The Effects of Forest Canopy Models on Damping of Turbulent Energy in a Flow

本研究主要包括三个部分：（1）中型风洞实验研究;（2）大型风洞实验研究;（3）有限差分法数值模拟研究。(1)本试验中的冠层模型的叶面积指数为6.6。用CTA测量了树木模型下游区域的流向速度分布，发现单个树木模型之间的流动不同于树木下游的流动。冠层模型下游流场表现出较强的三维特征。(2)该试验是在1998年1月于宫崎大学建造的大型风洞中进行的。冠层模型的叶面积指数为9.0。从单树模型的排列角度，分析了不同节距下冠层剪切层内湍流时均速度和湍流强度的分布。(3)采用FDM-SMAC方法对流场进行了数值模拟。冠层由大量的质点近似，质点之间通过弹簧和阻尼器连接。在时间推进中，气流的运动和树冠中颗粒的运动是联系在一起的。数值计算了各种稀疏和密集树冠的绕流场。这些结果与风洞试验结果吻合较好。

This research is composed of three parts ; (1) the first is the experiments with the medium wind tunnel, (2) the second is that with the large wind tunnel, and (3) the third is the numerical simulation with the finite difference method and the crown-particle dynamics like the molecular dynamics.(1) The canopy model in this testing has the leaf area index of 6.6. Distributions of streamwise velocity components in the downstream region of the model are measured with the CTA.Flows between individual tree models are different from flows downstream of trees. Flows downstream of the canopy models showed strong three-dimensional characteristics.(2) This testing is experimented with the large wind tunnel constructed in Miyazaki University on January 1998. The canopy model has the leaf area index of 9.0. Distributions of the time-averaged velocity and intensity of turbulence in the shear-layer above the canopy are changed with the different pitch from arrangement of individual tree models.(3) Flow fields are simulated with the FDM-SMAC method. The crowns of canopy are approximated with a lot of particles that are connected with neighbor particles by spring and damper. The motion of air flows and the motion of particles in the crown are linked in the time-marching. Flow fields around the canopies of various sparse and dense crowns are calculated numerically. These results are good agreement with the results of the experiments with the wind tunnel testing.