velocity distribution inside the porous medium is neglected.