强风作用下树木周围流场的数值模拟研究

Numerical simulation of flow field around the tree in strong wind

为了研究强风作用下树木的周围流场,将树木树冠简化为多孔介质,采用附加源项法模拟树木对风场的干扰作用,开展数值仿真研究。研究结果表明:在同一风速下,树木对树后流场的影响数值模拟结果与风洞实验结果一致,在顺风向,以树冠为中心,呈椭圆形以放射状向四周扩展,距离树冠中心越远,树木对风速的削弱效果越小,对湍流度的影响也越小;在横风向,树后1倍树高平面(X=H)内,树木遮蔽区域的形状与树冠的轮廓线相重合;在不同风速下,随着风速增加,树木孔隙率逐渐增大,阻力系数也相应减小,距离树干后1倍树高处风剖面的相对参考点风速最小值逐渐增大,相对参考点湍流度最大值逐渐减小。综合上述结论,模拟的风场与风洞试验测量的风场类似。

In order to study the flow field around the tree in strong wind, the tree canopy was simplified as porous medium, and the interference effect of trees on wind field was simulated by using additional source term method,and numerical simulation was carried out. The results show that at the same wind speed, the influence of trees on the flow field behind the tree is as follows: in the downwind direction, the tree takes the crown as the center and extends radially in an oval shape. The farther the tree is from the center of the crown, the less the tree weakens the wind speed and has less influence on the turbulivity. In the cross wind direction and in the plane of one-tree height behind the tree(X=1 H), the shaded area of the tree coincides with the size of the canopy, which is consistent with the wind tunnel experiment results. Under the condition of the different wind speeds, with the increase of wind speed, trees porosity gradually increases, drag coefficient decreases, the minimum wind speed of the relative reference point of the wind profile at the height of the tree after the tree gradually increases, the maximum relative reference point turbulence degree decreases when the appeal case, simulation of wind field and wind tunnel test of measuring wind field are considered.