两行一带式乔木固沙林带风速流场和防风效果风洞试验

Windbreak Effects and Wind Velocity Flow Field of Low Density Forest with Two-Line-One-Belt Distribution Patterns of Single-Belt Scheme

研究在风速为10和15m.s-1的风洞试验条件下,覆盖度为20%和25%的3种两行一带模式固沙林内的水平和垂直方向的风速变化情况,以期对3种模式的风速流场和防风效果进行比较分析。结果表明:3种配置模式在0.31H高度形成了风影区和风速加速区相互组合的复杂流场结构,覆盖度25%的两行一带模式的防风效果高于覆盖度20%的两行一带模式。3种模式在不同高度的风速变化规律相同,可划分为3层:微变化层(1.54H和2H)、显著变化层(0.46H和0.92H)和稳定变化层(0.06～0.12H)3个层次。3种模式降低风速的效果为:D=4H(H为带间距)L=4cm(L为行距)模式大于D=5H,L=0.08m模式和覆盖度20%(D=5H,L=0.04m),后2种模式相同。

In order to compare the wind-preventing effect of three patterns of wind flow field,horizontal and vertical wind speed changes was studied under the condition of tunnel,with the＂two-row in one-belt pattern＂in arbor sand-fixing forest and with the coverage of 20% and 25%,and the experimental wind velocity was set 10 and 15 m.s-1,respectively.The result indicated that：a complex wind flow field formed under four centimeters in height in three kinds of configuration mode,the field structure was composed of the wind shadow and the wind speed acceleration areas.The＂two-row in onebelt pattern＂with the coverage of 25% was better than that with the coverage of 20%.The change of wind speed showed the same pattern at different heights in the three different patterns.They were able to be divided into three layers—microlevel changes（1.54H and 2H）,significant change in layer（0.46H and 0.92H）,and stable changes in layer（0.06 ～ 0.12H）.The effect of reducing wind speed of three patterns showed that the windbreak effect of the D = 4H（H is the spacing interval between the forest belts）,L = 4 cm（L is row spacing）was better than D = 5H,L = 0.08 m and coverage of 20%（D = 5H,L = 0.04 m）,and the last two modes had the same effect.