低郁闭度乔灌混交林防风效果风洞试验研究

通过对均匀分布和行带式分布模式的风洞试验研究,得出2种分布的水平和垂直空间风速的变化存在差异。主要表现在：（1）2种分布模式形成风影区和风速加速区相互组合的复杂水平风速流场结构。均匀分布模式中产生＂狭管增速效益＂,出现了较大面积的三角形风速加速区,而行带式分布模式未形成风速加速区。（2）2种分布模式对风速的影响高度低于20 cm,20 cm以上的风速均为层流运动。均匀分布模式0.4-6cm高度的风速有一定变化,但风速运动方式仍为层流运动;行带式分布模式0.4-6 cm高度的风速变化较大,风速为湍流运动。2种模式末端的风速,行带式分布要低于均匀分布。因而,行带式分布模式乔灌混交林的防风效果高于均匀分布模式。

Wind Tunnel Test on Windbreak Effect in Mixed Forest of Arbor and Shrub at Low Canopy Density

Based on the wind tunnel test, the paper has researched that the change of vertical and horizontal wind speed have difference in even and single -belt scheme distribution. It mainly showed on two aspects. On the one hand, two kinds of disposition patterns have formed complex flow field of horizontal wind combined by the wind shadow and the wind speed accelerating area. Moreover, a larger triangular accelerating area of wind speed was ap- peared on the even distribution pattern because of steno - pipe effect, but the wind speed accelerating area was not generated in the. single - belt scheme distribution pattern. On the other hand, the two kinds of disposition patterns influenced the altitude of wind speed under 20 cm, the wind speed above 20 cm was flow movement. The wind speed between 0.4 cm and 6 cm could change in the even distribution patterns with flow movement as the wind speed moving pattern. The wind speed changed evidently between 0. 4 em and 6 cm in the single - belt scheme dis- tribution with turbulent motion as the wind speed moving pattern. The wind speed at the bottom of single - belt scheme distribution is lower than that one of the even distribution. So, the windbreak effects of mixed forest of arbor and bush in single - belt scheme distribution was higher than that one of even distribution.