城市冠层植被大气环境特性大涡模拟

 植被通过生物物理过程影响着周围微气候环境，对于城市植被环境流动的研究需要建立合理的植被模型。本研究发展了一套适于模拟植被边界层流动的大涡模拟数值方法，并通过水平均匀模型植被算例对其进行了验证。在此基础上，对空气流过三维非均匀分布钝体元阵列模型植被进行了大涡模拟，并将不同植被数值模型的计算结果与相应的风洞实验数据进行了比较。结果表明，树干部分采用刚性圆柱模拟、树冠用阻力模型的“阻力冠”方法相比于传统的“阻力元”方法能更好反映植被流动的影响。

Large eddy simulation of flow over urban vegetated regions

Vegetation exerts notable influences on urban microenvironment through biophysical processes. Studying the flow over urban vegetated region requires a proper treatment of the vegetation canopy. A large eddy simulation (LES) method is developed in the present work, which can well simulate the canopy flow. Using LES the turbulent flow over a model vegetation canopy is investigated under the neutral atmospheric condition. Each vegetation element consisting of a sphere-shaped tree crown and a cylindrical trunk is fully resolved. The resulting turbulence statistics and the drag force on vegetation agree well with the measurements from the corresponding wind-tunnel experiment. Two other numerical representations of vegetation canopies, referred to as drag element approach and drag crown approach, have also been developed to assess their performances. The drag crown approach yields better agreement between numerical results and experimental measurements than the traditional drag element approach, thus providing a promising numerical model for simulating canopy turbulence.