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

本研究由三部分组成：(1)中型风洞试验，(2)大型风洞试验，(3)有限差分法和分子动力学等冠层粒子动力学的数值模拟。(1)本次试验的冠层模型叶面积指数为6.6。用CTA测量了模型下游区域流向速度分量的分布，单木模型之间的流动不同于树木下游的流动。模型冠层下游的流动表现出较强的三维特性。(2)本试验于1998年1月在宫崎骏大学建造的大型风洞中进行。冠层模型的叶面积指数为9.0。树冠上方剪切层内湍流时均速度和湍流强度的分布随单株模型排列间距的不同而不同。(3)采用有限差分-SMAC方法对流场进行了数值模拟。通过弹簧和阻尼器将多个颗粒与相邻的颗粒连接起来，近似地表示冠层的顶端。气流的运动和冠内颗粒的运动在时间行进中联系在一起。对不同稀疏型和密型树冠冠层的流场进行了数值计算。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.